South Africa: Biocontrol of invasive water lettuce plant


Published: April 9, 2024 11:01am EDT


  1. Julie CoetzeeDeputy Director of the Centre for Biological Control at Rhodes University and Biological Control and Freshwater Alien Invasive Species Management, South African Institute for Aquatic Biodiversity

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Julie Coetzee receives funding from the National Research Foundation. She is affiliated with the South African Institute for Aquatic Biodiversity (SAIAB).


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A small insect with a light brown body and protruding mouth parts is pictured up close on a green leaf
The water lettuce weevil, Neohydronomus affinis, is a powerful biocontrol agent. David Taylor, Centre for Biological Control, Author provided (no reuse)


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Water lettuce (Pistia stratiotes L.), also known as Nile cabbage, is a free-floating aquatic plant from the family Araceae, the same family as the arum lily.

It’s found on every continent except Antarctica and grows well in tropical to sub-tropical climates. Research suggests it may have originated in South America because it has natural enemies there which have co-evolved with the plant. However, fossil records and ancient Egyptian hieroglyphics depicting water lettuce indicate that it may have been present in other regions for millions of years. It was likely spread around the world by early colonists as an ornamental plant for ponds and aquatic gardens.

Today, water lettuce is considered an invasive species in many parts of the world, including African countries, where it has caused significant negative impacts on aquatic ecosystems and human activities.

Recently, water lettuce has invaded one of South Africa’s most important rivers, the Vaal River, on the border of the Gauteng and Free State provinces. This has raised huge concerns for local communities, businesses and stakeholders, as well as Rand Water. Rand Water is the largest bulk water utility in Africa and is one of the largest in the world, providing bulk potable water to more than 11 million people.

An expanse of water is covered almost entirely with what looks like a mat of vividly green grass
Water lettuce blankets the surface of the Vaal River. Julie Coetzee, Author provided (no reuse)

I am the deputy director of the Centre for Biological Control at Rhodes University, where I manage the biological control programme on aquatic weeds in South Africa. My team and I are currently working with Rand Water on an integrated management plan for water lettuce control in the Vaal River. This comes after good results in controlling water lettuce in other parts of South Africa and in neighbouring countries such as Zimbabwe and Mozambique since 1985 – thanks to a small species of weevil.

The damage

Water lettuce forms dense mats on the water surface. This can reduce light penetration and oxygen levels in the water, negatively affecting all aspects of aquatic life from microscopic plankton to large fish. The mats can also impede water flow, leading to stagnation and increased mosquito breeding sites. Water lettuce can clog agricultural irrigation canals too. Its rapid growth can also interfere with fishing and boat navigation.

Management of water lettuce can include manual removal and the use of herbicides to prevent spread. Herbicides were routinely used to combat water lettuce in South Africa in the early 1980s, and are still relied on heavily in the US, particularly in Florida.

Read more: Invasive alien species are a serious threat to the planet: 4 key messages for Africa

However, these methods are labour-intensive and often insufficient to control the plant’s rapid growth. They can also damage other vegetation.

That’s where biological control comes in. This involves the introduction of natural enemies like insects or pathogens, which can help manage the plant’s population more sustainably and effectively. By importing and releasing a suitable biological control agent, such as the water lettuce weevil Neohydronomus affinis, the negative effects of water lettuce on the environment and local communities can be mitigated.

The weevil

This Brazilian weevil species was first introduced to Africa in 1985 via Australia, following successful control of water lettuce infestations there. The then Department of Agriculture gave permission to release it in South Africa and 500 weevils were released into a heavily invaded pan in the northern Kruger National Park.

Since then, it has been used to control water lettuce infestations in Botswana, Benin, Ghana, Senegal, Zimbabwe, Zambia, Republic of Congo, Côte d’Ivoire, Kenya, Nigeria, Togo, Mozambique and Morocco. Invasions at sites in these countries, no matter how extensive, were generally brought under control within a year.

Read more: New bugs, found in Kenya, can help to control major maize pests

The impact of N. affinis on water lettuce populations is significant: the combined feeding activities of adult and larval weevils cause substantial damage to the plants, reducing their growth and reproductive potential. Adult weevils chew small holes in the leaves, while larvae tunnel through the leaves, causing them to waterlog and sink.

The ability of N. affinis to produce multiple generations per year enables it to quickly build up populations and maintain pressure on water lettuce populations over time, making it an effective biological control agent for managing water lettuce in affected areas.

As a host-specific insect, N. affinis poses little risk to non-target species or the environment. Biological control of water lettuce in Africa is considered one of the most successful programmes in the fight against invasive species.

So, how are these powerful weevils being used in the Vaal River?

The Vaal River

Water lettuce was first identified on a tributary to the Vaal River in 2021, but local conditions (floods and cold winters) appeared to have limited the spread of this plant. However, at the end of 2023, a large infestation was noticed on the Vaal River and was reported to relevant authorities.

Since then, the infestation has covered up to 40km of the river in the Vaal Barrage area, around the town of Vanderbijlpark, and threatens to spread downstream of the 1,200km long Vaal River.

Rand Water is following an integrated strategy to control and reduce the invasion. Biological control, using the water lettuce weevil, is key to the long term management of the water lettuce invasion. The Centre for Biological Control at Rhodes University is working closely with Rand Water to ensure a constant and abundant supply of the weevils – to do so, the centre has established weevil rearing stations.

A group of ten people posing, smiling, alongside large pallets containing big leaves
The team that rears weevils in Makhanda at the Centre for Biological Control. Julie Coetzee, Author provided (no reuse)

Thousands of weevils have already been released into the Vaal River since November 2023 from our mass rearing facility in Makhanda. Weevils are also being reared by businesses and residents who live near the river, as well as Rand Water. The weevils will be released frequently and en masse, at crucial times, particularly after winter when the plants will germinate from seeds. This is termed inundative biological control.

Water lettuce is one of the easier invasive aquatic plants to control, biologically – soon the infestation will be under control. What lurks alongside this invasion on the Vaal River, however, is the water hyacinth, which remains South Africa’s most problematic aquatic invasive plant. It is a super competitor, thriving in the country’s nutrient rich waters. Efforts are underway by the Centre for Biological Control to highlight this threat. The quality of water upstream from the Vaal needs to be urgently remediated, as this is the ultimate cause of both the water lettuce and water hyacinth invasions.


XX International Plant Protection Congress, Athens, Greece, 10-15 June 2023


XX International Plant Protection Congress,
Athens, Greece, 10-15 June 2023

The Hellenic Society of Phytiatry (HSP) is very pleased and honored to announce that the International Association for the Plant Protection Societies (IAPPS) has accepted the Greek bid proposal for the organization of the XX International Plant Protection Congress in Athens, Greece. The congress is under the aegis of the Agricultural University of Athens and is going to take place at the MEGARON Convention Center in Athens 10-15 June, 2023.

Please note that most of the members of the local organizing and scientific committee are world-known scientists with experience in research, teaching and application in plant protection with profound scientific achievements either in Greece or  abroad.

As for the venue of the Congress, natural and cultural beauty of Greece and its cosmopolitan capital, the world famous city of Athens, the history, the tradition and the hospitality, are significant reasons justifying broad international participation. Apparently Athens, has a great organizational advantage since it is easily accessible from Europe, Africa and several countries of Asia, while several American countries have direct flights to Athens.

Greece, as a Mediterranean and South European country, covers a vast diversity of agricultural temperate, subtropical and even tropical cultivations with highly specialized scientists on plant protection sciences working in Universities, Research Centers and in the Private Sector.  Thus, Greece is one of the few countries where scientists can meet a very broad diversity of cultivations and plant protection problems.

It is certain that participants of the XX IPPC ATHENS 2023 beyond science will enjoy long-standing history, the ancient and modern city of Athens, the birth place of democracy, the fantastic environment and finally Greek tradition, special Mediterranean food and legendary hospitality.   The organizers are looking forward to the successful organization and realization of the congress at all stages till the final day of the congress.

On behalf of the Local organizing committee

Professor Eleftherios (Eris) Tjamos,
President of the Hellenic Society of Phytiatry
Agricultural University of Athens, Athens, Greece,
Department of Plant Pathology,
75 Iera Odos str., 18855 ATHENS, GREECE
e-mail:  and or  e-mail:
mobile phone 0030 6932 365566


Eris Tjamos



Argentina: Maize stunt disease cutting yields


Sunday, 21 April 2024 08:16:00

Grahame Jackson posted a new submission ‘STUNT DISEASE, MAIZE – ARGENTINA’




Source: Reuters [summ. Mod.DHA, edited]
Argentina’s maize harvest faces deep cuts due to a stunt disease spread by leafhoppers. The crop has been hit by an unprecedented outbreak of the insects that carry the harmful spiroplasma. Leafhopper populations tend to increase in hot and dry conditions. They have badly dented the 2023/24 maize crop, which is very badly affected.

In the worst-hit northern provinces the losses caused by the disease range between 40% and 50%, when normally the figure reached only 5% at worst. Severe cases of leafhoppers were also being seen in regions where they usually do not appear. The unusually damaging outbreak this year has reached areas where it never reached before.

In response, the government announced it was accelerating approval procedures for 2 insecticides recommended to combat the spiroplasma disease, although that comes largely too late for the current harvest. Another factor that will determine how the outbreak progresses is the arrival of low temperatures, as the insect cannot resist temperatures below 4 degrees Celsius. However, scientists at the University of Buenos Aires said that a rapid decrease in temperatures was not expected in northern Argentina, the location of the worst outbreaks.

[Byline: Maximilian Heath]

Communicated by:

[_Spiroplasma kunkelii_ causes maize stunt disease on _Zea_ species in the Americas. The maize leafhopper _Dalbulus maidis_ is the main vector. Some crop hybrids resistant to the vector have been identified which potentially may be helpful in disease control (see links below).

Spiroplasmas are plant cell parasitic bacteria without a cell wall and, like phytoplasmas, belong to the mollicutes. The name is derived from their helical morphology. Spiroplasmas can be cultured on artificial media, unlike phytoplasmas, which cannot be cultured in vitro. Mixed infections with phytoplasmas have been reported to occur.

The pathogens are transmitted by leafhopper species. Disease management for spiroplasmas mainly relies on exclusion by use of certified clean planting material, but may also include phytosanitation to remove inoculum and prevent spread within plantings. Vector control has not shown to be effective due to the very rapid transmission.

The related _S. citri_ causes citrus stubborn disease (CSD, also called little leaf); yield losses may be severe (ProMED post 20200710.7559217). The pathogen is also known to affect other crops causing, for example, carrot purple leaf (ProMED post 20110916.2824) and horseradish brittle root diseases.

Maize stunt symptoms:×512/1235015.jpg,,×512/1524072.jpg×437.jpg (ears) and
Citrus stubborn disease symptoms:, and
_S. citri_ microscopy:

Information on maize stunt disease:,,,,, and via
Citrus stubborn disease:,, and
Spiroplasma taxonomy via:
Information on leafhopper vectors via:
– Mod.DHA


New tools for science on the farm –


The value of “connected agriculture” in making life easier for farmers, and helping them reduce the environmental impact of their practices, is no longer unproven. Another of its advantages is beginning to emerge: by producing large amounts of data of near- research quality, it helps align agronomic and zootechnical research closer to farmers’ requirements, and could better inform agricultural public policies.Digital agriculture is a concept which is beginning to reach grass-roots level, as the high visibility of the subject at the Paris Agriculture Fair demonstrated. In the gloomy atmosphere generated by the feeling of “agri-bashing” experienced by many farmers, it was one of the few subjects that gave a positive and attractive picture of recent developments in agriculture.

Digital farming tools were first designed to make life easier for farmers (GPS guidance, herd monitoring sensors), and to help them optimise their farming practices on an environmental level (connected weather stations, crop models used to optimise input usage). They have also strengthened ties with the consumer, who, thanks to the development of traceability and social networks, can now put a face and a name to the food he buys.

More behind the scenes, connected agriculture is also beginning to have a new beneficial effect, which could in future play an even more positive role for the agricultural world: bringing farmers closer to the research world… and as a result to the policy makers who make use of it.

When science has to be done at the farm level

This development is already a reality in some areas of R & D in digital agriculture. To take the example of herd monitoring sensors: they were first developed to detect unusual and clearly identified events, such as detecting temperatures or calving. These initial applications were developed in a conventional research setting, top down from the lab to the field: algorithms for event detection were developed in tests in experimental farms at research or technical institutes, then tested on a small range of farms before being launched commercially.

As these initial applications have reached maturity, research is now focused on analyses of the daily behaviour and welfare of animals: for example, measuring time spent standing or lying, feeding and rumination times. In these areas it is important to detect more subtle changes in the “daily life” of animals, compared to their ordinary activity.

That makes it very difficult to develop this type of algorithm on experimental farms, where the usual activities of livestock (milking, being put out to pasture, etc.) are frequently disturbed by experiments that modify their usual behaviour, and generate movements or immobility that would not happen in a commercial farm. This type of work should therefore be carried out directly in the field, with experiments in controlled conditions being used only as spot checks in a minority of situations. This is an example of an inversion of the classic relationship between scientific experimentation and field data.

From the lab to the vineyard… and back!

Another example of linking research to farmers’ concerns is the use of mechanistic crop models in decision support tools. These models, derived from agronomic research, are increasingly being used for yield forecasting and management of the required inputs (irrigation, fertilisation). Similar epidemiological models are also used to predict the occurrence of diseases or pests threatening crops, in order to position pesticide treatments most accurately.

By design, the result of extensive research in ecophysiology, these models are sufficiently robust and predictive to lend themselves to plausible simulations on the potential effect of changing practices for agro-ecological reasons, or to adapt to climate change. They also have the advantage of objectively quantifying the environmental conditions to which crops are exposed.

Evapotranspiration is a classic example of a simple indicator for measuring crop water demand, which can then be used as a benchmark to check whether irrigation by the farmer has avoided water waste. However, it remains a relatively basic indicator, which is relevant only in the simplest cases: those where we are only seeking to maintain the yield potential by avoiding water deficit for the crop. For some produce, irrigation issues are more complex, because a small, well-controlled water deficit improves the quality of production: the best known case being vines, where the ideal method, defined by the specifications of the wine appellation, aims to create a moderate water deficit during the maturation of the grape, with varying degrees of severity depending on the type of wine you want to produce.

In this case, irrigation management requires much more complex models than a simple evapotranspiration calculation, and they will use not only climate data, but also soil characteristics and the volume of vegetation in the vineyard. At first glance this is once again a top-down approach to the maximisation of research value, from the laboratory to the field. But the use of these models on farms then permits valuable feedback, which will bring the theoretical work closer to the practice of farmers or their consultants.

The Vintel software, developed by iTK in partnership with (among others) INRA and CIRAD, offers a good example of these two-way exchanges between lab and field. Designed to optimise precision irrigation on vines, it is based on a model derived from research work, based on a classic indicator in research of conventional water stress, the basic leaf water potential.

This indicator is the most reliable for measuring the moisture condition of a vine plant, but its measurement is fiddly, which limits its use in vineyards: it has to be measured at dawn with a specific instrument, the pressure chamber. Some wine consultants, particularly in California, use pressure chambers to advise winegrowers. However, they use these measures at noon for convenience, but also to better understand the water deficit of the plot at the time of the day when it is at its height.

This way of measuring is much less common in research, and so originally it was impossible to develop a mechanistic model to simulate it. Vintel was initially released with a model which only estimated the basic leaf water potential. A few years of use of this first version, by consultants expert in the use of the midday potential measurement, then allowed the development of a second model for midday leaf water potential, combining meteorological data and indicators from the base potential, without going through the laboratory process again.

This example clearly demonstrates the new complementarity between research and digital tools for farmers: it is obviously the data from the field that made it possible to develop a model of midday leaf water potential, in line with the habits of winegrower technicians. But that alone would not have been enough to develop a reliable statistical model: only combining them with indicators from a mechanistic model derived from research could lead to the development of a model robust enough to be entrusted to winegrowers and consultants.

“Medium Data” vs Big Data

A few years ago, the explosion of Big Data technologies, and their introduction into the agricultural world, gave rise to a rather binary view split between two scientific approaches:

  • On the one hand, the classic approach of agronomic or zootechnical research, relying on high-quality but relatively sparse experiments, to develop predictive models that can be used in decision support, based on the human expertise of researchers,
  • On the other hand, the new data-centred Big Data approaches applying machine learning techniques (machine learning, deep learning) to massive volumes of data from new sensors deployed in agriculture (combine yield sensors, data collected by milking robots),

The enthusiasm for Big Data was based on the assumption that deep learning would allow the development of reliable predictive models, despite the “noise” generated by the information from the masses of data collected, which exceed what human expertise is capable of analysing. In fact, this hope quickly came up against the major pitfall of machine learning techniques: their lack of user-friendliness…both for end users (farmers or breeders), and service designers! Machine learning certainly now makes it possible to define seemingly satisfactory decision rules or models from any sufficiently large dataset.

But without knowing the “reasoning” underlying these models, even their designers are unable to predict to what extent these rules or models can be used in new contexts: a rather distressing uncertainty when developing new agricultural services beyond the region where they were initially proven, or in new climate situations.

In addition to its sensitivity to unpredictable climate risks, agriculture has another unfortunate feature for machine learning: the real data that can be accumulated on the ground is far from covering all possible combinations of cultivation techniques. The technical strategies used by farmers are influenced by their habits, experience and the expertise of their consultants, and are therefore absolutely implicitly limited by human rationales.  The situation is in this regard completely different from areas such as machine learning applied to games such as chess or go: in the latter case, the algorithm is able, based on the rules of the game, to test all possible and imaginable combinations, even those that a human expert would not think of. In agriculture, artificial intelligence is hampered by the fact that the available data is the result of human reasoning, which prevents it from finding original “solutions” to invent new practices.

The result of these constraints is that purely data-driven approaches are struggling to make a decisive breakthrough in agricultural decision support. The future is undoubtedly, as we have seen from Vintel’s example, the combination of data-driven approaches and mechanistic models to integrate human expertise into Artificial Intelligence. This new vision, hybrid AI, has been chosen as one of the major themes of ANITI, the new Institute of Artificial Intelligence currently being created in Toulouse… and agriculture has been identified as one of its priority areas of application.

This close interconnection between scientific expertise and farm data has an obvious corollary: the need to bridge the gap between Big Data and research data. This is the mission of what can be called “Medium Data”: well-founded data from farms, or at least from plots run under conditions similar to those of farms. Until now, this role of producing intermediate data has been entirely devolved to experiments at agricultural development agencies: technical institutes, chambers of agriculture, cooperatives[4]. Digital agriculture will allow for the emergence of a new category of “medium data”: data of near-research quality, but spread across hundreds or thousands of farms.

Between the scientific data of research, high quality but sparse, and the “Big Data” of sensors embedded on agricultural equipment, connected agriculture allows the emergence of a “Medium Data”: data of near-research quality, acquired on farms, and not small, unrepresentative experimental plots. It is this continuum of data that will fuel hybrid artificial intelligence (a combination of machine learning and mechanistic human expertise), one of the most promising avenues in today’s AI.


Information to ground agricultural public policy

We have seen, with the example of irrigation, that agricultural decision support tools lend themselves well to the creation of objective indicators of crop needs: the same approach is easily transferable to fertilisation, as well as crop protection. Epidemiological models, already used to advise optimal treatment dates for diseases and pests, could also be used at plot level to quantify the still vague and subjective idea of “threat of disease”  Such indicators would be valuable in improving the monitoring of Ecophyto, the plan to reduce the use of pesticides launched in 2010 following the “Grenelle de l’Environnement” debate.

It’s not overstating the case to say that, almost 10 years after its inception, the plan is far from the 50% reduction target (“if possible”) assigned to it: pesticide consumption shows no significant changes on the national average. Even more disturbing, even the plan’s flagship farms, the Dephy network, are a long way from achieving the expected goal. In view of what can hardly be described other than as a failure, the Académie d’Agriculture de France has recently made recommendations to improve the management of the Ecophyto Plan, including the creation of this kind of indicator of health pressure on crops. Digital agriculture could also play a major role in another of the Academy’s proposals: annual surveys of agricultural practices, the only references that can be used to calculate farmers’ pesticide consumption in any detail.

Indeed, the current indicator for the Ecophyto Plan, NODU, is not suited to an agronomic interpretation, which would allow calculation of the potential reduction in pesticide use at farm level. Another indicator, the TFI, would allow for this calculation, although it is currently calculated only every three years, due to the cost of the surveys currently required to collect the data. This still remains the situation, but plot management software enables the automatic calculation of this indicator for farmers who have the equipment. A representative network of farms equipped with this software would therefore allow the annual TFIs to be calculated at a lower cost and cross-linked with the health pressure indicators mentioned above. It should thus be possible to follow up the Ecophyto plan with greater accuracy… and probably to redefine a more realistic set of goals for it, differentiated by crop and region!

Participatory science, which draws on the knowledge of its future users and civil society stakeholders, is one of the key trends in current research. INRA has also been heavily involved in this area. However, much participatory science work remains very asymmetrical: researchers are often the only players putting forward the theories based on the informal and unorganised knowledge of the stakeholders involved in the project. Connected agriculture offers a unique opportunity for farmers to take ownership of research topics that affect them, producing data for themselves which is as understandable for them as for the researchers who will make use of it. Beyond its impact on the daily work of farmers, it therefore has great potential to bring research closer to their needs and enable politicians to better understand their practices. This is how agriculture will be able to meet society’s many expectations of it.


Predatory mites: Alternative to toxic insecticides


ABC Rural

 / By Jennifer Nichols

Posted 4h ago4 hours ago

A composite image with a red bug on the left and a man in a greenhouse on the right.
James Hill oversees the breeding of billions of Phytoseiulus persimilis bugs.(Supplied: Bugs for Bugs) link

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As concern over chemical use in food production grows and insect species become more resistant to poisons, farmers are turning to nature for solutions to pests that can cripple crop production.

Billions of tiny, blind, predatory mites are being bred, harvested, packed on ice, and posted to strawberry farms in the battle against destructive sap-sucking insects.

A man holds up a glass cup with red brown insects in the bottom of it.
James Hill with a cup of persimilis, from the arachnid family.(ABC Rural: Jennifer Nichols)

“We’re producing beneficial insects for farmers to use instead of insecticides,” Bugs for Bugs Donnybrook insectarium manager James Hill said.

“Ninety per cent of farmers in the strawberry industry are using our product.”

Ripe strawberries in a field.
Strawberries can now be grown with considerably fewer chemicals.(ABC Rural: Jennifer Nichols)

The battle

Australians love strawberries — 72 per cent of households bought them last financial year and on average we each ate around 2.27 kilograms of the fruit. 

One of the main insect enemies that farmers battle to produce tasty red strawberries is two-spotted mites, a sap-sucking species related to ticks, too tiny to spot with the naked eye.

A web like structure packed with tiny insects on a very sick looking bean leaf.
The two-spotted mite is bred to feed the Phytoseiulus persimilis bugs.(ABC Rural: Jennifer Nichols)

Left unchecked, you can see the damage two-spotted mites can do, sucking the life out of bean leaves in the polytunnels where they are raised as food for the predator mites that are sold to growers.

“If left unchecked the two-spotted mite would just devastate your crop, it would wipe you out,” Queensland Strawberry Growers president Adrian Schultz said.

A line of tiny insects hangs from a sick bean leaf.
A line of tiny insects hangs from a sick bean leaf.(ABC Rural: Jennifer Nichols)

The tiny warrior

An eight-legged member of the arachnid family, Phytoseiulus persimilis, is blind.

It hunts down two-spotted mites by touch and scent and can be dropped by drone to decimate populations of two-spotted mites and spider mites.

A magnified photo of a red coloured mite on a leaf.
Phytoseiulus persimilis thrives in humid conditions.(Supplied: Bugs for Bugs)

Just 0.5mm long, persimilis are voracious, specialised predators that breed twice as fast as their prey, can be carried on the wind, and are deployed to protect crops, greenhouses and commercial installations of indoor plants.

Once they have exterminated the pests they turn on their own eggs and larvae, posing no threat to other insects.

Mr Shultz said the insects have become real cost savers for big farms. Roy’s drone dropping beneficial bugs.

“In years gone by, we had to rotate different insecticides to control the two-spotted mite and you’d get a higher percentage of pests that were resistant,” he said.

“The advent of the predator mites enabled industry to use considerably less chemicals in controlling pests, now we also have the option of introducing lady beetles into our crops to control aphids.”

An older man dressed in blue farm work gear and brown boots kneels between rows of freshly planted strawberries. He smiles
Queensland Strawberry Growers Association president Adrian Schultz says the industry has embraced beneficial insects.(ABC Rural: Melanie Groves)

Integrated pest management

Integrated pest management (IPM) is increasingly popular with farmers and uses a range of preventive measures to control pests, including natural predators, parasites, nematodes, and pheromone traps.

“It’s not set and forget, you need to monitor the situation and you’ve got to be aware of the impacts of environmental conditions,” Mr Schultz said.

A man in a field of corn or maize.
Paul Jones helped pioneer beneficial insect breeding for horticulture in Australia.(Supplied: Bugs for Bugs)

Changing attitudes

The job satisfaction of helping farmers produce higher quality products with fewer chemicals is why Bugs for Bugs director Paul Jones has been working in integrated pest management for 30 years.

“When we first went out to farmers there was a lot of fear and scepticism about reducing the use of sprays and using beneficial insects to control pests,” the agricultural scientist said.

“The change has been quite radical, what was once considered a cottage industry for small organic and family farms has now become the backbone for pest management in conventional agriculture.” good bugs to fight bad bugs could be the key to pesticide-free farming

Bugs for Bugs is one of only a handful of commercial suppliers of beneficial insects in Australia.

From insectaries at Donnybrook, Toowoomba and Mundubbera, it sells 12 different species including predatory mites, ladybirds, lacewings, and parasitic wasps.

Home gardeners can also order the insects online.

Rows of polytunnels
Bugs for Bugs has expanded its insectaries.(ABC Rural: Jennifer Nichols)

Worldwide, predatory bioagents are being used to target gnats, thrips, caterpillars, scale, mealybugs, aphids, heliothis larvae, loopers, whitefly, and mites in crops including strawberries, raspberries, blackberries, cotton, macadamias, almonds, avocados, citrus, maize, cut flowers and hops.

Parasitic wasps kill fly maggots for the poultry, pig, dairy and feedlot industries, and black soldier fly larvae transform organic waste into compost.

A cup with tiny little insects in it.
Bugs for Bugs Phytoseiulus persimilis ready to be posted.(ABC Rural: Jennifer Nichols)

At the Donnybrook insectary, billions of persimilis are being harvested from polytunnels for the start of the Queensland winter strawberry season.

Each insect order is weighed and packed on ice to keep the persimilis mites in hibernation during transport.

A woman at a workbench.
Deb Hill packs predatory insects on ice and posts them to farmers.(ABC Rural: Jennifer Nichols)

A vermiculite mineral is included to make it easier for farmers to evenly spread the tiny predators on their fields.

“It’s evolved, refining the craft, we’ve got better and better,” Mr Jones said.

“Mainstream chemical companies now collaborate with us to ensure products are less harmful to beneficial insects.”

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Climate change is shifting the zones where plants grow


The Conversation

Published: March 22, 2024 8:34am EDT


  1. Matt KassonAssociate Professor of Mycology and Plant Pathology, West Virginia University

Disclosure statement

Matt Kasson receives funding from the US Department of Agriculture.


West Virginia University provides funding as a member of The Conversation US.

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With the arrival of spring in North America, many people are gravitating to the gardening and landscaping section of home improvement stores, where displays are overstocked with eye-catching seed packs and benches are filled with potted annuals and perennials.

But some plants that once thrived in your yard may not flourish there now. To understand why, look to the U.S. Department of Agriculture’s recent update of its plant hardiness zone map, which has long helped gardeners and growers figure out which plants are most likely to thrive in a given location.

A U.S. map divided into colored geographic zones with a numbered key.
The 2023 USDA plant hardiness zone map shows the areas where plants can be expected to grow, based on extreme winter temperatures. Darker shades (purple to blue) denote colder zones, phasing southward into temperate (green) and warm zones (yellow and orange). USDA

Comparing the 2023 map to the previous version from 2012 clearly shows that as climate change warms the Earth, plant hardiness zones are shifting northward. On average, the coldest days of winter in our current climate, based on temperature records from 1991 through 2020, are 5 degrees Fahrenheit (2.8 Celsius) warmer than they were between 1976 and 2005.

In some areas, including the central Appalachians, northern New England and north central Idaho, winter temperatures have warmed by 1.5 hardiness zones – 15 degrees F (8.3 C) – over the same 30-year window. This warming changes the zones in which plants, whether annual or perennial, will ultimately succeed in a climate on the move.

U.S. map showing large areas colored tan, denoting a 5-degree increase in average winter minimum temperatures.
This map shows how plant hardiness zones have shifted northward from the 2012 to the 2023 USDA maps. A half-zone change corresponds to a tan area. Areas in white indicate zones that experienced minimal change. Prism Climate Group, Oregon State UniversityCC BY-ND

As a plant pathologist, I have devoted my career to understanding and addressing plant health issues. Many stresses not only shorten the lives of plants, but also affect their growth and productivity.

I am also a gardener who has seen firsthand how warming temperatures, pests and disease affect my annual harvest. By understanding climate change impacts on plant communities, you can help your garden reach its full potential in a warming world.

Hotter summers, warmer winters

There’s no question that the temperature trend is upward. From 2014 through 2023, the world experienced the 10 hottest summers ever recorded in 174 years of climate data. Just a few months of sweltering, unrelenting heat can significantly affect plant health, especially cool-season garden crops like broccoli, carrots, radishes and kale.

Radishes sprouting in a garden bed.
Radishes are cool-season garden crops that cannot withstand the hottest days of summer. Matt Kasson, CC BY-ND

Winters are also warming, and this matters for plants. The USDA defines plant hardiness zones based on the coldest average annual temperature in winter at a given location. Each zone represents a 10-degree F range, with zones numbered from 1 (coldest) to 13 (warmest). Zones are divided into 5-degree F half zones, which are lettered “a” (northern) or “b” (southern).

For example, the coldest hardiness zone in the lower 48 states on the new map, 3a, covers small pockets in the northernmost parts of Minnesota and has winter extreme temperatures of -40 F to -35 F. The warmest zone, 11b, is in Key West, Florida, where the coldest annual lows range from 45 F to 50 F.

On the 2012 map, northern Minnesota had a much more extensive and continuous zone 3a. North Dakota also had areas designated in this same zone, but those regions now have shifted completely into Canada. Zone 10b once covered the southern tip of mainland Florida, including Miami and Fort Lauderdale, but has now been pushed northward by a rapidly encroaching zone 11a.

Many people buy seeds or seedlings without thinking about hardiness zones, planting dates or disease risks. But when plants have to contend with temperature shifts, heat stress and disease, they will eventually struggle to survive in areas where they once thrived.

Successful gardening is still possible, though. Here are some things to consider before you plant:

Annuals versus perennials

Hardiness zones matter far less for annual plants, which germinate, flower and die in a single growing season, than for perennial plants that last for several years. Annuals typically avoid the lethal winter temperatures that define plant hardiness zones.

In fact, most annual seed packs don’t even list the plants’ hardiness zones. Instead, they provide sowing date guidelines by geographic region. It’s still important to follow those dates, which help ensure that frost-tender crops are not planted too early and that cool-season crops are not harvested too late in the year.

Orange flowers blooming with other plants and grasses.
California poppies are typically grown as annuals in cool areas, but can survive for several years in hardiness zones 8-10. The Marmot/FlickrCC BY

User-friendly perennials have broad hardiness zones

Many perennials can grow across wide temperature ranges. For example, hardy fig and hardy kiwifruit grow well in zones 4-8, an area that includes most of the Northeast, Midwest and Plains states. Raspberries are hardy in zones 3-9, and blackberries are hardy in zones 5-9. This eliminates a lot of guesswork for most gardeners, since a majority of U.S. states are dominated by two or more of these zones.

Nevertheless, it’s important to pay attention to plant tags to avoid selecting a variety or cultivar with a restricted hardiness zone over another with greater flexibility. Also, pay attention to instructions about proper sun exposure and planting dates after the last frost in your area.

Fruit trees are sensitive to temperature fluctuations

Fruit trees have two parts, the rootstock and the scion wood, that are grafted together to form a single tree. Rootstocks, which consist mainly of a root system, determine the tree’s size, timing of flowering and tolerance of soil-dwelling pests and pathogens. Scion wood, which supports the flowers and fruit, determines the fruit variety.

Most commercially available fruit trees can tolerate a wide range of hardiness zones. However, stone fruits like peaches, plums and cherries are more sensitive to temperature fluctuations within those zones – particularly abrupt swings in winter temperatures that create unpredictable freeze-thaw events.

Packages for hardy fig and kiwi seedlings.
Following planting instructions carefully can maximize plants’ chances of success. Matt Kasson, CC BY-ND

These seesaw weather episodes affect all types of fruit trees, but stone fruits appear to be more susceptible, possibly because they flower earlier in spring, have fewer hardy rootstock options, or have bark characteristics that make them more vulnerable to winter injury.

Perennial plants’ hardiness increases through the seasons in a process called hardening off, which conditions them for harsher temperatures, moisture loss in sun and wind, and full sun exposure. But a too-sudden autumn temperature drop can cause plants to die back in winter, an event known as winter kill. Similarly, a sudden spring temperature spike can lead to premature flowering and subsequent frost kill.

Pests are moving north too

Plants aren’t the only organisms constrained by temperature. With milder winters, southern insect pests and plant pathogens are expanding their ranges northward.

One example is Southern blight, a stem and root rot disease that affects 500 plant species and is caused by a fungus, Agroathelia rolfsii. It’s often thought of as affecting hot Southern gardens, but has become more commonplace recently in the Northeast U.S. on tomatoes, pumpkins and squash, and other crops, including apples in Pennsylvania.

A stem dotted with small round growths.
Southern blight (small round fungal structures) at the base of a tomato plant. Purdue UniversityCC BY-ND

Other plant pathogens may take advantage of milder winter temperatures, which leads to prolonged saturation of soils instead of freezing. Both plants and microbes are less active when soil is frozen, but in wet soil, microbes have an opportunity to colonize dormant perennial plant roots, leading to more disease.

It can be challenging to accept that climate change is stressing some of your garden favorites, but there are thousands of varieties of plants to suit both your interests and your hardiness zone. Growing plants is an opportunity to admire their flexibility and the features that enable many of them to thrive in a world of change.

Before you go…

Information is flying at us from all directions. And it can be overwhelming. Wouldn’t it be easier if you could get trusted science information in one place? That place is The Conversation. As an editor here, I am fortunate to work with scientists and researchers who explain their latest research. And each week, our team sends an email that brings together the best of our coverage of science, technology and environment.


Vivian Lam

Associate Health and Biomedicine Editor

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Copyright © 2010–2024, The Conversation US, Inc.


Grahame Jackson posted a new submission ‘A single laccase acts as a key component of environmental sensing in a broad host range fungal pathogen’


Grahame Jackson posted a new submission ‘A single laccase acts as a key component of environmental sensing in a broad host range fungal pathogen’

Saturday, 23 March 2024 08:16:28


Grahame Jackson posted a new submission ‘A single laccase acts as a key component of environmental sensing in a broad host range fungal pathogen’


A single laccase acts as a key component of environmental sensing in a broad host range fungal pathogen


Communications Biology volume 7, Article number: 348 (2024) 


Secreted laccases are important enzymes on a broad ecological scale for their role in mediating plant-microbe interactions, but within ascomycete fungi these enzymes have been primarily associated with melanin biosynthesis. In this study, a putatively secreted laccase, Sslac2, was characterized from the broad-host-range plant pathogen Sclerotinia sclerotiorum, which is largely unpigmented and is not dependent on melanogenesis for plant infection. Gene knockouts of Sslac2 demonstrate wide ranging developmental phenotypes and are functionally non-pathogenic. These mutants also displayed indiscriminate growth behaviors and enhanced biomass formation, seemingly as a result of their inability to respond to canonical environmental growth cues, a phenomenon further confirmed through chemical stress, physiological, and transcriptomic analyses. Transmission and scanning electron microscopy demonstrate apparent differences in extracellular matrix structure between WT and mutant strains that likely explain the inability of the mutants to respond to their environment. Targeting Sslac2 using host-induced gene silencing significantly improved resistance to S. sclerotiorum, suggesting that fungal laccases could be a valuable target of disease control. Collectively, we identified a laccase critical to the development and virulence of the broad-host-range pathogen S. sclerotiorum and propose a potentially novel role for fungal laccases in modulating environmental sensing.

Read on:

Saturday, 23 March 2024 08:16:28

Jackson posted a new submission ‘A single laccase acts as a key component of
environmental sensing in a broad host range fungal pathogen’


A single laccase acts as a key component of environmental sensing in a
broad host range fungal pathogen


 volume 7,
Article number: 348 (2024) 


Secreted laccases are important enzymes on a broad ecological scale for
their role in mediating plant-microbe interactions, but within ascomycete fungi
these enzymes have been primarily associated with melanin biosynthesis. In this
study, a putatively secreted laccase, Sslac2, was characterized
from the broad-host-range plant pathogen Sclerotinia sclerotiorum,
which is largely unpigmented and is not dependent on melanogenesis for plant
infection. Gene knockouts of Sslac2 demonstrate wide ranging
developmental phenotypes and are functionally non-pathogenic. These mutants
also displayed indiscriminate growth behaviors and enhanced biomass formation,
seemingly as a result of their inability to respond to canonical environmental
growth cues, a phenomenon further confirmed through chemical stress,
physiological, and transcriptomic analyses. Transmission and scanning electron
microscopy demonstrate apparent differences in extracellular matrix structure
between WT and mutant strains that likely explain the inability of the mutants
to respond to their environment. Targeting Sslac2 using
host-induced gene silencing significantly improved resistance to S.
, suggesting that fungal laccases could be a valuable target of
disease control. Collectively, we identified a laccase critical to the
development and virulence of the broad-host-range pathogen S.
 and propose a potentially novel role for fungal laccases
in modulating environmental sensing.

Read on:


UK: Plant breeders to benefit from online research tools


United Kingdom – Plant breeders to benefit from online research toolsSelect
April 3, 2024
 An exciting new project will look to put cutting-edge research tools in the hands of plant breeders, providing access to genomic resources to accelerate the development of more resilient and climate-resistant crops.The collaboration brings together the collective expertise of the Earlham Institute, IBM Research, the Science and Technology Facilities Council (STFC) Hartree Centre, and RAGT Seeds UK with the aim of simplifying and speeding up the transition of cutting-edge genome research tools, workflows, and software into industrial applications.The one-year Excelerate project is part of the Hartree National Centre for Digital Innovation (HNCDI) programme from STFC designed to close the gap between academic and industrial applications of digital technologies – such as artificial intelligence (AI) and quantum computing.The UK is home to some of the most exciting and innovative life science research. Institutions are pioneering the use of new technologies to overcome issues of scale and complexity in data-intensive bioscience, such as developing approaches that could be used to accelerate crop breeding in line with EU safety and ethical regulations.At the Earlham Institute, this includes crop pangenomes and the tools required to analyse them, developed through its Decoding Biodiversity strategic programme – funded by the Biotechnology and Biological Sciences Research Council (BBSRC), part of UKRI.But the transition of this knowledge into usable technology – and its uptake by industry – remains a significant challenge.“Modern plant breeding practices are based on understanding and then using genetic resources – made possible by digital innovations – that breeders can incorporate into their programmes,” Professor Anthony Hall, project lead and Head of Plant Genomics at the Earlham Institute explained.“Bioinformatics and machine learning techniques are playing an increasingly important role in deciphering genetic diversity. But they bring significant overheads in terms of the bioinformatics skills and computing power required to develop and implement new workflows.”The plant breeding industry has a crucial role to play in addressing the global challenges of food security, water conservation, and net zero. To realise the enormous potential of UK science and innovation, initiatives are needed to bridge the gap between research and industry.This new project brings together leaders from academia and industry to provide cloud-based tools that can be easily adopted by the plant breeding companies to support the development of next-generation crops with greater climate resilience and improved nutritional properties.The Earlham Institute is working with IBM Research and STFC to develop new cloud-based tools – including those optimised for exploring plant pangenomes – which RAGT Seeds UK will be road testing.“The Earlham Institute is home to some amazing research infrastructure, innovation, and expertise,” says Professor Hall. “This helps us to develop the technology needed to answer the big questions that will be critical in addressing urgent global challenges, such as how we find new sources of diversity for breeding more resilient crops.”
 The project team photographed with the London skyline behind them.
The project team from left to right: Robin Kennedy Reid, STFC, Rachel Rusholme-Pilcher, Earlham Institute, Laura Jayne-Gardiner, IBM Research, Will Davies, STFC, Anthony Hall, Earlham Institute, Chris Burt, Heidi Town, and John Baison, RAGT Seeds UK.
 Dr Rachel Rusholme-Pilcher is a Senior Postdoctoral Researcher at the Earlham Institute, and has played a central role in developing the workflows that will be used in this partnership.“The tools we’re developing and optimising will allow plant breeders to interact with their complex datasets in a way they simply couldn’t before,” explained Dr Rusholme-Pilcher. “It should provide new information they can rapidly incorporate into their existing breeding programmes.“We’ll also be using this project to look at how we can embed the adoption of FAIR approaches – the movement to make all research data Findable, Accessible, Interoperable, and Reusable. Making this kind of research FAIR can be a challenge but these collaborations will hopefully change that – transforming the impact of emerging technologies.”Excelerate is one strand of a number of projects from HNCDI embedding AI solutions across UK industry. To both accelerate and simplify the adoption of compute intensive bioinformatics workflows in the plant breeding industry, this project will use an on-demand, scalable, Hybrid Cloud delivery model.Dr Laura-Jayne Gardiner, Senior Research Scientist at IBM Research, said: “Our HNCDI Excelerate projects are enabling businesses to adopt new technologies – including artificial intelligence and hybrid cloud – to overcome industrial challenges, such as allowing complex biological data analytics at increased scale and speed.”Robin Kennedy-Reid, Senior Research Software Engineer at the STFC Hartree Centre, said: “At the Hartree Centre, we use applied research and innovation to turn good ideas into industry-ready solutions for long-term societal and economic impact. This is made possible by working with a network of partners, both industry and academic leaders, as well as drawing on the work of open source communities like nf-core.“In this project, this will deliver new bioinformatics and machine learning capability to the plant breeding industry; with a view to assisting the search for more sustainable wheat varieties.”Dr John Baison, Cereals Research and Genomics Manager at RAGT Seeds UK, said: “Genome-based breeding holds promise for expediting wheat breeding, aiming to ensure sustainable wheat production by creating high-yielding, climate-resilient cultivars with superior nutritional quality.“The plant-breeding sector is positioning to confront these targets by leveraging the dynamic UK research community. However, bridging the gap between research and industry is crucial for optimising the potential of UK science and innovation.“As RAGT delves deeper into genomics activities, it has become increasingly evident that we must harness advanced computing tools to navigate the vast amounts of data generated from genetics and genomics projects. RAGT is excited to be at the forefront of this collaborative effort, which could revolutionise the application of genomics to plant breeding.” 

More news from:
    . Earlham Institute
    . RAGT Seeds Limited
Website April 3, 2024


new way to identify pesticide resistance


new way to identify pesticide resistance

Tina Deines

Sun, April 7, 2024 at 12:00 PM CDT·2 min read

Researchers are exploring an exciting new approach that uses genomics to help monitor and identify pesticide resistance in the insects that munch on our crops.

Pest management is important for farmers, but insects often become immune to pesticides, making them less effective. In the new research, published in the Proceedings of the National Academy of Science, a team of scientists from the University of Maryland (UMD) presents a new strategy that analyzes genomic changes in pests to monitor and identify emerging resistance to specific toxins early on.

They zoned in on one pest in particular: the corn earworm, a crop-destroying caterpillar that has developed widespread resistance to a number of natural toxins bred into corn. They were able to identify resistance to toxins among these caterpillars after just a single generation of exposure. They also identified how common strategies for avoiding resistance could actually be doing the opposite.

“As it currently stands, the evolution of resistance across many pests of agricultural and public health importance is outpacing the rate at which we can discover new technologies to manage them,” said senior author Megan Fritz, an associate professor of entomology at UMD, per “I’m really excited about this study, because we’re developing the framework for use of genomic approaches to monitor and manage resistance in any system.”

The new research is one of many that is helping farmers to produce more successful harvests.

For instance, a team of American and Chinese researchers found a way to genetically engineer plants that can survive heat waves. University of Minnesota scientists are on their way to developing a “Super Grape” that could stave off powdery mildew and reduce the need for fungicide.

Watch now: What’s the true environmental impact of renewable energy?

These developments in agriculture come at a critically important time — as our planet continues to warm, there are frequent heat waves and droughts, which threaten our food security. Plus, climate change scientists predict that a warming world will drive a surge in certain insect pests that attack our crops, further threatening food security and causing economic losses for those in the agricultural sector.

Join our free newsletter for weekly updates on the coolest innovations improving our lives and saving our planet.


Kansas, USA: Robots developed to take on a labor-intensive process — cutting weeds down


Harvest Public Media | By Celia Hack

Published April 8, 2024 at 4:00 AM CDT

LISTEN • 3:20

GreenField robots at sunset.

Greenfield Robotics, a Kansas-based company, is hoping to move agriculture away from herbicides. They’ve developed robots to take on a labor-intensive process — cutting weeds down.

Three yellow, bug-like creatures crawl in perfectly straight lines across the dead grass of a flat, brown February field in Cheney, Kansas.

These are the namesake of GreenField Robotics. Two lights peer out from each side of the boxy machines, almost appearing like eyes. Blades whir at their base, about a half an inch from the ground – the perfect height to chop weeds, though there’s nothing to cut down on a frigid winter day.

They stick out in an otherwise rural landscape – and GreenField CEO Clint Brauer said he frequently hears from curious passersby.

“All the time,” Brauer said. “I’m always surprised, though, how little people notice.”

Brauer founded the company in 2018. The start-up has now grown large enough to attract investment from Chipotle’s $100 million venture capital fund and to secure partnerships with dog food and baking mix brands.

Brauer grew up on a family farm in Haven, Kansas, but moved to California after high school to work in the tech industry. In 2010, he returned home after his dad was diagnosed with Parkinson’s disease. He attributes the use of herbicides to his dad’s diagnosis.

“The more I learned about farm chemicals and stuff … the more I thought there’s a decent chance that this came from that,” Brauer said.

GreenField Robotics CEO and Founder Clint Brauer with two robots in Cheney, Kansas.
GreenField Robotics CEO and Founder Clint Brauer with two robots in Cheney, Kansas.

The move sucked Brauer back into the world of agriculture, where he started seeking ways to eliminate herbicides. He tried farming organically, but it was too expensive to be accessible to many buyers.

Another option was no till farming, where farmers avoid turning over the dirt to reduce erosion and improve soil health. But it’s a method that leans on herbicides.

And in 2015, Brauer was starting to notice the weeds in his fields were becoming resistant to chemicals anyway.

“There was no good way to get rid of those weeds, even though we had sprayed many times,” Brauer said.

“So, what do we do? And so that was the beginning of this idea of – what if we just cut those weeds?”

Cutting weeds by hand wasn’t exactly a 21st-century answer. So Brauer thought: What about robots? He reached out to software and machine-vision experts and started prototyping robots.

By 2021, the company had manufactured a two-and-a-half foot-tall working robot. And it pulled together different technologies, like drones, to create extremely precise maps of crop fields. The robots follow the maps, so that they’re unlikely to accidentally chop down a crop instead of a weed.

“They plant the crop, we count about 10 days, normally, the crops emerge, and we fly over it with a drone,” Brauer said. “ … That’s where AI – we have machine vision that automatically recognizes everything that’s going on in that field.”

Thirty to 40 days later, Brauer sends out the robots.

GreenFields' robots working a field.
GreenFields’ robots working a field.

In 2022, the company partnered with MKC, a major agricultural cooperative, to reach farmers who might use the product. In 2023, GreenField Robotics worked with 25 to 30 Kansas farmers, Brauer said. The company currently has a fleet of 20 robots and 15 employees

This summer, Brauer said the company is planning to work the weed-cutting robots on over 20,000 acres.

John Niemann is a farmer in Reno County. He tested GreenField Robotics for the first time last spring on 80 acres of a sorghum field, leaving 10 acres untouched to compare results. He had treated the entire crop with herbicides earlier in the season.

“We saw higher yields where we used the robots, versus the 10 acres that we did not,” Niemann said.

That’s because the weeds that didn’t get chopped down in the 10 acres competed with the crop for moisture, hampering the yield.

“The robots are part of a toolbox, is how I would look at them,” Niemann said. “There is no magic bullet in farming practices. You need to have a lot of tools in your toolbox.”

Niemann says the robots are a useful tool to reduce reliance on chemicals. Plus, he said the cost was comparable to herbicides.

Brauer said the economics is always his first pitch to farmers, and the robots are compelling because they damage less of the crop than chemicals do.

The company is also adapting the robots for other uses, like planting cover crops and soil testing.

“We are on a mission,” Brauer said. “This is not about enrichment. This is – we’re building something that can’t be undone. And so we’re going to eliminate these chemicals.”

This story was first aired and produced by KMUW. It’s being distributed by Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.


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