By Lorena Lopez, Ph.D.
In the world of agricultural entomology, the quest for sustainable pest management solutions has led us down a fascinating path. Among the multitude of biocontrol agents, the predatory mite Amblyseius swirskii has emerged as a game changer. Its remarkable capabilities and versatility make it a highly valued asset in our efforts against pests in vegetable crops. However, several challenges and considerations must be addressed to realize its full potential.
Amblyseius swirskii, originally described in 1962 from almond trees in Israel, has taken center stage as a potent biological control agent—an insect or arthropod that can be deployed to suppress pests. Geographical boundaries no longer confine this predatory mite to the Mediterranean region; it has made its mark across the globe. From Europe to Asia, Africa, and the Americas, this commercially available predatory mite has been released in more than 50 countries worldwide and has established populations in many countries’ crops. This global distribution speaks loudly about its effectiveness as a biological control agent in various agricultural settings, from greenhouses to open fields.
In an article published in September in the open-access Journal of Integrated Pest Management, I profile Amblyseius swirskii and its biology, distribution, and various applications for biological control in IPM programs.
The Secret to Its Popularity: Versatility
What sets A. swirskii apart is its remarkable versatility. This predatory mite doesn’t discriminate when it comes to its diet. It feeds on various insect and mite species, including those notorious for wreaking havoc on vegetable crops. Its adaptability and effectiveness have propelled it to the forefront of integrated pest management (IPM) strategies. Amblyseius swirskii is a generalist predator that preys on various pests, including whiteflies, russet or gall mites, broad mites, spider mites, false spider mites, and first-instar thrips. Moreover, it can survive and thrive on non-prey food sources such as pollen, nectar, plant secretions, honeydew, and even a fungal secretion called pycnial fluid. This adaptability enhances its reproductive capacity and establishment during the early stages of crop growth when pest numbers are low.
Companion Planting: A Strategic Alliance
One of the most commonly used tactics employed in maximizing A. swirskii‘s performance is companion planting or intercropping. Growing specific companion plants alongside or within cash crops creates an ecosystem that promotes the establishment and dispersal of beneficial arthropods, including A. swirskii. These companion plants, such as sweet alyssum (Lobularia maritima), buckwheat (Fagopyrum esculentum), or ornamental peppers (Capsicum annuum, ‘Explosive Ember’ cultivar), offer alternative shelter and food sources to these predatory mites, promoting their presence when and where they are needed most: the periods of pest scarcity usually at early stages of the crop.
Additionally, providing pollen from crop or non-crop plants or using pollen supplements can be advantageous to enhance A. swirskii‘s performance. Cattail pollen (Typha spp.) is the most used source of pollen supplements that are commercialized and used to enhance A. swirskii establishment, followed by pollen from pepper species. Implementing additional suppression practices, including cultural methods such as sanitation and isolation, can complement A. swirskii‘s suppression efforts.
The Challenges: Nature’s Hurdles
While A. swirskii offers tremendous promise, it’s not without its challenges. One significant factor is its preference for glabrous (i.e., smooth or glossy) leaves or those offering specialized shelters like domatia. Glandular trichomes, small hair-like outgrowths common on newly unfolded leaves of plants like squash and tomato, are usually not preferred by A. swirskii. This preference can limit its establishment on certain crops, challenging growers who rely on these plants.
Pesticides: A Double-Edged Sword
Another challenge arises from the ever-present use of pesticides in agriculture. While A. swirskii can be a robust biocontrol agent, it is not immune to the effects of chemical insecticides and miticides. The impact of these chemicals varies depending on developmental stages, with immature stages of A. swirskii often more susceptible than adults. Some pesticides, like abamectin, were once considered selective but have since been shown to harm A. swirskii. Careful consideration and timing of pesticide applications are necessary to mitigate the risk to these beneficial predators.
Reduced-risk pesticides offer a glimmer of hope. Certain products, such as potassium salts of fatty acids (often called pesticide soaps), have minimal detrimental effects on A. swirskii when applied correctly. These products are known for their short environmental persistence, which can be advantageous when managing pest outbreaks. Moreover, conventional insecticides such as fenpyroximate have shown potential to be integrated into pest management programs if applications follow low levels indicated in the label and are scheduled properly when predatory mite populations in the field consist primarily of adults.
Timing Is Everything
Meanwhile, the timing of A. swirskii releases is crucial. Releasing them within three days after pesticide treatments should be avoided to prevent detrimental effects due to pesticide residues. Ideally, pesticide applications should be scheduled at least five days or one week after releasing A. swirskii, allowing the predators to acclimate and establish in the crop.
A Multi-Faceted Approach
The success of A. swirskii in vegetable crops centers on a multi-faceted approach. Growers or scouts must identify the pests requiring suppression and assess A. swirskii‘s efficiency in tackling them. Environmental conditions within the target crop—such as temperature, humidity, and water availability—must align with the predator’s optimal requirements. Choosing reputable providers for A. swirskii is equally vital. High-quality predatory mites from trusted sources are essential for the success of biocontrol programs. The provider’s reliability and adherence to best practices in rearing and distribution ensure that growers receive effective agents.
Amblyseius swirskii is the third-most researched predatory mite after Phytoseiulus persimilis and Neoseiulus californicus, ranking first and second, respectively. In the last two decades, A. swirskii has led a new era for biocontrol agents in vegetable crops by quickly becoming one of the most used and researched predatory mites. Its adaptability and global presence make it a compelling ally for growers seeking sustainable solutions. While challenges exist, careful planning, reduced-risk pesticides, and understanding A. swirskii’s unique characteristics can pave the way for its successful incorporation into IPM programs.
Journal of Integrated Pest Management
Lorena Lopez, Ph.D., is postdoctoral associate in entomology at Virginia Tech’s Eastern Shore Agricultural Research and Extension Center in Painter, Virginia. Email: firstname.lastname@example.org.