by Thomas Grandperrin

Published on December 1, 2020

This article was initially published on the


In an industry that is constantly shortening the list of allowed pesticides in the vegetable grower’s pest management tool kit, adopting alternative pest control strategies is not just “nice to have” or reserved for organic growers anymore – it is a way for farmers to ensure they’ll be able to stay in business in the long term.


Alejandro Del Pozo, a former University of California cooperative extension entomologist and now assistant professor at Virginia Tech, is a firm believer that alternative pest control methods are the way of the future and has made it his mission to help growers getting ready for upcoming regulations and adopt alternative pest management practices.


Originally from Perú, a country with a long history of using augmented biocontrol in outdoor crops, Alejandro identifies himself as an applied insect ecologist. He started his career as an asparagus farmer in his home country, where he was also in charge of a beneficial insects breeding facility. During his career he has worked with a wide variety of crops: from hybrid poplars during his masters, to soybean for his PhD, to corn and cotton during his postdoctoral work. Alejandro started to work as an Integrated Pest Management (IPM) and entomology advisor with the University of California cooperative extension in 2018. Based in Salinas, he developed successful research and extension programs focused on aiding growers of multiple types of leafy greens and cole crops to implement IPM’s best practices.

Vine mealybug infestation on a grape cluster

Alejandro Del Pozo in a Salinas Valley field during his previous assignment at the University of California cooperative extension

The relationship between macro-organisms in different agricultural systems and the alternative control tactics for implementing an IPM strategy has been a consistent theme throughout his career. This theme came up again during our conversation. We discussed the need for vegetable growers to get ahead of upcoming pesticide regulations by using conservation and augmentative biocontrol in vegetable crops as well as new technologies available to IPM practitioners, namely drones to release beneficial insects, manual weeding robots, and automated insect traps.


The need for growers to adopt pest control alternatives to stay in business


Most vegetable growers are making tremendous efforts to keep up with the switch in consumer demands and to respond to environmental and health concerns, but Alejandro observes that in conventional farming, “There are still a lot of pest control tactics that rely on pesticides like neonics because those chemicals are really effective. Growers currently use them to control devastating virus-transmitting pests such as aphids. But we started to pick up residues of neonics on surface water and we can see that they have a negative effect on pollinators, that pests develop resistance… and there’s more science constantly coming up looking at the non-targeted effects of those products.” 


So, will active ingredients like neonicotinoids be further regulated? Looking at areas of the world with stricter regulations, such as the European Union where the use of neonics is already prohibited, may predict what’s coming for growers in the United States and other countries. 


Alejandro reports that, “In the next three to five years, these regulations about the use of neonics and pyrethroid are gonna come. For example, the EPA is currently revising the use of seed treatments using neonics. Some of the crops will not be able to do in-farm seed treatments anymore. You’ll have to hire a specialized company to use seed treatments, because there is research to prove that in-farm treatments create dust which moves around the entire ecosystem”.


He advises growers to prepare for these scenarios as part of their risk management strategy. “We need to change our mindset about how we use pesticides. For example, you’re already no longer able to buy chlorpyrifos in the United States. So that set the example of what could happen. It is possible that the EPA or other regulators will restrain the use of neonics.”


Alejandro continued, “I always ask the growers I talk to: ‘What happens if tomorrow we are not allowed to use neonics and pyrethroid. Are you going to go out of business?’ The answer that I got is usually ‘yes’. And that’s scary, because that shouldn’t be the answer. The answer should be, ‘Well, this works now, so what could be the alternatives to overcome the lack of this really great chemistry that helps us do pest control right now? Is there any alternative?’” 


Are there any practices and technologies that can already help growers to reduce or at least improve the use of those pesticides? According to Alejandro, the answer is a resounding “yes”. He believes it’s a matter of intensifying extension efforts to promote those new pest management techniques and for the growers to change their mindset about pest control and look for those alternatives.


Biological control, an efficient pest management methods for vegetable row-crops


Potato aphids, foxglove aphids and lettuce aphids are some of the most economically devastating pests of leafy greens and other vegetables. In lettuce, those aphids like to infest the interior of the plant. When this happens, natural enemies have a clear advantage over insecticides. They have the ability to hunt their prey where they hide. Alejandro explains that, “Even if you’re spraying something like pyrethrins and spinosad, you’re not going to have control because you’re not going to get the product inside the head of the lettuce. The maggot of the syrphid fly, on the other hand, goes inside the lettuce head where it devours the lettuce aphids.”


So if natural enemies are so effective at controlling pests like the aphids, why aren’t all growers leveraging them? Alejandro believes that one of the strongest barriers to the adoption of biocontrol in vegetable production is that there are many negative preconceived ideas about conservation and augmentative biological control that deters vegetable IPM practitioners from implementing it, namely that it is too expensive and too much work.


In the case of augmentative biological control he explains that, “Beneficial rearing laboratories are getting better, the prices are getting cheaper, we have technology like drones to release the beneficials… So I think, based on my little experience (Note: Alejandro has been doing biological control since 2003), that now more than ever is a good time to actually consider using laboratory-reared beneficials to do augmentative biological control.” 


He believes that those preconceived ideas and barriers to adoption need to be fought through research projects and extension efforts, showing that biocontrol implementation can be done. “I led a couple of projects on conservation and augmentative biological control in vegetable production that show that it’s an investment that pays off. Once growers get into the routine and have a carefully planned program for augmentative biological control, I think it will flow seamlessly. It will be something that will become normal as part of their management strategy.” Forward-thinking growers are taking it upon themselves to lead the industry and adopt new technologies and practices, through field trials in partnership with commercial companies. Thanks to the efforts of these industry standard-bearers, new treatment protocols are available to growers located throughout the technology adoption curve.


How can vegetable growers get started with biological control?

How can conventional growers get started with biocontrol? “I used to be a farmer, so I understand that growers want to make sure that they can rely on an easy control tactic like an insecticide to get rid of a pest if they have an issue,” Alejandro empathizes.


Unfortunately, the overuse of broad-spectrum insecticides remains one of the main problems that forward-leaning growers need to address before starting with biological control. Alejandro encourages growers that, “Reducing the use of broad-spectrum insecticides will open the door for combining biological control in terms of conservation and augmentation.” Before completely removing insecticides he suggests that the first step would be to space apart the applications of broad-spectrum insecticides as much as possible. “If you are on a high intensive vegetable crop that you’re usually spraying once a week, can you spray the broad-spectrum insecticide once every other week? You can start playing around in between those two weeks to test something that could fit into your program, and start transitioning to newer chemicals that don’t impact beneficials as much.


After decreasing pesticide usage, the next step is intercropping. The implementation of conservation biological control techniques, like the addition of insectary habitats in the field such as sweet alyssum intercropping, is already widely used in the Salinas Valley. “Sweet alyssum provides pollen habitat and attracts the beneficials like the hoverfly, which will later move to the lettuce to feed on aphids.” This has been well documented in Salinas, and people from the University of California, the USDA, or private companies (like Gina Colfer of Wilbur Ellis) have played a crucial part in promoting this technique. 

Vine mealybugs on a grape vine cane
Sweet alyssum intercropping in an organic field planted with romaine lettuce in the Salinas Valley


Alejandro highlights one strong argument in particular which resonates with conventional growers who still need a little extra convincing before committing to the modest step of adding insectary plants. “The data that we generated from specific research projects prove that when you intercrop Alysum, you’re not losing yield, so it is a really good way for a conventional grower to step into the biological control world. I think that to break the barrier to the adoption of biocontrol, starting with those conservation biocontrol practices, namely reducing pesticide use and intercropping insectary habitats, are what brings everyone to the table.” 


Once this is done, he explains that, “Those insectary plants will become your islands where you can release commercially reared beneficials insects.


Augmentative biocontrol of aphids in the Salinas Valley leafy-greens


As growers reduce or remove broad-spectrum insecticides and start using sweet alyssum intercropping, they will start seeing effective aphid control thanks to the naturally occurring predators. But despite the best conservation biocontrol efforts, aphid outbreaks can happen. That’s when growers can start releasing commercially reared beneficial insects, such as green lacewing larvae, to keep the aphid population in check.

Mark Hoddle in Pakistan collecting Tamarixia radiata, a natural enemy of Asian citrus psyllid, Diaphorina citri.

On the left: adult lettuce aphid (Nasonovia ribisnigri). On the right: a green lacewing larvae feeding on an aphid (credit: JK Clark, UC IPM)

The moderate climate in the Salinas Valley allows beneficials to be released most of the year. Applications should be performed once, and in some cases twice, per crop cycle. For vegetable growers in the Salinas Valley getting started with augmented biocontrol, the beginning of the summer is probably an ideal time for a release. “That’s when the aphid infestation is coming up in Salinas. So you probably want to target those specific timeframes where there are a lot of pest populations out there,”Alejandro suggests.


The threshold that should be used to trigger a lacewing release for aphid control will depend on the area and the crop. As a generalist predator, lacewing larvae can also feed on pests like spider mites, thrips, whitefly, and small caterpillars, while adults will feed on the pollen of the insectary plants. But, as a general rule, the release should be performed when there are enough aphids that they can feed on. He reports that, “There is some literature that says that lacewings have this functional response, and it aligns with what we saw. So the more aphids that you have, the more predation you end up having.


He acknowledges that it can seem like a contradiction or a difficult thing to assess. “You don’t want to see the aphids. But you also need the aphids to actually provide the food for the beneficials. So it’s quite a dance, right?” But growers should be reassured that there are knowledgeable Pest Control Advisors (PCAs) and local IPM experts that can help them decide when it’s the right time to do a release.


Alejandro concluded by confirming his faith in the use of augmentative biological control. “Based on my experience, I can tell that lacewings really help knock down the aphid population. While they don’t completely wipe them out and growers might need to use complementary control tactics, the idea that you can reduce the population significantly was really impressive to document.


How drones can help vegetable growers implement biological control at scale.


When implementing augmentative biocontrol in large vegetable fields, growers can face challenges due to labor shortage or to the insufficient quality of manual beneficials releases. 


While at the University of California, Alejandro did a set of trials with a technology recently gaining in popularity among IPM practitioners: drones.


He explains that, “Using systems specially designed to release beneficial insects and mites mounted on commercially available drones, we released green lacewings in lettuce crops to target aphids.”


One of the goals of the study was to prove the survival rate of the beneficials being released through this kind of system. “We’ve been able to recover some of the lacewing larvae from those fields and we showed that aphids population can be reduced by up to 50%!


Alejandro also did field trials releasing Amblyseius cucumeris for thrips management in ice plants that some growers use on roadsides to control erosion. Since they always have flowers, they attract thrips. The idea was to use the ice plant as a trap crop and then release cucumeris in those ice plant patches. “Not only could we recover cucumeris from the areas where we released them with the drone, we were also able to show that there was a lower thrips population densities in the areas that we treated compared to the controls that were untreated.


Emerging technologies improving the efficiency of pest monitoring in vegetable production


Drones are not the only emerging agriculture technologies helping vegetable IPM practitioners. Alejandro believes that, “Mechanisation and automation is the way to go. It’s how agriculture is moving forward. I believe it’s not going to get anyone fired. It is not the evil of losing jobs. On the contrary, I think automation, remote sensing, you name it, is gonna help us get more efficient in our processes as growers.


He mentions his own experience with pest remote sensing in the past few years in the Salinas Valley. He’s been using pheromone traps equipped with four high-resolution cameras on top of it, taking pictures once a day. These pictures are then centralized in a cloud database and stitched together to create a single image. 


Alejandro explains that, “The computer has its own artificial intelligence algorithms to recognize the pest, in this case diamondback moth adults. They count them and automatically send an alert at the end of the day with the number of trapped moths it has detected. This new automated and remote monitoring gives growers that opportunity to be on top of a hotspot to try to be ahead of the game.” 

Phacelia and sweet alyssum cover crop in a vineyard

Insect trap from the company TrapView (credit: AgCeleration)


He adds that, “We proved the concept that those traps are really accurate compared with regular weekly checking of the monitoring traps. This technology is now getting mainstream, so it’s going to be more affordable for growers. It will be of great help for IPM practitioners to have this data and these alerts on the palm of their hand.” 


Alejandro is now exploring possibilities of implementing this technology at his new assignment in Virginia, in turfgrass or crops like hemp.


Solving labor shortage and sustainability issues in leafy greens with precision spraying and automated mechanical weeding.

Besides harvesting, one of the most important tasks of leafy greens growers is probably weeding and thinning. But when growers can only count on a limited number of workers and are constantly pressured to limit their herbicide use, what is the solution? 


Alejandro is excited about the advance of robotics in this field that will impact leafy greens IPM practitioners. He explains that, “If we get more regulations on insecticides, we need to prove that we’re doing a better job at spraying them. Precision spray allows spraying at the plant level. The computer that goes into the thinner with the tractor is recognizing every single lettuce and then taking some measurements before spraying the insecticide and the fungicide, that way growers avoid doing broadcast treatment.


He gives some examples. “Companies like Mantis are doing a great job using compounds that help do the thinning in vegetable row crops, which is usually a high concentration fertilizer and a little bit of herbicide. They also have a secondary tank where you can put a fungicide and an insecticide and it’s sprayed at the plant level. So you will have no drift and you are going to reduce the total amount of active ingredients per acre.” 

Phacelia and sweet alyssum cover crop in a vineyard

Automated thinner from the company Mantis


The other approach is mechanical weeding. He relates that, “Other companies like Farmwise do automated mechanical weeding, taking out the weeds using blades. But they’re thinking about putting spraying systems and also infrared sensors to actually help growers understand what is the health status of the plant. So the visual information that those robots will capture will allow for improved yield forecasts based on the diameters and the colors for example. That will be something that’s going to tremendously help the grower with the marketing and the contracts. So it’s a spiral of really great benefits that technology is bringing to the growers that actually need information to do the management. I really believe these companies are visionaries.”


Alejandro adds, “I’m going to sound like a broken record, but labor is getting scarce and difficult to get. Growers constantly need to prioritize how to which task they assign their crew. You need people to harvest to get the product out of the field. So if you can rely on automation to help with the weeding, thinning, and biological pest management this is something less that growers need to worry about. So these companies are filling the void.


An exciting time to work in agriculture


As a conclusion, and despite the challenges faced by the agriculture industry, Alejandro believes it’s an interesting time to work in agriculture, thanks to the progress brought by entomology and biology research in the field of natural pest control strategies in parallel to the advance in agriculture technology and robotization. “I am excited to do agriculture right now and in the future because we have all this, biocontrol, drones, sensors, and artificial intelligence… It’s going to be fun.” 


Hopefully, this enthusiasm will be reflected in the future generations’ eagerness to follow a career in agriculture.


Interested in learning more about how you can work with experts like Alejandro and get involved with research that will advance your industry’s IPM practices? Get in touch and we’ll explore options with you.


Do you have experience with the implementation of augmented biological control or conservation techniques to manage pests in vegetable row crops? Reach out to us, we’d love to hear your story and write about it!

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