How to Overcome Biocontrol Challenges by Thinking Outside the Box

How to Overcome Biocontrol Challenges by Thinking Outside the Box

Biocontrols Gary Vance

(top) Adult Aphidoletes females suspended from spider web, waiting to mate. Source: Bugguide.net; (bottom left) The Remay hammock made it easier to facilitate Aphidoletes reproduction in a safer environment and eventually led to greater control of foxglove and potato aphids; (bottom right) The “Love Shack” is a good example of improvising to find a way to make a biocontrol organism work when conditions are less than ideal.

Simply put, biocontrol is challenging. Before a successful program can be implemented, there is a number of hurdles and roadblocks to overcome. Many growers struggle with relearning what they know about pest management. It’s difficult making the switch, but what about the growers who have committed to the change? When we set them up with a program for the organisms that target their pests, why then do we hear the question we hate the most: Why aren’t these bugs working?

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Much like the hurdles of getting started, there are many to cross in maintaining a successful program. Here are some ways around what are considered roadblocks to a successful bio program.

Incompatible Chemistry

This one is a no-brainer and probably the most common cause of a bio program failing to launch. Chemical companies have definitely stepped up and many new chemistries are specific to pests, and new labels state their impact on biological control agents (BCAs), as well. Still, an insecticide is an insecticide. Even if the grower is making sure they’re using softer products that have minimal impact on their BCAs, they can risk losing their newly established program. If a grower is switching from a regular spray program involving synthetic pyrethroids, organophosphates, or other chemistries with long residual control, they will struggle to establish a system of BCAs. Some of these chemistries have a persistence of 16 weeks or more. Long after they’ve stopped controlling the targeted pest, they pose risks to many beneficial insects.

There is a wealth of information on chemical compatibility with BCAs for many products and organisms. While no source is complete, there are several free and paid options available.

Environmental Conditions (Temperature, Light, Humidity, Watering Practices)

Most organisms have specific temperature and humidity ranges they prefer and thrive in. Some also require a certain amount of light or shade to get started. In the greenhouse, there are some events that can be planned for and some that cannot.

For example, the Pacific Northwest is prone to unpredictable weather in spring. On days when the thick clouds that have been in place for weeks part and the sun comes out, some greenhouses heat up faster and more intensely than others do. Fessler Nursery, where I previously worked, was located on flat farmland with no shade available for most of the structures. Heat spikes make undesirable things necessary like watering with sprinklers for crops on the ground.

In such a range I also experienced high aphid pressure during spring. The bulk of the pressure was from the green peach aphid, which I maintained good control of with Aphidius colemani. We would get hotspot outbreaks of foxglove aphid in our hanging baskets and 4-inch pots, and potato aphids in a small veggie crop throughout the spring. We were usually able to knock them back using Aphidoletes aphidimyza. However, Aphidoletes have certain quirks that make them a bit more challenging to implement if you’re dealing with environmental conditions.

Creative Solutions Can Lead to Greater Control

Aphidoletes larvae arrive in cocoons and need to pupate in the top half inch of the soil. During this stage, they need to be in a shaded area. When the sun suddenly emerges and brightens your greenhouse immediately after application, that can be a challenge. I used to release the Aphidoletes into the canopy of a hanging basket to keep them moist and shaded. However, when the pressure was spread throughout the greenhouse, we needed adequate coverage. We also grew four crops of hanging baskets and were almost constantly shipping from this range. Houses would empty out in a matter of hours and our release point would be on a truck to wherever. Moist soil is also difficult to find during a time when the plants are drying out so quickly in the heat that we had to use the sprinklers on the ground.

Taking all of these things into consideration, I looked at what we had on hand that could work as a release and breeding station for Aphidoletes. I wanted to make something that could get us through the season and let us plan a different strategy for that range the following season.

Our team developed our “Love Shack” to get around the heat and light conditions of the range. We also found a way to boost their reproduction and get more control with our releases.

The “Love Shack” is a 14-inch basket base with a 4-inch square cut out in the top for an exit hole. The 4-inch pot inserted on the top keeps the sprinklers from running inside and creates somewhat of an igloo look. A small container of moist soil is placed on the floor, with the Aphidoletes applied to the top, and then everything is covered with a 14-inch pot.

Another quirk of Aphidoletes is that they like to suspend themselves in spider webs during mating . Since Aphidoletes are very fragile midges and a regular part of a spider’s diet, this mating ritual is almost a suicidal act.

By making a small hammock out of remay, we offered an artificial and much safer web-like structure for them to complete this bizarre and dangerous ritual. After making a few of these stations and spacing them evenly throughout the range, we saw our foxglove and potato aphid pressure diminish and were consistently finding more Aphidoletes on sticky cards further away from the release point. This system performed so well that we began to use it throughout the nursery with good success.

Challenge Yourself to Discover Solutions That Already Exist

This is one instance of finding a way to make an organism work in conditions that the tech sheet may not agree with. However, when something has shown success in the past, it’s important to look for ways to continue what worked, even when a wrench is thrown in to your routine. During these challenging times, we can do what’s easy: Go back to the tired old spray-and-pray method. But we know where that leads, the applicator staying late or coming in early when temps are cool enough to spray, and closing greenhouses due to re-entry intervals during the busiest time of the season.

On the other hand, we can adapt and adjust our strategy to find solutions already available.

It’s important not to abandon a bio program when the going gets tough. No system of pest management is foolproof or guaranteed. It’s equally important to learn the personality of your greenhouses. What advantages, as well as disadvantages do they come with? Is this the best location for the crop you plan to grow? Sometimes you can’t help where your plants end up. During peak season, growers take immediate advantage of any available area when it’s time to space crops. When a crop finds its way to one of these challenging houses, plan your program around it. Early communication between production/labor and the integrated pest management manager helps to strategize when and where to make your adjustments. When a crop is moving to a location that completely ties your hands, focus your effort on houses you can work with, but don’t give up immediately. Sometimes a con can be turned into a pro when you think outside of the bio-box.