Written by Tianna DuPont, WSU Extension. July 2, 2026.
With few current organic pesticide controls for aphids and mealybug, biocontrol from native and released natural enemies can provide an important tool to growers. Released natural enemies can be challenging to use effectively, as many factors can reduce their efficacy. Schmidt-Jeffris shared the what, when, and how of lacewing releases to make this biocontrol tool the most effective.
Results from a 3-year project funded by the USDA Sustainable Agriculture Research and Extension program (SARE) and the Washington Tree Fruit Research Commission.
What lacewing lifestage should I release?
- Larvae releases have been most effective, reducing aphid and mealybug populations by 40-70%.
- Egg cards may attract ants and other predators that eat lacewing eggs and, in some cases, increase pest populations.
Schmidt-Jeffris compared lacewing biocontrol application as loose eggs, egg cards, and larvae in her research trials. Across three years of trials, larvae were the most consistently effective. “We have found larvae to be so much better,” Schmidt-Jeffris explained to participants, “They are ready to go.” Partnering growers also agreed larvae were a good choice. “Lacewing larvae are definitely much more expensive, but also much more effective.” said field day host and biocontrol expert Teah Smith. “In my thirteen-year experience we see them clean-up aphids in 2 weeks.”
If you work with eggs you need to make sure to check that they are ready when they arrive and incubate them if they are not. “If you release green eggs, they will be eaten and not work, there are a lot of predators in the environment that eat eggs,” Schmidt-Jeffris explained. Egg cards are commonly used since they are easy to apply in an orchard. However, Schmidt-Jeffris found in her trials that concentrated eggs are easily consumed by other natural enemies. “Egg cards are a buffet for every natural enemy out there,” Schmidt-Jeffris shared with participants, “They are a protein rich snack for natural enemies.” In particular, if you have ants in your orchard, they will find the egg cards and eat every egg.
How to release?
- Both hand and drone release have been effective.
- Aim for even coverage throughout the treatment area.
Drone release has come a long way over the course of this project. There has been a “huge evolution in how we do this,” explained Chuck Weaver from Parabug. They are using an Ag drone, which “flies like a tractor,” Weaver explained. At 2,500 larvae per acre, he can apply 8 aces in a 15-minute flight. The drone is pre-programed in a route 16 to 20 ft above the tree canopy with 30 ft between each pass on the grid. The flight is designed to run perpendicular to tree rows. In previous trials when applications were done parallel to the row after multiple rows the drone route had drifted slightly, since rows are not perfectly spaced and applications were not hitting the row. When releasing larvae they always mix with a carrier to reduce cannibalism between larvae. “We like buckwheat hulls the best,” Schmidt-Jeffris explained. The weight and shape of buckwheat hulls seems to carry better into the canopy.
When to release?
- Release when daily low temperatures are >35°F and <0.1 aphid colonies per shoot.
“Early is better,” Schmidt-Jeffris explained. Lacewing releases work best when used before aphid populations become very high. Generally, the earlier you are in the season the better they will work but they should not be applied if overnight lows are below 35°F. Grower project partner Smith also emphasized the importance of early applications. “Generally we start early in May, when we are just starting to see aphids,” Smith explained, “If we do small doses and start early it works better.”
How many lacewings to release?
- Release trials were done with rates of 20,000 larvae per acre, applied 1-2 times.
- Lower rate, more frequent releases may be effective.
Important tips:
- Wait at least 24 hours after any pesticide application to release, and at least 10-14 days after a lime sulfur application.
- Avoid spraying any pesticides for at least 24 hours after a release.
- Pesticides harmful to lacewings should be avoided for 2-3 weeks after a release.
When using lacewing releases for aphid biocontrol it is important to incorporate applications into the other management practices in the orchard. Consider other orchard activities before and after applications. Wait at least 24 hours after a pesticide application to apply lacewings as well as 24 hours after lacewing application to put on a spray. Schmidt-Jeffris tested a range of organic products and found that OSO 5%SC, Entrust SC, and lime sulfur killed lacewing larvae when they were directly sprayed. After 24 hours, OSO and Entrust were no longer harmful, but “Lime sulfur is particularly a problem pre-release,” said Schmidt-Jeffris. Lime sulfur thinning sprays are going on in this time period. They found that even 7 day old lime sulfur residues killed 50% of exposed lacewing larvae. Grower project partners also shared additional tips. Smith explained they generally release at night a few hours before dark (e.g., 7 to 9 pm) so that the larvae have time to find shelter before exposure to hot temperatures. Smith also shared that in addition to avoiding sprays directly after releases they wait 24 hours before other orchard activities such as mowing or weed whacking in order to give lacewings time to establish.
Assess your shipment
Eggs. When using lacewings for biological control it is important to check your shipment when it arrives. Eggs should appear lavender to grey with a visible eye when they are close to hatching. If they are very green allow them to mature before applying. Never release green eggs. Hold them at 70-80°F for one to three days. Higher temperatures will make them hatch faster. Check them daily and apply when all eggs are mature, or at first sign of larvae hatching.
Larvae. Bulk larvae orders will come pre-mixed with buckwheat hulls to reduce cannibalism, which makes it difficult to assess their quality. Open the container and examine a small quantity of material to confirm that live larvae are visible and active.
Storage conditions
Prior to release, do not keep in a pickup truck or anywhere that will get hot. Use an insulated container, like a cooler. Gently shake release containers before use to ensure lacewings are evenly mixed in the carrier.
Eggs. If the eggs are mature and you need to hold them for a few days you can store at 50-55°F. However, this may reduce hatch rates. If you buy eggs in bulk you will want to mix in carrier, like rice or buckwheat hulls, before applying. Add a small amount to each container, for example enough to treat one row, and mix thoroughly.
Larvae. Larvae can be kept at 50-55 °F prior to release, but for no longer than overnight. Longer storage will decrease survival and increase cannibalism inside the container.
Additional information
Lacewings Webpage
Lacewing and Aphid Scouting Video
Checking Lacewing Shipments Video
Contacts
Tianna DuPont
Tree Fruit Extension Specialist, Associate Professor
Washington State University
tianna.dupont@wsu.edu
(509) 713-5346
Rebecca Schmidt Jeffris
Research Entomologist, USDA-ARS
Rebecca.Schmidt@usda.gov
