by Courtney Llewellyn
Insect pests can make or break a berry crop – but so can consumer sentiment regarding the insecticides you use to control them. Rufus Isaacs, Ph.D., of the Department of Entomology at Michigan State University, talked about integrating non-chemical strategies to minimize impacts of insect pests in berry crops at the 2021 Great Lakes Expo.
“If non-chemical works, you won’t need to spray as much,” Isaacs stated. But that starts with vigilance. Growers need to walk through their fields and catch things before they become a problem. Weekly crop walks can catch pests before they reach an economic impact. “Your eyes are your best tools, followed by monitoring traps and degree day models,” Isaacs said.
Identification of insects is really important. You need to know what you’re looking for. But non-chemical IPM strategies reach beyond scouting and monitoring. Cultural controls are important too, such as planting pest-resistant cultivars, mulching to reduce pest pressure and blocking pests using nets and tunnels.
The targets of pest cultural controls have different methods of remediation. Take away favorable crop habitats for insect eggs and larvae with regular pruning, trellising and mulches. Post-harvest, make sure you cool your crop appropriately to keep their numbers down. You can stop adults with unfavorable habitats (via pruning, trellising and irrigation) as well as exclusion netting. Be sure to clean up culled fruit.
“It starts with ground floor management,” Isaacs said – literally, from the ground up. Weed control can reduce pest survival under crop plants, and mulches provide physical barriers. Specifically, mulch can prevent spotted wing drosophila larvae from entering the soil to pupate. Isaacs also noted weed mats and Mylar reflective material can be effective. “Reflective mulch keeps things drier and reflected infrared light might help,” he said. “It’s not for everybody but looking into it is another option.”
On that subject, Isaacs said that higher canopy temperature (87º and above) has been correlated with lower SWD infestation. He suggested getting heat into your canopy to reduce pests – as long as it’s dry. Insects love humid conditions.
Physical exclusion can work in some instances. Mesh netting smaller than 1 mm can exclude flies, reduce fruit infestation and improve marketable fruit yield in raspberries and blackberries. High levels of control are possible, especially in blueberries. If it is installed before fruit ripening and SWD susceptibility begins, it will keep flies out of your tunnels – and you can add netting to high tunnels. Isaacs said tunnel-grown fruit is often of higher quality.
There is the harvest element too. Simply increasing your harvest frequency – for example, three times a day versus only once a day – reduces detectable larvae.
Biological controls are another non-chemical option. “Get the good bugs out there, and create a place for them to thrive,” Isaacs said. That means using fewer or more selective insecticides and providing the biocontrols with non-pest food resources (such as flowers).