By Clint Thompson
Predatory mites are an effective management option for strawberry growers dealing with mite infestations. But growers should understand the ramifications of pesticide impacts on the predatory mites.
Lorena Lopez, N.C. State assistant Extension professor of entomology and plant pathology, highlighted that topic during the Southeast Regional Fruit and Vegetable Conference in early January.
“In the case of predatory mites, because they have different reproduction rates, it’s a little bit slower in some cases compared to the pests, where they can be affected even more than the pests,” Lopez said. “They are easily killed with some of the pesticides. Herbicides are proven to be the most damaging to predatory mite populations compared to fungicides, insecticides and miticides.
“Some miticides, because they are designed to kill mites, can also be very harmful to some of the predatory mites. Some miticide products are more selective and not as damaging. It’s a matter of being able to use the miticides and insecticides that are not broad spectrum but more selective in specific groups. That way we can avoid those damaging effects.”
Lopez added that growers who apply pesticides must wait 5 to 7 days before releasing predatory mites. She said that predatory mites are released in strawberries for either insect pests or mite pests.
Effective is Used Correctly
They can be effective but only if applied in a timely manner.
“Specifically in strawberries, they’re usually released to reduce two-spotted spider mite which is a major pest in most strawberry-producing states. In some areas of the Southeast, they are released against thrips, like in Florida and Georgia. They have chilli thrips and other types of species of thrips that can also be reduced with predatory mite release,” Lopez said.
“The timing of the release is very important. There is a major predatory mite that it only feeds on spider mites and if that predatory mite is released too early, they won’t have anything to eat. If the numbers of spider mites are not adequate for them, they’re going to either starve or disperse.
“If the predatory mites are released too late when the numbers of the pests, whether that’s thrips or spider mites, are too high, they’re not going to be as effective. They’re not going to be able to do that much production on that population.”