Counting Natural Defenses with Aphids, Spider Mites

Taylor Hillman Pest Update, Tree, nut & vine crops

There are good natural defenses for aphids and spider mites and monitoring for those biological control agents is as important are scouting for the pest.

Monitoring Aphid Controls

Integrated Pest Management Advisor Emily Symmes reminds growers it’s important to see what the natural control levels are in an orchard and there are specific things to look for with aphids. “Aphids have a minute little wasp that lays eggs inside of them and when that happens the aphids turn brown and swollen. They look a little like parchment paper,” Symmes says. “Our treatment guidelines really are based on the amount of healthy or non-parasitised aphids are in the orchard. If you are seeing an abundance of parasitism, that may well mean that you should take measures to preserve those parasitoids and let them provide that natural control.”

Monitoring Spider Mite Controls

Symmes says spider mite control also has signs to look for. “It’s important to not just count spider mite numbers, but also the ratio of predators to spider mites,” Symmes says. “What we want to look for is predacious mites, which are easy to distinguish with a hand lens, and for sixspotted thrips which are another fairly common predator of spider mites. Whether or not we need to treat is based on the combination of how many pest mites and how many predators we are seeing in the orchard.”

Symmes reminds growers the UC IPM website has information and visuals for identification.