Caseload at the UW Insect Diagnostic Lab (IDL) remains low but is expected to gradually increase over the next few weeks. The low caseload isn’t too surprising given the recent cool temperatures and minimal accumulation of growing degree days in the state.  A summary of recent fruit crop insects reported to the UW Insect Diagnostic Lab as well as important insects to scout for can be found below:

European red mites:  I’ve recently seen a few cases of European red mites from eastern Wisconsin.  These mites can be occasional pests of fruit trees.  European red mites overwinter as eggs on the bark of fruit and landscape trees.  The eggs (tiny, reddish, spherical) can be laid in clusters of several dozen or more eggs.  Early in the season, dormant oil applications can help control overwintered eggs. 

Scale insects: I’ve had two cases of lecanium scales over the last two weeks.  Lecanium scales can be common and are known from a very wide range of host plants, including many fruit trees and grapes.  Like some of our other scale insects in fruit settings, lecanium scales can be managed with dormant oil applications in spring.  In addition, targeting the mobile juveniles (“crawlers”) during the growing season can provide good control.  For lecanium scales, the crawlers are active in late spring and early summer, so in a typical year growers should be scouting for the crawlers from early June onwards.  If left unchecked, lecanium scales can coat branches and secrete copious amounts of honeydew. 

Brown marmorated stink bug: I’ve had a number of reports of activity from overwintering adults over the last few weeks.  Most of these have come in from Dane County, SE Wisconsin or the Appleton/Green Bay areas.  The IDL saw fewer BMSB reports in 2021 compared to prior years, but growers should remain on the lookout for this invasive stink bug during the growing season this year.

Caterpillars and dormant oil treatments:  As mentioned in the last issue of WFN, certain spring caterpillar pests (such as eastern tent caterpillar and spongy moth) overwinter as eggs and can be managed with dormant oil applications.  The cool temps over the last two weeks have kept growing degree day accumulations low and I have not yet received any reports of hatched eggs.  Thus, growers still have a bit of time left to scout for and treat egg masses of tent caterpillars and spongy moth (formerly known as the “gypsy moth”).  The heaviest spongy moth activity in 2021 occurred in the eastern half of Wisconsin. 

Reminder about diagnostic support from the IDL: Growers and consultants in need of insect diagnostic services are always welcome to submit a sample to the UW Insect Diagnostic Lab.  Lab services are provided free of charge.  You can find additional information about the IDL here: insectlab.russell.wisc.edu

This article was posted in Insects and tagged Brown Marmorated Stink Bug, caterpillars, dormant oil treatments, European red mites, Insect Diagnostic Lab, insects, PJ Liesch, scale insects.