Caseload at the UW Insect Diagnostic Lab (IDL) has been very high in July. A summary of fruit crop insects reported to the lab in July as well as important insect trends can be found below:

Spongy moth (formerly known as “gypsy moth”): Spongy moth reports have continued to come into the UW Insect Diagnostic Lab from around the state in July.  Damage from caterpillars is wrapping up for the year, with limited caterpillar activity remaining in northern areas.  In much of the state, spongy moths have pupated and adults are currently active.  The brownish male moths can be seen actively flying during the day; pale colored females cannot fly and release a pheromone to attract the males.  Watch for beige, velvety egg masses; these can contain upwards of 1,000 eggs and can be physically removed or treated before next May to prevent them from hatching.

Japanese beetles: I’ve received many reports of Japanese beetles on fruit trees, grapes, and caneberries this month, but overall activity appears to be low in most areas.  The highest activity reported has been from east-central Wisconsin—areas such as Sheboygan, Green Bay, and Appleton.

Brown marmorated stink bug:  I’ve received a few reports of BMSB nymphs over the last few weeks from south-central Wisconsin, southeastern Wisconsin and the Fox River Valley.  Growers with a history of brown marmorated stink bug activity should watch for BMSB egg masses and nymphs (juveniles) while scouting.   These insects can cause direct injury to developing fruits. In addition, nymphs of other stink bug species, including members of the genus Euschistus and the green stink bug have also been recently reported.  Like BMSB, they can directly attack developing fruits.

Fall webworm: Reports of fall webworm started trickling into the IDL in late July.  Colleagues in more southern states have hinted at a strong year for that insect, so keep an eye out for skeletonized leaves (small caterpillars) and silken tents towards the tips of branches of fruit trees.  These insects can have an extended period of emergence with activity noted into late summer and fall.  Reports have been scattered around the state.

Spider mites: While we’ve finally received some rain, the dry conditions allowed spider mites to thrive in many parts of the state.  Damage typically results in a speckled or “sandpaper” appearance of leaves.  Rain can physically wash mites off of plants and high humidity can encourage pathogens that keep their populations in check.  Nonetheless, growers should continue to monitor for spider mite activity as drought conditions remain in many parts of Wisconsin.

Pearleaf blister mite: I’ve recently had a number of cases from southern, central, and northeastern Wisconsin.  These mites cause brownish, scab-like lesions on pear leaves.  Under the microscope, these lesions can be dissected to reveal the slender, pale mites which are approximately 1/100^th inch long.

Grapevine beetle: These large, conspicuous scarabs feed on grape leaves, but are typically encountered in low numbers and are not a general concern for growers. This species can be found statewide and reports have been sporadic and scattered around Wisconsin.

Asiatic garden beetle:  This invasive scarab can feed on a wide range of plants ranging from landscape trees and shrubs to various fruits and vegetables.  They were recently confirmed in Green Lake County for the first time; this detection is also the first confirmed report of damage from Asiatic garden beetles in the state.  These small, brownish scarab beetles resemble miniature May/June beetles and are especially active on warm evenings.  They can strongly be attracted to lights at night.  To date, they have only been confirmed in Dane and Green Lake Counties.  If you believe that you’ve found Asiatic garden beetles, please contact me at the UW Insect Diagnostic Lab to confirm with a sample.  Asiatic garden beetles can be common in states to the east of us and in northern Illinois, so we’ll likely see their range expand into Wisconsin over time.  

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 Insect Diagnostic Lab, insects, PJ Liesch.