Caseload at the UW Insect Diagnostic Lab (IDL) has been high over the last two weeks.  A summary of recent fruit crop insects reported to the lab as well as important insects to scout for can be found below:

Japanese beetles: Japanese beetles have emerged in many parts of the state.  I’ve recently received reports from most of Wisconsin ranging from the Illinois borer up to Oneida and Vilas counties in northern Wisconsin.  Some good news thus far is that Japanese beetle populations seem to be down this year in most areas and I have not yet received any repots of significant plant damage at the UW Insect Diagnostic Lab.  Nonetheless, Japanese beetle adults are out-and-about causing some damage to tree fruits, grapes, and landscape plants.  Japanese beetles are most active in July and August with activity generally starting to dip as we get into September.

Spongy moth (formerly known as “gypsy moth”): The spongy moth season seems to be wrapping up in southern Wisconsin, although a few caterpillar stragglers remain. Large caterpillars have entered the pupal stage with adults beginning to appear and activity expected to increase in the coming weeks.  Recent sightings in northern Wisconsin (Bayfield and Ashland counties) have indicated smaller caterpillars (between 1-1.5 inches long), so those will continue to feed for the next few weeks.  For growers that saw spongy moth activity this year, keep an eye out for egg masses once adults appear.  Egg masses tend to be 1-2 inches long, are beige in color with a velvety covering and spongy texture when pressed.  Each egg mass can contain upwards of 500-1,000+ eggs, so scouting for these can provide insight into how spongy moth populations could be in 2023.  Egg masses remain in place for 8-9 months (until hatching next spring) which gives lots of time to locate and either physically remove (scrape into container of soapy water) or treat with oils.

Sphinx moths: I’ve recently had a few reports of sphinx moth caterpillars from fruit crops, including the Abbott’s sphinx moth on grapes in southeastern Wisconsin and the wild cherry sphinx moth on stone fruit in north-central Wisconsin.  For many species of sphinx moths, the caterpillars can be decent sized (1 ½ – 2 inches long), but these caterpillars tend to occur in low numbers and are mostly a “curiosity”. 

Social wasps (paper wasps and yellowjackets):  As is typical this time of the year, I’ve started seeing an increase in reports of social wasps (paper wasps and yellowjackets) from around the state.  These insects have “annual” colonies that are started in spring or early summer and build up in size over the course of the season, peaking in late summer or early fall. These insects are strong fliers and can travel long distances, so it can be helpful to keep a general eye out for nests in orchards and vineyards.  Treating and eliminating a nest now could prevent larger issues when these wasps are very active in late summer and fall as many crops are being harvested.

Brown marmorated stink bug: I recently received my first report of BMSB nymphs (juveniles) from south central Wisconsin.  Growers with a history of BMSB should keep an eye out for juveniles.

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, Insect Diagnostic Lab, insects, Japanese Beetles, paper wasps, PJ Liesch, social wasps, sphinx moths, spongy moth, yellowjackets.