Caseload at the UW Insect Diagnostic Lab (IDL) is very high and is expected to remain high for the next few months.  A summary of recent cases at the IDL involving fruit crop insects can be found below:

Spongy moth:  Based on recent reports to the IDL, spongy moth caterpillars have finished feeding in southern parts of Wisconsin and have pupated; adults are now present in some areas.  Adult females cannot fly, but the brownish adult males can be active around trees during the daytime hours.  In northern areas (such as the Bayfield Peninsula) caterpillars are still active based.  Overall, reports from fruit growers suggest that spongy moth damage was down from last year and diseases that infected and killed spongy moth caterpillars may have kicked in before caterpillars reached larger, more damaging sizes.  Both the entomopathogenic fungus Entomophaga maimaiga and a Nucleopolyhedrovirus (NPV) have been infecting and killing spongy moth caterpillars in parts of the state.  Many reports of dead caterpillars have come in from southwestern, southcentral, and southeastern Wisconsin.

Grape flea beetle:  I’ve recently seen several reports of damage and larvae from southcentral and southwestern Wisconsin.

Japanese beetles:  Despite receiving an initial report of an adult Japanese beetle from Cross Plains (Dane County) from June 2^nd, things were otherwise quiet until late June.  We’re now in the key window for adult Japanese beetle emergence and activity is expected to pick up over the coming weeks.  Recent reports have come into the IDL from southcentral and southeastern Wisconsin.

In much of southern Wisconsin Japanese beetle pressure was down in 2023, but growers should remain vigilant with their scouting efforts.  Interestingly, Japanese beetles have been pushing farther north into the state over time and many reports last year came from parts of Wisconsin north of Hwy 29.  Growers in northern Wisconsin should have Japanese beetles on their radar if they have not yet encountered them.  Adults can be spotted into early fall.

Cutworms: I’ve recently seen a number of cases of cutworms at the UW Insect Diagnostic Lab.  While some cutworms prefer to stay close to ground level, others (such as the variegated cutworm) can be decent climbers and can get up onto plants.  I’ve recently had reports of damage to strawberries from southcentral Wisconsin from variegated cutworms.

Periodical cicadas: The activity of periodical cicadas is wrapping up in Wisconsin and we won’t see the adults again for 17 more years (2041).  In parts of southern Wisconsin where periodical cicadas did occur, “flagging” injury (broken twigs and browned leaves) is now obvious.  I did receive a number of reports of periodical cicada oviposition (egg-laying) damage to fruit trees and grapes.  This might impact this year’s yield, although this damage generally does not pose a significant threat to overall plant health (unless plants are very small).  Interestingly, it’s been noted that this damage can sometimes serve as a natural pruning process which could boost yields the following year.  

If you encountered periodical cicadas this year, consider submitting a report and photos to the Community Science project on the Wisconsin Periodical Cicada Website (cicadas.wisc.edu) to help document their presence in the state.

Slugs, earwigs, millipedes, and pillbugs: These creatures can be common and widespread, but usually don’t pose significant problems for fruit growers.  However, they can thrive under damp, rainy conditions and are now abundant in many areas.  Slugs can occasionally be pests of low-growing crops such as strawberries when they feed on foliage or fruits.  Millipedes and pillbugs are generally scavengers, but can also damage strawberry fruits on occasion if they are extremely abundant.  Earwigs also have a decent ability to climb and have been noted causing minor chewing damage on strawberries as well as leaves of fruit trees.  Scattered reports of these pests have come in from around the state.

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 cutworms, earwigs, Grape Flea Beetle, Insect Diagnostic Lab, insects, Japanese beetle, millipedes, periodical cicadas, pillbugs, PJ Liesch, slugs, spongy moth.