Indiana Department of Natural Resources sent this bulletin at 06/22/2022 09:00 AM EDT
Weekly Review for June 22, 2022
This informal report by the Division of Entomology & Plant Pathology is a commentary on insects, diseases, and curiosities division staff encounter on a week-to-week basis. Comments and questions about this report are welcome and can be sent to your respective Inspector.
Typically, you will only see the damage recorded by most wood boring insects and rarely an adult specimen, but in the last two weeks I saw two different Agrilus sp. on opposite sides of the state. A. bilineatus, two-lined chestnut borer, is a typically a secondary pest of Castanea and Quercus species that have been weakened by other factors. I saw a lone adult in Hendricks County and no signs of galleries, exit holes or tree wilting to indicate the adult came from the nursery.
The second Agrilus sp. I saw is a different matter. Agrilus planipennis, emerald ash borer, has caused the death of millions of ash trees since its introduction into the U.S. While in Wayne County, I again saw a lone adult with possible feeding damage on Syringa vulgaris var. alba. Unlike native species of wood borers, this introduced species attacks healthy trees not just those that are stressed. While the insect was on a Syringa sp. there was no sign of exit holes, bark splitting, woodpecker damage or tree die back to indicate infestation of this species by A. planipennis.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week, I found adult red-headed flea beetles actively feeding on many plants, especially Itea, weigela, hydrangea, and dogwood. At one nursery the Caryopteris ‘Dark Knight’ was absolutely loaded with flea beetles and the feeding damage was already heavy. I also found several varieties of hosta at one grower with virus symptoms, including yellow and green discoloration, faint ringspots, and mottling on the leaves. I sent samples to PPDL and they were confirmed for Hosta Virus X. I will go back this week to stop-sale and destroy these plants because once infected, there is nothing that can be done to treat the virus. The virus is spread through sap from infected plants, such as when plants are pruned using contaminated tools, and is also spread when plants are propagated from an infected mother plant.
Other finds last week include “Thriller” lady’s mantle with a heavy spider mite infestation, columbine leafminer, and the first Japanese Beetle of the season (found in Hendricks County). I also saw my first bagworm of the season in Tippecanoe County today.
Somewhat inspired by Jared’s oak investigation a few years ago (Weekly Review - July 3, 2018), I was recently thrilled to see the amount of insect diversity on the common milkweed I planted in my yard and thought I’d share. I have a 16’ by 6’ bed of common milkweed that I planted three years ago in an effort to attract monarch butterflies to my yard. I was checking out my milkweed a few evenings ago hoping to see evidence of monarch eggs or larvae.
Unfortunately, I didn’t find any yet, but the milkweed was absolutely teeming with other arthropod activity. As anyone who grows milkweed knows, the first thing I found was…. aphids. While they’re pesky and the honeydew they produce is a little gross to me, the other insects don’t agree, and the aphids and their honeydew seem to be the main reason other insects are visiting the milkweed. In just a few short minutes of observation, I saw four different species of ants, a paper wasp, a yellow jacket, several species of flies, and two species of beetles feasting on the honeydew.
Predaceous hoverfly larvae, spiders, and ladybugs (adult and larval stages) were feasting on the aphids themselves, and occasionally cannibalizing each other or catching other insects tempted by the aphids. I also saw a few species of wasps that may be parasitoids of the aphids, and mummified aphids were present on several of the milkweed plants. Some of the insects present were there for the milkweed itself, not just the tasty aphid excrement. I saw honeybees and bumblebees on the milkweed flowers, and red milkweed beetle happily chewing on the leaves. I know many people who follow our weekly review are probably fans of the idea of the “Homegrown National Park” (Doug Tallamy). I think anyone who wants to increase the arthropod diversity in their yard can’t go wrong with planting milkweed.
Photos 9-14 – Things found on milkweed: Bumblebee, Red milkweed beetle, Ladybug larva cannibal, Jumping spider, Aphids, and Hoverfly larva
What started as a slow pest year has really ramped up with the heat. I am seeing a lot more spider mite damage, especially in greenhouses. Hibiscus sawfly, Eastern tent caterpillars, and Japanese maple scale are among my finds this week. I also have a collection of unidentified caterpillars taken this week on iris, dogwood, crabapple, and oak. Most of these were causing only trivial damage, though a couple of the iris were chewed up pretty good. When I get some better identifications, I’ll share some details.
Speaking of the heat, keep up on the watering. Watering slowly over a long period of time is the best way to get the water to soak in. Maintaining even soil moisture throughout this hot, dry period is critical to avoid issues like blossom end rot on tomatoes. Raised beds are wonderful for a lot of reasons, but the elevation also means they will be the first thing to dry out. In fact, I just about lost the southern outside edge of one of my raised beds to drought. After a long soak, I hope it will rebound, but we’ll see.
The spongy moth mating disruption treatments will be taking place across northern Indiana this week. Check our website and follow us on Twitter for more information.
