Indiana Department of Natural Resources sent this bulletin at 11/03/2023 12:54 PM EDT
Weekly Review for November 3, 2023
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.
I have a few updates and notes that I wanted to share with you.
Purdue Extension – St. Joseph County is hosting a Spotted Lanternfly Lunch & Learn Virtual Meeting on Nov. 7, 2023 at noon ET. Purdue’s Bob Bruner will be speaking about SLF. You can register here. Questions about this meeting can be addressed to Emily Evers at everse@purdue.edu.
For those of you who ship plant material out of state, Wisconsin recently added quarantine rules for elongate hemlock scale and revised its state quarantine for hemlock wooly adelgid and Phytophthora ramorum. If we can help you navigate these or any other state quarantines, please contact your nursery inspector.
Will Drews (Nursery Inspector & Compliance Officer) - WDrews@dnr.IN.gov
While finishing my nursery inspections for the year, I found a couple interesting pests affecting several nurseries in my area. One of them was slug sawflies (Caliroa spp.), and the other was foliar nematodes (Aphelenchoides spp.).
There are many different species of slug sawflies—which are not true slugs, even though the caterpillars resemble them—that can affect nursery stock. Some of the species I came across at nurseries include pear slugs (Caliroa cerasi), blackgum leafslug sawflies (Caliroa nyssae), and oak slug sawflies (Caliroa quercuscoccineae), affecting plum and peach, blackgum, and oak, respectively.
Most slug sawflies have similar lifecycles. They often have two generations per year with one beginning in late April and the last ending in late August and September. They overwinter as pupa in the soil and emerge as adults—which are small black wasps—in late April to May, which start laying eggs on new leaves. Once the larvae hatch, they immediately start feeding on leaves. The larvae are skeletonizers and can cause defoliation with enough pressure. Management strategies can include hand picking larvae off affected individuals, washing them off, or using chemical treatments.
Foliar Nematodes were the other major issue affecting several nurseries. Foliar Nematodes (Aphelenchoides spp.) are similar to other nematodes in the fact that they are microscope roundworms. However, while most nematodes live and feed in the soil on decaying material, bacteria, fungi, and other microscopic organisms, foliar nematodes feed on live foliage and stems of plants. They are generalists and can feed on over 450 species of plants, including the commercials important species like anemones, begonias, chrysanthemums, hostas, ferns, orchids, azaleas, strawberries, tomatoes, and more. Damage to foliage includes angular blotches that are interveinal, which are often not noticeable until later in the season. Foliar nematodes can be spread via water once in adult form and move to another plant through overhead irrigation. Unfortunately, there is no good control for foliar nematodes. High temperature treatments can be effective but sometimes can kill the host plant as well. Bagging and disposing of infected plants is recommended to prevent an infestation.
