| Foliar Nematodes (cont) Biological control is Dr. Grewal�s area of expertise. Every person who attended the October meeting is now familiar with cadavers and eager to purchase some. The cadavers are wax moth larvae (wax worms grown commercially as fish bait) that are infected with a beneficial nematode, Steinernema carpocapsae. This nematode has a symbiotic relationship with a bacteria. The beneficial nematode carrying the bacteria enters the body of the wax moth larva. The bacteria are released into the insect to kill it and S. carpocapsae feeds on the bacteria and liquefying body of the insect. No one at the presentation will forget the image of the wax moth cadaver (WMC) with its skin peeled away to expose the tangled mass of beneficial nematodes. These WMC can be used directly by mixing them in soil. When container plants infected with foliar nematodes were treated with 10 of these cadavers per pot, there was a 50% reduction in leaves showing symptoms and a significant decrease in the leaf area showing discoloration. The beneficial nematode does not attack foliar nematodes nor can it ever feed on leaf tissue because it lacks a stylet. Its ability to suppress foliar nematode populations is thought to be chemical in nature. Dr. Grewal also noted that the plants treated with WMC had larger leaves as reflected by an increase in the dry weight per leaf. It may be that WMC may be helping the plant become resistant to foliar nematodes. Dr. Grewal has also used an extract (WMCE) of the wax moth cadavers to control foliar nematodes. It is made by macerating the cadavers, filtering the material, and diluting it with water. WMCE diluted 50% with water will kill almost all the nematodes. Biological control methods using the wax moth cadavers and their extract look very promising. Dr. Grewal and Dr. Jagdale will fine tune these methods for managing nematodes as they continue their research at Ohio Sstate. Foliar nematodes no longer seem quite as threatening as they did before our October meeting. My thanks to Dr. Grewal for answering questions that arose as I wrote this article and for reviewing the finished article. |
| Prevention 1. Use nematode-free propagating material 2. Buy plants in the fall 3. Isolate new plants for a year 4. Minimize foliage wetting when possible 5. Cut and destroy infected leaves 6. Sterilize tools 7. Isolate infected plants 8. Fall clean out 9. Apply ZeroTol or Insecticidal Soap early to areas infected the previous year 10. Add wax moth cadavers with Steinernema carpocapsae to your soil |
| For more information, check out Dr. Grewal�s website www2.oardc.ohio-state.edu/nematodes. You will learn about the biology, appearance, and specific characteristics of each species of beneficial nematode. Steinernema. carpocapsae controls foliar nematodes, cutworms, and fungus gnats. Other species control black vine weevils. Of particular interest is the list of commercial sources, links to publications and other related websites.. If you want to ask Dr. Grewal a question, you can do so at this site. This article was reprinted from The Hostaphile (the Newsletter of the Minnesota Hosta Society) |