Question
Dear Mack Jean,
Firstly let me say, thank you for being there. It must be very time consuming, and I am grateful for your help.
My problem involves Japanese beetles. I have been gardening for ten years and we have seen the populations increase, but last year there was an explosion of them. There were thousands. I have 23 roses (mostly old garden) and two lindens, one a little leaf and the other a Shamrock, and their health is being adversely affected by the damage the beetles are doing. Most of the other shrubs and trees are unaffected.

Please let me give you some perspective. I am a largely organic gardener.  Our home is built on former farmland, so I was dealing with hardpan and a Ph of 7.9. By composting heavily in spring and fall for ten years, piling the layers, slowly, higher and higher, I have neutralized the alkalinity and can grow fothergillas and other 搇ime hating?plants.  I prefer to fertilize with compost, fish meal, alfalfa meal, sea kelp, and I like to use Remedy, which I am sure you know is a take on the Cornell formula, for disease. I also use dormant oil in late winter.

Last year, when the japanese beetles got beyond the handpicking stage (and I can抰 get to the top of 30 foot trees) I decided to take action and applied milky spore in late August and September (I am in zone 5a). As I began digging up and reseeding the lawn, I saw a good ten grubs per square foot in some places (I must say that I was quite satisfied to find many dead and dying ones) but my neighbors have done nothing and I am concerned (one has a nearly dead linden from the chewing). I would like to take the next step and apply nematodes in the spring.

Could you kindly advise me as to what type of nematode would be effective, when it should be applied and from whom I should purchase it? I have read a number of recommendations but most seem to be written by sellers of the products. In desperation I was using some acephate and malathian, but it made me cringe and I truly don抰 want to do it again, since my garden attracts a lot of butterflies and hummingbirds.
Thank you for your guidance.

Donna Mack  

Answer
Dear Donna:

What a coincidence....your last name same as my first name "Mack" (actually, my middle name....).  I'm sure there must be some mutual affinity with gardening that likely causes this aberration!!

I'm pleased to see you have chosen to use Milky Spores disease as one of the combatants for the dreaded Japanese Beetle.  My experience with it has been very good.  In response to your question, I must tell you that I have no direct experience with the recommended nematodes for control of the Japanese Beetle.  However, I will share with you some of the reading and online information that I garnered while researching your question and searching my personal files:

1. Reference:  http://www.entomology.wisc.edu/mbcn/nema508.html

2. Reference: http://www.pueblo.gsa.gov/cic_text/housing/japanese-beetle/jbeetle.html  The two nematodes that are most effective against Japanese beetle grubs are Steinernema glaseri and Heterorhabditis bacteriophora. The latter is commercially available.

When using nematodes, remember they are alive and have a fairly high oxygen requirement. They are typically sold on a carrier, which they can survive on for a month or 2 under cool conditions. They can be applied with any standard insecticide applicator. Once mixed with water, nematodes must be applied fairly quickly. Follow accompanying directions carefully for best results.

Nematodes may be purchased in lawn and garden shops or through biological mail-order catalogs.

3. Website vendor source for Heterorhabditis bacteriophorahttp://www.arbico-organics.com/1220301.html

4. Website vendor source for Heterorhabditis bacteriophora - http://www.rinconvitova.com/nematode.htm

5. Function of Heterorhabditis bacteriophora -  actively seeks out pests. It is adapted to all climates and prefers undisturbed soils. NemaSeek?is most effective against sedentary pests, such as grubs, root weevils, queen ants/termites and more.

I hope you find the above useful and I wish you great success in your continuing battle with Japanese Beetles.  I'm very impressed with your strategy and logic in managing your lawn and garden.

Best regards,

Mack Jean
AllExperts
Master Gardener
Tennessee