Q: Is there a way to treat organically for Japanese beetle grubs at this time of year?

Answer: Yes, there are some beneficial nematodes which can be applied at this time of year which can help control Japanese beetle grubs. Nematodes are microscopic worms that live in the soil. Many are considered pests as they feed on plant roots, but there are many nematodes which feed on insect larvae which have part of their life cycle in the soil. The nematodes which feed target on larvae of pests of lawns and gardens are the species Steinernema and Heterorhabditis. Steinernema carpocapsae targets army worms, cutworms, billbugs, crane flies, lawn moths, and black turfgrass ataenius. This nematode species lives just below the soil surface and will not move very far away from where it is introduced. Steinernema glaseri preys on white grubs. Heterorhabditis bacteriophora will actively seek out its’ prey in the soil. It feeds on turfgrass antaenius, white grubs, and fiery skipper. The steps to follow when applying beneficial nematodes is first to identify the pest you want to treat for. Take a shovel full of soil and examine it for the presence of grubs. Many common lawn and garden pests like Japanese beetle’s live part of their lifecycle in the soil as grubs. By this time of year, the grubs are present and still active, although with cooling temperatures the grubs will become less active. Along with Japanese beetles, the turfgrass antaenius and the oriental beetle have grubs with cream colored bodies with yellow to brownish heads and hind parts. The grubs will have 6 legs. At maturity, the grubs are ¼ — ½ inch long. White grubs often are curled in a C-shape position. Billbug larvae look very similar to the other grubs, but will not have legs. For more information check out this page https://entomology.ces.ncsu.edu/white-grub/ . Sometimes beneficial nematodes may be purchased at local garden centers or by purchasing online from a reputable supplier. The University of California Extension has given the following directions for best practices for applying beneficial nematodes.

How to apply beneficial nematodes:

  • Select a nematode species that is most effective against the target pest. Make sure you purchase nematodes from a reputable supplier.
  • Apply when the caterpillar or grub stage of the pest is present and active. This can be throughout the late spring and summer for most pests. For white grubs, apply later in the summer or early fall when more mature larvae are present and active. A second application about 2 weeks after the first will enhance control.
  • Do not apply if the soil temperature is below 60°F.
  • Irrigate before application. The soil must be moist, but not soggy.
  • Mix up a solution of fresh, infective stage nematodes in cool, distilled water, pour the solution into a sprayer, and apply to the infected area.

Apply nematodes in the evening, especially in hot areas. Nematodes are killed by light and heat.

  • Irrigate after application. Several irrigations may be needed to keep the soil moist.
  • Follow up a week or so after each application. Look for red or yellow-brown infected larvae or pupae.

Q: Is there a good source for weather data for farmers in North Carolina?

Answer: The N.C. Climate Office maintains a website with links to weather stations across the state. The web address is http://climate.ncsu.edu/cronos. Enter your zip code to find a weather station close to you. There is data collected for precipitation, wind conditions, and soil conditions. This can be very helpful for planning purposes. For more detailed data and some very helpful tools check out the chilling days data on this page: http://climate.ncsu.edu/tools/agriculture.

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Mary Jac Brennan is the agent for fruit and vegetable horticulture for small farms and local food for the Forsyth Cooperative Extension. Contact Mary Jac about commercial production, local foods, and sustainable agriculture questions. For information on home and gardening issues, contact the Forsyth Cooperative Extension office at maryjac_brennan@ncsu.edu or call 336-703-2850.

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