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Managing Grubs without Pesticides
From Bill Duesing Executive Director CT NOFA Cultivating an Organic Connecticut
There are increasing opportunities for managing grubs without pesticides.
The most important thing is to grow healthy grass in healthy soil so that the grass has longer, more vigorous roots and can better resist grubs or recover from grub feeding. Encouraging biodiversity in the soil (ants and ground and rove beetles, for example) and in the surrounding areas (flowering plants which encourage beneficial wasps which pray on grubs) is very helpful for natural grub control and should also build stronger turf.
Regular pesticide and fertilizer use tends to limit biodiversity and the grub control it provides. Ants seem to be the most effective predators of grub eggs.
Certain cultural practices such a watering and fertilizing as particular times can encourage grubs, so avoiding those practices can help prevent infestations.
Some species of grubs can be controlled by various nematodes (very tiny worm-like organisms that are everywhere) that are exempt from EPA registration (therefore are not pesticides) but which live in the soil, lay their eggs inside grubs and kill them. There are specific species of nematodes for specific kinds of grubs, so the type of grubs needs to be discovered. Fortunately resources at the Connecticut Agricultural Experiment Station and at UConn can help with identification. There is lots of work on a variety of nematodes to control other species of grubs. It is a rapidly evolving control strategy.
It should be noted that the most common chemical grub control (trade named Merit) is not an IPM product. It must be used before any grubs are seen to be effective, so that it is completely contrary to the IPM policy of evaluating the damage before spraying. That product has also been implicated in the demise of honey bees in France and in ground water contamination on Long Island.
As I understand it, the other grub controls are more dangerous to humans.
[Another tip: Don't water the grass in July and August when the eggs and immature grubs are around. They like and need water.]