Diazinon is a chemical that was often used in our area to treat for grubs in the lawn during late August. The most common lawn grub Rochester has is the European Chafer Beetle grub ( Rhizotrogus majalis ). Diazinon was sold alone as well as in the Scott’s, Turf Line and Gro Green Annual 4-Step lawn care programs. Diazinon will no longer be produced or for sale in New York State.

Since Diazinon will no longer be included in Step-3 of these lawn care programs, other measures need to be taken to control lawn grubs. Scott’s offers GrubEX which contains imidacloprid (Merrit) in a granular form. This product should be applied in late May to early June for season long grub control. The soil should be wet before application and watered after application to allow for the pesticide to penetrate any thatch and reach the root zone. One inch of water is sufficient. This pesticide is actually considered a preventative and controls the grubs just as they hatch. It needs to be present in the soil before the grubs hatch. Imidacloprid is also available in a liquid form from Bayer called Advanced Lawn: Season-Long Grub Control. It comes as a liquid concentrate that hooks right up to your hose for application. Avoid liquid use when bees are active if you use them to pollinate fruit. Foliar sprays of imidacloprid are toxic to bees. It is much easier to control grubs in their early stage of development in August then the over-wintered grubs that feed on your lawn in the spring. If spring grub control is necessary only trichlorfon, which is found in Greenview Grub Control, is useful. Trichlorfon needs to be applied after soil temperatures reach 50 °F or it won’t be effective. This chemical kills grubs within 1-2 days but only stays active in the soil for one week. It will achieve 50-70% control.

An organic solution to grub control is the use of beneficial nematodes. Heterorhabditis bacteriophora will control European Chafer Grubs and Japanese Beetle grubs in the Rochester area. They can be watered into the lawn when the soil temperatures reach 68 ° F. One billion nematodes per acre (250,000 per m 2) is the rule-of-thumb.

Remember not every lawn has a grub problem. Often people think they have grubs because they believe they have a mole problem. In many cases they actually have a vole problem. Voles eat vegetation, not grubs. Check for grubs before applying any pesticides. Scout for grubs in August. Pull up a one foot square patch of grass, if there are 8-10 grubs visible then you should treat. Any less then that and they will not do visible damage.

Pesticide recommendations in this publication are registered for use in New York only. The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any chemicals mentioned in this publication. Always read and follow label directions for safe use of any chemicals. None of these products are intended to be used over any other. No endorsement is intended for products mentioned, nor criticism meant for products not mentioned. This article is intended for educational and informational purposes only. The authors and The Garden Factory® assume no liability from the use of these recommendations.