White Grub Control All white grub prevention chemicals seem to have one thing in common. They are expensive!  So it is important to first make sure you really will benefit from that treatment and use it when it will be most effective. In Ohio this means ignoring all the spring ads for grub control chemicals and resisting the peer pressure of seeing all your neighbors out with their broadcast spreaders. Finding a few grubs here and there doesn’t necessarily mean you want to run to the store for a bag of chemical granules.  A good test is to “peel” back a one foot section of sod in area you think may be affected and count the grubs in the top 3” of soil. A healthy lawn can  tolerate up to 10 grubs per square foot. If after that test you still would like to treat, go with a systemic insecticide labeled for grubs and hold off till they are in their young larvae heavy feeding stage. Sure they are big and ugly in spring and early summer, but that’s from all the roots they ate late LAST summer.  Check the Grub Cycle chart to see what I mean. Japanese Beetle Grubs are best controlled  just before feeding larvae are present in late summer. Grubs that go untreated in late summer/early fall  will reappear in spring. Contact chemical controls can be also be applied.  The downside with some of these chemicals is they also kill earthworms. A preventative grub control product known as Grub-X or Merit (imidacloprid) can be used for control of grubs. This product will not provide the intended results if applied at the incorrect time. Grub-X should be applied during the egg laying stage of the adult beetle. This timing varies by location and seasonal conditions year to year. You may be able to find where grubs are in their life-cycle by calling a local county extension office.  We look for clues of how the season is progressing  from sources like the Buckeye Yard and Garden Line that is emailed to us weekly during the  growing season.  (If you would like this Ohio State Extension newsletter see the notes below) For Ohio the time to apply Grub-X or Merit is usually July. I keep stressing OHIO because I get hundreds of inquiries every year from other areas of the nation where I simply don’t have my finger on the pulse of the grub. (and even then it’s hard to find a pulse on those little suckers!) Also in other areas there may be far more species of grubs whereas locally we are mainly dealing with the Japanese Beetle larvae and similar white grubs. The best insecticides for grubs are systemic and require time to be absorbed into the plant roots and shoots. The idea is to apply Grub or Merit, in July and water in the product. In about three weeks the Grub-X or  Merit, will be in the plant roots. As newly hatching grubs begin to feed on the  fine feeder roots, they will ingest the Grub-X or Merit, and die. Merit or  Grub-X does not work as well on mature, overwintering larvae and can only be applied once a year. In order to receive the benefit of full season grub control  as stated on the manufacturer's label, apply Grub-X or Merit in July during the egg laying stage, and control newly hatching grubs in late summer. Then there will be fewer overwintering grubs or spring grubs to contend with and less need to apply grub controls until the next year in July again. It is best to rotate  the use of Merit one year and use an alternative product the next to diminish the possibility of resistance from use. All controls whether chemical or biological must be watered in with 1/2 to 1 inch of water immediately after application to be effective. If water cannot  be applied to the area where a grub control has been applied and rain is not in the forecast, do not apply anything. Water is necessary to wash the material  through the thatch to the region where the grubs are located. Reasons for failure to control grubs. The most common reason grub control products fail to control grubs is that they are applied at the wrong time! These pesticides applied at incorrect times or without water, is a misuse of pesticides and waste of time and money. Excessive thatch and microbial degradation can also  account for failure when controlling white grubs on the home lawn. About the Buckeye Yard & Garden Line BYGL is available via email, contact Cheryl Fischnich   Additional fact sheet information on any of these articles may be found through the OSU FactSheet database http://plantfacts.osu.edu/ . BYGL is a service of OSU Extension and is aided by support from the ONLA (Ohio Nursery and Landscape Association) http://onla.org/ ; http://buckeyegardening.com/ to the OSU Extension Nursery, Landscape and Turf Team (ENLTT). BYGL is available online at:  http://bygl.osu.edu , a website sponsored by the Ohio State University Department of Horticulture and Crop Sciences (HCS) as part of the "Horticulture in Virtual Perspective." The online version of BYGL has images associated with the articles and links to additional information.