Question
I have significant grub damage to my lawn that has just become evident in early October in central Ohio. How and when should I attack the grubs, and how and when do I repair the lawn damage?

Answer
Answer: You might be tempted to treat grubs in the spring, when you see last fall抯 damage梑ut most spring treatments are a waste of time and money. The grubs have already damaged your lawn and are fairly resistant to insecticides at this time. Furthermore, even if you could eradicate them, summer will bring a new batch of beetles to your lawn.
Sample for grubs in the late summer. If you decide to treat, do so in the late summer or early fall, when grubs are susceptible to both biological and chemical insecticides and haven抰 had a chance to cause severe damage. Treat only the areas where grub populations exceed the suggested thresholds, in areas of your lawn that are aesthetically important.
Beneficial nematodes (microscopic worms) of the species Heterorhabditis bacteriophora are a non-chemical product that can be used on young grubs. A variety of chemical insecticides may also be applied. Selection depends on the species and life stage of grubs present. Products containing imidacloprid are unique in that you must apply them before egg-laying and should therefore base treatment decisions on past history of grub infestation. Consult product labels and your local Cornell Cooperative Extension office for legal and recommended practices.
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Curative controls
Most white grub insecticides belong to the carbamate and organophosphate chemical class. They are relatively fast-acting with short (2- to 3-week) residual activity. With these controls, you have a narrow treatment window. They are most often used curatively to treat existing infestations.
Following is a list of the controls labeled for white grubs and some information pertaining to their history and use. Also listed are two biological controls that have been used with some success.
? Bendiocarb (Turcam). A member of the carbamate family; production of Turcam will stop sometime and 2001. The most effective treatments are in late summer rather than spring.
? Carbaryl (Sevin and other brands). The first successful chemical in the carbamate family of insecticides, carbaryl was introduced in 1956. Apply it when grubs are actively feeding and near the surface. Control different species with different rates. If necessary, you can make multiple applications with a minimum of 7 days between treatments. The efficacy of carbaryl is dependent on soil pH so be sure to read label specifications.
? Chlorpyrifos (Dursban and other brands). An organophosphate; the EPA halted chlorpyrifos production for use in the residential turf and ornamental market in the summer of 2000, existing stocks are still available though. It is still registered for control of green June beetle grubs in golf course turf.
? Diazinon. An organophosphate, diazinon has been in use since 1952. In December 2000, Syngenta, the primary producer of diazinon for the turf and ornamental market announced a voluntary 4-year phase-out. It controls grubs of Japanese beetle, European chafer and Southern chafer. Apply between late July and early October. Irrigate thoroughly after application.
? Ethoprop (Mocap). Another organophosphate, ethoprop is only labeled for use on golf courses. It controls grubs of Japanese beetles, chafer beetles, May/June beetles and black turfgrass ataenius. Avoid applications to wet foliage.
? Isofenphos (Oftanol). Isofenphos also is an organophosphate. Some labels suggest use as a preventive with applications in mid-April through mid-May. For curative applications - the more typical use - apply in July or early August. Production of isofenphos was phased out at the end of 1999. However, existing stocks should be available at least through the end of 2001.
? Trichlorfon (Dylox and other brands). Trichlorfon is another organophosphate. Apply it when larvae are young, actively growing and feeding near the soil surface. Irrigate after treatment. If the thatch layer is greater than 0.5 inch, it must be removed. A second treatment can be applied on mature grubs.
? Beauveria bassiana (Naturalis T&O). This is a biological product containing an insect-specific fungus that works through contact action. The addition of a wetting agent helps soil penetration. Irrigation must follow treatment. It controls all major grub species. Because it is a fungus, you cannot apply this product with fungicides.
? Heterorhabditis bacteriophora (Cruiser). This also is a biological product consisting of parasitic nematodes. These nematodes are mobile in the soil and seek out insect hosts. It is effective for control of all major grub species and should be applied following egg laying by adult beetles.
Preventive controls
The preventive insecticides are typically slower acting (but no less effective) with longer residual activity. Use these treatments when a history of grub infestations or early scouting points toward a probable infestation. They are typified by low application rates and target specificity and are most effective when you apply them early in the season, before eggs hatch or while the grubs are still small.
? Halofenozide (Mach 2). Halofenozide is a member of the new diacylhydrazine class of insecticides. Registered for turf grub control in 1997, this compound interferes with larval molting but does not kill grubs immediately. However, feeding cessation does occur within a few hours following ingestion. Halofenozide has a long soil residual so you can make treatments preventively before eggs hatch. The residual will affect hatching grubs for many weeks. It controls most of the major grub species andbecause it is systemic it does not require irrigation for effective control.
? Imidacloprid (Merit). Imidacloprid is a member of the chloronicotinyl subclass of the neonicotinoid insecticides. Imidacloprid works by contact and ingestion to affect the insect's nervous system. This chemical has longer residual than traditional grub chemistries and is well suited for applications before or during the egg-laying stage. The residual remains through the hatching period and kills newborn grubs. Irrigate following application.
? Thiamethoxam (Meridian). Thiamethoxam is a member of the thianicotinyl subclass of the neonicotinoid insecticides. This chemical is in the final stages of registration and should be available later this year. It acts via contact or ingestion and will provide some control during all developmental stages, except the egg. Thiamethoxam has moderate soil persistence and insects demonstrate affected behavior within an hour of contact.
Refer to the Insecticide Update for a list of brands and manufacturers and other useful information on these grub controls.
Controlling this damaging pest involves more than knowing what chemicals to use. Identify the species you encounter to determine whether they pose a threat. Also, determine thresholds and prioritize treatments based on the location of your turf. Consistently monitor your sites to determine when to make your applications and whether your controls are working. If you follow these fundamentals, you will be able to consistently keep white grubs in their place - the ground.

Sod can be put down most anytime. Seeding is best in spring and early summer. Make the soil has been fertilized properly before sod or seed. Frequent watering is best not soaking the soil too much.

Ron
www.ronmowers.com