Important Changes to Season-long Grub Products
Apr 18, 2011 at 2:02pm — MSU Turf Team
Grub damaged turf is showing up all over. If it seems like those dead spots are getting bigger, you're right. Grub activity in the spring can cause major damage. Those little spots from last fall are not so little anymore. Although proper irrigation, fertilization and mowing height can limit the effect of grub feeding in a healthy lawn, this does little to comfort us when the grubs have taken over and the grass starts dying.
Stopping damage in the spring: There are many products available for sale at garden centers and other retail outlets. Only carbaryl (Sevin) or trichlorfon (Dylox) will work well when applied in the spring (from March to mid-May). These products stop feeding activity so you can start to re-establish the damaged areas. These products will not prevent future feeding (like this fall or next spring).
Preventing future damage: As previously mentioned, a vigorous lawn with deep roots will tolerate a lot of feeding before damage appears. However, once the grubs have made their presence known, the memory of the damage can be a powerful motivator. Season-long products must be applied before the damage appears. The next generation of grubs will get started in July and August, therefore the application of most season-long products should occur in early-to-mid July. Products containing imidacloprid, thiamethoxam, clothianidin, or halofenazide should be applied in mid-July.
New Ingredient in GrubEx needs to be applied in May: There is a new active ingredient called chlorantraniliprole that is also very effective in preventing grub problems, but it is less water soluble than the preventive compounds mentioned above. Since it takes quite a bit longer to move down to where the grubs will be, it is best to apply a product containing chorantraniliprole in late April or early May for it to be most effective when the grubs hatch in July and Aug.
Terry Davis, MSU Entomologist, has put together an excellent article summarizing the products you are likely to encounter at the retail stores. Check out his Homelawn Grub Control Products - 2011 here.