You Are Here: Management Updates 2000 Archive April 12, 2000

Date: April 12, 2000
Category: Insects
Subject: What's What With Spring Grub Control?

Some suppliers are marketing grub materials that imply "season long" grub control and are suggesting that those products should be applied now. Imidacloprid, sold as "Merit" in the commrcial market and sold in 1999 as "Grub Ex" by O. M. Scott, has been around for four years now. However, there have been some marketing decisions over the winter that have led to considerable confusion. The trade name, "Grub Ex", was retained by O. M. Scott, but Bayer, the company that produces imidacloprid, reclaimed its right to sell the product to homeowners, so now imidacloprid is available to the homeowner from Bayer in bags labelled "Advanced Lawn Season Long Grub Control Granules". (Usually the name "Merit" shows up in smaller print on the front of the label but near the bottom.)

Meanwhile O. M. Scott is continuing to use the trade name "Grub Ex" but now uses halofenozide as the active ingredient in the product. Halofenozide (also sold as "Mach 2" in the commercial market) is another product that is much more persistent than previous traditional grub materials, and the same "season long" control claim appears in some advertising.

Applications of either active ingredient (halofenozide or imidacloprid) made in April or May will not reduce grub populations that are already present in the spring. Spring applications often are persistent enough that they will reduce subsequent grub populations that start emerging in August, but turf managers should not expect spring applications to reduce spring populations.

Field trials conducted at UMass over the years and common sense indicate that imidacloprid should not be applied earlier than the first week of June in most cases, although there are some turf managers having success with earlier applications. We prefer that halofenozide applications (against grubs) not be made earlier than the first week of July. We recognize that situations vary and earlier applications of either compound can be successful, but in the greater scheme of things, we urge managers to target their applications whenever possible.

The confusion that has come about as a result of the names of the products is regrettable. So it all comes back to basics - you really do have to read the label every time! What was "Grub Ex" last year is a very different (although still very effective) material this year. Same name, different stuff....

- Submitted by: Dr. Pat Vittum