from The Ohio State University Extension Newsletter
November 10-26, 2003
C.O.R.N. 2003-38

Seed Treatments in Corn - Eisley & Hammond

There has been a lot of interest this past summer about the new seed treatment insecticides Cruiser and Poncho. Cruiser (thiamethoxam) was labeled on corn last fall and Poncho (clothianidin) was labeled this past spring. The crops and insects they are labeled on depend on the amount of material applied to the seed. The crops and insects are as follows:

1 - Cruiser 5FS @ low rate (0.125 to 0.8 mg ai/seed) is labeled on field, sweet, pop and seed corn and the insects chinch bug, cutworms (suppression), flea beetles, seedcorn maggot, southern corn leaf beetle, white grubs and wireworms.

2 - Cruiser 5FS @ high rate (1.25 mg ai/seed) is labeled on field corn only and in addition to the above insects also has billbugs, corn rootworms (light to moderate infestations) on the label.

3 - Poncho 250 @ low rate (0.25 mg ai/seed) is labeled on field, sweet and pop corn and the insects chinch bug, corn flea beetle, corn leaf aphid, cutworm (black), grape colaspis, seedcorn maggot, southern corn leaf beetle, southern green stink bug, white grubs (including European chafer larvae, May/June beetle larvae, Japanese beetle larvae), thrips and wireworms.

4 - Poncho 1250 @ high rate (1.25 mg ai/seed) is labeled on field, sweet and pop corn and in addition to the insects listed above also has corn rootworms (northern, western, southern and Mexican) and southern corn billbug on the label.

The question that is being asked at this time is whether or not the seed applied insecticides are needed and how well they will perform against some of the insects. We do not have information about how these seed treatments perform against many of these insects nor do we have some of these insects in Ohio. However, several trials were performed this past summer to evaluate the seed treatments against a couple of pests and to determine where, when and if the seed applied insecticides are needed.

Two trials were conducted to evaluate Cruiser and Poncho against seedcorn maggot (SCM). The plot area was in alfalfa, disked the latter part of April and left to lay for 2 weeks so that SCM adults would lay their eggs. In one trial, seed treated with 3 rates of Cruiser (0.125, 0.25 and 0.50 mg ai/seed) and a single rate of Gaucho was planted into the alfalfa plot area. The Cruiser treated seed resulted in significantly better stand and yield than the untreated check. The second SCM trial evaluated Poncho 250, the hopper box seed treatment Agrox Premiere, Gaucho and the granular soil insecticide Aztec 2.1G. All of the insecticide treatments resulted in significantly better stands and yield than the untreated check.

Another trial was conducted to determine whether corn planted at various times during the spring would benefit from the use of seed applied insecticides. The area, in soybeans in 2002, was sprayed with herbicides in the fall of 2002 to kill any winter annuals and did not have any known insect problems. Plantings were made on April 24, April 30 and May 22. The April 24 planting had the treatments of Cruiser @ 0.25 mg ai/seed, Gaucho @ 0.16 mg ai/seed and Poncho 250 @ 0.25 mg ai/seed. The April 30 and May 22 plantings contained Cruiser, Gaucho, Poncho and the hopper seed treatment Agrox Premiere. There were no significant differences in stand or yields with any of the treatments. Thus in this case there wasn't any benefit from using a seed treatment even though some of the plantings were made early in the season.

Two trials were established to evaluate Cruiser, Poncho and other insecticides and YieldGard Rootworm hybrids against corn rootworm larvae. Cruiser was applied at 1.25 mg ai/seed and Poncho was applied at 1.25 mg ai/seed. The corn rootworm populations were low in these 2 trials (2.8 and 2.6 root rating on a 1-6 scale in the untreated, 3 is considered economic) and all of the treatments had significantly lower root ratings than the untreated. However, there were no significant differences in yield between the treatments and the untreated. The seed treatments have done a good job in our trials against rootworm but the pressure has been low to moderate. However other states indicate that the seed treatments may not hold up under heavy rootworm pressure.

Two trials were planted side by side into an area that had been in wheat in 2002 at the Northwestern Branch of OARDC near Hoytville, Ohio. Two different hybrids were planted in this trial. The treatments included Gaucho, Cruiser @ 0.25 mg ai/seed, Poncho 250, and Poncho 1250. Although there were no differences in stand in the two trials the Poncho 1250 had a significantly higher yield in one of the trials.

The bottom line is that we need to determine where the new seed applied insecticides fit into a farming operation. Each field needs to be looked at individually and a treatment regiment decided for that field. If a field has benefited with the use of a seed treatment in the past, then one should probably be use now. However, if a seed treatment has not been used in the past, a grower should ask if there a need to use them now? We do know that a field with a history of insects such as wireworms or fields that may have seedcorn maggot problems, will benefit from a seed treatment. Additionally, Cruiser and Poncho could also be used to control rootworm in Ohio because our rootworm pressure tend to be normally low to moderate even under long-term continuous corn. However, there are still a lot of questions about where and when to use these new seed treatment insecticides, and hopefully we will be able to answer these questions in the future.