By Ron Hammond, Bruce Eisley
Ohio State University
We have seen almost everything in our crop fields in the way of insect pests this past year, with the possible exception of soybean aphid (which we would remind growers that we had predicted their low numbers).
Prior to getting into our winter meetings and what to expect in 2007, we thought it would be helpful to discuss what happened this past summer.
Spring was fairly normal, with problem calls received on slugs and the regular group of soil pests including seedcorn maggots and grubs. Of interest, slug problems appeared to be more numerous than normal on the eastern edge of Ohio and also around the Springfield-Dayton area. Does this mean that slugs are spreading in terms of their economic problems? We are not sure, but will keep an eye on it.
Soon after crop emergence, we began getting more calls than usual on cutworms and stalk borers on corn. Perhaps this is related to the heavier weed pressure that is occurring in field crops, perhaps because of favorable environmental conditions. The cutworm situation was of special concern because we received many calls from growers that had treated their corn with low rates of either Cruiser or Poncho and still had economic problems with cutworms in their fields. We will need to continue to examine these seed treatments as to whether they offer acceptable control of black cutworms.
During May and early June, we began receiving reports from southern states of adult armyworms being collected in high numbers. We then began trapping them in high numbers in our traps in Ohio. Soon thereafter, armyworm became a big concern in various crops including wheat, corn adjacent to wheat and corn planted into rye cover crops. Both these latter situations were severe enough to require insecticide applications.
For the first time in a quite a few years, we also saw more cereal leaf beetle, or should we say their larvae, on wheat and other cereal grasses requiring treatment in some instances. Normally this insect is held down by parasitoids; whether this is a sign of coming problems is not known. It will, however, also require further monitoring.
On alfalfa, we received the usual reports of alfalfa weevil causing problems in some areas of Ohio. Not too many problems were evident on early soybeans, although overwintering bean leaf beetles did show up in some fields.
As we moved into summer, numerous problems began, including one of the worst years for potato leafhopper on alfalfa in recent memory. It was not unusual to see completely yellow alfalfa in fields that had not been treated. Of note was that the newer, glandular-haired leafhopper resistant varieties held up very well, although in fields with extremely high leafhopper densities, the numbers exceeded the 3X treatment threshold that was established for resistant alfalfa. Even some of these fields might have benefited from a treatment. However, the resistant alfalfa performed admirably.
On other field crops, the usually cast of characters were around, including European corn borers and flea beetles on corn, defoliators on soybeans, and Japanese beetles on both.
A situation on corn that was different than normal was the higher levels of rootworm injury we saw, including more injury in corn following corn that had been treated with soil insecticides and seed treatments. This injury was then followed by higher numbers of adults feeding on silks in August.
Although we did not receive many reports of first-year corn problems, our yellow-sticky trap sampling in soybeans in August indicated some fields reached the established threshold of 5 beetles/trap/day and will need treatment for corn rootworm larva if the fields are planted to corn in 2007. Many fields did not reach the threshold and will not need to be treated for rootworm in 2007.
We are currently formulating our recommendations for rootworm control in 2007, including the use of transgenics and seed treatments in continuous and first year corn. As soon as we gather all the data from our efficacy tests and the yellow-sticky trapping in soybeans, we will publish our thoughts on 2007 in an upcoming Ohio C.O.R.N. Newsletter .
As the summer came to an end, we began receiving calls of heavier bean leaf beetle pod feeding in some late-maturing soybean fields. Although pod feeding occurs somewhere every year in Ohio, these reports suggested very high densities. This was especially evident in very late maturing fields that were still green in mid-September.
As mentioned in the first paragraph, the one pest that that did not show up at damaging levels was the soybean aphid. Populations, while present, came nowhere near the 250-per-plant threshold. However, observations so far suggest that the soybean aphid will be back next year, so keep abreast of the situation through this newsletter.
That, in a nutshell, was the season of 2006.
Two major issues for the 2007 season will be whether corn rootworms are indeed more damaging in corn following corn and first year corn, and the expected come-back of the soybean aphid. Keep reading this C.O.R.N. newsletter and attend one of extension meetings that will be held throughout the state to keep abreast of the potential insect problems and management options!
SOURCE: Ohio C.O.R.N. Newsletter, Sept. 18, 2006.
By Ron Hammond, Bruce Eisley