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I have been noticing a lot of worms in tobacco and it has been a problem most of the summer. There is still a lot of late tobacco so I bring them to your attention through this article.
The second and most damaging hornworm brood of the season is under way. On 8/11, 34 tobacco and tomato hornworm larvae and 12 eggs were found while examining 400 plants in one Fayette County research plot. Two of the larvae were over 3 inches long, the last of the first brood. They soon will burrow into the ground to spend the winter as pupae. The rest (all less than 0.5 inch long) are the beginning of the second brood which is normally most numerous between mid-August and mid-September. More eggs will be laid, so there is a lot of feeding left to be done.
Weekly field checks will allow detection of infestations that justify treatment. Look carefully at the lower surface of leaves in the upper third of groups of 5 plants at 10 randomly chosen locations in each field. Check for hornworm eggs and small larvae, and record the numbers and approximate size of the hornworms that are present.
In some cases, there can be damage, but no worms, grackles or other predators can eat them. Hornworms with white egg-like cocoons on their back are parasitized by a small wasp. These worms will not cause any more yield loss. By late August, up to 90% of the hornworm population may be parasitized.
An insecticide application is usually profitable if there is an average of 5 or more hornworms per 50 plants. Higher rates provide longer residual protection and usually are more effective against larger hornworms. Bt-based insecticides are best used when most larvae are small, but control is usually not as good against large ones.
Hornworm moths will be flying over the next 4 to 6 weeks. A single insecticide application may not provide control from topping until harvest. It is best to check for hornworms and apply a cleanup spray if necessary to prevent carrying these insects into the barn. Check the restricted entry interval (REI) and harvest interval on the insecticide label before treating.
The yellow striped armyworm can be found feeding on tobacco and many other crops. Eggs are laid in masses, so several may be found on a group of plants. They feed for about 3 weeks, full grown larvae are about 1.75 inches long, which helps to determine about how much more growing is in store for them.
Sidewall Compaction early Hurts Yields Late:
Chad Lee one of our grain specialists has sent us some information on corn yields and sidewalk compaction. As I am traveling through the county this is the biggest problem I see and I want some folks to think back as to when and how they planted and is thisgoing to happen with our yields.
Earlier in the season, we tried to warn about planting too early and the risks of sidewall compaction. They did some yield checks in a field with and without sidewall compaction.
All yield checks are from the same field.
Area 1) yield check: 161 bu/acre: no compaction found, good plant color:
Area 2) yield check: 130 bu/acre: some signs of compaction, fair plant color, occasional furrow open a little
Area 3) yield check: 80 bu/acre: furrow wide open about one-half to three-quarters inch wide and one-inch deep, sidewalls very hard, plants showing severe drought stress and N deficiency
These are yield checks from three separate areas of the field and there are no replications. The example provides an indication into how much yield loss sidewall compaction can cause. Avoiding sidewall compaction is a challenge, especially when some areas of the same field are suitable for planting and other areas are too wet.
The pressure to get something planted also makes it more difficult to wait a couple extra days, especially when planting is late and rain is in the long-term forecast.