Double cropped sorghum may still have some ragworm feeding during the whorl stage (see photo). In addition, there will probably be at least one more generation of headworms and thus later planted sorghum needs to be monitored for headworms between flowering and soft dough when it is vulnerable. Also, continue monitoring for aphids as there still seems to be a pretty good mixture of greenbugs, corn leaf, yellow sugarcane, and sugarcane aphids. Some of the fields treated for headworms have reduced numbers of beneficials so they may not be there in sufficient numbers to help control these aphids. However, some of the fields sampled this week that were sprayed for headworms at least 2 weeks ago had pretty good populations of beneficials already building back up.
The situation seems about the same throughout north central Kansas with regard to insect pests. Still finding mixed populations of aphids (greenbugs, corn leaf, yellow sugarcane, and sugarcane) but beneficial insect populations (mainly green lacewings, lady beetles, parasitic wasps, and occasionally syrphid fly larvae) still remain plentiful. Headworms are also plentiful in just about every field that is not yet at soft dough. Remember, expect 5% loss/worm/head between flowering and soft dough. Chinch bugs, both adults and nymphs, are also plentiful at the base of most plants but can also be found feeding on young developing berries in the heads.
Have you noticed that your geraniums and petunias are not blooming (flowering)? Well, the “critter” or culprit causing the problem may be the caterpillar or larval stage of the tobacco budworm (Heliothis virescens). Adults are pale-green to light-brown with the forewing marked with four light wavy bands (Figure 1).
Figure 1: Tobacco budworm adult
The wingspan is approximately 38.0 mm. Adult females can lay between 500 and 1,000 eggs within 2 to 3 days. Caterpillars are 38.0 mm in length when full-grown and vary in color depending on the host plants fed upon. The caterpillars (larvae) may be black, pale brown, yellow, green, and/or red. They may also possess stripes that extend the length of the body (Figure 2).
Figure 2: Mature larva (caterpillar) of tobacco budworm
Furthermore, caterpillars may have small hairs or setae on localized sections of the body. The caterpillars tunnel into buds (Figure 3)
and feed from inside or chew flower petals, which appear ragged (Figure 4).
Figure 4: Tobacco budworm larva (caterpillar) feeding on petals of petunia flower
Damage usually increases during the growing season. Furthermore, caterpillars feeding inside flower buds on developing ovaries will destroy flowers. Be on the look-out for black fecal deposits (“caterpillar poop”) (Figure 5)
Figure 5: Black fecal deposits (“caterpillar poop”) associated with tobacco budworm larva (caterpillar) feeding
on the flower petals or on leaves below the flowers, which is a clear indication that the caterpillars are feeding. Tobacco budworm caterpillars will feed on a number of annual bedding plants besides geraniums and petunias, including: ageratum, chrysanthemum, nicotiana, snapdragon, and strawflower. Ivy geraniums may be less susceptible than other geranium types. The way to deal with tobacco budworm populations is to apply insecticides before the caterpillars tunnel into the buds using materials containing the following active ingredients: spinosad, cyfluthrin, permethrin, or bifenthrin. Be sure to thoroughly cover all plant parts as tobacco budworm caterpillars will also feed on plant leaves.
You can find more information on tobacco budworm feeding on petunia in the following article:
Davidson, N. A., M. G. Kinsey, L. E. Ehler, and G. W. Frankie. 1992. Tobacco budworm, pest of petunias, can be managed with Bt. California Agriculture 46 (July-August): 79.
–by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing
Sorghum fields checked in north central Kansas this week indicated a variety of very active pests. Fields were anywhere from whorl-stage to flowering. Regardless of the stage of plant development, 100% of the plants sampled were infested with chinch bugs. Most are still small reddish to brown or black nymphs, but there are still mating adults as well. These bugs are feeding mainly around the base of the plants.
Some plants in the boot stage have populations of corn leaf aphids feeding right at the top of the about-to-emerge heads. Occasionally, these aphids are so numerous at the point of head extension that their honeydew interferes with the head’s emergence. Fortunately, aphid populations were not found frequently enough to potentially impact yield, just an occasional plant here and there.
Most of the whorl-stage sorghum (90%) is infested with a “ragworm”. These are a combination of corn earworms, armyworms, and fall armyworms, Mr. Tom Maxwell, Extension Agent in Saline County, even found a cattail caterpillar. They are in all larval stages, but mainly smaller, from 1st to 3rd instars. Thus, they will be feeding in the whorls for another 10-21 days, and then will pupate in the soil. In approximately 7-10 days, moths will emerge and start ovipositing in sorghum, which is vulnerable from flowering to soft dough, and/or soybeans. Some early flowering plants already had “headworms” feeding in the just emerging heads.
