Management & Crop Development Bulletin • No. 21 / August 14, 1998

UPCOMING

Come Take Part in Agronomy Day!

Don’t forget about the 42nd consecutive Agronomy Day, scheduled for Au- gust 27. The program will be held at the Crop Sciences Research and Educa- tion Center (South Farms) on the University of Illinois campus. The theme for this year’s event is “Agricultural Information: Seeds for Success.” Par- ticipants will be able to select those presentations of most interest to them. Four separate tours are planned and include the following topics: Tour A— Seeds for Your Needs, Sclerotinia Stem Rot of , Corn Rootworms, Planting Depth in Corn, To Bt or Not to Bt?; Tour B—Fall Strip Till and Cross-Slot Planters, Wheat Scab, Expanding Our Family Tree, Soybean Cyst Nematode, Do Soybeans Need Nitrogen?; Tour C—Herbicide Resistant Weeds, Weed/Crop Competition, Controlling Problem Weeds, FOR IMMEDIATE RELEASE Herbicide Carryover, Smart Sprayer; and Tour D—Soil Compaction, Con- No. 21 / August 14, 1998 trolling Feedlot Runoff, Automatic Guidance, A Neural Network to Predict Yield, and Reducing Spray Drift. In addition to the tours, many displays will be featured beneath the “big Executive editor: Kevin Steffey, Extension Entomologist top.” Tent displays will include AgrAbility and General Farm Safety, Global Soy Forum 99, Off-Campus Graduate Studies in Crop Sciences, Using Web subscriptions available: Benchmarks to Analyze the Financial and Production Efficiency of Your http://www.ag.uiuc.edu/cespubs/pest/ Farm Business, Soybean Cyst Nematode, Crop Sciences Extension on the For subscription information, phone Internet, Isolation of Chemoprotective Chemicals from Soybean Processing 217.244.5166, or e-mail By-Products, the Illinois Society of Professional Farm Managers and Rural [email protected] Appraisers, Plant Clinic, Pesticide Safety Education in Illinois, Solar Power for Remote Locations, and the Illinois Council on Food and Agricultural Research.

In This Issue As you can see, we have a diverse program available for you. Plan to join us for coffee bright and early at 7 a.m. After the tours have concluded, a lunch ❏ Come Take Part in Agronomy will be served. See you on August 27th! Day! 195 ❏ Prepare for Soybean Pod Mike Gray, ([email protected]) Extension Entomology, (217)333-6652 Feeders, 195 ❏ Update on European Corn Borers, 197 ❏ Yellowstriped Armyworms, Anyone? 197 ❏ Section 18 for Tilt, 198 Prepare for Soybean Pod Feeders

In last week’s Bulletin (no. 20, August 7), Kevin Steffey focused on soybean Next issue: August 28 defoliation. As we move into the latter half of August and into early Septem- ber, our attention turns toward soybean pod feeders. Bean leaf beetles, grass- hoppers, and stink bugs are all capable of inflicting yield losses to soybeans during the pod-fill stage of development.

195 Pest Management & Crop Development Bulletin • No. 21 / August 14, 1998

Holes small and rounded; Pods with numerous yellow or red colors and short, stubby, mostly within the intervenal scars on pericarp; areas of the leaf injury seldom extended nonfunctional wing pads. The adults into seed chambers are large (about 5/8-inch long), light green, shield-shaped bugs with fully developed wings. Both adults and nymphs have piercing and sucking mouthparts for removing plant fluids. Stink bugs feed directly on pods and seeds; however, their injury is difficult to assess because their mouthparts leave no obvious feeding scars. Stink Figure 1. Bean leaf beetle defoliation and pod injury. bugs use their mouthparts to penetrate pods and puncture the developing The last generation of bean leaf be the most important pod feeders in seeds (Figure 4). They inject digestive beetles will begin to feed on soybean the state. Watching for stink bugs, enzymes into seeds, and the feeding pods after the leaves become too old especially in the southern half of the wound provides an avenue for dis- (begin to lose some green coloration). state, should be a high priority for eases to gain entry into the pod. Seed The beetles scrape off the green tissue soybean producers. quality is also reduced by stink bug on the pods (Figure 1) but do not chew feeding, and beans are more likely to through the pod wall. The resulting Green stink bugs are believed to mi- deteriorate in storage. scars on the pods provide an opening grate northward from overwintering for entry of spores of various fungal sites (wooded areas under leaf litter) Other species of stink bugs also occur diseases that are normally blocked by as adults. During the early months of in soybeans. The brown stink bug has the pericarp. Mild infection results in summer, the adults feed on berries in feeding habits and a biology similar to seed staining; severe infection may trees, especially dogwoods. Stink bugs those of the green stink bug. The result in total seed contamination. are first found in soybean fields during brown stink bug should not be con- August. They undergo incomplete fused with the beneficial spined sol- Grasshoppers cause more direct injury (immature bugs re- dier bug. These two species can be to the soybean seeds. Because they semble the adults), which requires distinguished from each other if you have strong chewing mouthparts, roughly 45 days from egg hatch to look at the feeding beak and underside grasshoppers often chew directly (Fig- adult emergence (Figure 3). There is of the abdomen. The beak of the ure 2) through the pod wall and take usually only one generation of green brown stink bug is slender and embed- bites out of or devour entire seeds. If stink bugs per year in Illinois. ded between the lateral parts of the more than 5 to 10 percent of the pods head. The base of the beak of the are injured by grasshoppers or bean Immature stink bugs (nymphs) have a is stout and free leaf beetles, an insecticide application flashy display of black, green, and may be warranted.

Most individuals tend to overlook stink bugs and the potential injury they can cause, even though they may

Seed destroyed by insects feeding externally

Figure 2. Grasshopper injury to soybean pods. Figure 3. Life cycle of a stink bug.

196 Pest Management & Crop Development Bulletin • No. 21 / August 14, 1998

Pods not formed normally; during the first week of August. How- one or more seeds aborted ever, the captures dropped to zero on Yellowstriped Armyworms, or pods completely collapsed August 10. In addition, Maria Venditti, Anyone? my graduate student, and her crew With so much late-planted corn in the Constricted found several freshly deposited egg state this year, none of us was sur- masses in some corn fields in prised when fall armyworms reared Sangamon County on August 5. their ugly heads, especially in south- Although this slight increase in corn ern Illinois. Well, a “cousin” of the fall borer activity this late in the summer armyworm, the more attractive is somewhat surprising, we doubt that yellow-striped armyworm, has also this “blip” represents anything signifi- appeared this year. John Shaw ob- cant for field corn. However, we served that one of his trials wanted to let you know that people are in Champaign County is heavily in- fested. Therefore, we assume that this Collapsed pod Normal pod still monitoring for corn borers. We have received no reports of any sig- infrequent pest also may be present elsewhere. Figure 4. Stink bug injury to soybean pods. nificant corn borer activity anywhere else in the state. Like the fall armyworm, the yellow- striped armyworm is a tropical and from the lateral parts. In addition, the Scouting guidelines and management subtropical species that migrates spined soldier bug has a dark round suggestions were offered in last northward as weather conditions per- spot located centrally on the underside week’s issue (no. 20, August 7, 1998) mit. When they arrive, the females of its abdomen (belly). Be sure you of the Bulletin. Although the threat deposit eggs, which are covered with are aware of the species present in a posed by second- or even third-gen- the female’s body scales, in irregular soybean field before making a control eration (southern Illinois) corn borers masses on plant foliage. As soon as decision. seems insignificant right now, contin- ued vigilance will do no harm. Larvae the eggs hatch, young larvae begin An insecticide application for control that infest more mature corn cause less feeding on the leaves. The mature of stink bugs may be warranted when physiological damage than larvae that yellowstriped armyworm is 1 to the level of infestation reaches one attack earlier in the season, but stalk 1-2/5 inches long and glossy black to adult bug or large nymph per foot of breakage and ear drop are always gray, with dark triangular spots along row during pod fill. Suggested insecti- concerns. Recall 1997. the midline of the back. A yellow- cides are Asana XL at 5.8 to 9.6 stripe is evident along each side of the ounces per acre, Lorsban 4E at 2 pints Densities of European corn borers in triangular spots, and there is a black per acre, Penncap-M at 1 to 3 pints per 1998 will be among the lowest densi- spot above the hind legs. The head is acre, and Warrior 1EC at 3.2 to 3.84 ties we have recorded in the past sev- brown, with a netlike pattern. Among ounces per acre. Use of Asana, eral years. The weather this year un- caterpillars that feed on corn, yellow- Penncap-M, and Warrior is restricted doubtedly had a profound effect on striped armyworms are one of the to certified applicators only. survival of corn borers, emphasizing prettiest. (Maybe you have to be an once again that densities of corn bor- entomologist to appreciate this.) Mike Gray ([email protected]) Exten- ers during any given year cannot be sion Entomology, (217)333-6652 relied upon to predict what might Yellowstriped armyworms are occa- happen the next year. Last year’s sional pests of corn, usually feeding widespread and intense infestations of on the leaves of young corn plants or Update on European Corn corn borers were followed this year by in the whorl. Moderate infestations are Borers infrequent occurrences of corn borers. not harmful, as long as the growing The reverse could be true in 1999: The point of the plant is not injured. Con- Although the numbers are not large, low numbers of overwintering larvae trol with insecticides is not economi- captures of European corn borer could turn into heavy infestations of cal unless feeding would cause heavy in at least one trap in Champaign first- and/or second-generation corn damage. increased recently. John Shaw, coordi- borers if survival is good and the nator of the Management and Kevin Steffey ([email protected]), Ex- weather is more agreeable. Conse- tension Entomology, (217)333-6652 Insecticide Evaluation Program at the quently, farmers who are considering Illinois Natural History Survey, re- whether or not to invest in Bt-corn ported that captures in his light need to keep this in mind. trap recently increased from 1 to 2 per night to more than 10 to 20 per night Kevin Steffey ([email protected]), Ex- tension Entomology, (217)333-6652

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PLANT DISEASES Therefore, Tilt applications made very late probably have minimal impact. Producers should scout fields and Section 18 for Tilt choose those with highest yield poten- tial, greater disease susceptibility, or a The State of Illinois has received a past history of gray leaf spot prob- The Pest Management & Crop Development Bulletin is brought to you Section 18 label for Tilt fungicide on lems. Tilt should not be applied to corn for control of gray leaf spot by the Cooperative Extension Service every field. and Information Technology and Communication (GLS) and rust, to be applied post- Services, silk. This label is in effect only until Following are the guidelines for the College of Agricultural, Consumer August 25, and all applications must Tilt label: and Environmental Sciences, be made on or before that date. University of Illinois at Urbana-Champaign; The Illinois Department of Agriculture and the Natural History Survey, Urbana, IL. Tilt fungicide is designed to preserve has declared a crisis exemption under This newsletter is edited by Mary Overmier yields in the presence of disease; it Section 18 of the Federal Insecticide, and formatted by Oneda VanDyke, does not improve plant performance if Fungicide, and Rodenticide Act for the ACES/ITCS. diseases are not present. The basic use of Tilt Fungicide (propiconazole) guideline is that Tilt is most effective to control gray leaf spot and rust in on susceptible hybrids showing le- corn in Illinois. The effective dates are sions at or above the ear leaf following from 12:01 a.m. August 10, 1998 to tasseling. If plants are 6 weeks past 11:59 p.m. August 25, 1998. The ap- Helping You Put Knowledge to Work tasseling, then the effect from Tilt is plication rate shall be 4 fl. oz. per acre State • County • Local Groups U.S. Department of Agriculture Cooperating minimal. Research studies by Dr. with no more than 12 ounces per sea- The Cooperative Extension Service provides equal Hooker here with northern corn leaf son and a 30 day preharvest interval.” opportunities in programs and employment. blight demonstrated that leaf diseases cause the most loss if the upper leaves Walker Kirby ([email protected]. edu), Extension Plant Pathology, are infected either before tasseling or (217)333-8414 no later than 6 weeks post-tasseling. 198