Issue No. 20, Article 6/August 6, 2004
We have received very few reports of crop pests over the last week throughout the region. Soybean aphid numbers per field continue to be few to nonexistent. The corn crop has benefited from the mostly moderate temperatures experienced from pollination through August 1, with only a few scattered stressful temperature days. An exception is cornfields on some lighter soils; they were beginning to show moisture stress, but the region received widespread precipitation on August 3.
The workshop "Diseases, Invasive Species, and Crop Management Issues" will be held on August 25 beginning at 8:30 a.m. at the U of I Northern Illinois Agronomy Research Center, Shabbona. Reservations are due by August 16 to Dave Feltes, Quad Cities Extension Center, (309)792-2500. For more details, refer to last week's issue of the Bulletin (issue no. 19, July 30, 2004).
Almost all corn is in the dough or early dent stage (R4 to R5). Overall, it is in excellent condition, though gray leaf spot can be easily found on susceptible hybrids. Rainfall has been adequate across the region, and sunny days with warm temperatures bode well for high-yield potential.
Soybean also looks excellent, with only scattered reports of sudden death syndrome to date. Many fields are showing the presence of late flushes of waterhemp and giant ragweed where sequential ap-plications of herbicide were not made.
Now is an excellent time to apply nitrogen to tall fescue pastures in order to stockpile forage for deferred grazing later on in the winter.
The main interest continues to be the variant "first-year" western corn rootworm. Yellow sticky traps have been distributed in various parts of the region. The numbers of beetles captured on sticky traps, especially in the areas that previously "bordered the variant problem," appear to be impressive as we begin the trapping period. The intensity of captures in some areas has led individuals to again explore the use of insecticide in beans in an effort to reduce next year's rootworm pressure. While the apprehension is understandable, we continue to discourage this practice, noting mobility of the variant and concern for the environment. How far west has the variant western corn rootworm problem now reached? U of I educators have been collecting roots from first-year cornfields throughout the west-central region in an effort to answer that question.
Sudden death syndrome continues to be the topic of soybean field discussions. Symptomology in some fields has already shifted from chlorotic to necrotic lesions. The southern portion of our region appears to have developed the most extensive symptoms to date, with substantial yield penalties expected in the most "progressed" SDS fields. We continue to note later-season root rots. Potato leafhoppers continue to be sprayed in various areas, having developed exceptional populations in some newly cut alfalfa fields.