1969 ASSESSMENT OF BLACKBIRD DEPREDATIONS ON FIELD CORN IN OHIO AND MICHIGAN

In 1966, when the annual damage survey was initiated, Dr. C. R. Weaver, Statistician at the Ohio Agriculture Research and Development Center, Wooster, Ohio, drew up a sampling plan, balancing costs against desired precision. The plan included three combinations of fields to be sampled and stations per field for high damage areas, three combinations for moderate damage areas, and two combinations for light damage areas. Alternatives for the high damage area included (1) 497 fields with two stations per field (± .48), (2) 775 fields with two stations per field (± .26), and (3) 235 fields with ten stations per field (— .68). For the moderate damage areas, the alternatives were (1) 441 fields with three stations per field (± .26), (2) 155 fields with three stations per field (± .50), and (3) 235 fields with ten stations per field (± .32). The light dam¬age area alternatives were (1) 297 fields with three stations per field (- .26), and (2) 81 fields with three stations per field (± .50). The original survey in 1966 sampled eight counties in three regions. In 1967, 14 counties in the same three regions were sampled. Two new counties were added to one region and two new regions with two counties each (treated as one region for sampling purposes) were added to the 1968 survey. The 1968 survey was of sufficient size to be representative of the corn damage picture in Ohio and Southeast Michigan. The 1969 survey was identical to the 1968 survey.

G93-1167 Spider Mite Management in Corn and Soybeans

This NebGuide describes the two common spider mites found in Nebraska corn and soybeans, their natural enemies and management. Two species of spider mites, the Banks grass mite and twospotted spider mite, commonly feed on Nebraska corn. Banks grass mites (BGM) feed almost exclusively on grasses, including corn and sorghum. Twospotted spider mites (TSM) not only feed on many species of grasses, but also on soybeans, fruit trees and a variety of vegetables and ornamental plants. Although these two species are somewhat similar in appearance, they differ in several biological characteristics and in their susceptibility to pesticides. Banks grass mites usually appear earlier in the season, feed mostly on the lower leaves of the corn plant, and in Nebraska are moderately susceptible to many of the commonly used miticides. On the other hand, TSM tend to appear in mid to late season, increase rapidly, feed over the entire plant, and often are not consistently controlled by available pesticides.