General
Production of soybeans occurs throughout the state of Illinois but is heaviest in the central and southern two-thirds of the state. Planting may begin as early as the 25th of April in Southern Illinois and the 5st of May in Northern Illinois. Soybeans are typically grown in a rotation with field corn and sometimes in a double-crop after winter-wheat is harvested. Conservation tillage practices are regularly used for soybeans and about 25 to 30 percent of the annual acreage is no-tilled. Approximately two-thirds of all soybeans are solid seeded. This eliminates the possibility of row cultivation and late season application of pesticides by ground application. The benefits of solid seeding a soybean crop is that the canopy closes quickly and can reduce weed growth and, hence the need for late season post emergence herbicides.
 
 Soybeans are used for oil and meal. A number of major processing centers are located in the central part of the state. Some soybeans are shipped to export markets. Group II and III soybeans are most commonly grown.
 
 Because most farmland is owned by landlords, the tolerance for poorly managed fields is very low. This is further exacerbated by the level terrain of much of the state and the ease with which uneven stands or weeds can be seen. This low tolerance often drives farmers to maintain exceptionally clean and aesthetic fields.
Insect Pests
Insect pests are seldom a problem in soybeans for the state of Illinois. On occasion, in extremely dry years, spider mite outbreak can result in crop injury and yield reductions. During the last such outbreak in 1992, approximately 30% of all soybeans in the state were treated for the two-spotted spider mite. Treatments for other pests listed below is extremely rare and would be for localized infestations only. Less than two percent of the soybean acreage is treated for insects in a typical year.
 
Bean Leaf Beetle(Cerotoma trifurcata)
Adults overwinter under little near fields, and as spring temperatures rise, the beetles fly into alfalfa and cover fields but do not lay eggs there. As soon as soybean seedlings emerge, the beetles leave the forage fields and colonize soybean fields. The adults feed on emerging soybean plants and lay eggs in the soil near the plants. Larvae feed and develop in the soil but cause little damage. First generation adults emerge from mid-July and peak in late July or early August, and lay eggs in soybeans. Second generation adults occur in late August and September. As soybeans mature, the beetles return to alfalfa fields, and later return to the woods to overwinter. Heavy beetle infestations can cause significant reductions in soybean stands. Economic damage results when defoliation by beetles exceeds 30% in July and August during pod fill. Fungal diseases may infect pods with beetle feeding scars, leading to seed staining or total seed contamination. When favorable conditions exist, up to 5% of soybean acres have been treated; on average, 1% or less are treated annually for been leaf beetle.
 
Grasshoppers, Differential (Melanoplus differentialis), Migratory (M. sanguinipes), Redlegged (M. femurrubrum), and Twostriped (M. bivitatus)
Grasshoppers overwinter as eggs in the soil. Nymphs hatch in the spring and feed for several weeds, usually completing their development by mid-summer. Adults feed throughout the remainder of the summer. Grasshoppers thrive during hot, dry summers when naturally occurring pathogens are suppressed, and tend to be more numerous the year after a drought.
 
Grasshoppers prefer to feed on weeds, but when these are unavailable, they will move readily into crop fields. The amount of control varies, but during outbreak years up to 11% of field edges are treated.
 
Green Cloverworm (Plathypena scabra)
Each spring, green cloverworm moths fly northward from breeding sites in the South. The adult females lay eggs on soybean plants. After hatching, the larvae feed on leaves and have six larval instars. Mature larvae pupate in the soil; moths emerge and begin another generation. There are several overlapping generations per year.
 
Green cloverworms are usually suppressed by natural enemies and diseases. Infestations of green cloverworm are favored by conditions that are detrimental to its predators, parasitoids and pathogens. When natural controls failed, up to 7% of soybean acres have been treated with insecticides. On average, less that 0.5% of acres are treated for green cloverworm.
 
Potato Leafhopper (Empoasca fabae)
Potato leafhoppers are carried into Illinois by prevailing spring winds off the Gulf Coast . Female leafhoppers lay eggs in stems and large leaf veins. The eggs hatch within one week, and the larvae feed on the plant. The larvae has five larval instars until adulthood. An entire generations can be completed in three weeks; there are several overlapping generations per year.
 
Potato leafhopper feeding injury is rarely economic, though hot and dry seasons may favor feeding. Most commercial varieties of soybeans were developed with pubescent leaves, which helps deter leafhopper feeding. If the winds and storm fronts are not especially strong, the prevalence off potato leafhopper in Illinois is reduced. 

Diseases

The loss of seed-treatment fungicides, with the exception of captan, would not adversely affect soybean production. Nematicides and foliar fungicides play an equally limited role in crop production. A major reason for this is that nonpesticidal management measures are equal to or better than pesticides for control of many common pathogens. A second reason is that fewer products are available when compared with herbicides or insecticides. Plant disease management has always relied more on agronomic practices than on pesticides. Thus, while it is highly unlikely that all products would lose registration, the loss of one or more would not play a highly significant role in increasing crop production costs or in decreasing yields. Since most production practices serve to reduce disease inoculum, the role of these pesticides is not as important as with other crop production chemicals. Of more importance is the need to control common pathogens for which no chemical treatments are available. The list of common pathogens previously given has many for which there are no direct controls. Thus, although crop production pesticides are important, there is a much greater need for research into alternative methods for control of these important crop production problems.
 
 Since the cost of seed-treatment fungicides rarely exceeds $2.00 per acre, these products do not contribute significantly to overall production costs. Materials such as captan ($.30/acre), thiram ($.50/acre), and carboxin ($.60/acre) provide seedling blight control at a very affordable price. When these fungicide treatments are combined with other practices, disease control is easily maintained.
 
 Soybean seed treatment usage is not as widespread as corn. Carboxin is a most widely used seed treatment, with captan and thiram as acceptable primary alternatives.
 
 It is difficult to assess the impact on soybeans of replacing any primary seed-treatment fungicide because no single leading fungicide used on soybeans plays the same role as captan does on corn. Thus, if any product were withdrawn, it is likely that one or more other compounds would be an adequate substitute.
 
 Costs of production for soybeans in the absence of seed treatments does not increase substantially, as does cost of production for corn. Costs of production were estimated to increase an average of less than 5% if all seed treatments were withdrawn. Losses if primary products were not available were similar, with less than a 5% loss expected if substitutions had to be made for the primary products.
 
 Five primary seed-treatment products were listed for soybeans. Only one, metalaxyl, has a limited spectrum of activity. All others can substitute almost equally. Thus, elimination of any of these products will have a negligible impact on soybean stand establishment. Carboxin and thiram, for example, have almost identical activity against a wide range of seedling pathogens. If they canceled registration for either, the remaining product would adequately compensate.
 
 For carboxin and metalaxyl the costs of using alternatives are actually expected to decrease, suggesting that other practices would suffice at lower costs. Metalaxyl seed treatment, for example, is expensive and effective against only two common seedling pathogens. Changes in planting time, soil preparation, and the selection of resistant soybean cultivars can completely replace the need for this product. In the case of carboxin, thiram can be used at a lower cost.
 
 However, the increases in costs for lost yield may be significant. Costs of yield reductions from stand losses for the use of alternatives to captan are expected to be about $17 million and for carboxin about $69 million. The cost of yield losses where substitutes are used for metalaxyl is estimated at $12 million and at $14.7 million for thiram.10
 
Unlike insecticides and herbicides, fungicides and nematicides are not primary methods of disease control. Most pathogens of field crops can be managed through a combination of plant resistance, crop rotation with non-hosts, high seed quality, and similar practices. For many common plant diseases (viruses, bacteria, and many fungi), no pesticides are available. Thus, the use of these materials is of less consequence than for other types of pesticides. Although there would be additional potential dollar costs if registration were canceled, only captan appears to be of major economic importance.