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Soybean Growth Stage Critical to Late Season Insect Control Decisions- (John Obermeyer, Rich Edwards, and Larry Bledsoe)
Spider mites are starting to come on strong in some moisture stressed soybean fields, especially in eastern Indiana. As well, scattered reports of grasshopper damage continue to be received. Many producers seem unwilling to put any more money into this year’s crop to protect the yield potential. Many growers are convinced that these fields are beyond hope. However, the stage of development of most of these plants indicates that there is still hope for seed filling. This is especially true for those fields that received recent rains. Treatment decisions for spider mites or insect defoliators should be based on the crop’s growth stage (refer to Pest&Crop #19 and 20). Throughout the state, soybean growth is at the point considered by many to be “pretty far along.” However, this does not precisely describe stage of soybean development. Incorrectly identifying the growth stage can make the difference between unjustified pesticide applications and a considerable loss in yield. The following soybean growth stages are determined by looking at one of the four uppermost nodes on the main stem. R5 - (beginning seed) - The pods are flat because the seeds are very small (1/8'). Leaf tissue is beginning to pump photosynthates into the pod. Insect defoliation of 15-20% should be considered as economic. Remember, this is average defoliation for the whole plant! R6 - (full seed) - The pods are plump and the seeds are called “green beans” or “butter beans.” Defoliation is still of concern because seed fill is now maximizing in all pods. However, not as many photosynthates are required, so insect defoliation of 25% or greater should be considered economic. R7 - (beginning maturity) - The pods are beginning to yellow. Once a pod begins to lose its green color, no more seed fill will occur. Foliage will also begin to yellow, thus there is no need to protect the plants from spider mites or insect defoliators. See Ellsworth Christmas’ article “Drought Soybeans Still Have a Chance,” in the Agronomy Tips for further information on the status of this year’s soybean crop.
Black Moths Around the Farm– (John Obermeyer, Rich Edwards, and Larry Bledsoe) Most likely you have seen some black moths flying around farms, homes, and yards. These moths are actually mottled grayish-black and when at rest they have the shape of a stealth fighter jet. These are likely the adult green cloverworm (Noctuidae: Plathypena scabra). The slender green caterpillars feed on soybean foliage, as well as alfalfa, clover, and other leguminous plants. Normally, fungal pathogens, as well as insect parasites and predators, keep green cloverworm populations below economic levels. This year’s drier weather likely hampered these natural controls and allowed the cloverworms to increase in number. The result is lots of the black moths flying around lights and residences. These moths are only a nuisance and will not harm people, houses, or yards. The moths will pass the winter in leaf litter and/or other sheltered areas and next spring will emerge and begin egg laying in fields.
Some Reports of Corn Borer Moth Splattered Wind Shields– (John Obermeyer) European corn borer moth flights in northwestern and west central counties of Indiana. This will not be a problem for most corn, as many fields are in the milk to early dough stage of development and not very attractive to moths. It does indicate that late planted and/or late pollinating fields should be monitored for egg laying and larval activity. This is especially important in seed production fields or late market sweet corn. |
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Feeding and Grazing Restrictions for Corn and Soybean Herbicides– (Glenn Nice, Thomas Bauman, and Tom Jordan) If you do this regularly or have made the decision to use corn or soybean as a forage or to graze it there are some important things to keep in mind. If planed from the beginning, herbicide grazing, forage, and hay restrictions have been part of the planning process. However, if this has been decided after the herbicide applications, the restrictions should be investigated. The table on the next page has been adapted from the Agriliance Crop Protection Guide for 2002. |
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Soybean Sudden Death Syndrome- (Gregory Shaner)
Scott Abney, a USDA soybean pathologist at Purdue, reports that sudden death syndrome is present in a few fields and in his research plots in central and northern Indiana. Ron Blackwell, the state survey specialist, saw a field with severe SDS in Pulaksi County. The disease seems to be evident only on the most susceptible varieties at the present time. Because of widespread epidemics of SDS in the years 1998 and 2000, it is likely that soil in many fields planted to soybeans this year is infested with the SDS fungus, Fusarium solani f. sp. glycines. Even though the fungus may be in a field, SDS may not appear. Early season growing conditions and rainfall during early reproductive stages have a strong influence on the development of SDS. Fields that receive a soaking rain when the beans are flowering or filling pods are more likely to develop SDS. |
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FEARMONGER ALERT: Scout stressed Fields for Root & Stalk Rots– (Bob Nielsen)
The 2002 growing season has been anything but kind to the Indiana corn crop. The delayed planting season put the crop behind the proverbial 8-ball from day one. Various combinations of stresses (including soil compaction, corn rootworm injury to roots, initially wet soils, and eventually dry soils) subsequently affected crop development throughout the summer months. Areas of the state are still in the grip of unusually dry weather that is limiting the photosynthetic ability of the corn plant “factory” during the important grain filling period. What triggers this fearmonger alert is the fact that corn under such photosynthetic stress during grain fill tends to cannabilize and remobilize a portion of its stalk carbohydrate reserves to satisfy the physiological demands of the developing kernels. The subsequently lower stalk carbohydrate concentrations, plus the fact that root health may be suffering from the season-long stresses plus the current dry soil conditions and the limited carbohydrates available for maintenance of root tissue, increases the susceptibility of the crop to infection by various root and stalk rot organisms. The inspection techniques are simple. Where plants appear to be healthy, dig up a few plants, shake or wash off the soil from the root ball, and inspect the roots for obvious discoloration or death from root rot diseases. Split the lower stalk and look for obvious discoloration or deterioration of the inner stalk tissue. Where the plant appearance itself suspiciously suggests diseased stalk tissue, squeeze the lower stalk. If it collapses easily, you’ve got trouble. If you cannot squeeze it easily, you’re probably okay for now. Don’t forget, this and other timely information about corn can be viewed at the Chat ‘n Chew Café on the World Wide Web at <http://www.kingcorn.org/cafe>. For other information about corn, take a look at the Corn Growers’ Guidebook on the World Wide Web at <http://www.kingcorn.org/ >.Doughy Soybeans Still Have A Chance– (Ellsworth Christmas) Soybeans are entering an important growth phase. Plants are now filling pods with seeds. Unfortunately, more than two-thirds of the soybean fields aren’t getting the moisture necessary to progress normally. It depends on where you’re located in the state as to the condition of the crop. The soybeans in east central Indiana are very dry and under tremendous stress. They’re still very, very short, the plant canopy has not closed, and with the moisture stresses that we have we’re seeing quite a bit of floral — and some pod — abortion in those fields. On the other hand, west central Indiana has received good rainfall during July and the soybeans look very good at this time. We are in desperate need of 2 to 3 inches of rain within the next week for the soybeans to resume normal growth. Soybeans, like corn, need an inch of rain per week during critical growing phases. It’s not too late to turn this crop around. There is still time for the beans to flower and set pods, but we need the rains rather quickly for that to occur. If we do have adequate rain for normal growth to resume, we’re going to need the rain to carry through to at least the second week of September. We normally say August, but with the late planting of this year’s crop we need rain through the first two weeks of September to give us a reasonable yield. Yield is determined by the number of pods for a given area, the number of seeds in those pods and the weight of the seed within the pod. Stresses at reproductive stages 3 and 4 can reduce the number of pods. Stresses at reproductive stages 5 and 6 can reduce the number of seeds within the pod, and also can reduce the size of the seed. If any one of those things occurs, it’ll have a negative impact on the final yield. Dry conditions are hurting soybeans in another way. Spider mites are thriving on hot, parched crops. Farmers should monitor their fields for outbreaks. Nutrient deficiency also is a problem, some have reported a lot of fields that tend to be yellowing. Under those conditions look for two things. First of all, look for the possibility of soybean cyst nematode that may be restricting the root system, particularly if the deficiency symptoms appear to be a potassium deficiency. The other element that’s causing the yellowing is manganese deficiency. It tends to be more severe on our sandier, well-drained soils. If deficiency symptoms appear, about the only solution is an application of one pound of elemental manganese per acre, as a foliar application.Drought-Damaged Corn as Livestock Feed– (Kern Hendrix and Keith Johnson, Department of Agronomy) Hot, dry July weather is taking its toll on the corn crop in many areas of Indiana. Forage Nitrate Testing and Making Feeding Recommendations Based on the Results– (Kern S. Hendrix, Department of Animal Sciences) Several areas of Indiana have experienced lack of adequate rainfall in the early-mid summer growing season this year.
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