Crop Growth and Yield risks
Lodging can occur as a result of excessive growth promoted by above average ambient temperatures. Freeze events affect the base of the plants, increasing their susceptibility to lodging if heavy spring winds occur.
A shorter growing season, especially one characterized by a shorter grain-filling period, is likely due to these drier, warmer conditions. If drought occurs during the grain-filling period, yield loss might occur.
Nitrogen is usually applied from late January to mid-February to promote tillering. If, under warm conditions, rapid growth is observed, growers should consider a split nitrogen application. Excessive growth increases the risk of freeze damage, diseases, and lodging, all of which contribute to reduced yields.
- Select early maturing varieties, which are the best choices for warmer and drier growing season conditions.
- Split nitrogen application is recommended to avoid excessive growth.
- Plant growth regulators can be used to control growth and prevent lodging problems.
Higher Hessian fly infestations should be expected during warmer winters
(La Niña years), especially if above-average ambient temperatures occur from October through February. These infestations are typically larger on susceptible wheat varieties than on resistant ones.
Hessian flies enter dormancy with the approach of the grain-filling period. Because Hessian fly is a cool-season insect, it oversummers on the soil surface as a dormant puparium in the previous year’s wheat stubble. See Alabama Extension publication, Biology and Management of Hessian Fly in the Southeast (ANR-1069) at http://www.aces.edu/pubs/docs/A/ANR-1069.pdf.
Warmer, drier winters and springs also are associated with increased populations of grain aphids.
Grasshopper populations increase under these conditions. Chinch bugs and stinkbugs may occasionally invade wheat in the spring.
Warmer climatic conditions in the spring favor cereal leaf beetle development. Cereal leaf beetle can cause significant defoliation during the flag leaf stage, which will result in yield losses.
- Early planting should be avoided because of the risk of Hessian fly. Planting, preferably of Hessian fly–resistant varieties, should occur at the recommended date for the grower’s location.
- During these warm, dry periods, scouting for Hessian flies should also be accelerated.
- Aphid scouting and the use of insecticides are critical management tools. Seed treatments also provide protection against aphids and minimize the transmission of the barley yellow dwarf virus.
- Wheat should be scouted at heading and treated if grasshoppers are clipping heads.
- Although cereal leaf beetles are easy to control, scouting is necessary. Application of foliar insecticides to control this pest can be included with fungicide sprays if a fungicide spray is needed at the time. Insecticides applied at or before spike emergence can significantly reduce cereal leaf beetle injury.
Producers often face an increased risk of barley yellow dwarf virus outbreaks because of increased aphid populations.
Producers should also expect reduced risks of septoria and rust diseases.
Powdery mildew is more likely to occur under dry and cold conditions. The risk of powdery mildew is higher with heavily fertilized wheat and/or dense stands.
- Because February is the time of the season when aphids transmit barley yellow dwarf virus, extra scouting for these insects is even more important during this period.
- Several effective insecticide seed treatments are available to manage aphids. Seed treatments can provide protection for as long as 30 to 40 days after planting. These treatments not only reduce aphid infestations but also minimize the transmission of barley yellow dwarf virus.
- Scouting for rust and septoria should remain a standard practice even though the risk is lower under these climatic conditions.
- Powdery mildew develops on the surface of infected leaves and can easily be detected during scouting. Two fungicide applications are typically needed for control of powdery mildew. The second application should be scheduled during flowering if the disease is still active and weather conditions are favorable for disease development.