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| Agriphones and Crop Updates Index Page |
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Sweet Corn, Bean and Pea Edition
Spraying for Pea Diseases Monitoring for Corn Earworm New Matador Rate in Sweet Corn European Corn Borer - Accumulated Growing Degree Days Foliar diseases such as ascochyta and downy mildew can have a significant impact on the yield and harvest ability of the pea crop. When it comes to fungicides, timing is crucial. Fungicides are most effective when they are used preventatively. Waiting until a significant infection has occurred, or timing a spray to coincide with the pre-harvest interval will likely result in poor results. From a control standpoint, the pre-harvest interval is not an indication of the appropriate time to spray a product; it is strictly a method to mange residue limits in the harvest product. The economics of the pea crop is unlikely to justify a routine, preventative fungicide program. The goal is to suppress any potential infections and keep them in lower canopy, away from the pods. Be aware of the weather conditions during early bloom. If the 7-day forecast is calling for cool, wet weather, this is a good indication that disease problems may begin to develop. A fungicide application at this time may help to suppress any developing outbreaks thereby preventing later pod-infections or “sliming-off” of the crop as it approaches harvest. If the weather conditions continue, scout the field within 7 days of the fungicide application to determine if a second spray will be necessary. Keep in mind that if a foliar disease is present in the crop prior to bloom, it is still advisable to apply a control as soon as it is identified.
Figures 1 and 2; Downy Mildew on Pea Leaves at Bloom Corn earworm adults typically begin to arrive in Southwestern Ontario in early July to early August. The timing and severity of the flights is impossible to predict from year to year. Adults from the Southern US become airborne and travel for long distances on the prevailing winds. Flights often occur during summer storms. Weather fronts originating in the south and mid-west are of particular interest when tracking earworm activity. Trap count reports from locations across the US are available on the Penn State University website: http://www.pestwatch.psu.edu/sweetcorn/tool/tool.html. The best way to track corn earworm populations is with pheromone trapping. The hartstack trap is the most effective trap type. It will consistently catch 3 times more moths than a mesh heliothis trap. Unfortunately hartstack traps are not readily available commercially and can be expensive to manufacture. Growers interested in building hartstack traps can contact OMAFRA for instructions (elaine.roddy@ontario.ca or 519 674 1616).
New Matador Rate in Sweet Corn The rate of Matador rate to control European corn borer and corn earworm in sweet corn has been increased to 187 mL/ha (77mL/ac). This should help to improve the control of European corn borer; however the spray timing is essential. Delayed applications are the most common source of control failures. European corn borer insecticides should be applied at the mid-whorl stage when feeding injury or eggs masses exceed the 5% threshold. Scout corn regularly as soon as it reaches the mid-whorl stage. Control measures must be taken before the young larvae begin to bore into the leaf veins and stalk. European Corn Borer - Accumulated Growing Degree Days Bivoltine European Corn Borer adults emerge from the overwintering pupae at 150 GGD. Peak moth flights for the first generation bivoltine occur at 300-350 GDD. Second generation adults usually emerge at 700 GDD. In the univoltine areas the first moths usually emerge at 300 GDD with peak flights occurring at 650-700 GDD.
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