There are a few pests to keep an eye on over the next few weeks.
Western Bean Cutworm
We likely reached peak moth flight either last week for most of the southern counties or this week for the rest of the province, except Northern Ontario, based on the Degree Day Prediction Model and trap counts in the Great Lakes and Maritimes Pest Monitoring Network.
WBC Threshold and Management in Corn
Scout at least 100 plants (20 plants in 5 areas of the field) every five days and target fields or areas within each field that are in the pre-tassel to full tassel stages. Scout a minimum of three scouting events before, during and after peak flight during pre-tassel to R2 stage corn to determine if threshold has been reached. If 5% of the plants scouted across the two or three scouting events have egg masses on them, a spray is recommended. Target the application to when the majority of the egg masses are about to or recently hatched but no later than R3 stage corn.
Time insecticide application to when fresh silks (R1) are present, but prior to silks turning brown (R3). Direct the spray at the ear zone for maximum effectiveness. Research has found that most WBC insecticides provide up to two weeks of protection after application. Tankmix insecticides with fungicides that target ear moulds and time application close to R2 stage for the best protection against both WBC and ear moulds. Registered insecticides for WBC in corn can be found here: Western Bean Cutworm Chemical Control Options (Crop Protection Hub)
WBC Threshold and Management in Dry Beans
WBC are nearly impossible to find in any stage in dry beans. If WBC has reached threshold in the neighbouring corn field, then adjacent dry edible bean fields are likely at risk, especially if the corn fields have passed the pre-tassel stage. If entry holes are observed in the pods prior to R6 stage (seed development), an insecticide application is necessary. Spraying insecticide for western bean cutworm (WBC) control in Ontario dry bean fields is warranted only if ALL of the following criteria are met.
- At least 150 moths have been captured in a trap at the field.
- Peak moth flight has passed, and the number of moths caught in traps is starting to decline.
- There are pods on the plants.
- You can find pod damage.
A reminder that only Coragen and Coragen Max are available for use in dry beans since all lambda-cyhalothrin products can not be used in field crops.
Corn Leaf Aphids
A large flush of corn leaf aphids have blown in from southern US states. Many states and provinces in the Great Lakes region are finding relatively high numbers in corn and other crops. Corn leaf aphids rarely reach threshold in Ontario. In droughty conditions, tassels may become gummy, causing poor pollination. Given much of Ontario has experienced some or too much rain, this risk is very low. Only if 50% of all plants have 400 aphids per plant during the first half of pollination, and plants are under moisture stress, is control warranted. Control is not warranted once the corn is past the first half of pollination. Natural enemies have been spotted coming into fields to feed on the aphids and can reduce the population in a matter of days.
Corn Rootworm
Corn rootworm adults are starting to build in some fields to the point that some are concerned about silk clipping. Field corn can withstand heavy adult activity, usually requiring at least 10 adults per ear before control is necessary, but seed corn may require control if adult populations are causing extensive silk clipping, disrupting pollination. Dry conditions may keep the plants from growing more silk to compensate for the feeding injury. Foliar treatment is warranted when the silks are on average being clipped down daily to within 1.25 cm (1/2 in.) of the ear tip. After 50% pollination is complete, beetle feeding no longer poses a threat to yield.
Soybean Pests – Soybean aphids and spider mites are popping up or increasing in some fields. Stay tuned for details on those pests in next week’s Crop Report.