A weekly report prepared by the staff of the Ministry of Agriculture, Food and Rural Affairs (OMAFRA). If you require further information, regarding this report, call the Elora Resource Centre at 519-846-0941. Office hours: 8:30am to 4:30pm. For technical information, call the Agricultural Information Contact Centre at 1-877-424-1300 or visit the OMAFRA website: www.ontario.ca/omafra
Been waiting for these bean insects
There is a long way to go before we reach crop maturity and a few insects are thriving right now in late planted soybeans and dry beans.
Bean leaf beetles are a risk for both soybeans and dry beans. Reports are starting to come in of some activity at various locations. This is the first generation of adults; what comes from the overwintering generation that mated and laid eggs in the soil in late spring. They feed on leaves but this injury is less of a concern after R3. The real concern is when they start to feed on pods or clip pods off the plants, especially in IP, Food-Grade, Seed Soybeans and Dry Beans.
Defoliation is always overestimated and edge rows and top leaves will always have more feeding than the rest of the field so make sure to step at least five meters into the field before sampling leaves.
From 10 random plants nearby, pluck tri-foliates from the middle of the canopy and discard the worst and best of the three leaflets before estimating how much defoliation is on the remaining leaflet. My trick to determine how much defoliation is done is to visually push all of the holes to one end of the leaflet to determine how much is gone versus what is remaining. Do this for 5 areas of the field. Also look for any signs of pod feeding or clipped pods on the ground as you are walking the field.
Defoliation threshold: If the average defoliation taking place is 15% during R1 to R4 stage, than a spray is warranted. If the crop is in R5 or R6 stage, a spray is only warranted if defoliation is 25% or higher.
Pod feeding threshold for IP, Food Grade and Seed Soybeans: If 10% of the pods on the plants have feeding injury and the beetles are still active in the field, a spray is warranted. If pods are being clipped and found on the ground, an application is warranted if beetles are still active in the field.
For dry beans: With higher value and stringent quality standards in dry edible beans, if 5 to 8% of the pods inspected have feeding scars, control may be necessary. If pods are being clipped and found on the ground, an application is also warranted. Ensure that adults are still active in the field before a spray is applied.
Written by Tracey Baute, Entomologist-Field Crops, OMAFRA.