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
Potato leafhoppers, thrips and spider mites
What wild weather we’ve had this year. It has gone from too wet to too dry in a matter of weeks! Young crops and only a little canopy, a few pests could quickly become a problem. Especially if hot dry conditions continue to stress the crop further. Scout fields frequently for these three pests; Potato leafhoppers, thrips and spider mites.
Potato leafhoppers (PLH) are in high numbers in many counties. Both dry beans and forages are at risk. Scouting information and thresholds are available here: https://fieldcropnews.com/2017/06/leafhopper-alert/
Thrips are starting to show up in some corn and soybean fields. They are usually not a concern unless the crop is young and stressed from hot dry conditions and can’t produce new leaves quickly to compensate. Thrips are tiny cigar shaped insects that feed on individual plant cells on the underside of the leaves and cause a mottling appearance on the upper leaf surface, usually along the leaf veins. You should use a hand lens to look for thrips on the underside of the leaves. Injury rarely justifies spraying unless the plants are not growing out of the injury. Scout new leaves in 20 areas of the field. If 75 per cent of the plants scouted have injury on the newest leaves and/or there are eight or more thrips per leaf, spray may be warranted. Rain can help the plants grow out of the injury, so hold off on spraying if rain is forecasted and scout again a few days after the rain to see if the plants are growing out of the injury.
Spider mites are starting to show up on time, but crops are a lot younger than usual. Soybeans, dry beans and even corn are at risk. Similar to thrip damage, they too feed on the individual plant cells on the underside of the leaves. Upper leaf surface becomes stippled and eventually dies and falls off the plant. Scout field edges first and look for signs of plants starting to yellow or bronze. Shake injured leaves on a piece of paper to confirm that mites are present.
Action Threshold for beans and soybeans: four mites per leaflet or one severely infested plant. Rain can help knock populations down so re-scout after a rain event before deciding to spray.
Dimethoate (Cygon/Lagon) is the only product registered for spider mites on soybeans and edible beans. DO NOT use Matador, it does not control spider mite and will kill beneficial insects which include ladybird beetle, thrips, and predaceous mites.
As always, more information on scouting and control options are available in the Pest Manager app – https://gfo.ca/about/mobile-apps/, or Agronomy Guide and the Field Crop Protection Guide. http://www.omafra.gov.on.ca/english/crops/pub811/pub811ch15.pdf
Written by the Tracey Baute, Entomologist-Field Crops, OMAFRA
For list of all Ontario Fairs, please visit the Ontario Association of Agricultural Societies (OAAS) website – https://ontariofairs.com/
July 26 to 28 Zurich Country Fair – 15 East St, Zurich, Ontario. For more information please visit website www.zurichcountryfair.com or phone 519-868-4725.
Aug. 9 to 11 Dungannon’s Little Country Fair – 36897 Dungannon Rd, Dungannon, Ontario. For more information please visit website www.dungannonagsociety.com or phone 519-525-9207.
Aug. 9 to 11 Drayton Fair – 49 Elm St, Drayton, Ontario. For more information please visit website www.draytonfair.com or phone 519-638-3323.
Aug. 9 to 11 Hanover Fair – 265 5th St, Hanover, Ontario. For more information please visit website www.hanoverfair.ca or phone 519-364-4443.
Aug. 16 to 18 Bayfield Fair – 16 John Ave, Bayfield, Ontario. For more information please visit website www.bayfieldfair.ca or phone 519-440-1252.
Aug. 16 to 17 Mount Forest Fall Fair – 320 King Street East, Mount Forest, Ontario. For more information please visit website www.mfagriculturalsociety.weebly.com or phone 519-323-1659.