Vermont vegetable pest alerts from the UVM Plant Diagnostic Clinic

Onion leek moth - still getting lots of reports, mainly from home gardeners but be on the lookout. There are 3 different flights of the adults so you can have all life stages going at once. We are probably at the second flight of adults. Pupae are distinctive with a net-like covering (sort of like diamond-back moth larvae on brassicas.) More information:

Brassicas - Lots of rhizoctonia wirestem samples in the lab. If plants are struggling, look at the root and lower stem to see if it has that ‘wirestem’ appearance. This happened earlier in the season during wet/cool conditions, but plants are showing symptoms now due to stress of no roots. More information:

Look for Swede midge damage-rotting growing points (maggots feed and soft rotting bacteria move in), scarring on leaf edges and petioles. More information:

Tomato - not seeing any leaf spots yet, but I suspect they show up this week with all the rain last week. Keep up fertility to ‘outrun’ the disease, rotate, use mulches, regular fungicides to slow the spread. Late blight reported in NY on Long Island on potato. Hot dry weather slows the disease. To track use Leaf mold (Fulvia fulvia) seen in high tunnel tomatoes due to high humidity. Keep below 85% rh. Roll up sides, open ends, use fans, prune lower leaves and use resistant plants. More information:

Corn - 3 European corn borers trapped in CH co. VT. Caterpillar infestations are likely going up in pre-tassel corn this week, so scout. Infestations will vary from field to field but some fields are over the 15% threshold. Treatment may be most effective as tassels emerge so as to target the more exposed caterpillars feeding in the tassel or moving down the stalk. For more details on sweet corn pest ID, monitoring and management see the online edition of the Sweet Corn Insect Management Field Scouting Guide, page 21.

Cucurbits - Squash Vine Borer moths (UMASS Veg notes) have been captured in pheromone traps in CH co. VT. UMASS recommends spraying when 1 moth found per trap if you are organic. This pest is very site specific. Wilting plants are usually seen in July/Aug. Check base of plants for frass and feeding damage.

Downy mildew is not in the area yet and is still in southern US. This fungus blows up on storm fronts like late blight and potato leafhopper. Crops infected this year include: butternut, acorn squash, giant pumpkin, cucumber, cantaloupe, watermelon, and summer squash. We often see it wipe out the last planting of cucumbers in VT. The current CDM forecast indicates a low risk for Southern New England. You can track the disease here

Three lined potato beetle are now hatching along with Colorado potato beetle on potato, however, they prefer feeding on husk cherries and tomatillos and are generally not damaging in potato. Treatment is similar to CPB. Larvae are distinctive because they carry feces on their backs.

For more pest/disease info go to


Ann Hazelrigg