Welcome to the UConn Vegetable Pest Message. This message is being recorded on Thursday afternoon, July 18th, by Jude Boucher.
This message will cover:
Corn earworm
Fall armyworm
Downy Mildew on cucumbers
Watch for Downy Mildew on Basil
Late blight update
Tomato hornworm
Corn earworm
The corn earworm pressure was all over the map this week. Farms in Berlin and W. Suffield failed to capture any CEW moths after multiple checks during the last week. Another farm in W. Suffield, up by the Agawam line, captured 0.25 moths per night and is on a 6-day schedule on fresh silking corn. Farms in Wallingford, E. Hartford and Somers captured between 1 and 2 moths per night and are on a 4-day schedule.
Fall armyworm,
My scouting in W. Suffield didn’t turn up any FAW larvae in whorl or pre-tassel stage corn and traps were empty this week in Suffield and in Berlin. However, one pre-tassel stage field in Northford had 5% of the plants infested with FAW larvae and 5% infested with borer larvae. Long Island is reporting that most of their sweet corn fields are over threshold for FAW. So, remember to scout whorl and pre-tassel stage corn and spray if more than 10% of the plants are infested. If you can’t scout all your whorl plantings, concentrate your efforts on the pre-tassel stage plantings because when that tassel opens, the FAW caterpillar will make a beeline for the ear, before you can get a silk spray on for CEW.
Downy Mildew on cucumbers
A grower in Shelton reported finding downy mildew on cucumbers this week and had the pictures to prove it. I haven’t seen any DM on any of the cucumber or other cucurbit crops that I have scouted in the valley or in eastern CT, but you should scout your cucumbers and other cucurbits for signs of this disease. Look for yellow polka-dots, or brown squared-off lesions about a quarter-inch across, or the upward curling of older leaves on the plants. You can stop this disease with an effective water mold product such as Ranman, Presidio, Previcur Flex or Tanos. These should be mixed in with your powdery mildew application if possible, but do not wait more than 3 days to make the DM application or the plants will lose a lot of foliage. See the pest message from last week for an effective PM program.
Watch for Downy Mildew on Basil
MA has detected downy mildew on basil in two western counties. This disease can spread long distance on the wind just like the species that infects cucurbit crops. Look for upper leaves that have yellow blotches that resemble N deficiency problems. Turn the leaf over to see if there is a patch of grey sporulation on the lower surface under the yellow patch. The grey sporulation almost looks like soil was splashed up on the bottom side of the leaf but it confirms that the plant has DM. Products registered to control this disease include Ranman, Quadris and ProPhyt. Organic growers can use Oxidate, copper, Milstop or actinovate. I haven’t seen any DM on Basil in CT yet, but will be watching for it this coming week.
Late blight update
There is still no sign of Late blight in CT even though it was detected in NY and MA last week. If you still don’t have any pink or red fruit, continue your early blight and Septoria leaf spot sprays with a mancozeb product such as Manzate, Dithane or Penncozeb. If you have a bacterial disease in your planting such as spec, spot or canker, then you should add copper to the mix. Copper is also your best choice if you are organic. If your tomato fruit have color, then you should alternate between a Bravo-type product and Cabrio on a 7 to 10 day schedule. Wait until we find LB in CT to use the water mold products.
Tomato hornworm
Last week I reported finding a THW moth. Well, this week we were finding quite a few large caterpillars in one tomato planting in Somers. Remember that there is a Braconid wasp that helps you control the number of THW on your farm. Sometimes you find caterpillars with the white pupal cases of the wasp attached to the caterpillar’s back. When you spray try to use a selective product like BT, which will not harm the adult wasps or the pupae. Keep in mind that Radiant and Entrust do kill these type of wasps. Another effective option that will provide extended control and spare the wasps would be an insect growth regulator such as Intrepid, which only kills caterpillars. You can scout for hornworms by looking for their droppings on the plastic mulch. Most farms only have a small number, but occasionally they can be numerous and require control.
That’s all for this week. This message will be updated next Friday afternoon July 26th.