Welcome to the UConn Vegetable Pest Message. This message is being recorded on Friday afternoon, July 12th, by Jude Boucher.
This message will cover:
Corn earworm
Fall armyworm
Late blight update
Powdery mildew on pumpkins and winter squash
Pepper maggot detected
Japanese beetles on basil
Tomato hornworm
Cross-stripped cabbageworm
Magnesium deficiency
Corn earworm
Last weekend the number of CEW moths in traps went up to 1.3 or 1.4 per night, putting growers in the CT River Valley on a 4-day spray schedule of fresh silking corn. This week the numbers dropped back down at most locations. Growers captured 0.2 to 0.5 moths in traps in Northford, Shelton, Berlin and Suffield, dropping those farms back to a 6-day schedule. A second farm in Suffield failed to capture any moths over Monday and Tuesday nights, while fields in Wallingford captured 1.3 moths per night and are still on a 4-day schedule. Traps on your farm can save you a lot of work at this time of year and take all the guesswork out of spraying sweet corn. Remember to move the traps to fresh silk as it begins to brown and change the pheromone lure every three weeks. Hercon brand lures should be stored in a zip lock bag in the freezer until needed.
Fall armyworm,
We captured our first FAW moth of the season this week in Suffield. That means it is time to scout all your whorl and pre-tassel stage fields again, but this time look for larger feeding holes. We didn’t see any FAW feeding in Suffield or any other fields this week, which means that the eggs were just being laid and you should start to see feeding injury next week.
Late blight update
LB was confirmed in MA and Central NY yesterday. That means you should continue on your early blight and Septoria leaf spot fungicide applications with protectant products such as copper, mancozeb-type products, and Bravo type produces. Apply copper on a 5 to 7-day schedule, and Manzate or Bravo on a 7 to 10 day schedule, depending upon how much rain we get. You still don’t need the more expensive mobile and systemic fungicides specifically labeled for LB until we find the disease in this state. You should scout your tomato and potato plantings at least weekly for LB. If LB shows up in CT this coming week, you can alternate with Tanos (3dh) and Revus Top (1dh) every 10 days to cover all the fungal diseases and LB. You can also add the following LB products to your Manzate, Bravo, or Cabrio. Some of the most effective LB materials include : Ranman, Previcur Flex, Presidio and Curzate. Ranman is 0dh while Presidio is 2dh.
Powdery mildew on pumpkins and winter squash
We found the first small spot of PM of the season on the underside of a winter squash plant in Hampton. Remember that the spray program for full-season cucurbit plants, like pumpkins and winter squash, involves using one application each systemic fungicide family or resistance group, mixed with a protectant fungicide that also works on PM. This year we have a new product called Torino, in a new resistance group (U6). Other universities report that it is at least as effective as anything on the market against PM only. It should be used in your first application once your scouting detects the disease, and should be mixed with Bravo for resistance management and to cover other fungal diseases such as black rot and Plectosporium. The second application 10 days later should include Quintec and sulfur or Bravo. The third spray should include Procure and Bravo, and the fourth should be Pristine and sulfur. If you need more then switch to a combination of the two protectant fungicides, sulfur and Bravo for the rest of the season. That is the Cadillac program for wholesale growers with a lot of acreage to protect. Organic growers can use sulfur.
Pepper maggot,
We found the first PM stings of the year at an organic farm in Suffield this past week and at an IPM farm in Berlin. We didn’t find any eggs when we cut the fruit open so that indicates that egg laying is about to begin and insecticides should be applied now. See the message from last week on our web site at www.ipm.uconn.edu/ for a list of control tactics and products.
Japanese beetle
Japanese beetles are out in force and feeding on your basil. Radiant or Entrust will control the beetle. You can also plant the variety Nufar as a trap crop down one end of your planting to lighten the injury to other varieties in the block.
Tomato horn worm
We found a THW moth on a tomato stake yesterday in Salem. Some years some poor farmer get more than their share of these insects, which can quickly defoliate plants and chew holes in fruit is at high numbers. As your scouting tomatoes for disease, check the plastic under the plants from the large droppings of these huge caterpillars. If you have dropping on most plants, a selective insecticide will be needed. The caterpillars consume so much leaf area that just about any product including a Bt will control them.
Cross-striped cabbageworm
Last week I described how to scout for our three most common caterpillar pests on Brassica crops: imported cabbageworm, diamondback moth larvae and cabbage loopers. Unlike these three pests, the CSCW lays a whole batch of eggs on one plant rather than laying its eggs singly. So, if you are scouting your cabbage or Brassica crop and find a couple of plants that are completely skeletonized, that means you have up to 20 CSCW on that plant, which should be dealt with by hand crushing or with a spot spray. The threshold is much lower for CSCW because the plants it infests are usually damaged so severely, that they are unmarketable. Spray when 1 to 5% of the plants are infested with CSCW, but use the higher 20% threshold for any combination of the other three caterpillars.
Magnesium deficiency
We saw magnesium deficiencies this week on Brassica greens, radishes and Totsoi. This shows up as yellowing between the veins on the lower leaves on the plant. The book states that nitrogen deficiencies intensify the development of Mg deficiencies. It has been particularly hard for organic growers to keep their N levels at a sufficient level, because the cold wet soil has not been contributing much in the way of nitrate this season. Organic growers may need to feed much more frequently than usual if they see lower leaves turning yellow, which indicates N shortage, or if the area between the green veins turns yellow, which indicates Mg shortage. These areas of the field should be spread with high Mg or dolomitic lime this fall or next spring. You can also apply 10-15 pounds of Epsom salts per acre, dissolved in 100 gallons of water, as a foliar application. The plants should green up within days.
That’s all for this week. This message will be updated next Friday afternoon July 19th.