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Welcome
to the weekly Vegetable Pest Message
from the University
of Connecticut Cooperative Extension System
Week of June 29th Vegetable Pest Message
Click here for previous Pest Messages
Welcome to the University of Connecticut Cooperative Extension System’s Vegetable Pest Message.
This week’s message will cover:
• LATE BLIGHT ALERT
• corn earworm
• European corn borer
• Phytophthora on “resistant” peppers
• treating eggplant for leafhoppers
LATE BLIGHT ALERT
This message didn’t get posted on the IPM web page last week so I am repeating the late blight alert. The CT Ag Experiment Station in New Haven reported finding late blight on 3 tomato plants that were purchased by a homeowner from Prospect in a nearby supermarket. So there could be more sites with infected plants out there. This recent hot weather should breakdown any spores because they do not like strong UV light or hot weather. The disease is favored by the cool, wet weather and is capable of spreading for many miles on the wind.
At this time we are recommending that all commercial growers, especially those in New Haven County, apply a cover spray to their tomatoes and potatoes for late blight. Please pass this warning on to local growers in your area, as this disease is best managed through area-wide control. We are recommending mancozeb type products, such as Dithane, Pencozeb and Manzate up until the fruit start to color, as these products have a 5 dh restriction, but are very inexpensive. You could also apply a Bravo-type product that contains chlorothalonil and organic growers should apply a copper product such as Camelot O. Certified organic growers should check with their certifier to see which copper products are allowed. If more infected sites are detected and this starts to turn into a full blown epidemic, we will have you switch to stronger and more expensive fungicides, like the products we use for downy mildew on cucurbits. These include: products such as Ranman, Presidio, Previcur Flex, Tanos, Curzate, Revus Top. Revus Top is not registered for potatoes.
If your mind needs refreshing since the big epidemic in 2009, there are pictures of late blight leaf and stem lesions in the vegetable section of the UConn IPM Web Site (www.hort.uconn.edu/ipm/). If a single plant is detected with late blight at a site, or just a few plants, they should be bagged and discarded off farm. If your planting becomes highly infested, the whole planting should be sprayed with a burn-down herbicide like glyphosate and plowed under to reduce spore spread and plant destruction on neighboring farms.
Corn earworm
Growers captured 0.2 or 0.33 CEW moths per night in pheromone traps in Shelton, Berlin and Canton which calls for a 6-day spray schedule on fresh silking corn. One grower in Northford captured 0.66 moths per night and is on a 5-day schedule, while a grower in the Rocky Hill Meadows captured 2 per night and is on a 4-day schedule. That same grower captured zero moths about five miles away from the river, so not all his fields need spraying at this time. You may remember that CEW moths use the sheer winds along the coast to migrate up from the south. The moths then tend to migrate up the major river systems and spread inland from there. That means that growers on the islands like the fellow out on Mather’s Vineyard always get more and earlier moths than those farther inland, and fields along the coast and the CT River, get moths before farms even a few miles inland. What’s that old saying: location, location, location!
European corn borer
There were no ECB moths captured in pheromone traps in Shelton, Berlin or New Hartford this this past week. This means that we are currently between the two generations and there is no danger of whorl or pre-tassel stage corn becoming infested by this pest at this time. On all the farms that I helped to scout, only a single planting became infested with worms above threshold this year. This represents the lightest ECB season we have had in my 26 years of monitoring. I just wanted to share that bit of good news with you for those of you who thought I only bring tidings of destruction!
You should continue to scout pre-tassel stage plantings and very young whorl stage plantings for FAW activity, or run FAW traps to monitor for this pest. No fall armyworm has been detected thus far this season, but we don’t want to let our guard down between the two generation of corn borer.
Phytophthora on “resistant” peppers
After the severe thunderstorms we experienced last week, there are large scale reports of Phytophthora blight damage to peppers around the state. On peppers, Phytophthora produces black lesions on the stem just above the soil line. If you rub the black lesion the outer skin of the stem will slip right off, revealing that the plant has been girdled. Some of the severe losses occurred on the variety ‘Intruder” and others that are supposed to have a certain degree of tolerance or resistance to this disease. Paladin still seems to be the variety that holds up best to this disease. Phytophthora produces a sudden wilting of the plants followed by plant death. This usually occurs soon after heavy precipitation events and where there was standing water. With more heavy rain storms it will spread uphill out of the wet holes and kill the plants in a row or a few rows all the way across the field. No matter what any salesman tries to tell you, there are no fungicides that will control Phytophthora on susceptible varieties. Weekly spraying of resistant plants, like Paladin, will lessen the percent of dead plants in the field slightly over the course of a season, but not enough to pay for all the sprays. The best way to combat the disease is through water management…or put another way…you can’t let any standing water stay in a susceptible crop for more than 24 hours. I visited a grower right after the thunder storm on Monday who had standing water behind every raised bed in his pepper planting…a sure recipe for Phytophthora. Hopefully, by the end of the day, he had hand dug trenches through the beds to let the water out. It also helps to run a sub-soiler between the beds so that the water can soak down through the plow pan. Other hosts include: tomatoes, eggplant, squash, melons, pumpkins, cucumbers and beans.
Treating eggplant for leafhoppers
Last week I reported higher PLH numbers, but this week they got even higher. One farm in Salem had over 25 adults per potato plant and the grower from Shelton reported the same thing. A grower in Rocky Hill had far more than 1 leafhopper per leaf on eggplant and had to spray as the leaves began to develop the yellow tips and margins indicative of hopperburn. All susceptible crops including potatoes, beans, eggplant and artichokes should be protected from leafhoppers at this time.
That’s all for this week. This message will next be updated on Friday afternoon July 6th.
Jude Boucher
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