to the weekly Vegetable Pest Message
from the University of Connecticut Cooperative Extension System
Week of June 8th Vegetable Pest Message
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Welcome to the first Vegetable Pest Message of the season from the University of Connecticut Cooperative Extension System. This message is being recorded on Tuesday afternoon June 5th by Jude Boucher. Messages can also be downloaded from our UConn IPM Web Site at www.hort.uconn.edu/ipm/.
This weeks message will cover:
• Late blight
• Cucurbit downy mildew
• Asparagus Beetles
• European corn borer
• Potato leafhopper
• Deep zone-tillage
• Ordering insect traps and pheromones.
• Summer cover crops
• perimeter trap cropping for cucumber beetle control
• Colorado potato beetle management
Late blight, the disease that caused the Irish potato famine, was found in a potato field in NJ on May 24th and in one potato field on Long Island on May 29th. It was just found yesterday in PA and has been found in many states to our south. If you remember, LB started early on Long Island in 2011 and they eventually had the worst LB epidemic in their history. However, even though they were having such a bad problem all summer, late blight didn’t show up here in CT until September last year. I’m letting you know that LB is on our boarder so that you can be prepared in case it blows into the state early, since this disease can move up to 30 miles on the wind. I do not think you need to spray for this disease at this time unless it shows up in CT.
The strain that has been identified in LI, is the same one that they had last year. It can also infect tomatoes, and is sensitive or susceptible to treatment with mefenoxam, the active ingredient in Ridomil fungicides. Some other products that usually control late blight real well include Ranman, Presidio, Previcur Flex, Tanos, Curzate, and Revus Top, while older protectants such as Bravo and macozeb-type products offer some protection. Copper offers less protection that Bravo or mancozeb, but may be the best option for organic growers. Presidio is not registered on potatoes. If we find LB in CT then I will call for statewide Bravo or mancozeb sprays at 7-10 day intervals on both tomatoes and potatoes, at least up until tomato fruit starts to color. If we start to find LB on multiple farms, then we will switch to the more expensive and more effective fungicides.
Wet, cool weather favors LB, so you should be scouting your tomato and potato fields weekly. Most of you probably remember LB symptoms from the epidemic we had back in 2009 that was caused by the big box stores selling contaminated plants. LB usually has large, dark (olive green, brown or black) leaf lesions at least the size of a quarter, and may have 1-3 inch long black stem lesions that may girdle the plant at that point. Tomato fruit have large, firm, brown or black lesions that render them unmarketable. You can see pictures of LB at www.hort.uconn.edu/ipm/.
Cucurbit downy mildew
As if the early arrival of late blight wasn’t enough, NJ also sent out an alert that they had found downy mildew on cucumbers last week. This is months earlier than they usually find the first DM on cucurbits, unless it has been brought up from the South on transplants. Again, I am not calling for a fungicide spray at this time, I am just letting you know that things are showing up early in states surrounding CT. Scout your first summer squash plantings for powdery mildew, which usually shows up in late June as the plants age. Barring an accidental early introduction of downy mildew, your first cucurbit fungicide spray will probably be when you first find PM on summer squash unless you are ready to till it under and move on to the next planting when the disease is found.
Scout for asparagus beetles and eggs on sunny afternoons to prevent damage to spears and defoliation of ferns. Treat spears if >10% of the plants are infested with beetles or 1-2% have eggs or damage. Treat ferns if 50-75% are infested with beetles or larvae. Radiant or Entrust will help spare some of the beneficial insects in the planting.
European corn borer
ECB moths are flying, eggs are hatching and caterpillar infestations should be starting to occur in whorl and pre-tassel stage sweet corn plantings. The threshold calls for spraying twice, 3-7 days apart, during the pre-tassel stage if you find more than 15% of the plants infested.
To assess the population as you walk through the field, scout 50 plants per block in sets of 10 plants. Count the number of plants infested with caterpillars and double the number to get an estimate of the percent infested plants in the field.
The following insecticides are effective for controlling ECB: Radiant, Entrust, Avaunt, Intrepid, Group 28 products like Coragen or Belt, synthetic pyrethroids such a Warrior and Mustang, and B.t products such as Dipel DF and XenTari. Other products that work include Lannate and Larvin. B.t corn varieties like BC0805 also completely control corn borers.
Continue to scout each planting as it comes into the mid-whorl and pre-tassel stage. Only control ECB in the mid-whorl stage if more than 30% of the plants are infested with caterpillars and moth numbers in pheromone traps are still rising. Be aware that there have been some true armyworm infestations reported in western CT. These caterpillars will attack younger whorl stage plants and produce larger ragged hole like its cousin the fall armyworm. The same products that control ECB will also control true armyworm.
Potato leaf hopper
Low levels of adult leafhoppers are now present on beans and potatoes. Feeding can severely damage potato and bean plants and higher levels can damage eggplants. You should be watching your beans and potatoes for leafhopper infestations. Adults are small, pale-green, wedge-shaped insects that usually feed on the underside of the leaves, and can be seen streaking away from the plants as foliage is disturbed. If you have trouble seeing these insects you can monitor with a sweep net. Later on, bright-green nymphs will be produced and can be monitored by visually inspecting the underside of the lowest leaves. Treat potatoes if more than 1 adult leafhopper or 15 nymphs are found on 50 compound leaves or 1 adult per 5 feet of row. Seedling beans should be treated if you find more than 2 PLH per foot of row. Between the third leaf and bud stage, treat beans if you find 5 PLH per foot of row. Do not treat beans once they begin to bloom. If you are scouting with a sweep net, treat beans if you find more than 5 adults per sweep and potatoes if you find more than 1 adult per sweep. On small bean plantings, leafhoppers can be controlled until bloom with row covers, which will prevent yield losses. Remove the row covers after the bud stage and before bloom. Treat eggplant if more than 1 or 1.5 leafhoppers are found per leaf. Quarter rates of dimethoate have been very effective to control PLH for up to 2 weeks. Do not use dimethoate if copper has been applied. See the NEVegetable Management Guide for more options.
I’d like to welcome Pine Croft Farms in Somers, CT as the latest farm in the state to convert to deep zone tillage. They bought a 6-row Zone Builder and began using it to plant their sweet corn in May. Gordon said it took him longer to drive to the farm than it did to make a planting of sweet corn using DZT. They are also using special DZT application methods to put down all their fertilizer as liquids when they prep the field, which eliminates the need for side-dressing. So, it cuts down field preparation time by 66%, you reduce your fuel bill by about the same amount, and then you can eliminate the need for side-dressing and reduce your N use too.
For those of you who came to the twilight meeting at Donny and Joe Dzens Farm last year, they credited DZT for allowing them to plant their 60-acres of pumpkins with such wet weather last June and for being able to harvest healthy fruit in one of the wettest Septembers on record.
I have been working with the rep from Unverferth, the manufacturer or the Zone Builder, to help bring a demo machine to a CT Equipment dealer next spring. This will be on a first come first serve basis, for growers that have a tractor capable of pulling it and are willing to prepare a field correctly for a fair trial. Let me know if you are interested in getting on the list to try DZT in 2013.
Ordering insect traps and pheromones
If you plan to monitor for corn earworms in your sweet corn this summer you will need at least 2 Scentry Heliothis traps, and a pack of 10 Hercon brand CEW lures. If you want to monitor for ECB too then you should will need another couple of Scentry Heliothis traps and 5 of each type ECB lures (both E & Z lures). Store the lures in a zip-locked bag in your freezer until they are needed. It is important that you get the Hercon brand CEW lures because the thresholds that we use to tell you how often you need to spray are based on the emission rate of this type of lure. Other lures will catch moths, but they won’t tell you what spray schedule you should be on. Set up your CEW traps just before your first sweet corn planting develops silk. Great Lakes IPM in Vestaburg, Michigan, carries the Hercon brand CEW lure and other IPM supplies, and has low prices. Some better-known companies do not carry Hercon brand lures. You can reach Great Lakes IPM at 1-800-235-0285 or check their web site at www.greatlakesipm.com
Before ordering your pheromone lures, you should check the tops of your old traps to make sure the mice didn’t chew holes in them while trying to get to dead insects inside over the winter. Replacement tops for your Scentry traps are only about $17
Fall Armyworm can be monitored with a $10 green Universal Moth Trap and 3 to 4 FAW lures. You will also need a Vapona (DDVP Vaportape) killing strip for your FAW trap. FAW traps tell you that the moths are in the area and when it is time to scout your corn for larvae. Any brand lure will do for monitoring ECB or FAW. Keep your unused lures in the freezer until they are needed (but not the killing strip). Replace the lures on your traps every three weeks. Again, that number for ordering supplies from Great Lakes IPM is 1-800-235-0285.
Summer cover crops
You can use summer cover crops to help build organic matter levels, loosen hard soils and reduce root-knot nematodes. Think about using summer cover crops either after an early short-season crop like peas or lettuce, before a late planted cash crop, or for the whole season to rest a field and improve fertility. Sorghum-sudangrass is best to help build organic matter, loosen soil and control nematodes but buckwheat can also help improve soil structure and is the better choice for suppressing weeds as it establishes faster. These cover crops can be planted from June through August. Use 30-50 pounds/A of sorghum-sudangrass or 40-100 pounds of buckwheat seed per acre. Kill the buckwheat at bloom or before seeds form to avoid volunteer plants. Mow both these cover crops after about 40 days. For sorghum-sudangrass, let it re-grow and flail mow again at 60-70 days before incorporating and planting a winter cover crop or just let it regrow again and winter kill.
Perimeter trap cropping for cucumber beetle control
One of the best ways to control cucumber beetles on summer squash, cucumbers, melons, butternut and acorn squash is to use perimeter trap cropping. To use this technique, simple plant 1 to 2 rows of Blue Hubbard squash all the way around your main crop and spray the trap crop with Sevin or a synthetic pyrethroid as soon as the first beetles appear. You may need to repeat applicationson the trap crop at 5-7 day intervals through June depending upon the beetle pressure on your farm. Most growers are surprised to find that they can sell Blue Hubbard squash for $7-8 per box (2 squash).
Perimeter trap cropping can also be used to control pepper maggots in bell pepper plantings by surrounding the block with one or two rows of hot cherry peppers as a trap crop. In July when pepper maggot stings or shallow depressions are detected on the surface of the cherry pepper fruit, treat just the trap crop with an effective insecticide like Orthene or Dimethoate.
Colorado potato beetle management
Adult CPB are just emerging. The most important alternative control you can employ for this pest is crop rotation. If you rotate your solanaceous crop to a field as little as 1/4 mile away you will delay colonization and reduce the number of beetles by over 90%. If you only have one field, rotate your susceptible crops from one side of the field to the other, and plant two rows of potatoes between the new and old plantings as a trap crop. You can treat the trap crop at planting with a nicotinoid insecticide like Admire or Platinum, or wait until the beetles arrive and treat the foliage with one of the products listed below. Another great preventative practice is to strip-till or DZT through a killed, rye cover crop residue. Potato beetle damage is dramatically reduced by organic mulches because most beetles walk to the crop from overwintering sites, and the mulch impedes their progress and increases the number that perish to disease. Planting after 15 June is also supposed to reduce the number of beetles because most emerging adults should have already dispersed and found a host plant by then.
This pest will become resistant to any chemical in as little as 3 years. For resistance management you can use the same product 2-3 times in a row on one generation, but you need to rotate to a different chemical group with a different mode of action for the second generation in late July and for the next year. If you do a good job cleaning up the first generation, usually there is no second generation in July to worry about.
Here are some of the most effective insecticide groups and products for CPB:
Group 4, the nicotinoids, such as Actara, Admire, Assail, Belay, Cruiser, Goucho, Provado, Platinum, and Venom;
Group 5, spinosad-type products, such as SpinTor, Entrust or Radiant
Group 6, abamectin products, such as AgriMek and Abba, (larvae only)
Group 9B, cryolites, such as Kryocide, Prokill and Cryolite (larvae only)
Group 16B and 17, insect growth regulators, such as Rimon and Trigard (larvae only)
Group 18, azadirachtins, such as Neemix and Azatin (larvae only)
Group 26, indoxacarb, know as Avaunt (larvae only)
Group 28, Coragen
Remember that the synthetic pyrethroids are very hard on beneficial insects, which help keep secondary pests in check and control more than half the CPB population. Use these and other broad-spectrum insecticides only as a last resort for CPB.
That’s plenty for this week. This message will be updated next on Friday afternoon June 15th.
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