Welcome to the UConn Vegetable Pest Message. This message is being recorded on Wednesday afternoon, July 3rd, by Jude Boucher.
This message will cover:
European corn borer
Setting up fall armyworm traps
Corn earworm
Pepper pests
Imported cabbageworms
Potato leaf hoppers
Onion thrips
Weeds and excess water (from Rich Bonanno)
European corn borer
Infestation of pretassel stage sweet corn dropped this week in the Suffield area to 10-12% of the plants infested. Younger corn in the mid- to late-whorl stage only had 2-6% of the plants infested and will probably not need spraying until the silk stage unless fall armyworm shows up. Spray for borers if pretassel stage fields have more than 15% of the plants infested.
Setting up fall armyworm traps
Since we are between generations of ECB, you are mainly concerned with FAW showing up on whorl or pre-tassel stage corn. FAW caterpillars will ride the tassel up out of the whorl as the plant grows and then migrate to the ear once the tassel pops open. Growers with larger acreage to check on a weekly basis may save time by running a FAW trap, at about whorl height, within the corn field. Set up a green Unitrap, baited with a Trece or Scentry brand pheromone lure, in your young whorl stage plantings and check the traps instead of scouting those fields. The trap should also contain a Vapona strip to kill the insects that enter the trap. This equipment can be purchased from Great Lakes IPM in Vestaburg, MI. When you start to catch FAW moths in the trap, which have iridescent purple back wings, then you should start scouting your field. If you find more than 10% of the plants infested at pre-tassel, then you should spray. FAW are sometimes tougher to kill than borers. Growers have had good luck with products such as Coragen, Radiant and Avaunt. Other products may also work well.
Corn earworm
If you have silking corn, then you should have set up two Heliothis traps baited with Heron brand CEW lures. Traps at two farms in W. Suffield captured an average of 0 and 0.3 moths per night, while a farm in Glastonbury also captured 0.3 moths per night. Traps down near the coast in Northford captured 0.5 moths per night. Most growers in the valley should be on a 6-day spray schedule on fresh silking corn at this time. If the level goes up to between 0.5 and 1 moth per night, then move to a 5-day schedule. If it gets as high as between 1 and 13 moths per night move to a 4-day schedule.
Pepper pests
You should be scouting your pepper plantings once a week for BLS. BLS appears as irregular-shaped, brown spots on the leaves of several adjacent plants in a row. If you find the first few infested plants in the field, you can rogue out those infected plants, and a couple that might be infected but not yet showing symptoms on each side, and you just might head-off an epidemic that could damage your whole block or field. Growers should always use BLS resistant plants for bell peppers. If you find BLS on your plants, apply copper every 7-10 days. This disease spreads easily when night temperatures remain above 70 degrees and relative humidity is above 85%: in other words, during heat waves. You can extend the spray interval by one night for every night that the temperature drops below 60 degrees F.
Pepper maggots flies lay eggs inside fruit on some farms, but not all farms, in the CT River Valley and near the Coast during July. This pest can be monitored by planting hot cherry pepper plants in the outer row of your pepper block, and checking the fruit for stings during July, especially the fruit near the tree line, as the flies move back and forth between the trees and the peppers. You can also monitor with a yellow, sticky AM trap, baited with a vial of ammonium hydroxide, hung 20 feet up in a maple tree adjacent to your pepper field. I admit, this is not the easiest trap placement, but it works to catch the flies, where other sites in and around the field do not. If you find PM flies on the trap or stings in the fruit apply dimethoate or Orthene within the next week and again 10 days later. Organic growers can use GF-120 liquid Fruit Fly bait, but it is incredibly difficult to apply correctly. One organic grower is trying Seduce solid bait this year, which also contains spinosad, the same active ingredient in the GF-120 and Entrust. However, foliar applications of Entrust or Radiant do not control this pest. The bait in the Seduce and the GF-120 is very attractive to the adult fly and supposed to cause the fly to consume a lethal dose of the product, which they do not do after a foliar application of Entrust or Radiant. You can also stop this pest using perimeter trap cropping by planting a row of hot cherry peppers all the way around your pepper field, and just treating the trap crop when flies or stings are detected.
Imported cabbageworms
Growers should scout their heading broccoli or cabbage plantings once a week and treat if you find 20% of the plants infested with any one of three caterpillar pests. Start at the center of the plant and check the back side of each leaf for live caterpillars. Check 10 or 20 plants, depending upon the size of the block. This week two plantings had 20% of the plants infested and one planting had 50% on the plants infested with mostly imported cabbageworm. Try to use products that will spare beneficial insects that help hold down the number of caterpillars and secondary pests. ICW is easy to kill, so BT products like Dipel, XenTari, and spinosad products such as Entrust and Radiant will work well. The XenTari will work better than Dipel on diamondback moths if you have a mix of caterpillars in your planting. The insect growth regulator Intrepid will provide 10 days of residual control while Coregen may provide up to 3 weeks of protection.
Potato leafhoppers
Adult PLH have returned. Fields of young beans, potatoes and artichokes in W. Suffield had up to 8 leafhoppers per foot of row. This level of feeding will cause hopper burn and reduced yields. Organic growers should apply PyGanic to the underside of the foliage and cover the plants with row covers within 24 hours.
Onion thrips
One grower who had high levels of OT on onions and cucumber beetles on summer squash last week, treated both with Assail plus an adjuvant to help it penetrate between onion leaves where the thrips hide. The Assail provided a very good kill of the cucumber beetles, but only lowered the OT to about half the level it had been at. They will try again this week using Radiant plus an adjuvant.
Weeds and Excess Water: options (Rich Bonanno)
When it comes to weed management, excess water is more of a problem than too little water. For those, using herbicides, rain allows herbicides to be activated so that they are in the zone where weeds are germinating. This is only in the top inch of soil though, so excess rain can move the herbicide below that zone and control will be reduced. When weeds emerge after the crop is up and preemergence herbicides have already been used there are a few options left. First, cultivate whenever it is dry and sunny, take advantage of those few days and don’t delay. Weeds die better when they are small and remember not to cultivate too deeply. Deep cultivation destroys crop roots and brings new weed seeds closer to the soil surface. Second, check the New England Vegetable Management Guide for postemergence weed management options. As with cultivation, small weeds die easier and faster so do not delay if you have a window. Annual grasses, especially, have been a huge problem this year. They are thick, fast growing, and can easily take over a field. Just about every crop has a postemergence grass herbicide option available. Depending on the crop, these products include Poast (sethoxydoim), Fusilade (fluazifop), Select (clethodim), Assure (quizalofop), and for sweet corm only, Accent Q (nicosulfuron). Finally, hand weeding is always an option but take care not to drop those weeds back onto the soil where they might catch again. Consider using buckets to put the weeds into and carry them out of the field. When pulling weeds in the holes on plastic mulch, have employees shake the weeds to remove excess soil and then place the weeds on the plastic where they have a much greater chance of dying. Good luck and stay dry
That’s all for this week. This message will be updated next Friday afternoon July 10th.