Vegetables

Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Beet Armyworm Alert # 2

We continue to find high beet armyworm populations in many crops. In addition to the crops listed last week, they have also been found causing defoliation in apples as well as feeding on the rinds of watermelons. Remember, the pyrethroids, Lannate and Larvin have not provided effective control. Depending on which crop you are looking at, Avaunt, Spintor or Confirm have provided the best control.

Cucumbers.

Although we have not had reports of beet armyworm feeding on fresh market or pickling cucumbers, we know that we can find larvae in the field. Since larvae have been found feeding on watermelon vines, anything is possible at this point. Be sure to watch for larvae and possible feeding. The only available and effective option at this point would be Spintor at 6-8 oz/acre.

Watermelons.

There have also been reports of beet armyworms feeding on the rinds of watermelons. Spintor is labeled for armyworm control on melons and should provide good control at 6-8 oz/acre. Remember, it does have some contact activity, but it is also a stomach poison so enough leaf area should be present to get the product to work well.

Cabbage.

Economic levels of diamondback (DBM), cabbage looper (CL) and beet armyworm(BAW) continue to be found in cabbage. A treatment should be applied if 5% of the plants are infested and before larvae move deep into the hearts of plants. If DBM and CL are present, Avaunt (3.5 oz/acre), a Bt, Proclaim (3 oz/acre), or Spintor (4-5 oz per acre) will provide control. If cabbage looper is the predominant species, a pyrethroid or Confirm (8 oz/acre) will also provide control. If beet armyworm is the predominant, Avaunt, Confirm or Spintor should be used.

Lima Beans.

Be sure to sample fields carefully for corn earworm, beet armyworm, lygus and stinkbugs A treatment should be applied if you find one corn earworm per 6 foot of row or 15 tarnished plant bugs and/or stinkbugs per 50 sweeps. Since corn earworm populations are high and moths are readily attracted to blooming fields, multiple applications may be needed to achieve control. When possible, fields should be scouted twice a week to effectively time insecticide applications. If you are using Lannate, the rate will depend on the larval size at the time of treatment. If worms are small, 1.5 to 2 pts. per acre will be adequate. However, if the worm size is mixed at the time of treatment, 3 pts./acre will be needed. There are no thresholds for beet armyworm; however, a spray should be considered when worms are small and you can find 20% of the plants defoliated. Lannate, Mustang or Capture can be used to control corn earworm, lygus and stinkbugs. If beet armyworm is causing problems, Spintor is labeled on lima beans and will provide good beet armyworm control.

Peppers.

At the present time, all peppers should be sprayed on a 5 to 7-day schedule for corn borer, corn earworm, fall armyworm and beet armyworm control. Orthene or Address will not provide corn borer control; however, we are limited to 2 applications. A pyrethroid or Lannate will be needed for earworm control. If beet armyworms are present, Avaunt, Spintor, or Confirm will provide the best beet armyworm control. Depending on the pest complex present, a combination of products will be needed. Avaunt is a stomach poison, so you should not evaluate control for 3-4 days after treatment. It stops insects from feeding immediately; however, worms may still be observed on plants. Spintor is a stomach poison, but it also has contact activity.

Snap Beans.

Processing snap beans in all areas of the state should be treated at the bud and pin stages for corn borer control. Orthene or Address should be used at the bud and/or pin stages for corn borer control. In all areas, a pyrethroid should be combined with Orthene at the pin spray for earworm control. Beet armyworm can also be found defoliating snap beans. There are no thresholds for beet armyworm; however, a spray should be considered when worms are small and you can find 20% of the plants defoliated. Lannate will only provide control of small larvae. Spintor is also labeled on snap beans and will provide good control of beet armyworms. After the pin stage, Lannate, Capture or Mustang should be used for corn borer and earworm control. Sprays will be needed on a 5-day schedule from the pin spray until harvest. Since this can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html).

Spinach.

Small beet armyworm and webworms have been found in recently emerged fields. Controls should be applied when worms are small and before they have moved deep into the hearts of the plants. Also, remember that both insects can produce webbing on the plants. Since Lannate cannot be applied before plants are 3-inches in diameter and it only provides control of small larvae, Confirm or Spintor will be needed for beet armyworm control. If webworms are the predominant species, Ambush, Pounce, Confirm (6-8 oz/acre) or Spintor (4-8 oz/acre) should be used. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm. The unusually high beet armyworm population may result in the need to treat multiple times this fall.

Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 2-3-day schedule in all areas of the state. Since corn earworm catches continue to be high and fall armyworm can be found in silk stage corn, you should consider combining Lannate LV at 1 to 1.5 pt/A with the highest rate of a pyrethroid. Be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in fresh market sweet corn.

(http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html ) .

Vegetable Diseases - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu

Cucurbits.

Downy mildew on cucurbits is present here on the Delmarva Peninsula. The disease can be recognized by brown to gray sporulation that occurs on the underside of leaves. The sporangia can be seen with a 10X hand lens and appear as barely distinguishable black or purple spots. All cucurbits are susceptible to downy mildew and cool wet weather, like we are now experiencing, is very favorable to this disease. Several fungicides have specific activity on downy mildew. Gavel was recently registered for use on melons, summer squash and watermelon (but not winter squash or pumpkin). Acrobat is available for use on cucurbits under Section 18 status for 2002. Ridomil Gold/Bravo or Ridomil Gold /Copper are also effective against Downy mildew.

Acrobat is specific for control of oomycetes, such as the organism that causes downy mildew, and should be applied with a broad-spectrum fungicide. Ridomil Gold/Copper or Ridomil Gold/Bravo should be applied every other week and be alternated with a broad-spectrum material like Bravo, Equus or Echo. Read labels carefully, some muskmelon cultivars are sensitive to Gavel.

MELCAST for Watermelons.

From the University of Maryland and University of Delaware

Latest EFI values from local weather stations

Any questions please call (410) 742-8788

EFI Values (Environmental Favorability Index)

Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program.

Location 08/28/02 08/27/02 08/26/02 08/25/02 08/24/02 08/23/02 08/22/02 08/21/02

Bridgeville, DE 0 3 3 3 2 2 1

Charles Co. 0 9 0 1 3 0 0

Collins Farms 2 3 3 5 3 2 1

Galestown, MD 1 1 3 5 3 0 1

Georgetown, DE 0 2 2 4 2 1 2 3

Glenville, MD 0 2 0 9 4 5 0

Hebron 2 2 3 5 3 1 1

Hog Creek Rd. 0 4 3 8 3 0 0

Salisbury, MD 3 1 3 3 3 0 2 0

Vincent Farms 4 3 3 5 3 1 2

Westminster 0 3 0 7 4 5