Vegetables

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

Lima Beans.

Be sure to watch for spider mites on seedling stage lima beans, especially in areas of the state that have not been receiving adequate rainfall. Both field interiors as well as field edges should be examined for mites. Look for the white stippling along the veins on the underside of the leaves. A treatment should be considered when you first notice the stippling and you find 10-20 mites per leaflet. Kelthane or Capture (6.4 oz/A) have provided the best control in lima beans. The earliest planted field should be scouted for lygus bugs and stinkbugs. Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. Lannate, Capture or Mustang can be used if both species are present. The higher labeled rates of Capture (4 oz/A) and Mustang (4.3 oz/A) will be needed if stinkbugs are the predominant insect present.

Peppers.

Corn Borer catches have dropped below 2 per night in all areas of the state except the Harrington, Greenwood and Milford areas. Once trap catches increase to above 2 per night and pepper fruit is ½ inch in size or larger, fields should be sprayed on a 7-10 day schedule for corn borer control. Trap catches are updated three times per week on the IPM website - http://www.udel.edu/IPM/traps/latestblt.html .

Potatoes.

As we approach harvest on the earliest planted potatoes, be sure to continue to sample for potato leafhoppers and aphids. Both potato leafhopper adults and nymphs can be found in fields. The treatment threshold is 0.5 - 1 adult per sweep or 1 nymph per 10 leaves. Actara, Provado, Furadan or a pyrethroid will provide control. Aphid populations are still low. If fields are greater than 2 weeks from harvest, the threshold is 4 aphids per leaf. Within 2 weeks of harvest, the treatment threshold increases to 10 aphids per leaf. In general, Colorado potato beetle populations are moderate in most fields. If Admire, Platinum or Tops MZ Gaucho were used at planting be sure to alternate to cryolite, Agri-Mek or Spintor when threshold levels of larvae or newly emerged adults are detected.

Snap Beans.

In the Harrington, Greenwood and Milford areas, fresh market and processing snap beans in the bud to pin stage will need to be sprayed for corn borer. Seedling beans should still be watched carefully for thrips and leafhopper activity. We continue to see an increase in leafhopper and thrips activity. If both insects are present, the threshold for each should be reduced by 1/3. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep.

Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 5-6 day schedule in all areas of the state except in the Harrington, Georgetown and Wyoming areas where sprays are needed on a 4-day schedule. Be sure to check the IPM website for the most recent BLT catches in your area (http://www.udel.edu/IPM/traps/latestblt.html ).

Pea Enation Mosaic Virus - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

Many pea fields exhibit the pea enation virus disease on some small percentage of plants, but it is noticeable. Stunted plants, distorted leaves, and the small, distorted pods, with only one or two peas are the typical symptoms. Some fields may have as much as 3-5% of the plants showing these symptoms.

The virus is spread by aphids. Aphids have not been a huge problem this year, but the symptoms indicate the presence and spread of the virus.

Licensed and Bonded Produce Buyers and Dealers - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

Licensed and Bonded Produce Buyers and Dealers.

The State of Delaware law requires produce buyers and brokers of large quantities to be bonded and licensed with the State. A list of licensed buyers is available from Cliff Hudson, Delaware Department of Agriculture, at 302-739-4811.

Cold Weather Affects Fruit Set of Early Watermelons – Derby Walker, Extension Ag Agent, derby@udel.edu and Tracy Wootten, Extension Associate-Vegetable Crops, wootten@udel.edu

Some early planted watermelons havelittle to no crown fruit set due to cold growing conditions. Cool weather conditions early in the growing season may result in female flowers opening several days before male flowers, resulting in delayed fruit set.

Watermelons produce separate male and female flowers on the same vine. A female flower can be easily recognized by the swelling of its base which resembles a tiny watermelon. Normally a female flower may be found at every seventh to tenth node. Thus, plants usually produce about 10 times more male flowers than female flowers.

Female (left) and male
(right) flowers

(Photo taken from University of Georgia Watermelon Fact Sheet)

For successful pollination to occur, both female and male flowers must be open on the same day. The minimum temperature for the opening of watermelon flowers is 59° F.

Optimum growth of watermelon plants is achieved at temperatures of 68-86°F.

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

Watermelons.

From the University of Maryland and University of Delaware

Latest EFI values from local weather stations

Any questions please call (410) 742-8788

MELCAST for Watermelons

EFI Values (Environmental Favorability Index)

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

Location 06/19/02 06/18/02 06/17/02 06/16/02 06/15/02 06/14/02 06/13/02 06/12/02

Bridgeville, DE 1 1 2 0 3 5 1

Charles Co. 1 0 0 1 9 9 2

Collins Farms 1 1 3 1 3 4 1

Galestown, MD 1 2 4 0 3 4 1

Georgetown, DE 1 1 2 1 2 1 3 0

Glenville, MD 2 2 0 1 5 7 3

Hebron 1 2 3 1 3 4 1

Hog Creek Rd. 1 0 0 2 7 8 4

Salisbury, MD 2 1 0 0 0 0 0

Vincent Farms 1 2 2 1 3 7 1

Westminster 4 0 0 1 7 8 3

White Marsh 1 2 0 1 6 7 3

The first fungicide spray should be applied when the watermelon vines meet within the row. Additional sprays