Vegetables

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

Cucumbers.

Continue to scout for aphids. A treatment should be applied for aphids if 10 to 20 percent of the plants are infested with aphids.

Lima Beans.

Be sure to watch for economic levels of leafhoppers in fields throughout the state. Remember, most labeled insecticides will only provide 7-10 days of control. In fields with pin pods, you should sample for earworm, 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. Lannate, Mustang or Capture can be used to control all 3 insects on lima beans.

Peppers.

At the present time, all peppers that have fruit ½ inch in size or larger should be sprayed on a 7-10 day schedule for corn borer and pepper maggot control. We are also starting to see an increase in aphid populations in peppers. Remember a continuous pyrethroid program should not be used to avoid aphid explosions.

Snap Beans.

In areas where we have started to see an increase in corn borers moth catches - Bridgeville, Dover, Harrington, Milford , Laurel and Seaford ---a corn borer spray will be needed at the bud and pin stages on processing snap beans. Orthene or Address should be used on processing snap beans for corn borer control at the bud and/or pin stages. After these stages, Lannate, Capture or Mustang should be used. In these same areas, you should begin treating fresh market snap beans for corn borers on a 7-day schedule from the pin stage until harvest. Lannate, Capture or Mustang should be used. Continue to watch for defoliators feeding on the pin pods. A treatment should be applied if defoliators are feeding on pin pods. Lannate, Asana, Mustang or Capture will provide the best control of defoliators. Be sure to check for the most recent trap catches in your area by calling 1-800-345-7544(in-state), 1-302-831-8851(out of state) or checking our website - http://www.udel.edu/IPM/traps/latestblt.html.Trap catches are updated on the IPM website three times per week. We have also included a new link on this page for ECB moth trap thresholds for processing snap beans.

Sweet Corn.

Fresh market silking sweet corn should be sprayed on a 4-day schedule except in the Harrington and Seaford areas where sprays are needed on a 3-day schedule. The first spray should be applied as soon as ear shanks are visible. Be sure to also sample late-planted fields for fall armyworm larvae. No controls will be needed until 15% of the plants are infested. Spider mites have also been reported in fresh and processing sweet corn. If numbers are increasing and plants are yellowing, a treatment should be considered. Metasystox-R is the only insecticide labeled for sweet corn in our area. Capture is not labeled for coastal counties. Be sure to check for the most recent trap catches in your area by calling 1-800-345-7544(in-state), 1-302-831-8851(out of state) or checking our website at http://www.udel.edu/IPM/traps/latestblt.html. Trap catches are updated on the IPM website three times per week. We have also included a new link on this page for ECB and CEW moth trap thresholds for silking sweet corn. In many years, dry weather conditions often lead to quick increases in corn earworm populations so be sure to check trap catches frequently.

Pickling Cucumber Yields and Quality -Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

The varieties used for the machine harvest pickling cucumbers are female (gynoecious or predominantly female) hybrids. The typical ratio in a mixture of seed is 88% female hybrid and 12% male variety to provide the pollen for fertilization and subsequent fruit set. The use of the female hybrids at high populations (50-60,000 plants per acre) helps achieve a concentrated set of fruit, which facilitates the once-over mechanical harvest.

High temperatures will induce male flower development in the female hybrids. This is aggravated by long days and any moisture stress. We have seen examples of this in some non-irrigated corners of fields or in fields where mechanical problems have hindered irrigation. Other stresses, such as fertility, herbicide injury, or soil compaction can also cause a change in sex expression.

Yield reductions obviously occur under such situations, but increased deformed fruit, known as crooks and nubs also occurs. Pickling cucumbers that are blossoming, setting fruit, and planted in high populations for mechanical harvest are using over ¼ inch of water per day when temperatures are in the 90s.

Good irrigation management is needed to maximize the investment in production and in bee rentals and to achieve good yields and quality.

Laurel Auction Market Opens - Tracy Wootten, Extension Associate – Vegetable Crops, wootten@udel.edu

The Laurel Auction Market officially opened on July 8, 2002. Current prices reflect a strong market for sellers. Daily prices at the Auction Market, can be accessed at the following website:

http://auctiondata.delmarvaproduce.com/dailypricereport.cfm

or by phone at (302) 875-3358.

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

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 07/10/02 07/09/02 07/08/02 07/07/02 07/06/02 07/05/02 07/04/02 07/03/02

Bridgeville, DE 1 0 1 1 1 1 1

Charles Co. 2 0 0 0 0 0 0

Collins Farms 2 0 1 1 0 1 0

Galestown, MD 2 0 1 1 0 2 1

Georgetown, DE 0 1 1 0 1 2 4 3

Glenville, MD 2 0 0 0 0 0 0

Hebron 2 0 1 1 0 1 0

Hog Creek Rd. 1 0 0 0 0 0 0

Salisbury, MD 3 0 2 0 0 1 3 0

Vincent Farms 2 0 1 1 2 3 0

Westminster 2 0 0 0 0 0 0

White Marsh 2 0 0 0 0 0 0

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

should be applied using MELCAST. Accumulate EFI (environmental favorability index) values beginning the

day after your first fungicide spray. Apply a fungicide spray when 30 EFI values have accumulated by the

weather station nearest your fields. Add 2 points for every overhead irrigation. After a fungicide spray, reset

your counter to 0 and start over. If a spray has not been applied in 14 days, apply a fungicide and reset the

counter to 0 and start over. The first and last day listed above can be partial days so use the larger EFI value

of this report and other reports for any specific day.

If, for some reason, a serious disease outbreak occurs in your field, return to a weekly spray schedule.

More detailed information concerning MELCAST and sample data sheets are available on the web at http://www.agnr.umd.edu/users/vegdisease/vegdisease.htm.

Vegetable Diseases - Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Potato Disease Advisory.

Late Blight Advisory

Disease Severity Value (DSV) Accumulations as of July 9, 2002 are as follows:

Location: Joe Jackewicz Farm, Magnolia, DE. Greenrow: April 10, 2002

Remember that 18 DSV’s is the threshold to begin a spray program for late blight.

Date	Total DSV	Spray Recommendation
5/1	12	None
5/11	19	5 days, low rate
5/19	23	10 days, low rate
5/22	23	10 days low rate
5/27	27	10 days low rate
5/29	30	7 days, low rate
6/3	33	7 days, mid-rate
6/5	33	10 days, mid-rate
6/9	38	7 days, high-rate
6/13	39	10 days, high-rate
6/16	58	5 day mid- rate
6/19	60	10 day mid-rate
6/23	63	7 day high rate
6/26	64	10 day high rate
6/30	66	10 day high rate
7/9	66	10 day high rate

Late blight has not been a problem here in Delaware for many years and unless you have seed from an unknown source the risk of late blight is very low.

NOTE: For this greenrow date and location we have accumulated 644 P-days as well. P-days are a measure of potato plant growth somewhat similar to growing-degree-days. When 400 P-days have been exceeded conditions for early blight infection are more favorable and disease may begin to show up 5-7 days later. Continue fungicide sprays for early blight.

The hot, dry weather is not conducive for foliar diseases except early blight.

With harvest underway I have seen the first samples of pink rot. Look for darkened lenticels and infection from the stem end. When infected tubers are cut the infected creamy white but firm potato flesh turns pink in 10-15 minutes depending on conditions. Grade carefully to remove infected potatoes. Leave any areas in the field and harvest after the potatoes have decayed. Pink rot favors low areas or compacted areas.

Sweet Corn.

Be on the lookout for foliar diseases on irrigated sweet corn. We have seen some isolated outbreaks of gray leafspot and Northern corn leaf blight on processing sweet corn. Unfortunately, there is not much information from our area on the impact of these diseases on quality or yield. Under most circumstances fungicides are not warranted but Tilt, Quadris, and mancozeb are labeled for control of most foliar diseases of sweet corn. Bravo (chlorothalonil) is not labeled for processing sweet corn.

Also be on the lookout for sweet corn rust. Look for the small red pustules, once observed on corn in the whorl stage or earlier, apply a fungicide such as Bravo (fresh market only), Quadris, Tilt or mancozeb for control. Older corn will not benefit from an application.

MELCAST for Watermelons.

Location: Joe Jackewicz Farm, Magnolia, DE. Greenrow: April 10, 2002

Remember that 18 DSV’s is the threshold to begin a spray program for late blight.

Field Crops

THURSDAY, JULY 18, 2002

Weather Summary

Week of July 3 to July 10, 2002