Volume 9, Issue 10 June 1, 2001
Volume 9, Issue 10 June 1, 2001
Vegetables
Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Cucumbers.
Both pickles and slicers should be watched for increases in aphid and cucumber beetle populations. Fresh market cucumbers are very susceptible to bacterial wilt vectored by cucumber beetles. Although pickling cucumbers grown in high-density rows can compensate for about a 10 percent stand loss, beetle feeding can reduce plant growth. If moderate feeding can be found in the cotyledons and/or the first true leaves and there is a history of bacterial wilt on your farm, a cucumber beetle spray should be applied. Actara, Thiodan, a pyrethroid or Lannate will provide control. A treatment should be applied for aphids if 10 to 20 percent of the plants are infested with aphids. Actara, Thiodan or Lannate will provide control.
Melons.
Economic levels of cucumber beetles, aphids and spider mites continue to be found. As vines begin to run, be sure to sample carefully for spider mites. The threshold is 20- 30% infested crowns with 1-2 mites per leaf. If populations of mites have exploded and adult mites are the predominant life stage, Capture, Danitol or Kelthane should be used. If the population is a mixture of eggs, immature mites and lower levels of adult mites, Agri-Mek should be used at 8 oz/acre. A second miticide application may be needed in 3-7 days depending on the population level at treatment time. If populations are heavy or numerous eggs are present at the time of treatment, at least 2-4 miticide applications will be needed. Be sure to also sample melons for aphids. The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf. Actara, Fulfill, Lannate and Thiodan are labeled on melons and will provide melon aphid control. Actara, Lannate and Thiodan will also provide cucumber beetle control. Capture will provide cucumber beetle and spider mite control.
Peas.
Be sure to sample fields for pea aphids starting at the bud stage and continuing through harvest. Populations have increased in fields throughout the state. With the recent cool, weather beneficial insect activity has started to lag behind.
Peppers.
When fruit is ½-inch in size or larger, peppers should be sprayed on a 7 –10 day schedule for corn borer control. Orthene or Address (both acephate) should be used on a 10-day schedule and will also provide pepper maggot control. Remember - only 2 applications of acephate at the 1 1/3 lb per acre rate can now be used. If a pyrethroid or Lannate is used, sprays should be applied on a 7-day schedule and dimethoate should be added to the mix for pepper maggot control. If no fruit is present, be sure to watch for larvae tunneling into the main stems of peppers. Sprays must be applied before larvae move into the stems to achieve effective control.
Potatoes.
Economic levels of CPB adults and small larvae can still be found in the earliest planted fields. Actara, Spintor or Provado will provide control. The first ECB egg masses and stem entrances have been detected in potatoes. Be sure to check our website (http://www.udel.edu/IPM/traps/latestblt.html) for the most recent moth catches in your area. If trap catches are being used to time sprays, the first application will be needed this week. Ambush, Baythroid, Furadan, Penncap, or Pounce will provide control. If you are scouting for infested terminals, the first treatment should be applied when 20-25% of the terminals are infested. Furadan or Monitor will provide the best control if you are waiting until you see infested terminals. Continue to sample for potato leafhopper adults and nymphs. As a general guideline, controls should be applied if you find ½ to one adult per sweep and/or one nymph per every 10 leaves. A pyrethroid, Actara or Provado will provide control.
Sweet Corn.
Be sure to watch the earliest planted fields for European Corn Borer larvae. We are starting to see our first larvae in whorl stage sweet corn. A treatment should be applied if 15% of the plants are infested. The best timing for a treatment is just as the tassels are emerging from the whorls. In recent years, the best corn control has been achieved with Ambush, Pounce, Penncap or Warrior.
Update on Sandea Herbicide for Cucumbers - Ed
Kee, Extension Vegetable Crops
Specialist; kee@udel.edu and Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
Sandea has received a 24c third party label in Delaware for use on cucumbers, both fresh market and pickling. The material can be used pre-emergence after planting,but before cracking at 2/3 to 1 ounce per acre. This application will control many broadleaf weeds, including redroot pigweed, lambsquarter, jimsonweed, and ragweed. It will also provide some control of yellow nutsedge. It can be tank-mixed with Command to obtain grass control.
Sandea can also be used as a post-emergence treatment at 2/3 to 1 ounce with nonionic surfactant at a rate of 0.25% of the spray solution (1 quart/100 gallons). The same weeds will be controlled, with better control of nutsedge to be expected. Check the label for a complete listing of weeds controlled.
Postemergence applications can be made after the crop has reached the 1-2 true leaf stage, but before the 5-6 true leaf stage. Applications must be made 30 days before harvest, and by ground application only.
Sandea cannot be applied to crops treated with soil applied organophosphate insecticides, nor should such insecticides be applied 7 days before Sandea application, or 3 days after.
Cucumber producers interested in using this material must sign a waiver of liability with the dealer, and with the Vegetable Growers Assn. of Delaware, which is the third party labeling organization. This waiver will be mailed out to the pickling cucumber growers and other slicer growers we have identified. If you are interested, contact Ed Kee at 856-7303 or by email (Kee@udel.edu).
Read the label carefully for other instructions and restrictions.
Vegetable Diseases
- - Bob Mulrooney,
Extension Plant Pathologist; bobmul@udel.edu
Potatoes.
To control pink rot caused by Phytophthora erythroseptica and P. nicotianae, and leak caused by Pythium apply Ridomil Gold MZ, Ridomil Gold /Bravo, or Flouronil between the time the potatoes are nickle-sized until flowering, and repeat 14 days later.
Late Blight Update - - Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
|
Emergence Date |
DSV’s May 16 |
DSV’s May 17 |
DSV’s May 20 |
DSV’s May 30 |
Recommendation |
|
April 28 |
0 |
11 |
29 |
51 |
5-day, low rate |
Potatoes that have reached greenrow (50% emergence) since May 18 have all reached more than 18 DSV’s.
Growers should be applying a fungicide for late blight control at this time. Please check the University of Delaware’s IPM website http://www.udel.edu/IPM for the most current DSV accumulations. DSV’s are updated twice a week.
Vegetable Diseases - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu
EFI Values (Environmental Favorability Index)
Do not use MELCAST if there is a disease outbreak in your field, it is a preventative program. Any questions, please call David Armentrout at (410) 742-8788 or e-mail: da88@umail.umd.edu
|
Location |
5/23 |
5/24 |
5/25 |
5/26 |
5/27 |
5/28 |
5/29 |
5/30 |
|
Bridgeville, DE |
|
0 |
0 |
2 |
4 |
1 |
1 |
0 |
|
Laurel, DE (Collins Farms) |
|
0 |
0 |
2 |
1 |
1 |
1 |
1 |
|
Galestown, MD |
|
1 |
0 |
2 |
4 |
0 |
1 |
1 |
|
Georgetown, DE |
1 |
1 |
0 |
1 |
2 |
1 |
1 |
0 |
|
Hebron, MD |
|
0 |
0 |
2 |
3 |
1 |
2 |
1 |
|
Salisbury, MD |
|
1 |
0 |
2 |
2 |
1 |
2 |
1 |