Volume 9, Issue 11 June 8, 2001
Volume 9, Issue 11 June 8, 2001
Vegetables
Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Cucumbers.
Continue to watch pickles and fresh market cucumbers for economic levels of aphids and cucumber beetles populations. Beetles can easily be found in seedling stage cucumbers. Actara, Thiodan, a pyrethroid or Lannate will provide control. Aphid populations are starting to build so scout fields carefully for aphids. As temperatures increase, populations will quickly explode since predators were lagging behind with the recent cooler weather. 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. If Agri-mek is used for spider mite control, it should not be combined with fungicides with sticker formulations similar to the sticker in Bravo Weatherstik. Since Agri-mek is translaminar, these stickers prevent the material from moving into the leaves. Recent applications of Agri-Mek applied when numerous eggs and nymphs were found have provided good spider mite control. Capture has provided good control of exploded mite populations. Be sure to rotate miticide chemistries to avoid the development of resistance.
Peas.
Continue to sample fields for pea aphids starting at the bud stage and continuing through harvest. Populations continue to increase in fields throughout the state. A treatment is needed if you can find 50 or more aphids per sweep.
Peppers.
The first corn borer sprays will be needed when fruit is ½-inch in size or larger. Sprays should then be applied on a 7–10 day schedule depending on material selection and corn borer pressure. 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, small and large larvae can be found in many fields. Actara, Leverage, Spintor, or Provado will provide control. Agri-Mek will also provide control of larvae and should be considered as a rotational material. ECB egg masses and stem entrances can be found in potatoes. If trap catches are being used to time sprays, a treatment will be needed this week. Ambush, Baythroid, Furadan, Leverage, 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. Potato leafhopper populations have started to increase and nymphs can be found. 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, Leverage or Provado will provide control. Cutworm activity has also been detected by a consultant in later planted potatoes. Although no thresholds are available, a treatment should be considered if 3-5% of the stems are cut and larvae are less than 2 inches long. A pyrethroid will provide control. Aphid populations are still low in most fields. From bloom until 2 weeks from harvest, the treatment threshold is 4 per leaf. If melon aphids are found, the threshold should be reduced by one-half. Actara, Provado or Fulfill will provide control.
Snap Beans.
Fresh market and processing snap beans in the bud to pin stage should be sprayed for corn borer in areas when corn borer trap catches range from 2 to 5 per night. Orthene or Address should be used at the bud and pin stages on processing beans. Once pins are present on fresh market snap beans, a 7-10 day schedule should be maintained for corn borer control. Lannate, Asana or Capture are labeled. Capture has a 9-day REI (restricted re-entry interval) in fresh market snap beans. Continue to watch for thrips and leafhoppers in seedling beans. We are starting to see an increase in the levels of both insects. A treatment is needed if you find 5-6 thrips per leaflet or 5 leafhoppers per sweep. If both insects are present, the threshold of each should be reduced by ½ the level for each insect. If plants are small and no buds are present, dimethoate will provide cost-effective control of both insects. Asana, Capture or Orthene will also provide thrips and leafhopper control.
Sweet Corn.
We continue to find economic levels of true armyworms in sweet corn planted into a burned down small grain cover. The treatment threshold is 15% infested plants. Continue to watch the earliest planted fields for European Corn Borer larvae. We continue to find 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. Since corn earworms are starting to fly, a silk application will be needed as soon as corn planted under plastic begins to silk. Be sure to check local trap catches which are updated on the IPM website three times per week at http://www.udel.edu/IPM/traps/latestblt.html .
Vegetable Diseases - - Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Potatoes.
Late Blight Update
|
Date |
Total DSV |
Spray Recommendation |
|
5/16 |
0 |
|
|
5/17 |
11 |
|
|
5/20 |
29 |
|
|
5/30 |
51 |
5-day, low rate |
|
6/3 |
57 |
5-day, low rate |
|
6/5 |
57 |
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. Early blight susceptible varieties will also benefit from a fungicide application beginning now. The early blight prediction model, which is part of the WISDOM software I use for late blight predictions, recommends beginning a spray now for early blight. We will exceed the 300 P-days in a few days, which is the target for beginning a spray program for early blight caused by Alternaria solani.
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 nickel-sized until flowering, and repeat 14 days later.
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 |
5/30 |
5/31 |
6/1 |
6/2 |
6/3 |
6/4 |
6/5 |
6/6 |
|
Bridgeville, DE |
|
0 |
0 |
5 |
4 |
0 |
1 |
1 |
|
Laurel, DE (Collins Farms) |
|
0 |
0 |
3 |
1 |
0 |
1 |
2 |
|
Galestown, MD |
|
0 |
0 |
5 |
3 |
0 |
1 |
2 |
|
Georgetown, DE |
1 |
0 |
0 |
4 |
3 |
0 |
0 |
1 |
|
Hebron, MD |
|
0 |
0 |
5 |
2 |
0 |
1 |
4 |
|
Salisbury, MD |
0 |
0 |
0 |
4 |
2 |
0 |
1 |
4 |
|
Laurel, DE (Vincent Farms) |
|
0 |
0 |
4 |
3 |