Volume 9, Issue 15 July 6, 2001
Volume 9, Issue 15 July 6, 2001
Vegetables
Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Lima Beans.
Continue to scout fields for lygus bugs, stinkbugs and green cloverworm. Treatment for lygus bugs and/or stinkbugs should be considered if you find 15 adults and/or nymphs per 50 sweeps. A treatment for cloverworms will be needed if defoliation exceeds 20% prebloom or 10% during podding. Lannate or Capture will provide control of all 3 insects. The 4-oz per acre rate should be used if stinkbugs are present.
Potatoes.
Second generation Colorado potato beetle adults have started to emerge and larvae are still present in fields. Spintor, Leverage, Provado, and Actara will provide control. We continue to see an increase in green peach aphid populations. The treatment threshold is 2 per leaf in later planted fields and 4 per leaf in the earliest planted fields. Provado, Leverage or Fulfill will provide control.
Snap Beans.
Continue to sample seedling beans for thrips, leafhoppers and green clover worm activity. Corn borer activity remains low.
Sweet Corn.
Fresh market silking sweet corn should be sprayed on a 6-day schedule in most areas of the state except in the Dover, Laurel and Seaford areas where a 3-4 day schedule is needed. Be sure to watch the latest planted fields for fall armyworm larvae present in the whorls. A treatment will be needed if you find 15% of the whorls infested. In general, 2 applications are needed to achieve control. Lannate, Spintor or Warrior have provided the best fall armyworm control in whorl stage sweet corn. Avaunt should also provide good control.
Vegetable Diseases
- - Bob Mulrooney,
Extension Plant Pathologist; bobmul@udel.edu
Phytophthora fruit rot control. Phytophthora fruit rot continues to be a problem for pickle and slicing cucumber growers. Since Ridomil Gold is only labeled for at planting applications and has not provided Phytophthora fruit rot control when we have heavy rain events, Acrobat 50WP was approved for use under the EPA Emergency Exemption program last April. Acrobat 50WP is manufactured by BASF. This fungicide will help manage Phytophthora blight caused by Phytophthora capsici. Recent research work done in various areas of the country has shown that it can be effective in reducing Phytophthora blight on cucurbits including cantaloupes, cucumbers, squash (summer, winter and pumpkins, and watermelons) Acrobat will provide control of Phytophthora only and needs to be tank mixed with another protectant fungicide such as chlorothalonil (Bravo) or mancozeb (Dithane). Because it has a unique mode of action,it must be mixed with a tank-mix partner.
Acrobat can provide some protection of the fruit rot stage of Phytophthora blight on cucumbers. The crown rot phase of the disease does not appear to affect cucumbers so we get no early warning that the fungus is present. On summer squash,the disease produces a crown rot as well as a fruit rot. Phytophthora has been present in New Jersey on summer squash and peppers for several weeks following the heavy rains. In cucumbers it is suggested that if Phytophthora fruit rot needs to be prevented and the disease is present in your area, the best time to apply Acrobat would be when the fruit are present and repeat 7 days later. This is not a systemic fungicide so applications should be made to maximize coverage by increasing the volume of water.
For other longer season crops such as pumpkins or winter squash wait until fruit are present before beginning a program. A maximum of five applications are allowed so watch your timing to prevent infection during this hot, humid weather.
Acrobat is not a magic bullet for control of Phytophthora
blight, it is meant to be part of an integrated control program. The following
bears to be repeated. The best control is to grow the plants on beds, if
practical, to get them out of the water and to rotate for long periods of time
(3 years or more) away from susceptible crops. For vegetable growers this is
difficult because many crops are susceptible, and irrigation availability
limits rotation intervals. A combination of rotation and other horticultural
practices combined with fungicides may provide some relief. Fungicides alone
have not provided a solution as results from New Jersey on Phytophthora blight
on peppers has shown. What drives this disease is water. Choosing well-drained
fields, avoiding planting wet areas, and planting on high beds combined with
fungicides that are labeled for the crop have provided a measure of control.
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 |
|
6/7 |
57 |
7-day, low rate |
|
6/11 |
59 |
10-day, mid rate |
|
6/13 |
60 |
10-day, mid rate |
|
6/17 |
76 |
7-day mid rate |
|
6/20 |
76 |
7-day high rate |
|
6/24 |
88 |
7-day high rate |
|
6/27 |
88 |
7-day high rate |
|
7/1 |
89 |
10-day, high rate |
|
7/4 |
90 |
10-day, high rate |
Growers should be applying a fungicide for foliar diseases. There have been no reports of late blight on potatoes from our region.
Pythium vine rot was seen on vines in wet, low areas. Infection by Pythium is very dark almost black and white fuzzy growth can usually be seen on the infected areas of the vine. Soft rot bacteria have also been seen on vines where corn borer has wounded the vines. The bacteria splash from the soil onto the damaged vines, causes a black slimy decay, and the vine yellows and dies.
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 |
6/25 |
6/26 |
6/27 |
6/28 |
6/29 |
6/30 |
7/1 |
7/2 |
|
Bridgeville, DE |
2 |
2 |
2 |
1 |
2 |
1 |
0 |
3 |
|
Laurel, DE (Collins Farms) |
2 |
3 |
3 |
3 |
3 |
1 |
1 |
3 |
|
Galestown, MD |
2 |
2 |
3 |
3 |
3 |
3 |
1 |
3 |
|
Georgetown, DE |
1 |
2 |
3 |
4 |
3 |
5 |
1 |
2 |
|
Hebron, MD |
2 |
3 |
2 |