Volume 9, Issue 13 June 22, 2001
Volume 9, Issue 13 June 22, 2001
Vegetables
Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Insect Trap Catches.
The decision to treat peppers, snap beans and sweet corn for corn borers and corn earworm is based on a combination of field scouting and trap catches. Be sure to check our website, (http://www.udel.edu/IPM/traps/latestblt.html) for the most recent BLT and pheromone trap catches in your area. Trap catches are updated 3 times per week on the website. You can also call the Crop Pest Hotline at 1-800-345-7544 (in-state only) or 302-831-8851. Trap catches are updated on Tuesday and Friday on the hotline.
Lima Beans.
Watch for spider mites on seedling stage lima beans. 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 of spider mites in lima beans. The earliest planted fields should also be scouted for lygus bugs and stinkbugs. Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. Lannate or Capture can be used if both species are present. A higher rate of Capture (4 oz/A) will be needed if stinkbugs are the predominant insect present.
Peppers.
Corn Borer catches have dropped to < 2 in all areas of the state. 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.
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. Provado, Furadan or a pyrethroid will provide control. Aphid populations have also started to increase. Before 2 weeks from harvest, the threshold is 4 aphids per leaf. Within 2 weeks from harvest, the treatment threshold increases to 10 aphids per leaf. In general, Colorado potato beetle populations are light to moderate in most fields. If Admire was used at planting, be sure to alternate to Agri-Mek or Spintor when threshold levels of larvae or newly emerged adults are detected.
Snap Beans.
Once corn borer catches start to increase, 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 6-day schedule in most areas of the state except in the Rising Sun areas where sprays should be applied on a 4-day schedule. Be sure to begin sampling your latest planted fields for fall armyworm larvae. We expect to see the first larvae during the next 7-10 day period. No controls will be needed until 15% of the plants are infested. The best options for whorl stage infestations will be Avaunt, Lannate, Spintor or Warrior. In general, two applications are needed to get effective fall armyworm control in whorl stage sweet corn.
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 |
|
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 |
The wet weather over the past weekend was favorable for the accumulation of 16 DSV’s. Growers should be applying a fungicide for late blight control at this time. Early blight susceptible varieties will benefit from fungicide application now that 416 P-days have accumulated.
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.
Note: Late blight has not gone away! Be sure to keep up with protective fungicide applications. The following is from an email to Bob Mulrooney from a PA pathologist:
Late blight was recently detected and confirmed on tomato transplants in a
greenhouse in southwestern PA. Some plants likely were planted in some gardens before the problem was detected. When the problem was detected, all remaining plants were destroyed. PDA is working on isolation for further testing (US type, etc).
I suspect that potato tubers infected last season (seed potatoes, cull piles, or compost bins) are the source, but we do not have evidence at this
time. I am warning growers in southwestern PA that late blight inoculum likely is lurking somewhere nearby, and that fungicide protection will be necessary whenever BLITECAST indicates conditions favor development of the disease.
Although we are shocked to detect late blight so early in the season, I am glad we have the early warning. Last season, fungicide programs gave us excellent control in PA, and I do not know of any commercial loss where fungicides were applied as recommended.
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 |
6/13 |
6/14 |
6/15 |
6/16 |
6/17 |
6/18 |
6/19 |
6/20 |
|
Bridgeville, DE |
0 |
2 |
0 |
0 |
7 |
1 |
1 |
2 |
|
Laurel, DE (Collins Farms) |
2 |
3 |
2 |
1 |
6 |
1 |
1 |
3 |
|
Galestown, MD |
2 |
3 |
0 |
2 |
7 |
1 |
1 |
2 |
|
Georgetown, DE |
2 |
2 |
0 |
1 |
6 |
2 |
1 |
1 |
|
Hebron, MD |
2 |
4 |
2 |
1 |
7 |
3 |
1 |
3 |
|
Salisbury, MD |
3 |
4 |
2 |