Volume 9, Issue 19 August 3, 2001
Volume 9, Issue 19 August 3, 2001
Vegetables
Vegetable Insects
- Joanne
Whalen, Extension IPM Specialist; jwhalen@udel.edu
Cabbage.
Diamondback and cabbage looper larvae can both be found in fall cabbage. A treatment is recommended when 5% of the plants are infested with larvae. If both species are present, Avaunt (3.5 oz/acre), a Bt, Proclaim (3 oz/acre), or Spintor (4-5 oz per acre) will provide control. If cabbage looper is the predominant species, a pyrethroid or Confirm (8 oz/acre) will also provide control.
Cucurbits.
Striped cucumber beetle and squash bug populations continue to increase in cucumbers (fresh market and pickling), squash, pumpkins and watermelons. In addition to leaf damage and bacterial wilt transmission in cucumbers, they both can cause damage to the rinds of cucurbit fruit. A treatment should be applied for cucumber beetles if populations are increasing and before rind damage occurs. A treatment should be applied for squash bugs if you find just one egg mass per plant or when nymphs are first detected. Thiodan or a pyrethroid generally provide effective cucumber beetle control; however, multiple applications may be needed. Multiple applications of the highest labeled rate of a pyrethroid are generally needed for squash bug control.
Lima Beans.
As soon as pin pods are present, 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 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. A continuous pyrethroid program should not be used to avoid aphid explosions.
Snap Beans.
All processing snap beans in the bud and pins stages should be treated with Orthene for corn borer control. At the present time, a third treatment with Asana, Capture or Lannate will be needed within a week of harvest. If corn borer catches increase, multiple applications will be needed between the pin spray and harvest. In addition, when corn earworm catches increase to 10 per night, a pyrethroid should be combined with Orthene at the pin spray. As soon as pin pods are present, fresh market snap beans should be sprayed on a 7-day schedule with Lannate or Capture. Be sure to check blacklight trap catches in your area. Trap catches are updated on the IPM website three times per week at http://www.udel.edu/IPM/traps/latestblt.html .
Sweet Corn.
All fresh market
silking sweet corn should be sprayed on a 3-day schedule in Kent County and on
a 4-day schedule in Sussex County. Watch for aphid populations that are
increasing on the tassels and silks. Although this feeding does not cause a
direct yield loss, it can result in quality problems. A combination of Lannate plus
a pyrethroid will help to reduce aphid populations.
Correction to Days to Harvest for Pounce Use on Watermelon From Issue 18
Ambush and Pounce have 0 days to harvest with a 24 hour re-entry time, Thiodan is 2 days to harvest and 48 hour re-entry, and Capture has a 3 day restriction with a 24 hour re-entry.
Always read the label before mixing and applying any pesticides. Thank you for catching the error.
Vegetable Diseases
- - Bob Mulrooney,
Extension Plant Pathologist; bobmul@udel.edu
Lima Bean.
Lima Bean -Downy Mildew Alert.
Downy mildew was reported to be seen in the Milton area where they had 5 inches of rain last weekend. Be on the lookout, where there has been sufficient rainfall to favor downy mildew infection. Remember that prevention is the key to success with fungicides.
Since rainfall amounts can vary widely, fieldmen and growers should be keeping track of rainfall and average daily temperature for their area. Using the Hyre system and weather data from Georgetown, there was an infection period between July 5th and 10th which would predict downy mildew appearing about 10 days later, which apparently has happened. A second infection period has occurred between July 26 and August 1 indicating that mildew could appear in 7-10 days if the fungus is present. We presume that the fungus is present.
The Hyre system for predicting the occurrence of downy mildew on limas is as follows: when fields receive 1.2 inches or more of rain within 7 days and when the average daily temperature during this period is 78°F conditions are favorable for infection. Periods of fog or heavy dew can lower the amount of rain necessary for infection to occur. It appears from our data that a single day of 90°F does not cancel the prediction as the old predicting system would state. It may take several days above 90°F or a single day of 95°F or above to break the cycle. We do not know the upper temperature limits for the new races E and F.
Preventative applications of fixed copper Kocide 2000 or Champ DP are recommended for fields in flower or in later stages of plant development. The days-to-harvest interval is 0 days.
Important correction.
The rate for fixed copper for downy mildew control in lima beans is incorrect on page 84 in the 2001 Commercial Vegetable Productions Recommendations EB 137. It should read 2.0 lbs of product per acre not 0.66 lb.
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 |
|
7/8 |
92 |
10-day, high rate |
|
7/11 |
94 |
10-day, high rate |
|
7/15 |
94 |
10-day, high rate |
|
7/18 |
99 |
7-day, high rate |
|
7/22 |
102 |
7-day, high rate |
|
7/25 |
106 |
10-day, high rate |
|
7/30 |
116 |
5-day, mid rate |
|
8/1 |
117 |
5-day, mid rate |
Some low levels of bacterial soft rot are present in some fields. As potato vines decline, I am seeing black dot caused by the fungus Colletotrichum. It produces light- tan cankers at the base of stems and the infected areas are covered with the black fruiting bodies of the fungus, which looks like black dots thus the name. It is unclear if black dot reduces yields in the eastern states, but it is very common here.
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 |
7/25 |
7/26 |
7/27 |
7/28 |
7/29 |
7/30 |
7/31 |
8/1 |
|
Bridgeville, DE |
0 |
0 |