Volume
11, Issue 24
September 5, 2003
Vegetables
Vegetable Insects
-
Cabbage.
Diamondback (DBM)levels have increased significantly in untreated fields. However, we can still find both DBM and cabbage looper in fall cabbage fields. The treatment threshold is 5% of the plants infested. 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, Intrepid (8 oz/a) or Confirm (8 oz/acre) will also provide control.
Cucumbers.
Continue to watch for aphids in pickling and fresh market cucumbers. A treatment should be applied if 10 to 20 percent of the plants are infested and populations are increasing. Lannate (3 days to harvest) should provide aphid control. Fulfill will also provide control. A penetrating surfactant (e.g. LI-700 or AD-100) is recommended with Fulfill (14 days to harvest). Thiodan has also provided control as long as populations are not exploded at the time of application.
Lima Beans.
Continue to scout fields for lygus bugs, stinkbugs and corn earworm. For lygus and stink bugs, treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. A treatment is recommended for corn earworm if you find one worm per 6 foot of row.
Peppers.
At the present time, all peppers should be sprayed on a 5-7 day schedule for beet armyworm, corn borer, corn earworm, and fall armyworm. You should also watch for increases in aphids and spider mites. If aphids are present and leaves are not curling, Lannate at 1.5 pt/A (3 days to harvest) should provide control. Actara (0 days to harvest), Assail (7 days to harvest), Fulfill (0 days to harvest), and Provado (0 days to harvest) will also provide aphid control. A penetrating surfactant should be used with Fulfill. Agri-Mek, Capture or Kelthane are labeled for spider mite control in peppers.
Snap Beans.
Sprays are still needed at the bud and pin stages on
processing snap beans for corn borer control. A corn earworm material will also
be needed at the pin spray for corn earworm.
After the pin spray, sprays will be needed on a 5-day schedule until
harvest, except in the
Spinach.
As soon as plants emerge, fields should be scouted for webworm and beet armyworm larvae. Controls should be applied when worms are small and before they have moved deep into the hearts of the plants. Also, remember that both insects can produce webbing on the plants. Confirm, Intrepid or Spintor will be needed for beet armyworm control. If webworms are the predominant species, Ambush, Pounce, Confirm (6-8 oz/acre), Intrepid (8-10 oz/acre) or Spintor (4-8 oz/acre) should be used. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm.
Sweet Corn.
Fresh market silking sweet corn should be sprayed on a 2-3 day schedule throughout the state. Be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in fresh market sweet corn (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html ).
UD IPM Black Light and Pheromone Trap Counts
Average Number of Moths per Night: September 1 to
|
Trap Location |
European Corn Borer Black Light |
Corn Earworm Black Light |
Corn Earworm Pheromone Trap |
|
|
|
|
|
|
2 |
15 |
15 |
|
|
27 |
58 |
7 |
|
|
Killens Pond |
3 |
17 |
0.5 |
|
Little Creek |
3 |
17 |
- |
|
6 |
41 |
34 |
|
|
1.5 |
9 |
19 |
|
|
1 |
4 |
9 |
|
|
|
|
|
|
|
1.5 |
6 |
2 |
|
|
|
- |
- |
3.5 |
|
1 |
15 |
18 |
|
|
21 |
44 |
- |
|
|
3 |
20 |
4 |
|
|
2 |
9 |
12 |
* Numbers can change
quickly. For the most recent trap
counts, access the website at (http://www.udel.edu/IPM/traps/latestblt.html)
or call 1-800-345-7544 (in-state); 1-302-831-8851 (out-of-state). Counts are updated on Tuesday and Friday.
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Vegetable Crop
Diseases –
Lima Beans.
Downy mildew
caused by the fungus, Phytophthora
phaseoli, was detected this Wednesday in the
A revised 24(c) label for Ridomil Gold/Copper is available
for

Downy mildew on baby
limas.
Lima bean pod rot
was also seen on lima bean pods. This can look very similar to downy mildew but
only the pods are infected not the petioles (leaf stalks) or the racemes
(flower stalks) that you see infected by downy mildew. Pod rot is caused by the
soil born fungus Phytophthora capsici
and there are no chemical controls for this disease. There are no resistant
varieties and crop rotation away from susceptible crops such as lima beans,
cucumbers, peppers, watermelons, squash, cantaloupes, and tomatoes for 5 years
is recommended.

Lima Bean Pod Rot.
Note
sparser growth; only pods will be infected
Sweet Corn.
Leaf diseases in late processing sweet corn have been
detected on susceptible hybrids. Southern
corn leaf blight, anthracnose leaf spot, and common rust have been
observed.
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Field Crop Insects
-
Forages.
We can now find low levels of webworms and fall armyworm in alfalfa and mixed stands, and fall armyworms grass hay fields. With the heavier fall armyworm populations in late-planted corn, emerging moths will be looking for attractive places to lay eggs. If fall armyworm is observed immediately after a cutting, a treatment may be needed if you find five or more per square foot in established stands. A treatment may be needed for webworms if you are greater than 2 weeks from harvest and 25 percent of the terminals have webbing. Baythroid, Mustang MAX and Warrior are all labeled for webworms and small armyworms in alfalfa. If fall armyworm is the predominant species, Steward should be considered in alfalfa. Sevin is labeled for alfalfa, pastures and grasses grown for seed.
Soybeans.
With the increase in corn earworm trap catches this past
weekend, the potential for podworms will remain moderate in late-planted beans
for the next two weeks. A combination of rainy weather, cool evenings and warm
days, generally results in populations
crashing from disease organisms so be sure to watch for diseased worms before
making a treatment decision. In addition, if most worms are large and you
already see old pod damage, the damage may already be done. As we move into
September, corn earworm will begin to enter their diapausing (overwintering)
stage so do not treat too quickly. Begin
scouting as soon as blossoms are present for corn earworm (CEW), beet armyworm
(BAW) and fall armyworm (FAW). Low levels of corn earworm (1-2 per 100 sweeps)
have been found in all counties and an occasional BAW and FAW have been found
in fields in
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Field Crop
Diseases –
Soybeans.
Downy mildew has
been seen on soybeans. Look for small angular yellow spots on the upper surface
of the leaf and a corresponding gray tuft of fungus growth on the underside of the
leaf. This is a disease of minor importance and has never resulted in any
detectable yield loss in DE.
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Grain Marketing Highlights -
Crop
Condition Ratings Lowered Again.
USDA has lowered weekly crop
condition ratings the past two weeks in a row. This has left commodity traders
scrambling to get on the right side of potential price moves. Market analysts
are now anticipating that the next supply and demand report to be released on
September 11th will show a further drop in production forecasts for both the
Market
Strategy.
Assuming new crop sales are up to
date, then it is time to hold up sales and see what develops. Commodity prices
could take on some new volatility going into next weeks release of the
September crop report. The next six weeks promises to present good sales
opportunities for finishing up '03 corn and soybean sales and in making initial
sales for '04 corn, soybean, and wheat production.
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Alfalfa Stand
Survival in a 2003 Season of Multiple Stresses - Richard W. Taylor, Extension Agronomist, rtaylor@udel.edu
;
In last week’s issue of Weekly Crop Update, we talked about the effects of potato leafhoppers (PLH) on alfalfa stands. However, PLH burn was not the only problem alfalfa producers experience in 2003. Among the other problems were compaction caused by harvest weather delays, mowed hay sitting in the field or windrowed in the field for long periods, baled hay left on the production field, delayed or infrequent harvests, and grassy weed competition.
What impact does
compaction have on alfalfa stands?
Once in place, compaction exists until the next renovation/rotation cycle. A layer of deep compaction is best alleviated by deep fall tillage when the soil has dried out and will fracture better with subsoiling equipment. Meeting these requirements can end up adding an extra half to full-season to the usual rotation cycle out of alfalfa.
What are the effects of windrows left for long-