Volume
10, Issue 6
May 3, 2002
Volume
10, Issue 6
May 3, 2002
Vegetables
Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Asparagus.
We have started to see an increase in asparagus beetle egg laying activity on spears. A treatment is recommended if 2% of the spears are infested with eggs. Since adults will also feed on the spears, a treatment is recommended if 5% of the plants are infested with adults. Sevin, Lannate, Ambush, or Pounce will provide control.
Potatoes.
Continue to check potatoes for an increase in Colorado potato beetle egg hatch. The treatment threshold is 4 small larvae per plant or 1.5 large larvae per plant. If both small and large larvae are present, these thresholds should be reduced by ½ for each. Actara, Spintor or Provado will provide good control of adults and larvae. Corn borer moth populations are still low -- generally less than one moth per night. The most recent blacklight trap catches can be found at http://www.udel.edu/IPM/traps/latestblt.html. Trap catches will be updated on the IPM website 3 times per week (Mon., Wed., and Friday) starting May 6. As of this date, no potato leafhoppers have been found in potatoes.
Watermelons.
As soon as plants are set in the field, you should begin scouting for cucumber beetles, aphids and spider mites. Since cucumber beetle populations were high at the end of last season and overwintering conditions were favorable, be sure to look for beetles, especially on field edges near overwintering sites. Foliar products can provide good cucumber beetle control; however, multiple applications of a pyrethroid or Sevin may lead to spider mite outbreaks later in the season. So be sure to scout fields and only treat if populations are causing damage. Admire or Platinum can also be applied through the drip and should provide both beetle and aphid control. There have been reports of low levels of aphids on plants in the greenhouse. If plants are ready to set out, the best option is to check plants for aphids as soon as they are set in the field. The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf. Actara, Fulfill, Lannate and Thiodan are labeled on melons and will provide melon aphid control. These materials should be applied before aphids explode. Overwintering conditions were also favorable for spider mites so begin checking small plants for mites within a week of setting them in the field. If populations increase gradually and you find a high percentage of immature mites, Agri-mek has provided good control. However, if populations explode quickly and you are finding mostly adult mites, Capture, Danitol or Kelthane should be used. No controls should be needed until 20- 30% of the crowns are infested with 1-2 mites per leaf.
Vegetable Diseases
- - Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Section 18 Granted.
For the second year EPA has granted Delaware and Maryland a section 18 emergency exemption for the use of Acrobat (dimethomorph), manufactured by BASF, to control Phytophthora blight (Phytophthora capsici) in squash (summer, winter, pumpkins), cantaloupes, watermelons, and cucumbers. The section 18 label can be found at the following address: http://www.rec.udel.edu/Update02/Updatepdf.htm
in PDF format. This product is labeled at 6.4 oz/A for a maximum of 5 applications per season and a 4 day pre-harvest interval. It is a useful tool in an overall program to manage Phytophthora blight. It must be tank mixed with another fungicide labeled for Phytophthora blight, eg., fixed copper, but not mefanoxam (Ridomil Gold 4E, UltraFlourish 2E) or metalaxyl.
Sweet
Corn.
To control the flea beetles that transmit Stewart's wilt plant seed treated with Gaucho, apply Counter 20CR at planting or apply insecticides once thresholds are reached or at the spike stage of growth. Plant resistant varieties whenever possible.
Snap
Beans.
To prevent Pythium damping-off apply Ridomil Gold in a band over the row at seeding or apply Ridomil PC 11G in the furrow. For added control of Rhizoctonia pre and post emergence damping-off use Maxim treated seed.
Pickling Cucumber Weed Control - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Strategy is a pre-mix product from UAP that combines Command 3ME and Curbit 3E. It is labeled for cucumbers, melons, pumpkins and squash. In pickling cucumbers, it can be used as a pre-emergence material, not incorporated. The two pint rate of Strategy equals 5.3 oz/A of Command and 17 oz/A of Curbit. If using Strategy for pickling cucumbers, 8 to 15 ounces of Curbit should be added to obtain the desired Curbit rate of 1.5 to 2 pints/A.
Most pickling cucumber growers have been successfully using 4-5 ounces of Command 3ME plus 1.5 to 2 pints of Curbit per acre.
Breakouts of grass can be controlled with Poast. Nutsedge can be controlled with Sandea, which received a 24c local needs label last year for cucumbers.
Field Crop Insects
- Joanne Whalen, Extension IPM
Specialist;
jwhalen@udel.edu
Alfalfa.
At this time, all spring planted fields should be sampled for leafhoppers. Within a week of first cutting, be sure to begin sampling all alfalfa fields for potato leafhopper adults. The first adults have migrated from the south and generally cause the most damage in spring planted fields. The treatment threshold is 20 per 100 sweeps in alfalfa 3 inches tall or less. In 4-6 inch tall alfalfa, the threshold increases to 50 per 100 sweeps. Ambush, Baythroid, dimethoate, Mustang, Pounce or Warrior all provide effective control.
Field
Corn.
With recent rains and cooler weather, be sure to watch spike to 3-leaf stage corn for slug activity. Slugs can easily be found under the trash in no-till situations. Treatment options for slugs include the application of metaldehyde baits ( e.g.Deadline MPs and TrailsEnd LG) or the use of liquid nitrogen at the spike to one leaf stage. In general, both treatment options will help to reduce the slug activity buying time to enable the crop to outgrow the problem.
Small
Grains.
In addition to grass sawflies, the first true armyworms have
been found in wheat and barley in
Black
Cutworm Pheromone Trap Counts
April
20 through
Trap
Counts Provided by UAP Inc.,
|
Location |
# Moths |
Location |
# Moths |
|
|
0 |
|
1 |
|
Bridgeville |
2 |
Little Creek |
19 |
|
Cheswold |
0 |
|
10 |
|
Dagsboro |
1 |
|
0 |
|
Delmar |
0 |
|
0 |
|
|
0 |
Sandtown |
1 |
|
|
0 |
|
0 |
|
Harrington E |
1 |
Selbyville |
0 |
|
Harrington N |
3 |
|
2 |
|
Kenton |
0 |
Townsend |
6 |
|
|
0 |
|
2 |
|
Lewes |
0 |
|
|
Field Crop
Diseases - - Bob Mulrooney, Extension
Plant Pathologist; bobmul@udel.edu
Wheat.
Powdery mildew is
increasing since the return of the cool weather and rain. Be sure to check your
fields regularly for the presence of mildew. Most wheat is headed out so the
window for fungicide application is narrowing. Fungicides (Tilt or Stratego) cannot be applied after flowering (Feekes Growth state 10.5). Many varieties have some mildew
in the lower part of the canopy, but none in the upper part (the flag leaf and
the two leaves below). If the wheat is flowering or has flowered and there is
no mildew on the top three leaves, fungicides are not necessary for powdery
mildew under most conditions. Some varieties such as Roane, Pocahantas,
Century II, Coker 9025, need to watched. They have
heavy infection levels in the lower canopy in our
Grain Marketing Highlights - Carl
German, Extension Crops Marketing Specialist; clgerman@udel.edu
Commodity
Prices Await Market News
Weekly export
inspections for the week ending 04/29 were friendly for
Grain
Stocks Decline
Stocks of grain
held in terminals and elevators included in USDA's weekly Grain Stocks report
dropped another 2%, to 38% last week. That's 5% below stocks at this time a
year ago.
Marketing
Strategy
We are currently
getting a "mild" bounce in the corn and wheat pits. The bounce is
said to be mild because there doesn't appear to be any news that can sustain
much of a rally at this point in time. We are in a continuing holding pattern
for advancing new crop sales for corn, wheat, and soybeans. With about 26% of
the nation's 2002 corn crop planted, the market will be paying attention to the
advancement of planting progress over the next three to four weeks. Corn needs
to be planted on or before June 10th in the
In looking at fields early this week, we found that a number
of newly emerged corn fields were showing up as bright yellow in color rather
than the green one would expect. In
addition, wheat fields that had been dark green the week before were much
lighter green in color and gave the appearance of loosing vigor. These observations have not been limited to
We suggest that much of this yellowing that we’re seeing is
due to the cloudy, cool, and moist weather the corn has been experiencing the
past week to ten days. Root growth has
been slow, nutrient uptake has been below normal and subsequently the ability
of the plant to produce chlorophyll (the pigment that gives plants their green
color) has been limited, so the plants have turned yellow. We would expect that with the
long-range forecast predicting warm, sunny weather from Friday through the
weekend that much of the poor coloration in corn and the lighter green color in
small grains will disappear.
Keep
in mind that plants growing under stress will not be as tolerant of
herbicides. Check the label before
making any post treatments to avoid injury. Some materials will have a label
statement “not to apply when corn is under stress (moisture, injury, poor
growing conditions, etc) or below a minimum temperature”.
Frost Damage on
Wheat - Richard
W. Taylor Extension Agronomist,
rtaylor@udel.edu
, Derby Walker, Jr. ,
Extension Ag Agent, Sussex County, derby@udel.edu , Bob Uniatowski, Associate Scientist, bobuni@udel.edu
In the past few weeks, we’ve had a number of fields that
have shown frost or freeze damage. The
injury occurred as late as last week when some small corn that was planted
generally in fields protected from the wind showed severe frost damage. In most, if not all cases, the below ground
growing point was not injured so little permanent damage was done to the
corn.
For wheat injured last week, we were seeing dead growing
points on small newly emerged tillers as illustrated in the photo below. We suspect yield impact will be minimal since
in the fields we looked at the number of tillers per plant was very high and
only the small, weak tillers appeared affected.
Examination of some of the small tillers that were not injured showed
heads in the boot with only about 6 potential kernels. Keep in mind that these tillers often are too
short to even get caught by the combine.
Another type of injury that we observed was leaf tip burn and chlorosis as illustrated in the photo below. We were seeing it occur mostly on the flag leaf and symptoms and amount of leaf area affected was unlikely to impact yield potential. It should be noted, too, that the wheat had actually begun to shed pollen which is about three weeks earlier than normal.
Finally, we also have seen wheat plants that were severely
impacted by the hard freeze of several weeks ago. The photos below show how the lower nodes of
the primary tillers were killed by the freeze.
In many cases, the leaves above the injury point were still green and
appeared alive although we suspect that the hot weather of last week finished
the job the freeze injury began. Most of
the plants observed were sending out new tillers. This damage was likely to severely impact
yield even with the new tiller production.
We suspect that at harvest the field will have heads in all states of
maturity as well as of variable size (number of kernels and grain height above
the soil surface).
For more detailed descriptions and the implications of cold
damaged wheat, please refer back to the Weekly Crop Update for
UPCOMING MEETINGS:
Strawberry Twilight
University of
Special Guests and
Topics:
Ø
Strawberry
Nutrient Management: Dr. Gordon Miner, NCSU
Ø
SkyBit for Frost
Protection: Dr. Joe Russo, Agricultural Meteorologist
Ø
Strawberry
Weed Control: Scott Rowe and Dr. Ed Beste
Ø
Laminating
Plastic Beds: Mike Newell and Paul Clarke
Ø
Plus:
More on varieties, strawberry plasticulture, and
carryover with Dr. Harry Swartz, Bob Rouse, and USDA.
For more information, call 410-827-8056, ext. 115
TWILIGHT CROP MANAGEMENT SESSION
When:
Where:
¾-mile
east of Armstrong Corner, on
What:
Come join your fellow
farmers and our Extension Specialists for an interactive and hands-on experience as we address “in-season”
wheat/barley, corn, and soybean
production issues to include:
·
variety trials,
·
agronomics and fertility,
·
insect,
weed, and disease management.
As always there will be time to discuss your
questions.
Important:
DDA will award (1) private applicator re-certification
credit in the agricultural plant category.
Credits will also be available for Certified Crop Advisors.
Whether or not you can join us on the 7th, stop
by at your convenience throughout the season. Handouts and maps will be
available in the plastic information box mounted behind the UD sign. This meeting is free, and
everyone interested in attending is welcome. For more information or special
consideration in accessing this meeting, please contact our office in advance
at (302) 831- 2506.
HOPE TO SEE YOU ON THE 7th!
Carl P. Davis
Ag Fact
Americans
spend 10% of their income on food;
Many people
think processors and retailers extract an exorbitant share of the consumer’s
dollar, but the record shows (through consolidations and closures), that the
food industry is highly competitive and works on thin margins.
Week of April 25 to
|
|
Rainfall: April 25: 0.27
inches April 27: 0.04
inches April 28: 1.32
inches |
|
|
|
Air Temperature: |
|
Highs
Ranged from 75°F on April 28 to 60°F on April 25 & 27. |
|
Lows
Ranged from 53°F on April 28 to 39°F on April 26 & 30. |
|
Soil Temperature: |
|
58°F
average for the week. |
|
(Soil
temperature taken at a 2 inch depth, under sod) |
Web Address for the U of D
Compiled and Edited By:
Tracy Wootten
Extension
Associate - Vegetable Crops
Cooperative
Extension Education in Agriculture and Home Economics, University of Delaware,
Delaware State University and the United States Department of Agriculture
cooperating, Robin Morgan, Dean and Director.
Distributed in furtherance of the Acts of Congress of
May 8 and