Volume 10, Issue 6
Vegetables
Vegetable Insects - Joanne Whalen, Extension
IPM Specialist; [email protected]
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.
May 3, 2002
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.
Watermelons .
As soon as plants are set in the field, you should
begin scouting for cucumber beetles, aphids and
Weekly Crop Update 1
Vegetable Diseases - - Bob Mulrooney, Extension
Plant Pathologist; [email protected]
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.
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 Crops
Field Crop Insects - Joanne Whalen, Extension
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;
[email protected]
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
IPM Specialist; [email protected]
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.
Weekly Crop Update 2
Small Grains .
In addition to grass sawflies, the first true armyworms have been found in wheat and barley in Kent and
Sussex Counties. Since sawflies can quickly clip heads in both crops, early detection is critical. Be sure to
shake plants to dislodge larvae feeding on the plants during the day. In both crops, the treatment threshold
for sawflies is 2 per 5 foot of row innerspace or 0.4 per foot of row. The armyworm threshold is one per foot
of row in barley and two per foot of row in wheat.
Black Cutworm Pheromone Trap Counts
April 20 through April 26, 2002
Trap Counts Provided by UAP Inc ., Seaford, DE and University of Delaware IPM
Location
# Moths
Location
# Moths
Argos Corner
0
Lincoln
1
Bridgeville
2
Little Creek
19
Cheswold
0
Middletown
10
Dagsboro
1
Milford
0
Delmar
0
Milton
0
Georgetown
0
Sandtown
1
Greenwood
0
Seaford
0
Harrington E
1
Selbyville
0
Harrington N
3
Smyrna
2
Kenton
0
Townsend
6
Laurel
0
Wyoming
2
Lewes
0
Field Crop Diseases - - Bob Mulrooney, Extension
Plant Pathologist; [email protected]
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 cond itions. Some varieties
such as Roane, Pocahantas, Century II, Coker
9025, need to watched. They have heavy infection
levels in the lower canopy in our Middletown
variety plots and have the potential for infection in
the upper leaves as well if the current weather
pattern continues.
Grain Marketing Highlights - Carl German,
Extension Crops Marketing Specialist;
[email protected]
Commodity Prices Await Market News
Weekly export inspections for the week ending
04/29 were friendly for U.S. wheat, with exports
reported at 23.769 million bushels, well above
Weekly Crop Update 3
trade expectations. Soybean exports totaled 9.767
million bushels, considered to be neutral to the
market coming in the middle of trade guesses.
Corn inspections were considered bearish, at
26.478 million bushels, coming in well below the
low end of trade guesses.
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 Central
corn belt.
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.
Yellowed Newly Emerged Corn - Richard W.
Taylor, Extension Agronomist, [email protected] ,
Derby Walker, Jr., Extension Ag Agent, Sussex County,
[email protected]
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 Sussex County, Delaware
but are observable up and down the state and also
appear in southern New Jersey.
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,
Weekly Crop Update 4
poor growing conditions, etc) or below a
minimum temperature”.
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.
Frost Damage on Wheat - Richard W. Taylor
Extension Agronomist, [email protected] , Derby
Walker, Jr. , Extension Ag Agent, Sussex County,
[email protected] , Bob Uniatowski, Associate
Scientist, [email protected]
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.
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).
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
Weekly Crop Update 5
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:Tuesday, May 7, 2002 – 6:00 PM – till(?)
For more detailed descriptions and the
implications of cold damaged wheat, please refer
back to the Weekly Crop Update for April 19,
2002, volume 10, number 4, pages 8-10.
UPCOMING MEETINGS:
Strawberry Twilight
University of Maryland Wye Research & Education
Center
Queenstown, Maryland
Thursday, May 16, 2002
6:00 pm- until
Where:University of Delaware Research and
Demonstration Area
¾-mile east of Armstrong Corner, on Marl
Pit Rd. (Rd. 429).
What:
Come join your fellow farmers and our
Extension Specialists for an interactive and
hands-on experience as we address “inseason” 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 recertification credit in the agricultural plant
category. Credits will also be available for
Certified Crop Advisors.
Special Guests and Topics:
Ø Strawberry Nutrient Management: Dr.
Gordon Miner, NCSU
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
Weekly Crop Update 6
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) 8312506.
HOPE TO SEE YOU ON THE 7th!
Carl P. Davis
Extension Agent, Agriculture
Weather Summary
Week of April 25 to May 1, 2002
Rainfall:
April 25: 0.27 inches
April 27: 0.04 inches
April 28: 1.32 inches
Readings taken for the previous 24 hours at 8 a.m.
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 Research & Education Center:
http://www.rec.udel.edu
Ag F ac t
Compiled and Edited By:
Americans spend 10% of their income on food;
Japan 17%; and India 52%. American farmers,
on average, get 29% of the consumer’s retail
dollar. This ranges from 7% for the wheat
producer, and near 100% for the pick-your-own
farm operation.
Tracy Wootten
Extension Associate - Vegeta ble Crops
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.
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 t he Acts of Congress of May 8 and June 30,
1914. It is the policy of the Delaware Cooperative Extension System that
no person shall be subjected to discrimination on the grounds of race, sex,
disability, age or national origin.
Weekly Crop Update 7