Volume 12, Issue 14
June 25, 2004
Volume 12, Issue 14
June 25, 2004
Vegetables
Vegetable Crop Insects -
Cucumbers.
We continue to see an increase in aphid
populations. A treatment should be applied for aphids if 10 to 20 percent of
the plants are infested with aphids with 5 or more aphids per leaf. Fulfill, Thionex or
Lannate will provide aphid control. Be sure to watch
for bees foraging in the area and avoid insecticide applications on blooming
crops.
Melons.
Continue to scout all melons for aphids, cucumber beetles, and spider
mites. We continue to see an increase in the number of fields with spider mite
and aphid infestations. If spider mite populations are high at the time of
treatment, 2 sprays spaced 5 days apart may be needed. The threshold for mites
is 20-30% infested crowns with 1-2 mites per leaf. Acramite, Capture, Danitol, Agri-Mek or Kelthane will provide control, but should be rotated to
avoid the development of resistance. We just received our 24C label allowing
aerial application of Acramite on melons. Only one application is permitted per
season and the rate is 1 lb/acre. This registration remains valid, unless
disapproved by EPA within 90 days of issuance, for 5 years (Federal) and one
year (
Peppers.
In
areas where corn borer trap catches are 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.
You will also need to consider a treatment for pepper maggot. If Orthene
is used, it will also provide pepper maggot control. Otherwise, dimethoate
should be added to the mix.
Potatoes.
Continue
to scout fields on a weekly basis for Colorado potato beetle
(CPB)
adults and larvae. The larval threshold is 4 small larvae per plant or 1.5
large larvae per plant. The threshold for each should be reduced by 1/3 to ½ if
all stages of larvae are present. Avaunt + PBO, Actara, cryolite, Spintor, Provado or newly labeled Rimon will provide control. We
just received our state label for Rimon. Although labeled at 9-12 oz/acre, the
12 oz rate is recommended. Remember from the last newsletter, it will
not control adults and has buffer zone and buffer strip restrictions for aerial
application. We are also starting to see the emergence of summer
adults. Unfortunately, most of our labeled products are most effective on
larvae. The higher labeled rates of Spintor and cryolite have provided some
level of adult suppression; however, may not be adequate under high population
pressure. Actara, Leverage and Provado provide adult control but should not be
used where Admire, Platinum or Gaucho were used at planting to avoid
development of resistance. Economic
levels of potato leafhopper adults and nymphs can still be found in many
fields. As a general guideline, controls should be applied if you find ½ to one
adult per sweep and/or one nymph per every 10 leaves. Dimethoate, a pyrethroid, Actara or Provado will provide
control. We have just found our first green peach aphids in potatoes. No
controls will be needed until you find 2
aphids per leaf during bloom and 4 aphids per leaf post bloom. If melon aphids
are found, the threshold should be reduced by ½. If green peach aphid is the predominant
species, Fulfill, Lannate, Monitor, Provado, or Vydate will provide control. If
Fulfill is used, a penetrating surfactant should be used to achieve good
coverage and achieve optimum control.
Snap Beans.
All
seedling stage beans should be scouted for leafhopper and thrips activity. The thrips threshold is 5-6 per
leaflet, and the leafhopper threshold is 5 per sweep. If both insects are
present, the threshold for each should be reduced
by 1/3. Dimethoate, Lannate, Asana, Capture, or Warrior will provide control
of both insect pests. Once corn borer catches reach 2 per night, fresh market
and processing snap beans in the bud to pin stages should be sprayed for
corn borer. Acephate should be used at the bud
and pin stages on processing beans. Once pins are present on fresh market snap
beans and trap catches are above 2 per night, a 7-10 day schedule should be
maintained for corn borer control. Lannate, Asana, Capture, Warrior
or Mustang are labeled. Acephate has a 14-day wait until harvest. Since this can
change quickly, 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 processing snap beans
(http://www.udel.edu/IPM/traps/latestblt.html and
http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html).
Sweet
Corn.
All
silking sweet corn should be sprayed on a 5- 6 day schedule. 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 silking sweet corn (http://www.udel.edu/IPM/traps/latestblt.html
and http://www.udel.edu/IPM/thresh/silkspraythresh.html).
Pickling Cucumber
Harvest Begins – Harvest Timing Means $$$ – Ed
Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Pickling
Cucumber Harvest began last Saturday, one of the earliest starts in memory. This reflects the warm growing conditions we
experienced through most of the spring, and probably more sunshine than usual.
Growers
are reminded that choosing the proper day for harvest can make a significant
positive economic impact. With the once-over
destructive harvest and the contract structured for different values for
different size pickles, the gross return on any given harvest is directly
affected by maturity. A good “rule of
thumb” is to harvest when 5% (by weight) of the pickles reach the 4A category,
or between 2 and 2/18 inches. Probably
70 to 80% of the load is in the 3A (1.5 to 1.75 inches) and 3B (1.75 to 2.00
inches) categories. This seems to
reflect the proper compromise between weight and declining value for the
largest sizes.
Many
growers sample 2-3 days prior to harvest to track the rate of maturity. Growers are also encouraged to “do the math”
when they get their grade sheets on particular loads. Run the calculations based on the contract
prices of each size and the percent of the load in each size. Change the percentages and do the
calculations to see how the value of the load can be affected by harvest
timing.
Emerged Lima Beans Can Be Injured With Dual -
Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
Dual is labeled and quite safe for preemergence use
on lima beans. However, I have seen
fields and situations when Dual was applied as the beans were just emerging, or
lima beans followed a small grain that was only disked in. Only disking it in resulted in poor soil
coverage of the lima bean seed. In these
situations, lima bean injury can occur.
To avoid these problems, be sure the seed slit is filled in with soil
and do not delay application more than one to two days after planting.
Bee Hive Strength Related to Fruit Set – Derby
Walker, Sussex County Extension Ag Agent, derby@udel.edu;
Tracy Wootten, Extension Horticulture Agent, wootten@udel.edu
We have received questions on pollination of
watermelon fields this week. Lack of
good pollination can be a result of weak bee hives. A good hive should have 6 frames of brood with
enough bees for 8 frames. Information on evaluating honey bee colonies for
pollination can be found at the following Pacific Northwest Extension
Publication: http://wwwagcomm.ads.orst.edu/AgComWebFile/EdMat/PNW245.pdf. Information on what is a colony, worker bees,
colony size and efficiency, colony strength, disease, amount of comb, number of
bees, food requirement, a normal queen and colony flight is discussed. As mentioned in
Manganese Toxicity on Muskmelon – Derby
Walker, Sussex County Extension Ag Agent, derby@udel.edu;
Tracy Wootten, Extension Horticulture Ag, wootten@udel.edu
Manganese
toxicity on muskmelon was observed this week.
Characteristic signs in the field are yellowing, lighter green spotting
on the upper surface of the leaf and watersoaked “pin holes” on the lower
surface of the leaf. Holding the leaf up
to the light will help with diagnosis.
These areas will become necrotic, and eventually the whole leaf will
die. Manganese toxicity is the result of
low pH – below 6.0. Unfortunately, this
usually does not reveal itself until approximately 2 weeks before harvest. We experienced this at the
http://www.rec.udel.edu/veggie/manganese.htm
Vegetable Crop Diseases -
Extension
Plant Pathologist, bobmul@udel.edu
Late Blight Advisory.
Disease Severity Value
(DSV) Accumulation as of
|
Date |
Daily DSV |
Total DSV |
Spray Recommendation |
|
4/25-
5/18 |
4 |
18 |
7-day |
|
5/19 |
4 |
22 |
7-day |
|
5/20 |
2 |
24 |
7-day |
|
5/21 |
2 |
26 |
7-day |
|
5/25 |
5 |
31 |
7-day |
|
5/27 |
3 |
34 |
7-day |
|
5/30 |
8 |
42 |
7-day |
|
5/31 |
1 |
43 |
7-day |
|
6/1 |
1 |
44 |
7-day |
|
6/4 |
17 |
61 |
5-day |
|
6/7 |
2 |
63 |
5-day |
|
6/8 |
1 |
64 |
5-day |
|
6/10-6/13 |
9 |
73 |
7-day |
|
6/14-6/15 |
3 |
76 |
7-day |
|
6/16 |
3 |
79 |
7-day |
|
6/17 |
3 |
82 |
7-day |
|
6/22 |
1 |
83 |
7-day |
|
6/23 |
1 |
84 |
10-day |
Application rates for
protectant fungicides (Dithane, Bravo, etc.) should be at the high end of the
rate with the amount of foliage present and likelihood of favorable weather for
infection.
Early blight and black dot. Many fields are flowering
or approaching flowering and this is a good time to consider switching to an
application or two of Gem, Headline or Quadris (Amistar) for early blight
susceptible varieties. This can also be helpful for late season varieties
including russets if stress makes plants susceptible to black dot. Make one or
two applications at the end of flowering and repeat 14 days later. Apply
mancozeb or chlorothalonil 7-days later between the two applications.
If
pink rot control is important and
you did not treat at planting, foliar applications of either Ridomil Gold MZ or
Ridomil Gold/Bravo, or Flouronil when tubers are nickel-sized is
suggested. A second application should
be made 14 days later.
For specific fungicide
recommendations, see pages F132-33, 2004
Field Crop Insects -
Alfalfa.
Continue to sample all fields on a weekly basis for
leafhopper adults and nymphs. If economic levels are present, early cutting may
be the best option for control. However, be sure to check fields within a week
of cutting for leafhoppers that can quickly damage small plants. The treatment
thresholds are 20 per 100 sweeps on alfalfa 3 inches or less in height, 50 per
100 sweeps in 4-6 inch tall alfalfa and 100 per 100 sweeps in 7-11 inch tall
alfalfa.
Soybeans.
Grasshoppers, thrips and potato leafhopper can be found in economic
levels in many fields throughout the state.
The treatment threshold for grasshoppers is 1 per sweep and 30%
defoliation. Asana, dimethoate, Furadan, Lorsban, or Warrior will provide grasshopper control. The
treatment threshold for thrips is 8 per leaflet with plant growth is being held
back. Be sure to sample carefully for thrips since populations are higher
compared to past years. The treatment threshold for leafhoppers is 4 per sweep
in drought stressed fields and 8 per sweep in non-stressed fields. Dimethoate
or a pyrethroid will provide control of thrips and leafhoppers. Caution: OP insecticides (like dimethoate or
Lorsdan) should not be combined with SU/ALS herbicides (like Harmony GT).
Continue to watch for spider mites, especially in
no-till fields where a heavy weed cover was present before planting as well as
early planted fields that are starting to bloom. Treatment will be needed when
you find 20-30 mites per leaflet or 10% of plants with 1/3 or more leaf area
damaged. At this point, the only materials available for mite control in
soybeans are dimethoate and Lorsban.
Yellowing Soybeans Can Be Symptoms of
Several Different Problems
– Derby Walker, Sussex County Extension
Ag Agent, derby@udel.edu
Yellow
soybeans can be a symptom of several different problems including pH, insect, diseases,
nutrient deficiencies or nematodes. This week, I have found spider mites and
thrips in one field. Leafhoppers are
another insect that can cause soybeans to yellow. One field had several spots showing manganese
deficiency, most likely caused by high ph.
The beans were blooming and needed to be sprayed with a foliar manganese
product to correct the problem. A couple of fields were dropping their older
leaves because of a minor leaf spotting disease. It looks like Septoria Brown
Spot.
Three
fields appeared to be nitrogen deficient. They were nitrogen deficient, but the
problem was soybean cyst nematodes that prevent nitrogen fixing nodules from
developing. They were soybean cyst resistant but they were not resistant to the
Race in these fields. Planting same race resistant beans year after year will
shift the race of cysts to another race most likely to Race 1 or Race 5. How
can you tell which it shifted to? Hoe out a section of beans where there is
cyst problem and plant varieties that have different Race resistances
(non-resistant, Race 3, Race 1, and any other race you can find). Then 30 to 35 days later dig up of plants and
count the number of cyst on each variety. The one with fewest is type of
resistant beans you need. The odds are good that Race 3 shifted to Race 1. We
do have some Race 1 resistant varieties, however most are very late group 4 or
group 5 beans. Also you will probably have to return to standard soybean
varieties and herbicide programs instead of Roundup Soybeans.
Even
combining glyphosate with certain herbicides and other products can give you a
temporary yellowing and sometimes a stunting.
Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu
General Comments.
The
old crop soybean supply situation has gotten the attention of traders in the
soybean pits again this week, with old crop July futures currently at
$9.27
and new crop Nov. futures at $7.02 per bushel. To paraphrase the comments of
one veteran trader this morning: "If old crop soybeans go to $9.50 today
then they will most likely move to $10.00. Further, if we don't see $9.50 today
then it will be awhile before old crop beans go higher, if at all." The trader went on to say that "If USDA
raises their ending stocks estimate in the June 30th report for soybeans, then
we are not likely to move much higher on old crop soybeans".
Soybeans.
It is likely to be August before we get a realistic handle on the actual size
of this year's
World
soybean carryover supplies are estimated to be 46.69 mmt versus 33.01 last
year, a 41% increase. World soybean consumption, estimated at 210 mmt versus
195 mmt for the '03/'04 crop, continues to climb. However, production
forecasts
are currently projected to outpace consumption.
Corn.
Corn
export sales were disappointing this week, reported at a combined
old-crop/new-crop total of 13.7 million bushels. The low end of the estimate
was 15.7 million bushels. Pressure on the corn market could come from rains
moving through parts of the
Wheat.
Wheat
futures are being influenced by harvest pressure and disappointment over
$3.85
per bushel.
Market
Strategy.
The
corn and soybean markets have trended lower over the past month. Each passing
rain through the corn belt has resulted in the 'highs' and 'lows' getting a
little lower. Technically speaking, these markets are bearish, and barring any
significant weather development, we are not likely to see the month ago highs
reached any time soon. For those who are sitting unpriced on new crop corn and
soybeans it is time to bring forward cash sales to the 40% to 50% level of
intended production. Current new crop price levels for corn and soybeans
represent profitable sales opportunities. It is better to get sales done on the
first 1/2 of intended production at profitable levels than to take a chance on
holding out for higher prices that may or may not materialize.
UPCOMING MEETINGS:
2004
The 2004 Delaware Weed Day will be held Wednesday,
June 30, at the
Week of June 17
to
|
|
Rainfall: |
|
0.15
inches: June 17 0.06
inches: June 18 0.05
inches: June 22 |
|
|
|
Air Temperature: |
|
Highs
Ranged from 89°F on June 17 & 18 to 76°F on June 20. |
|
Lows
Ranged from 71°F on June 17 & 18 to 52°F on June 21. |
|
Soil
Temperature: |
|
80°F
average. |
|
(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
Compiled and
Edited By:
Tracy Wootten
Cooperative
Extension Education in Agriculture and Home Economics, University of Delaware,
Delaware State University and the United States Department of Agriculture
cooperating. Distributed in furtherance
of the Acts of Congress of May 8 and