Volume
10, Issue 13
June 21, 2002
Volume
10, Issue 13
June 21, 2002
Vegetables
Vegetable Insects
-
Lima Beans.
Be sure to watch for spider mites on seedling stage lima beans, especially in areas of the state that have not been receiving adequate rainfall. Both field interiors as well as field edges should be examined for mites. Look for the white stippling along the veins on the underside of the leaves. A treatment should be considered when you first notice the stippling and you find 10-20 mites per leaflet. Kelthane or Capture (6.4 oz/A) have provided the best control in lima beans. The earliest planted field should be scouted for lygus bugs and stinkbugs. Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. Lannate, Capture or Mustang can be used if both species are present. The higher labeled rates of Capture (4 oz/A) and Mustang (4.3 oz/A) will be needed if stinkbugs are the predominant insect present.
Peppers.
Corn Borer catches have dropped below 2 per night in all
areas of the state except the Harrington,
Potatoes.
As we approach harvest on the earliest planted potatoes, be sure to continue to sample for potato leafhoppers and aphids. Both potato leafhopper adults and nymphs can be found in fields. The treatment threshold is 0.5 - 1 adult per sweep or 1 nymph per 10 leaves. Actara, Provado, Furadan or a pyrethroid will provide control. Aphid populations are still low. If fields are greater than 2 weeks from harvest, the threshold is 4 aphids per leaf. Within 2 weeks of harvest, the treatment threshold increases to 10 aphids per leaf. In general, Colorado potato beetle populations are moderate in most fields. If Admire, Platinum or Tops MZ Gaucho were used at planting be sure to alternate to cryolite, Agri-Mek or Spintor when threshold levels of larvae or newly emerged adults are detected.
Snap Beans.
In the Harrington,
Sweet Corn.
Fresh market silking sweet corn should be sprayed on a 5-6
day schedule in all areas of the state except in the Harrington,
Pea Enation Mosaic Virus - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Many pea fields exhibit the pea enation virus disease on some small percentage of plants, but it is noticeable. Stunted plants, distorted leaves, and the small, distorted pods, with only one or two peas are the typical symptoms. Some fields may have as much as 3-5% of the plants showing these symptoms.
The virus is spread by aphids. Aphids have not been a huge problem this year, but the symptoms indicate the presence and spread of the virus.
Licensed and Bonded Produce Buyers and Dealers - Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Licensed and Bonded
Produce Buyers and Dealers.
The State of
Cold Weather
Affects Fruit Set of Early Watermelons –
Some early planted watermelons havelittle to no crown fruit set due to cold growing conditions. Cool weather conditions early in the growing season may result in female flowers opening several days before male flowers, resulting in delayed fruit set.
Watermelons produce separate male and female flowers on the same vine. A female flower can be easily recognized by the swelling of its base which resembles a tiny watermelon. Normally a female flower may be found at every seventh to tenth node. Thus, plants usually produce about 10 times more male flowers than female flowers.
Female (left) and male
(right) flowers
(Photo taken from
For successful pollination to occur, both female and male flowers must be open on the same day. The minimum temperature for the opening of watermelon flowers is 59° F.
Optimum growth of watermelon plants is achieved at temperatures of 68-86°F.
Vegetable Diseases - Kate
Everts, Extension Vegetable Pathologist, University of
Watermelons.
From the
Latest
EFI values from local weather stations
Any questions please call (410) 742-8788
EFI Values (Environmental Favorability Index)
Do
not use MELCAST if there is a disease outbreak in your field, it is a preventative program.
Location
Charles Co. 1 0 0 1 9 9 2
Collins Farms 1 1 3 1 3 4 1
Vincent Farms 1 2 2 1 3 7 1
White Marsh 1 2 0 1 6 7 3
The first fungicide
spray should be applied when the watermelon vines meet within the row. Additional sprays
should be applied using
MELCAST. Accumulate EFI (environmental
favorability index) values beginning the
day after your first
fungicide spray. Apply a fungicide spray
when 30 EFI values have accumulated by the
weather station nearest
your fields. Add 2 points for every
overhead irrigation. After a fungicide
spray, reset
your counter to 0 and
start over. If a spray has not been applied in 14 days, apply a
fungicide and reset the
counter to 0 and start
over. The first and last day listed
above can be partial days so use the larger EFI value
of this report and other
reports for any specific day.
If, for some reason, a
serious disease outbreak occurs in your field, return to a weekly spray
schedule
More detailed information
concerning MELCAST and sample data sheets are available on the web at http://www.agnr.umd.edu/users/vegdisease/vegdisease.htm.
Vegetable Diseases
-
Late Blight Advisory
Potato Disease Advisory.
Disease Severity
Value (DSV) Accumulations as of
|
Date |
Total DSV |
Spray
Recommendation |
|
5/1 |
12 |
None |
|
5/11 |
19 |
5 days, low rate |
|
5/19 |
23 |
10 days, low rate |
|
5/22 |
23 |
10 days low rate |
|
5/27 |
27 |
10 days low rate |
|
5/29 |
30 |
7 days, low rate |
|
6/3 |
33 |
7 days, mid-rate |
|
6/5 |
33 |
10 days, mid-rate |
|
6/9 |
38 |
7 days, high-rate |
|
6/13 |
39 |
10 days, high-rate |
|
6/16 |
58 |
5 day mid- rate |
|
6/19 |
60 |
10 day mid-rate |
All potatoes have reached more than 18 DSV’s. The Wisdom potato software program generates spray recommendations.
Late blight has not been a problem here in
NOTE: For this greenrow date and location we have accumulated 512 P-days as well. P-days are a measure of potato plant growth somewhat similar to growing-degree-days. When 400 P-days have been exceeded, conditions for early blight infection are more favorable and disease may begin to show up 5-7 days later. Sprays for early blight susceptible varieties should begin if early blight is expected to be a problem.
The period from June 12th to the 15th was very favorable for late blight and other foliar diseases. Accumulated 19 DSV's during that period
Field Crop Insects
-
Alfalfa.
Continue to sample fields for potato leafhopper. Remember that nymphs can quickly cause damage and once you see yellowing yield loss has already occurred. Since small plants are most susceptible to damage, the treatment threshold is 20 per 100 sweeps in alfalfa 3 inches or less in height and 50 per 100 sweeps in 4-6 inch tall alfalfa. Since many fields are close to harvest or have just been cut, be sure to check fields within a week of cutting for leafhoppers feeding on regrowth. Ambush, Baythroid, Lorsban, Mustang, Pounce or Warrior will provide control.
Soybeans.
As part of a Delaware Soybean Board funded project, we have
begun a statewide survey for the Soybean Aphid. This survey is being
coordinated with survey efforts conducted by the Delaware Department of
Agriculture as part of the Cooperative Agricultural Pest Survey Program.
Although the soybean aphid has never been detected in
www.pmcenters.org/Northcentral/Saphid/Aphidindex.htm
Grain Marketing Highlights - Carl
German, Extension Crops Marketing Specialist; clgerman@udel.edu
Commodity Markets Expected to Trade Mixed Until Finding New Direction.
Futures prices at the Chicago Board of Trade are expected to bounce
around for the remainder of this week and next, at least until the release of
the June 28th Stocks in All Positions report, and the 2002 Acreage report.
Currently Dec '02 corn futures are trading at $2.27; Nov '02 soybeans at $4.69;
and Jul '02 wheat at $2.92 per bushel. The end of this week will mark the first
notice day for nearby Jul '02 corn, soybean and wheat futures.
Sparks Releases June Acreage Estimates.
Sparks Commodities is now forecasting
Marketing Strategy.
With the '02 wheat harvest now underway it is necessary to
note the spread between the Jul '02 and Dec '02 wheat futures, and the
price strength being bid into nearby Jul' 02 futures. The spread is
currently 13 cents per bushel, with Jul '02 at $2.92 and Dec '02 at $3.05 per
bushel. More distant futures contracts are within a close proximity to the
nearby contracts. This type of bidding pattern is indicative
of trader expectations for a short crop, the extent of which won't be
known until the July 10th crop report for winter wheat and the September 10th
crop report for spring wheat. Therefore, any '02 wheat not sold at harvest will
need to be stored at least until December before the market delivers its final
tally. Expectations for a short crop should result in strong basis offers for
wheat sold at harvest. Last year's
-11), and 31 under on the
Clarity Injury on Soybeans
Richard
W. Taylor,Extension Agronomist, rtaylor@udel.edu,
and
Extension Ag
With many folks spraying their Roundup Ready® soybeans in the past
couple of weeks, an occasional problem we’ve seen in the past has developed. That problem is related to the ability of
glyphosate formulations to solubilize residues of previously used herbicides,
if tank cleanout has been inadequate. In
particular, the growth regulator type of herbicides, Clarity, Banvel or 2,4-D,
used on corn, and can cause significant visual injury on soybeans. We recently observed a soybean field that had
been sprayed with Roundup and was showing typical injury symptoms, leaf
cupping, dark green leaves, and crop stunting.
In areas of one field that had been irrigated since the contaminated
spray was applied, symptoms were worse in areas of the field that had not been
watered.
Photo 1. Severe
cupping of newly emerging soybean leaves and effect on terminal growing point
due to Clarity residue injury following spray application of Roundup (Photo by
R. Taylor)
Photo 2.
Cupping of soybean leaf due to Clarity residue injury following spray
application of Roundup
(Photo by R.
Taylor)
Photo 3.
Stunting of soybeans (2 rows on right) compared to unaffected rows on
left due to Clarity residue injury following spray application of Roundup
(Photo by R. Taylor)
How do you avoid this problem if you must switch back and forth among
crops and herbicides? Proper tank
cleaning is the most effective answer to the dilemma. The procedure is often listed at the end of
the herbicide label. For Clarity, a
relatively complicated process, must be followed but the important aspect is
the use of 1 gallon of household ammonia per 100 gallons of water to fill the tank
and flush the boom and nozzles. After it
is run through the nozzles for a short time, the entire ammonia water solution
should be left in the tank for several hours or preferably overnight and then
flushed through the tank. The tank is
then filled half full of water and again flushed out. The above is not the complete procedure, but
does give you an idea of how important using the right proportion of ammonia
and letting it sit for a long time is.
Be sure when rinsing out tanks, to follow all label directions to avoid
spray injury on non-tolerant crops.
Another issue is leaving a “few gallons” of 30% in the bottom of a spray
tank or nurse tank. These few gallons may be enough to cause serious leaf
burning and may even kill some plants where there is overlap.
Manganese
Deficiency is Showing Up on Soybeans - Richard W. Taylor, Extension Agronomist,
In many fields, manganese deficiency
symptoms are showing up. Manganese
deficiency is characterized by dark green veins and light green (mild
deficiency) to yellow (moderately severe deficiency) to white (severe
deficiency) interveinal leaf tissue. The
symptoms often are most severe on the most recently emerged leaves. Manganese deficiency symptoms are similar to
the deficiency and toxicity symptoms of some of the other micronutrients.
Photo 1. Severe
interveinal chlorosis on no-till single-crop or full-season soybean. Note dark green veins with tissue between
veins yellow to almost white. Younger
leaves are most affected since Mn is not mobile in the plant
(Photo by R. Taylor).
Yield reductions can be avoided to a large degree by early diagnosis and
treatment with foliar application of Mn.
Ignoring or not catching the problem until later in the season can not
only reduce yield potential, but make a foliar application more difficult and
possibly more expensive.
Photo 2. Severe
interveinal chlorosis on no-till single-
crop or full-season soybean. Note dark green veins with tissue between
veins yellow to almost white
(Photo by R. Taylor).
Where the symptoms are widespread and
moderate to severe, foliar Mn applied at 1 to 2 lbs Mn per acre can boost
yields significantly. Since the crop is
still in the vegetative stage, mild to moderate symptoms can be alleviated with
a 0.5 lb Mn per acre foliar spray.
Research in Delaware, Virginia, and North Carolina have shown that
soybeans are very responsive to foliar Mn especially when applied early although
sometimes on very young beans a second application may be needed.
Even if you do not apply foliar Mn, you
should be making note of which fields and where in the field symptoms occur so
you can monitor these areas in the future.
If wheat or barley are to be planted this fall, careful monitoring early
will allow you to apply Mn to the small grains before they are severely injured
by Mn deficiency. You should also note
the areas so you can do soil testing to determine the underlying problem. Check to see if the native Mn concentration
in the soil is too low or whether the soil pH is too high since the higher the
pH the lower the availability of Mn in the soil. Also, any factor restricting root growth
(compaction, drought, etc.) can aggravate Mn deficiency symptoms and should be
corrected if possible.
Alfalfa and
Alfalfa Grass Mixtures Approach Second Hay Harvest - Richard W.
Taylor, Extension Agronomist, rtaylor@udel.edu
Many of the alfalfa and alfalfa-grass hay fields I have observed this
week are approaching 1/10 bloom stage of growth for the alfalfa component. With warm, sunny weather in the forecast for
this weekend, many of you may want to consider going for that second cutting. After removing the hay, keep in mind that
this is the ideal time to apply the potash (K), phosphorus (P), and boron (B)
that the crop will need to do well during the summer stress period. Generally, we recommend that you apply about
half your potash at this time and the rest in the late summer following the
fourth cutting if you’re on a five-cut system or following the third cutting if
you’re on a four-cut system. All of your
crop P and B needs can be applied at this time.
Photo 1.
Alfalfa-orchardgrass mixture regrowth ready for second hay harvest. (Photo by R. Taylor)
Photo 2.
Alfalfa component of an alfalfa-orchardgrass mixture is approaching the
1/10 bloom stage of growth.
(Photo by R.
Taylor)
Ag Fact
There are approximately
100,000 acres of pickling cucumbers in the
In
UPCOMING
EVENTS:
A Day On The Farm
Date: Saturday, June 22
Time:
Location: Ramsey’s Farm
For more
information and directions, see page 10.
Week of June 14 to
|
|
Rainfall: 0.09 inches: 0.05 inches: 0.03 inches: |
|
|
|
Air Temperature: |
|
Highs
Ranged from 82°F on June 17 and 19 to 72°F on June 14. |
|
Lows
Ranged from 63°F on June 17 to 56°F on June 16. |
|
Soil Temperature: |
|
74°F
average for the week. |
|
(Soil
temperature taken at a 2 inch depth, under sod) |
Web Address for the U of D
Tracy Wootten
Extension
Associate - Vegetable Crops
