Vol. 5 No. 4 April 25, 1997 |
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Vol. 5 No. 4 April 25, 1997 |
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Field Crops:
Field Crop Insects -
Joanne Whalen, Extension IPM Specialist.
Field Corn - Low levels of cutworm leaf feeding activity
have been observed in the earliest planted corn. With the higher
than normal pheromone trap catches and the cool, wet weather,
fields should be scouted at emergence for the presence of leaf
feeding, cut plants and larvae. A treatment will be needed if
you find 10% leaf feeding or 3% cut plants and larvae are
present. Rescue treatments should be applied before larvae are
one-inch long. Asana, Ambush, Pounce or Warrior will all provide
control.
Small Grains - Although cereal leaf beetle egg hatch was
significantly reduced by the cold spring weather and freezing
night temperatures, adults can still be found mating and laying
eggs. In addition, the first grass sawfly larvae have been
found on the lower eastern shore. So far, no armyworm
larvae have been detected. As temperatures increase, all three
insects could be found in wheat. The following thresholds can
be used to make a treatment decision: cereal leaf beetle - 0.5
per leaf; grass sawfly - 0.4 per linear foot of row; and armyworm
- 1-2 per foot of row. Remember, armyworms can cause greater damage
in barley so the lower threshold should be used. When all three
insects are present, the threshold of each should be reduced
by at least one-third. If all 3 insects are present in wheat,
Warrior, Lannate, or Parathion will provide the best control.
Remember only Lannate and Parathion are labeled on barley. Also,
Parathion can only be applied by air and has set back restrictions.
Soybeans - If you plan to plant full season no-till soybeans,
be sure to treat the seed for seed corn maggot. Flies are still
laying eggs and larvae will be present in fields with high amounts
of organic matter. A seed treatment containing diazinon will be
needed to control seed corn maggot larvae.
Herbicide News -
Mark VanGessel, Extension Specialist.
ISK Biosciences will discontinue the production of Dacthal. Dacthal inventories will be depleted with time. It is estimated that there is an 18 months supply of Dacthal. Expect prices to increase as supply declines.
Speaking of prices, BASF manufacturer of Poast and Poast Plus,
has decided to reduce the price of Poast. The reduction will bring
the cost of amount active ingredient to about the same level for
both Poast and Poast Plus. Remember the formulations are not the
same for Poast 1.5L and Poast Plus 1.0L, so price per gallon will
not be the same. This will reduce the cost of postemergence grass
control in vegetables.
Field Crop Diseases -
Bob Mulrooney, Extension Plant Pathologist.
Wheat. Keep checking for powdery mildew. Disease development is progressing. Depending on the variety susceptibility, stand, nitrogen fertility, and the weather. Tyler, Pennmore, and Mason have significant mildew at the present time in the New Castle county test plots near Middletown. Barley yellow dwarf symptoms have been seen in several areas in Sussex county. Infected wheat will be yellow, slightly to severely stunted, and surrounded by normal wheat. It often occurs in spots where aphids have fed or are feeding. Leaf discoloration can vary including shades of yellow, red, or purple. Discoloration often occurs from the tip to the base of the leaf and from the margin to the midrib. The only definite way to confirm the diagnosis is by a serological test.
Lastly, I have detected some Septoria leaf
spot caused by Septoria nodorum, on some lower canopy
leaves from Georgetown. So be on the lookout for Septoria
as well.
Plant Soybeans Early -
Richard W. Taylor Extension Agronomist, and Bob
Uniatowski, Extension Associate for Field Crops
Although it=s the first
of May, you probably aren=t
planning to plant soybeans just yet. But, farm and research experience
suggests that the first full week of May is the best time to plant
varieties from maturity group IV and V. Based on a 4-year project
sponsored by the Delaware Soybean Board, delaying planting until
the first of June reduced yield by an average of 10 to 15 bu/A
depending on variety.
What about earlier-maturing varieties, maturity group III and
II? For group III beans, the ideal planting date was mid-May and
for group II beans it was mid-June. Yield potential declined after
the ideal date and by late-June and early-July yield reductions
of 1 to 1.25 bu/A/day occurred.
If you have some fields that are fit for soybean planting and
your corn fields are still not fit to plant, switch over and plant
your group IV and V soybean varieties and see how they respond
to early planting.
Some Keys to Successful Soybean Planting -
Richard W. Taylor, Extension Agronomist, and Bob
Uniatowski, Extension Associate for Field Crops
In the previous article, we mentioned what early planting can
do for your soybean yields but there are other keys to success
too. Most importantly, success depends on establishing a vigorous
stand of beans. The following are some ideas on ensuring a vigorous
stand.
First, use high quality seed of a high performing variety. Many
studies have compared bin-run seed to Certified seed. On average,
Certified seed will yield 3. 5 bu/A more than bin-run seed. If
you choose to use bin-run seed, be certain to treat it special
from the time it is planted until its harvested, and then treat
it even more special during harvest and during storage.
Have it cleaned of weed seeds and broken or damaged beans. Have
a germination test run. Although soybean seed is not traditionally
treated with a fungicide or insecticide, early planting in cooler
and wetter soil conditions may make seed treatments pay. After
mid-May when soils are warmer, seed treatments will not be required
unless the germination percentage falls below 80 percent. Seed
with a germination of 70 percent or less should not be planted.
Once you purchase quality seed, remember to handle it carefully
as soybean is more sensitive to rough handling then most other
crop seed. Check you planters to be sure the seed coat is not
being broken during planting.
A seeding depth between 1 and 1.5 inches is best for soybeans.
Emergence problems can occur at seeding depths greater than 2
inches. At the deeper seeding depths, emergence is slower and
can increase the chance for damage from insects and diseases.
Consider using a soybean inoculant (Bradyrhizobia) if you haven't
used one in your field recently. Many new inoculants are available
on the market. The inoculant organism is what supplies the soybean
plant with nitrogen. Research by Dr. Jeff Fuhrman with the University
of Delaware's Department of Plant and Soil Sciences has demonstrated
that many of the native Bradyrhizobia bacteria in our soils are
either not very effective at fixing -nitrogen or actually produce
a toxin that can limit soybean yields. It only takes a few minutes
to treat your soybean seed with the inoculants and costs less
than $2 per acre.
Once planted and emerged, scout your fields to guard against early
insect problems, weed breaks, and nutrient imbalances.
Follow these suggestions and you should end up with a vigorous
stand with top yield potential.
Vegetable Crops:
Vegetable Crop Insects -
Joanne Whalen, Extension IPM Specialist.
Asparagus - With the warmer temperatures, we are starting
to see an increase in asparagus beetle activity. Spot treatments
along field edges will only work if the beetles have not moved
into the field. A treatment is recommended if you find 5 or more
beetle per plant and/or egg laying has begun. Sevin, Ambush, or
Pounce will provide cost effective control.
Seed Corn Maggot - Adult flies continue to lay eggs and
larvae can be found feeding on the seeds and in the stems of spring
planted vegetable crops. Unfortunately, once damage occurs there
is no cost effective rescue treatment. Since the potential for
damage will continue throughout the month of May, preventative
controls should be applied in all spring planted vegetable crops.
If a seed treatment is a viable option, be sure to choose a product
that contains diazinon or chlorpyrifos. Although not available
for all crops, research from New York still indicates that a chlorpyrifos
seed treatment is the best option. In many cases, a broadcast
application of diazinon is the only available control option.
In order to be effective, it should be incorporated into the top
3-4 inches of soil immediately before planting.
Section 18 Granted For Pre-emergence Use of Command on Watermelons -
Ed Kee, Extension Vegetable Specialist
The EPA has approved a Section 18 Emergency Label for the pre-emergence use of Command on watermelons. A maximum of one application of Command 4EC may be applied using ground equipment at a rate of 0.3 to 0.4 pint of product/acre (0.15 to 0.20 a.i./acre) when applied pre-emergence and at a rate of 0.4 to 0.5 pint of product/acre (0.2 to 0.25 lb a.i./acre) for pre-plant incorporated applications. Command may be applied in a band over the row, adjusting the rate and carrier volume to the band width. Do not exceed 0.25 lb a.i./acre per year. A preharvest interval of 80 days is required. Follow all directions on the label.
Sinbar, a broadleaf material, has also been submitted. When we
receive the EPA rating, we will advise you.
Vegetable Crop Diseases-
Kate Everts, Extension Plant Pathologist,
Universities of Maryland and Delaware
Cucurbits - As early transplants of muskmelon, squash or
watermelon go the field, they are at risk of developing scab.
This fungal disease is favored by cool wet weather. To control,
apply a chlorothalonil product (Bravo or Terranil) every 5 to
7 days.
Phytophthora Root and Crown Rot of Cucurbits - Losses to
Phytophthora root rot on peppers and squash were severe
in 1996. Field location and field preparation should be made with
those losses in mind, since chemical control of Phytophthora
is difficult to achieve. Peppers and squash should not be planted
into fields which have been cropped to cucurbits, tomatoes, eggplant
or pepper within the last 3 years. Phytophthora root rot
development is favored by warm, wet weather and begins in areas
of the field where excessive water accumulates as a result of
high rainfall or poor drainage. Ideally these crops should be
planted on well prepared raised beds where water from heavy rain
will not pool around the base of the plant (subsoil if necessary
to improve drainage). A soil application of Ridomil before or
just after planting or transplanting may be beneficial. The key
is to plan ahead to avoid disease outbreaks wherever possible.
Spinach - White rust on spinach is present and severe in
some areas due to our cool wet weather. If Ridomil 2E was applied
at planting on the spring crop, the spinach will be protected
in the early season. However, intensive scouting should now be
underway. The disease usually appears first on the edges of the
field. Apply fungicides when the first sign of disease appears.
Vegetable Diseases -
Bob Mulrooney, Extension Plant Pathologist.
Snapbeans. If damping-off and root rot are a concern in
early plantings, apply Ridomil Gold 2E in a 7-inch band over the
row at seeding, or apply Ridomil Gold PC-11G in the furrow at
planting.
Potatoes. Growers should note the date when each field
emerges. Field emergence is defined as the time when a green row
can be seen or 50% of the plants have emerged. This date will
be used later for determining disease severity values (DSVs).
The late blight hotline will be in service this week, hopefully.
The number will be 831-6400 in New Castle county, and 1-888-831-SPUD
for long distance callers. We are looking forward to providing
this information again this year.
Upcoming Meetings:
Quarterly Pesticide Applicator Training and Exam
Date:
June 3 & 4, 1997
Location:
Delaware Department of Agriculture Conference
Center, Rt 13
Dover, Delaware
Training Date &Time:
June 3 - 8:30a.m.- 4:00p.m.
June 4 - 8:30a.m.- 12 noon
Exam Time:
June 4 - 1:00p.m.- 3:30 p.m.
To register, contact the Delaware Department of Agriculture at
302-739-4811 or 1-800-282-8685 (DE only) and ask for the Pesticide
Compliance Section.
Compiled & Edited By:
Tracy Wootten
Extension Associate - Vegetable Crops