Field Crop Insects -
Joanne Whalen, Extension IPM Specialist
Small Grains. As a result of warmer, late winter temperatures,
aphids can be found in small grain fields at this time. If temperatures
remain warm, beneficial insects should be able to keep these populations
in check and prevent population explosions seen in 1996. Fields
should be scouted by early April for potential aphid problems.
Be sure to include sites that are showing plant stress in your
sampling plan. Plant damage may appear as circular yellow to brown
spots with dead plants in the center. Treatment may be needed
if you find 150 aphids per linear foot of row throughout the field
and beneficial activity is low. Dimethoate (wheat only, do
not apply when temperatures are below 60EF),
Disyston, Malathion, Penncap-M and Warrior (wheat only) will
Field Corn. The decision to use a soil insecticide should
be based on a combination of factors including field scouting,
history of a pest problem, planting date and conditions favoring
a pest problem. If scouting and/or field history information is
not available the following factors can be used to determine the
potential for a soil insect problem:
(Pest Species/Conditions favoring Outbreaks)
Late planted corn (black cutworm); Combination of
poorly drained soil, heavy broadleaf weed growth, soybean stubble,
Seed Corn Maggot
Cool and/or wet springs with delayed germination;
Warm weather in late winter resulting in early fly emergence and
egg laying before spring tillage; Early planting in fields with
poor drainage, heavy crop residues, and/or manure applications.
Planting into old sod, pasture, hay or set aside
acreage; Planting into double crop or full season soybean stubble,
especially fields with heavy grass infestations the previous season.
High organic matter soils, sod covers, and heavy
grass pressure the previous season; More prevalent in continuous
corn with the above conditions.
Continuous corn planted on heavier soil types; rotated
corn planted on heavier soils following soybeans with heavy infestation
of volunteer corn or weeds.
Changes in Corn Herbicides for 1997 - Mark VanGessel,
Extension Weed Specialist.
There will be a few new herbicides available for corn in 1997.
Some of these are new products, others are old products just re-packaged
and renamed. Many will be in limited supply for the Delmarva region
but undoubtedly you will you hear of them.
Balance (Rhone-Poulenc). Preemergence use for annual broadleaf
control and some grass suppression. It needs more research in
our area to determine effective rates that minimize crop injury.
Basis (DuPont). Pre-package mix of matrix plus pinnacle
for early postemergence use. Early postemergence means maximum
corn size is 4th leaf stage. Has soil insecticide restrictions
similar to Accent. Excellent product for lambsquarters and pigweed
(triazine resistant and susceptible) and good on a variety of
annual weeds. Check the label for precautions when tank-mixing
with Basis. It is labeled for preemergence use but none of the
universities in the Mid-Atlantic region have looked at this application
Basis Gold (DuPont). Pre-package mix of matrix plus accent
plus atrazine for postemergence use. Has soil insecticide restrictions
similar to Accent. This product does not have pinnacle in it and
as a result it is weak on triazine resistant pigweed and lambsquarters.
Check the label for precautions when tank-mixing with Basis Gold.
Broadstrike (DowElanco). Preemergence use by itself. Can
be a help with triazine lambsquarters and pigweed management.
Use it in later planted fields to minimize crop injury or use
with IR corn hybrids.
Fultime (Zeneca). Pre-packaged mixture of topnotch plus
atrazine for preemergence use. Topnotch is the encapsulated form
of acetachlor (Harness, Surpass). It still has ground-water restrictions
(ground water is less than 30 feet deep and soil
texture is sand with less than 3% organic matter; or
soil texture is loamy sand and less than 2% o.m.; or
soil texture is sandy loam and less than 1% o.m.).
Hornet (DowElanco). New name for Broadstrike Plus, pre-package
mixture of broadstrike plus stinger for preemergence application.
Use it in later planted fields to minimize crop injury or use
with IR corn hybrids. Stinger will control Canada thistles emerged
at time of application.
Liberty Link corn (AgrEvo). Corn hybrids genetically altered
for resistance to Liberty herbicide. Liberty is a broad spectrum
herbicide that will kill conventional corn hybrids. Liberty can
be weak on larger grasses and velvetleaf. It is doubtful that
one application of Liberty by itself will provide full-season
control. Liberty does not provide residual weed control. Current
recommendation is to use a soil-applied program and then use Liberty
as the postemergence product.
Sethoxydim Resistant corn (SR) (BASF). Corn hybrids genetically
altered for use with Poast Plus herbicide. This can be a big help
in fields with bermudagrass (wiregrass) or severe crabgrass infestations.
There is little to no resistance of SR corn to other postemergence
grass herbicides such as Select, Assure II, or Fusilade. Headline
is a co-pack of Poast Plus and Laddock (atrazine plus basagran).
Headline is weak on triazine-resistant pigweed and lambsquarters.
Touchdown (Zeneca). Burn-down herbicide for use with no-till.
Similar properties to Roundup and should be used a similar manner.
Field Crop Diseases - Bob Mulrooney, Extension Plant
Wheat. Early season diseases that may be present now are powdery mildew, Ascochyta leafspot, barley yellow dwarf virus, and soilborne wheat mosaic virus. Ascochyta leafspot often appears at greenup and resembles
Septoria leafspot. Symptoms include large graybrown spots on the lower leaves that tend to be oval shaped. It will also produce small black to
brown pinhead sized fungal structures in the dead leaf tissue. This fungus leafspot gets established on winter damaged tissue, but has been of minor importance and does not need to be controlled. This early in the season if you see circular areas in the fields where the wheat is shorter than the surrounding areas and lighter in color, barley yellow dwarf (BYD) or wheat soilborne mosaic virus (WSBM) may be the cause. Closer observation may reveal that the oldest leaves are bright yellow which may mean BYD, if leaves are mottled yellowgreen it may indicate WSBM. The only way to be sure is to have a sample of infected plants tested for the
presence of the virus. BYD is transmitted by aphid feeding in
the fall and spring, WSBM is transmitted by a soil inhabiting
fungus. These viruses can be confused with manganese deficiency
caused by high pH, so take a soil test also and check the pH from
the good and bad areas.
Soybeans. It is still not too late to check for the soybean cyst nematode. Soil samples can be checked for the presence of SCN at any time of the year as long as the ground is not frozen or flooded. If you are planting susceptible soybeans in an area where SCN is present, I would not plant them without a nematode test. Nematode Assay bags are available from each of the county Extension offices. The Delaware Soybean Board pays for half the cost with checkoff funds. Growers in Delaware pay $5.00 per sample. If a soybean grower with a 40 acre field with a yield potential of 40 bushels per acre, plants a susceptible variety on SCN infested ground, he can lose 350% of the yield to SCN. If you figure a 30% loss which is 12 bu/A over the 40 acres that is 480 bushels lost at $6.50/bushel. This results in a loss of $3,120 as a result of not taking a $5.00 Nematode Assay Test. Can you afford not to test? PP2 Management of Soybean Cyst Nematode has recently been revised. This fact sheet outlines the SCN situation in Delaware, and makes management suggestions for growers. If you have not received a copy yet, please stop by a county office or request one. A list of some SCN resistant varieties was recently revised as well, request PP13 Soybean Variety Reactions to SCN and Root Knot Nematodes.
What Temperature Did You Store Your Herbicides? -Mark VanGessel, Extension Specialist/Weed.
The ideal situation for pesticide storage is a dry room with a temperature above 50EF. But many pesticides are stored in unheated facilities where temperatures drop below freezing. Low temperatures can cause the active ingredient of certain pesticides to breakdown and the pesticide loses its effectiveness. Below is a series of tables for minimum temperatures for some of the common herbicides. This is not meant to be a comprehensive list. If your herbicide is not listed, check the label, or with your county agent, or your dealer for this information. Note this list does include Adry" herbicides as well as Aliquids". The majority of herbicides can be stored at any temperature without a problem.
|Do Not Store||Do Not Store||Do Not Store|
|Below 40EF||Below 32EF||Below 0EF|
|Broadstrike + Treflan||Basagran||Buctril|
|Commence EC||Devrinol 2E||Laddock|
|Prefar 4-E||Hoelen EC.||Roundup|
|Prowl 3.3||Kerf 50-W||Weeder 64|
|Pursuit Plus Lares DF||Poast and Poast Plus|
Grain Marketing Highlights - Carl German, Extension
Crops Marketing Specialist
Delaware farmers should note two interesting points reported in
the grain markets this past week:
These two key points have resulted in significant price increases
in corn and soybeans since the end of February. Cash forward pricing
opportunities are available to contract initial 1997 intended
production at $3.00 or better of corn and $7.00 or better for
soybeans. For further information contact me at 302-831-1317.
Access the Weekly Crop Update on the Internet -
The Weekly Crop Update can be accessed on the World Wide Web at
the following address:
Hourly weather information and a daily summary from the Campbell
Weather Station located at the University of Delaware Research
and Education Center can also be accessed at this site. Past issues
of Update from 1996 are also available. We encourage those of
you who are currently using the internet, to obtain this information
from Athe Web@.
It=s fun and it=s
Assure II - New Postemergence Grass Herbicide- Ed Kee, Extension Vegetable Specialist
Assure II is now cleared for postemergence control of grasses
in peas and beans. In peas, it may have its best fit to control
volunteer small grains. These can be a special problem after plowing
during a wet spring, when the small grain tillers back. The grain,
especially barley, can be a real quality control problem when
mixed in with the peas at harvest. Assure II is labeled at 6 to
12 ounces and can be used with either crop oil concentrates or
nonionic surfactants. Check the label for the precise rates of
the additives. Repeated applications are allowed, however, the
total amount applied cannot exceed 14 ounces. The preharvest interval
is a minimum of 15 days.
Matrix - A new Herbicide for Potatoes - Ed Kee,
Extension Vegetable Specialist
Matrix is a new herbicide for potatoes that has been tested by University researchers in the mid-Atlantic area and has even been put out in limited commercial trials. However, it is important to note that the formulation of Matrix that is now available is rimsulfuron only. Several years ago, many of us tested a Matrix formulation that was a combination of rimsulfuron and metribuzin (Sencor or Lexone).
Matrix is labeled for preemergence uses, in combination with many standard grass control materials. However, its best fit in Delaware may be as a postemergence material, used after the standard preemergence materials, for example, Dual and Lorox. Matrix may be applied postemergent when the potatoes are emerged but before the crop reaches 14 inches in height. Excellent control of many grasses and broadleaves can be achieved (See label). The material will also provide suppression and some control of purslane.
The postemergent rate is 1 to 1.5 ounces/acre, combined with a
nonionic surfactant. Please read the label carefully for all details.
There are crop rotation restrictions that must be considered and
are listed on the label.
Vegetable Crop Insects - Joanne Whalen, Extension
Seed Corn Maggot. The warm temperatures in late winter
has favored early fly emergence and in many cases egg laying has
occurred before spring tillage operations. If spring conditions
turn cool and wet and crop germination is delayed, seed corn maggot
problems will be seen in many spring planted vegetables. Unfortunately,
there are few materials available for effective seed corn maggot
management. In addition, chemical controls alone may not always
provide adequate control. The most effective controls will be
achieved when early, complete tillage is combined with a seed
treatment (containing diazinon or chlorpyrifos) and/or a soil
insecticide. If surface vegetation is still exposed after tillage,
egg laying flies will still be attracted to the field. All the
soil insecticides labeled for sweet corn (Counter, Lorsban, Fortress,
and Force) will provide seed corn maggot control. However, if
conditions are extremely favorable then a seed treatment and complete
tillage will also be necessary. In most other spring planted vegetables,
a broadcast application of diazinon is the only available soil
insecticide. The diazinon must be applied immediately before planting
and incorporated in the top 3-4 inches of soil to be effective.
Winter Temperature Index For Predicting Stewarts Wilt in Delaware Sweet Corn 1997 - Bob Mulrooney, Extension Plant Pathologist
The winter temperature index is severe for both Georgetown and Newark. The mean temperature for Dec., Jan., and Feb. were measured at both sites. The sum of these averages provides the bacterial wilt index for predicting Stewarts wilt severity. Since the disease is transmitted by overwintering, the sum of these averages provides the bacterial wilt index for predicting Stewarts wilt severity. Since the disease is transmitted by overwintering
flea beetles that have the bacteria in their alimentary tracts, conditions affecting flea beetle survival influence the occurrence of this disease.
The index is as follows:
The index for Newark is 114.2, and 118.5 for Georgetown. This is the warmest winter since I have been keeping these figures starting in 1993. The use of bacterial wilt resistant varieties is encouraged as well as atplanting insecticides (Counter 15G or Furadan 4F) to control the flea beetle vector on susceptible varieties. Scouting at emergence and applying
foliar insecticides if needed is another option.
Vegetable Diseases -
Kate Everts, Extension Specialist, Vegetable Pathology
Universities of Maryland and Delaware
Spinach. Begin scouting for white rust on fall planted
spinach fields which have overwintered. Due to our winter weather
conditions, spinach die back was light this year and the abundant
green tissue may harbor infections. White rust has been found
in Sussex County. Now that the weather is warming up, not only
will the plants begin to grow again, so will any disease which
is present. Initial symptoms of white rust are chlorotic lesions
on the upper surface. The under side of the leaf. Will have white
circular pustules, often in the shape of concentric rings. Because
much of the leaf tissue which has overwintered is chlorotic, flip
the leaves over to look for the white concentric ring shaped pustules
in order to confirm the diagnosis. Leaf spots and anthracnose
are often prevalent in fall planted overwintered fields. Once
the plants begin growing in the spring, apply a copper containing
fungicide such as Champ 2, Kocide LF, or Ridomil/Copper for white
rust, leaf spots and anthracnose, or Alliette primarily for white
rust. Remember that you should not plant a spring crop of spinach
near overwinter fields.
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Compiled & Edited By:
Cooperative Extension Education in Agriculture and Home Economics, University of Delaware, Delaware State College and the United States Department of Agriculture cooperating, John C. Nye, Dean and Director. Distributed in furtherance of the 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, color, sex, disability, age or national origin.
Extension Associate - Vegetable Crops