Volume
10, Issue 1
March 15, 2002
Volume
10, Issue 1
March 15, 2002
The Weekly
Schedule Begins –
Issue 1 of Weekly Crop Update is a sample of the type of
information you will receive each week with a subscription or access via the
Internet. This newsletter is designed to
provide subscribers with the latest information on disease and insect problems
as they are developing, weed control information, crop progress reports, and
other timely topics related to agronomic and vegetable crop production in
Fruit
Fruit Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Peaches.
A Section 18 Emergency Use request was again submitted to EPA in February for the use of Provado on stone fruit to control aphids that vector the Plum Pox Virus. We will let you know as soon as we get a response from EPA.
Vegetables
Agricultural Fact -
46% of
Pea Planting Has Begun – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Pea planting on Delmarva began in late February and
subsequent plantings have occurred as weather and temperature allow. Approximately 275,000 acres of peas for
processing are grown in the
Vegetable Diseases
- Bob Mulrooney, Extension Plant
Pathologist, bobmul@udel.edu
Back to Basics: Root Rot
Control in Peas, Lima Beans, and Snap Beans.
Root rot diseases are widespread and often cause significant yield losses. These diseases usually appear every year to some degree depending on weather and soil conditions. Root rot diseases are most severe and damaging when we have cool, wet conditions early in the season, followed by dry periods or other stresses like herbicide or insect damage, other diseases, or fertility problems. Poor soil conditions such as poor soil drainage and soil structure, low organic matter, low fertility and compaction make root rots worse.
Symptoms of root rot damage include poor seedling emergence and establishment, damping-off, stunting and uneven growth, chlorosis, and lower yield. Decreased root size, discoloration and decay characterize damage from soilborne fungi such as Rhizoctonia, Pythium, Fusarium on beans and Aphanomyces, Rhizoctonia, and Fusarium on peas. Many times, more than one pathogen is present which makes visual diagnosis difficult.
Management of these diverse soil fungi is difficult if you only utilize one management option. Effective management will be possible if you use an integrated approach of using a combination of cultural, biological and/or chemical control with appropriate soil management practices.
It is known that almost all crop and soil management
practices have a direct or indirect impact on root disease incidence and
severity. The use of cover crops and green manures can reduce or increase root
rot. Cover crop grain rye was shown in
In summary, root rot can be reduced if you can follow these steps:
· Use high quality disease-free seed treated with the appropriate fungicide for the pathogens you are likely to encounter.
· Practice crop rotation.
· Utilize cover crops, green manures and compost whenever possible.
· Reduce compaction and improve soil tilth.
· Plant at the appropriate time, depth and density.
· Select the best-adapted and tolerant varieties, if available.
Adapted for
Vegetable Diseases - Kate Everts, Extension
Vegetable Pathologist, University of
Pickling
Cucumbers.
Phytophthora fruit rot is a disease that can infect all cucurbit fruit including pickling cucumbers. Fruit rot is a different phase of crown and root rot, all caused by Phytophthora capsici. The symptoms of fruit rot are large water soaked lesions, which develop a white dense growth on the fruit. The disease can spread rapidly, causing fruit collapse during the growing season and after harvest. Like the crown and root rot phase, high soil moisture (typically standing water) for two days allows the sporangia to form and release zoospores. Secondary infections then occur. Heavy rain events, such as those resulting from hurricanes, may lead to complete crop loss. High disease levels can also occur in fall pickles that follow a spring crop that was under standing water.
Growers that have suffered losses due to this disease should plan ahead to minimize damage. Water management is critical to reducing damage from Phytophthora fruit rot. Select fields that have excellent drainage and avoid planting susceptible crops in low-lying areas where standing water is common. Plant on raised beds and subsoil (or “V-rip”) before planting to avoid soil layers that are impervious to water. A three-year rotation is important. Crops to avoid in the rotation are: cucurbits (including melon, watermelon, squash and pumpkin), pepper, tomato and eggplant. Broadcast soil fumigation can provide some benefit (for example, K-Pam and Telone list Phytophthora diseases on their labels). If fumigation is used, prevent nontreated soil from washing into the treated area.
Use of fungicides during the growing season is not always effective because of the presence of resistant strains of the fungus, difficulty obtaining adequate coverage and the aggressiveness of the disease when environmental conditions are favorable. However, Ridomil Gold Bravo applied when the vines begin to run, on a 14-day schedule may provide some disease control.
2002 Commercial
Vegetable Recommendations Guide Available at Local Extension Offices
You may obtain copies of the Commercial Vegetable
Recommendation Guide from
your local
Field Crop Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
New Field Corn
Registrations for Soil Insect Management 2002:
As you make plans to plant field corn, understanding the factors that favor soil insect pests can be used when making a treatment decision and selecting the best treatment option :
Seed Corn Maggot (SCM).
Since winter temperatures have been warmer than normal, we
are starting to find seed corn maggot flies laying eggs in recently plowed
and/or manured fields. Cool wet conditions at
planting, the use of manure and/or plowing under of green cover crops close to
planting all favor maggot problems. Depending on spring weather conditions,
most early planted conventional corn and all no-till plantings will be
susceptible to seed corn maggot attack. In addition to soil insecticides, seed
treatments have provided effective control. Hopper-box treatments containing diazinon or permethrin as well as
seed commercially treated with imidacloprid (Gaucho
or Prescribe) will
provide effective seed corn maggot control. A new 2(ee)
registration was issued on
Wireworms.
High soil organic matter, sod covers, and heavy grass weed pressure the previous season all favor wireworm populations. Fields having a combination of high organic matter and heavy grass weed pressure are the most susceptible to damage. Wireworm larvae spend multiple years in the larval stage and the larvae move up and down in the soil profile following moisture gradients. Therefore, good control is often difficult to achieve. Seed treatments containing lindane or permethrin will only control larvae feeding on the seed when population levels are low to moderate. They will not control larvae that have moved to the growing point of a plant and started to feed. However, Gaucho and Prescribe seed treatments have provided excellent control of both seed and seedling damage from wireworms under high population pressure. Soil insecticides including Regent, Force, Fortress, Furadan, Lorsban and Counter have provided control. All materials must be placed in-furrow to get effective control and applied at the higher end of the labeled rate. If Regent is used, fields can not be planted to leafy vegetables for one month, root crops for five months, or small grains and other rotational crops for 12 months following an application. The new 2(ee) registration for Warrior also applies to wireworm control and should be used at a rate of 1.92 oz/acre.
White Grubs.
In general, grubs are favored by a number of factors
including planting into double crop soybean stubble, old sod, hay, pasture or set-aside acreage. Overwintering
populations were higher this season and warmer soil conditions may have favored
survivorship. However, spring conditions as well as the recent cooler weather
may help to reduce populations. The most accurate way to measure the potential
for a grub problem is to sample fields for grubs before planting, but it should
be done before a field is tilled. The most accurate results will be obtained
when the soil temperatures at 6-inches deep are at least 45 degrees F. At each
site, sample one square foot of soil dug six inches deep. One to two samples
should be taken for every 10 acres with no less than 10 samples per field. A
treatment is recommended if you find 1-2 grubs per foot in heavy soils or 0.5 –
1 grubs per foot in sandy soils. Soil insecticides need to be placed in-furrow
to get effective grub control. Counter, Force, Fortress, Regent and Prescribe
will provide effective control. Remember, at planting insecticides are only
designed to provide control of grubs present at planting time. You should not
expect control of larvae present in August and September that resulted from
eggs laid in early July.
Black
Cutworm.
This insect is favored by late planting, broadleaf weed growth (especially chickweed) present before planting, poorly drained field conditions and reduced tillage. Rescue treatments can be applied for this soil insect if you are able to scout fields twice a week once leaf feeding is detected. If you are unable to scout and you have conditions favoring cutworms, a pyrethroid (Ambush, Asana, Pounce, Mustang or Warrior) tank mixed with a herbicide and applied close to planting has provided effective control. Pounce, Mustang and Warrior can also be applied as a liquid t-band application at planting for cutworm control. The granular insecticides Force, Lorsban and Fortress are labeled for cutworm control, but must be applied as a T-band to be effective. Pheromone traps placed in the field by mid-March can be used to determine when to look for cut plants as well as areas of the state most likely to experience economic levels. Look for pheromone trap counts in future reports.
Wheat.
Although we still find
spotty distribution of Barley Yellow Dwarf Virus (BYDV) in the state, aphid
management can play an important role in reducing losses from BYDV. It still
appears that the most important time to control aphids and help reduce problems
from BYDV is the first 30 to 60 days after plant emergence. Information from
The aphid causing the greatest amount of damage last fall
was the Greenbug. This aphid can be easily identified
by the green stripe down the center of the body. The most significant losses
occurred on the eastern shore of
|
#/Foot of Row |
Plant Height |
Time of Year |
|
20-50 |
4-6 " |
Fall - late Winter |
|
200 |
7 - 10 " |
mid-March |
|
300 |
18-20 " |
mid-April |
|
800 |
30 + " |
mid-May |
|
|
||
|
Greenbug Aphid with green stripe down the back |
||
Alfalfa.
During the last two growing seasons, alfalfa weevil populations have been higher than normal. A combination of warm winter weather and dry conditions could result in early feeding damage this season. Therefore, you should begin sampling fields for early feeding signs by the last week in March. Look for small larvae feeding in the tips of plants producing a round, pinhole type of feeding. Once you detect tip feeding, a full field sample should be taken. You will want to avoid treating fields too early since it may result in multiple applications. In general, no treatment should be needed before you observe 50% of the tips with feeding damage.
Precautions for Herbicide Use with Nitrogen
Applications to Small Grains - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
It is common to add herbicides when nitrogen is applied to small grains and small grain-legume mixtures. These precautions are from manufacturer’s label:
Harmony Extra or Harmony GT- slurry in water first and may result in temporary crop yellowing. If liquid nitrogen is less than 50% of the spray mix, then include a surfactant. For 2,4-D it varies with the formulation. The ester formulation can be mixed directly with nitrogen, but labels recommend good agitation. Amine formulation of 2,4-D should be mixed with 3 to 5 parts of water before adding it to the nitrogen solution. Buctril label cautions about potential leaf burn when mixed with liquid fertilizer, but leaves emerging after application are not affected. For MCPA, it varies some with the manufacturer. The ester formulation should not be applied with liquid nitrogen. The amine formulation varies, ranging from no mention of liquid nitrogen to application is allowed.
Grain Marketing Highlights - Carl
German, Extension Crops Marketing Specialist; clgerman@udel.edu
Commodity Markets Rally on
General consensus at the Chicago Board of Trade among
commodity traders is that we need some fresh fundamental news to help provide
price direction in the trading pits. News along that line came at the end of
last week as the rumor hit the market that
Other News in Brief
The Southern Hemisphere harvest is well underway. Preliminary reports from
The corn market has held steady in spite of recent, large cancellations of
Market Strategy
Price level has much to do with deciding what one's marketing strategy should
be. Current price levels for soybeans and wheat are too low to make
advancing sales an attractive venture, at this point in time. The corn market
has now nearly recovered to its mid-January price level, when farmers were
advised to make their first new crop corn sale on 10 to 30% of intended new
crop production. For the time being, we'd like to see a Chicago Board of Trade
price of $2.40 per bushel or better (with a basis of 10 over or better) before
advancing new crop corn sales.
Small Grain Fertilization in 2002 - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu
I just want to make
a few comments on wheat fertilization from the perspective of the advanced crop
maturity status of wheat and barley this year.
The highly variable weather we’ve experienced this fall and winter seems
to have small grains advancing far ahead of their usual pace. Many fields appear well along in the jointing
stage when normally it is the end of March before they reach this point. For this reason, growers who had been
planning to split nitrogen (N) applications may want to consider applying all their needed N now, rather than some now and some later
in the spring. In our usual pattern, we
have or will be applying the first “at greenup”
application in late February or early March and the second split application
just prior to jointing in late March.
With many fields already jointing, it is critical to get the recommended
rate of N applied. As a caution, we do
run the risk of loosing some N, if we get heavy rains in the next couple of
weeks. However, much of the small grain
crop is large enough to rapidly take up the N that is applied.
Irrigating Small Grains - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu
The prolonged dry
weather we’ve experienced since last fall has lead many growers to reconsider
if irrigation of their small grain crops might pay off. I thought it would be helpful to review the
research on the topic and then offer my advise for what its worth.
You may recall an
article from the April 2000 issue on this topic. In it, I reviewed the results of two years of
work on irrigation timing on winter wheat.
The study used a high-yielding, disease resistant wheat variety that was
heavily fertilized with split applications of nitrogen including fall-applied
nitrogen. Excellent stands were achieved
both years. Fungicide was applied to
minimize disease impact on yields and insecticides were used when needed. Irrigation treatments began one week after
the wheat flowered. The crop was irrigated
with 1.5 inches of water per week less the amount of rainfall received. Irrigation treatments were a control that
received no irrigation, and irrigation for one, two, three, and four weeks
following flowering. The center of a 30
by 30 foot plot was combine harvested for a yield
estimate.
No significant
differences were observed between the control and any irrigation
treatment. Although not significant, the
trend both years was for lower yields with longer periods of irrigation and
especially when irrigated for three or four weeks. Test weight was not affected significantly by
irrigation.
What about work done
prior to the above study? I read back
through the old Wheat and Barley Reviews and found that Frank Webb had done
work on both wheat and barley with and without irrigation. The timing of water applications varied a
little from year to year, but in three of the four years, water was applied in
mid- to late-March, late-April, and mid-May, and in the fourth year irrigation
was not needed until mid-May and mid-June.
In the first year, there was a significant decrease in yield of wheat
with irrigation. Across the four years,
there were no significant differences between irrigation and no irrigation for
barley or wheat. The numerical
difference between the treatments was a 2.7 bu/A increase for irrigated barley and a 0.6 bu/A decrease for irrigated wheat. The wheat data follows very closely with the
data I developed during the 1998 and 1999 growing seasons.
Should you irrigate
small grains? This question ultimately
must be answered by individual producers.
Certainly, based on my research in 1998 to 1999 and research from the
early 1980’s, irrigation of wheat or barley will not pay economically.
If you intend on
irrigating wheat anyway, follow these guidelines.
Ž
Irrigate only the best fields with high yield
potential.
Ž
Limit the number of irrigations while
building the soils available water to near maximum.
Ž
Do not irrigate during flowering.
Ž
Stop irrigating by two weeks after flowering.
Ž
Irrigation prior to heading should occur only
under extreme drought conditions.
If you feel you
must irrigate, the most useful thing you can do for both your small grain crop
and your planned following crop is to irrigate enough to bring not only the top
soil, but the subsoil that’s in the rooting zone of the crops to field
capacity. Because of the occasional
yield reductions we’ve seen with irrigated wheat, I would not irrigate after
getting the soil up to field capacity.
What rainfall we receive should be enough to take the crop on through to
maturity especially since these crops appear not to need a large amount of
water.
You may obtain copies of the Pest Management Recommendations
for Field Crops 2002 from the
New 911 Address
for the University of
Please make a note of the new address for the University of Delaware Research & Education Center (and Sussex County Extension Office).
Thanks!
Pesticide Briefs
On-Line – Susan Whitney, Extension
Specialist, Pesticides, Urban Entomology, swhitney@udel.edu
Short news articles from EPA, USDA, and the Pesticide Industry. Our
goal is to promote informed regulatory decisions on registered pesticides.
http://www.udel.edu/pesticide/briefs.htm
UPCOMING MEETINGS:
Pesticide Applicator Training and Testing:
Date: March
22 (Friday) and 25 (Monday), 2002.
Location:
New Castle Co. Extension Office.
Date:
Location:
Sussex Co. Extension Office.
Date:
Location:
Kent Co. Extension Office.
The first day
is training --
For more information, contact Susan Whitney (swhitney@udel.edu) at 302-831-8886 or your
local extension office:
Variety
Trial Results Online
Variety trial results for Small
Grains, Grain Sorghum, Soybeans, and Corn can be found at the following
address:
http://ag.udel.edu/extension/information/varietytrials/index.html
or contact your county cooperative extension office for a copy.
Weather
Summary
Week of March 1 to
|
|
Rainfall: |
|
0.52 inches: March 2 0.29 inches: March 3 |
|
|
|
Air Temperature: |
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Highs Ranged from 66° F on March 7 to 40° F on March 5. |
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Lows Ranged from 42°F on March 3 to 16° F on March 5. |
|
Soil Temperature: |
|
43.3°F average for the week. |
|
(Soil temperature taken at a 2 inch depth, under sod) |
Web Address for the U of D
Compiled and Edited
By:
Tracy Wootten
Extension Associate -
Vegetable Crops
Cooperative
Extension Education in Agriculture and Home Economics, University of Delaware,
Delaware State University and the United States Department of Agriculture
cooperating, John Nye, Director. Distributed in furtherance of the Acts of Congress of May 8 and
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