Volume 10, Issue 22
August 23, 2002
Volume 10, Issue 22
August 23, 2002
Vegetables
Vegetable Insects
-
BEET ARMYWORM ALERT
Beet armyworms can be found in many fall vegetable crops including cabbage, lima beans, snap beans and spinach. Moths can be readily observed laying eggs in fields. Identification is critical because pyrethroids will not provide control. Young larvae will often web the leaves together and larger larvae can produce significant amounts of defoliation. Please refer to the description of larvae under the field crops section of the newsletter. Labeled products will vary with the crop so please refer to controls under each vegetable. See page 9 for photos.
Cabbage.
Diamondback (DBM) and cabbage looper (CL) larval populations continue to increase. We are also seeing an increase in beet armyworm populations. The treatment threshold is 5% of the plants infested. If DBM and CL are present, Avaunt (3.5 oz/acre), a Bt, Proclaim (3 oz/acre), or Spintor (4-5 oz per acre) will provide control. If cabbage looper is the predominant species, a pyrethroid or Confirm (8 oz/acre) will also provide control. If beet armyworm is the predominant species, Avaunt, Confirm or Spintor should be used.
Lima
Beans.
Be sure to sample fields carefully for corn earworm, beet armyworm, lygus and stinkbugs. A treatment should be applied if you find one corn earworm per 6 foot of row or 15 tarnished plant bugs and/or stinkbugs per 50 sweeps. There are no thresholds for beet armyworm; however, a spray should be considered when worms are small and you can find 20% of the plants defoliated. Lannate, Mustang or Capture can be used to control corn earworm, lygus and stink bugs. If beet armyworm is causing problems, Lannate will only work if worms are small at the time of treatment. Spintor is also labeled on lima beans and will provide good beet armyworm control.
Peppers.
At the present time, all peppers should be sprayed on a 5to7-day schedule for corn borer, corn earworm, and beet armyworm control. Orthene or Address will not provide satisfactory earworm control. A pyrethroid or Lannate will be needed for earworm control. If beet armyworms are present, Avaunt, Spintor, or Confirm will provide the best beet armyworm control. Depending on the pest complex present, a combination of products will be needed.
Snap
Beans.
Processing snap beans in all areas of the state should be treated at the bud and pin stages for corn borer control. Orthene or Address should be used at the bud and/or pin stages for corn borer control. In all areas, a pyrethroid should be combined with Orthene at the pin spray for earworm control. Beet armyworm can also be found defoliating snap beans. There are no thresholds for beet armyworm; however, a spray should be considered when worms are small and you can find 20% of the plants defoliated. Orthene should provide good control of beet armyworm. Lannate will only provide control of small larvae. Spintor is also labeled on snap beans and will provide good reduction in beet armyworm numbers. After the pin stage, Lannate, Capture or Mustang should be used for corn borer and earworm control. Sprays will be needed on a 5-day schedule from the pin spray 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 decisions in processing snap beans (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html). You should treat fresh market snap beans for corn borers, corn earworm and beet armyworm on a 5-7-day schedule from the pin stage until harvest. Lannate should be used if beet armyworms are small. Lannate, Capture or Mustang should be used if corn borer and corn earworm are the predominant species.
Spinach.
Fields should be scouted at emergence for webworm and beet armyworm larvae. Controls should be applied when worms are small and before they have moved deep into the hearts of the plants. Also, remember that both insects can produce webbing on the plants. Since beet armyworms are more difficult to control and populations are increasing in our area, chemical selection is important. Since Lannate cannot be applied before plants are 3-inches in diameter and it only provides control of small larvae, Confirm or Spintor will be needed for beet armyworm control. If webworms are the predominant species, Ambush, Pounce, Confirm (6-8 oz/acre) or Spintor (4-8 oz/acre) should be used. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm.
Sweet
Corn.
Fresh market silking sweet corn should be sprayed on a 2-3-day schedule in all areas of the state. Since corn earworm catches continue to be high and fall armyworm can be found in silk stage corn, you should consider combining Lannate LV at 1 to 1.5 pt/A with the highest rate of a pyrethroid. 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 fresh market sweet corn.
(http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html ) .
Vegetable Diseases
- Kate Everts, Extension Vegetable Pathologist, University of
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. 0 0 0 3 0 1 0
Collins Farms 3 4 3 2 1 0 0
Vincent Farms 3 4 2 1 1 0 1
White Marsh 0 0 0 0 0 0 0
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.
Field Crop Insects
-
Corn Earworm and Beet Armyworm Alert
Soybeans.
Corn earworm moth activity and egg laying
has significantly increased in full season and double crop fields throughout
the state. Significant populations can be found on the eastern shore of
Beet Armyworm (BAW): The beet armyworm is a light-green to black larva with four pairs of abdominal prolegs and a darker head compared to corn earworm. There are many fine, white wavy lines along the back and a broader stripe along each side. There is usually a distinctive dark spot on each side just above the second pair of true legs. See page 9 for photos.
Corn Earworm: (CEW): The corn earworm larvae can vary from light green or pink to brown or nearly black. You can also see alternating longitudinal dark and light stripes marking its body. Coloration is so variable that it is not dependable for identification.
Short microspines, which are visible through a hand lens, can be seen on the skin. In general, the head capsule is yellow to amber in color.
See page 9 for photos.
As indicated in
previous newsletters, the pyrethroids WILL NOT
control beet armyworms. There have been a few fields sprayed in
Therefore, all fields should be scouted for pod feeders as soon as blossoms are present. Although many producers feel that their beans are too "far-gone" and not worth treating, you will need to consider treating if you plan to harvest the field. A potential yield of even 8-10 BU/A justifies a treatment. In addition, if you have purchased Crop Insurance you can not abandon a field on your own, since you risk loosing your payment. You should have both your insurance agent and adjuster come to your field to make a decision. If you plan to salvage the field, you will need to control worms if they reach economic levels.
Since earworms can also act as defoliators, a treatment may be needed prebloom if 30% of the plants are defoliated or if 15% of the plants are defoliated during bloom. This defoliation threshold should also be used for beet armyworm. The treatment threshold for pod feeders is 3 per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields (20-inches are greater). At the present time, there is no threshold for beet armyworm pod feeding; however, once pod feeding is detected, you may want to consider the same threshold used for corn earworm. A drop (shake) cloth can also be used to estimate populations. The drop cloth should be placed between 2 rows and then the plants are shaken over the cloth in 6 foot of row. A treatment is needed if you find 1-2 larvae per foot of row.
The following materials will provide corn earworm control in soybeans: Ambush, Asana, Mustang, Pounce, Warrior (all pyrethroids) or Larvin. If population pressure is heavy, the higher rate of the older pyrethroids will be needed. You should use 2.56 of Warrior and 3.2 oz may be needed if mixed size larvae are present at treatment time. If beet armyworm is the predominant species, Steward should be used at 5.6-8.0 oz/A.
Grain Marketing Highlights -
Commodity Markets Undergo Major Correction
Commodity prices for
Currently, the
The
This year's
General Comments
Commodity prices are currently reacting to major uncertainty
concerning the eventual size and quality of this year's crop. As the days get
shorter and autumn draws near, time will be running out for that portion of the
Questions on Irrigating Soybeans -
Richard W. Taylor,Extension Agronomist, rtaylor@udel.edu
,
Associate Scientist,
bobuni@udel.edu
In the last week or
two, I’ve been asked several questions with regard to the irrigation management
of soybeans. I’ll list them below along
with some information to consider if you have a similar question.
If you have
full-season soybeans and have been irrigating them since planting, you may be
surprised by the amount of vegetative growth the crop has achieved. On a good fertile soil, beans can become
nearly six feet tall so long as outside factors do not cause them to begin
lodging. You might think that with beans
that large, you will see tremendous flower production and pod set with the
potential for record yields. More often
than not what happens is that you will have a second but unpleasant surprise by
how few beans are ever set by the plants.
Without some stress early in the season, full-season (and only
full-season) beans often yield
Is there anything
that can be done in a situation like the one described below? After the beans reach the reproductive stage,
they will use about 0.28 inches of water per day. This rate declines gradually reaching 0.2
inches per day at pod filling or the R6 (full seed) growth stage in mid- to
late-August. If you tried stressing the
crop at this stage, you would only further reduce yield potential so about all
you can do is to keep enough water on the crop to prevent stress and hope they
remain upright as long as possible. One
of the factors that may reduce yield potential in these beans is the lack of
sunlight penetration into the lower canopy.
This is especially a problem when the beans begin to lodge.
Another question
asked is how much water beans are using and whether one could reduce the amount
of irrigation applied on double-crop beans.
Double-crop beans (wheat beans more so than barley beans) use a little
less water than full-season beans. The
water use curve is steeper than with full-season beans but from about the fifth
node stage through R5 stage (beginning seed), double-crop beans use from 0.2 to
0.26 inches of water per day. During pod
fill R5 through R7, the rate of water use declines from about 0.15 inches per
day to less than 0.1 inch per day. The exact amount of water used per day and when the beans reach
different maturity stages varies by cultivar and the specific cultural
practices used on a particular field.
Use your best judgment to decide how much water to apply but until the
beans begin to mature (one normal pod on the main stem has reached its mature
pod color—R7 stage), water stress will cause yield reduction. As a general rule in mid-August, figure beans
will be using about 1.5 to 2.0 inches of water per week and by mid-September
water use will be around 1.25 inches per week (and declining swiftly).
Maturity Groups Selection in Soybeans -
Richard W. Taylor,Extension
Agronomist, rtaylor@udel.edu,
If you have never
taken the time to stop at the soybean variety evaluation plots, this year would
be an ideal time to do so. On a visit to
the plots in
Photo
1. Maturity group III soybean cultivar trial at
Group IV varieties
were still alive at the
Photo
2. Maturity group IV soybean cultivar trial at
In a sustained
drought like the one we’ve had this year, the best hope for yield if rains do
occur soon are the group V varieties since many of they are still in the bloom
stage of growth and with sufficient rain could still produce reasonable yields
(Photo 3 and 4 below).
Photo
3. Maturity group V soybean cultivar trial at
Photo
4. Maturity group V soybean
cultivar trial at
Even within a
maturity group, some individual varieties are able to tolerate the drought a
little better than others, so take a little time out of your schedule and run
by the nearest test plots to see the differences yourself. If you’d like directions or a list of
varieties in the test and a field map of the site, email us or call one of us
at 302-831-2531 (Dept. of Plant and Soil Sciences).
Managing Pastures During Prolonged Drought
Conditions - Richard W. Taylor,Extension Agronomist, rtaylor@udel.edu
From a hay point of
view, the aggressive growers have been pretty lucky so far. Many of you have gotten as many as four cuts
off alfalfa and three cuts off orchardgrass and some
of the other grasses. Unfortunately,
unless the weather pattern changes drastically and soon and a tropical storm
heads this way, there is unlikely to be enough of either alfalfa or grass for
an additional harvest. Those producers
who started cutting later in the spring or did not hold tight to a schedule
have one or more fewer cuttings of hay and have little chance of another later
this fall. Alfalfa is very deep rooted
and grasses such as tall fescue, bromegrass, reed canarygrass, and Kentucky bluegrass have rhizomes that help
them survive long periods of drought. I
am worried about orchardgrass as it must come back
from the crown and in some cases I see little life left even in the crown
area. Let’s hope for rain soon so we can
see which fields will be able to recover and which ones we may need to plan
renovating.
In the last week or
two, I’ve been asked questions about pasture management by several folks
concerned with what their pastures look like.
If you fertilized earlier this spring with potash fertilizer, you did as
much as you could do for your pasture.
At this point the only thing that you can do is to observe it carefully
to see if there are weeds actively growing that should be mowed (Photo 1 and 2
below).
Photo
1. Lambsquarter
actively growing in Kentucky bluegrass pasture during a prolonged drought (Photo by R.
Taylor)
Photo
2. Weed patches (lambsquarter)
actively growing in Kentucky bluegrass pasture during a prolonged drought (Photo by R.
Taylor)
If there are patches
of weeds that somehow are actively growing, mowing will reduce the leaf area of
the weeds and help reduce the removal of soil moisture by the weeds. Also, mowing will help reduce the potential
for these weeds to contribute to the weed seed bank in the pasture. When mowing though, try not to cause any more
damage to the pasture than possible.
Since most pasture
grasses are not growing much at this time, you should also consider limiting
the use of pastures to protect the grasses and legumes. Do not graze any closer than that recommended
for the species in your pasture. Grazing
too close will further reduce the chance that the pasture will be able to successfully
recover when rain returns.
Finally, hold off
applying any additional fertilizer especially that contains either nitrogen or
potassium since these fertilizers act as salts and would place additional water
stress on the pasture plants.
Triazine Carryover to Small Grains - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
The lack of rain has made the potential of atrazine and simazine carryover to small grains a real threat for dryland fields. (Irrigated fields are not an issue because the herbicides would have adequate water.) Under normal rainfall patterns, atrazine and simazine levels are so low at this time of year that carryover to small grains in many areas are not a concern. However, with the limited rainfall in many areas, there has not been the chance for these herbicides to breakdown or become diluted. I do not have a good rule of thumb to say when to avoid planting small grains and when the risk is low. It will depend on rate of herbicide used, soil type, and amount of rainfall the particular field received. Carryover is a greater concern with simazine (Princep) because it has a lower water solubility level. Atrazine at levels over one pound per acre is a risk (some situations with less than a pound are at risk as well). Bicep Magnum at 1.3 qts/A contains 1 lb of atrazine, Harness Xtra at 2.3 qt/A contains 1 lb of atrazine, and Fultime at 2.4 qt/A contains 1 lb of atrazine.
As far as differences in small grain sensitivity to atrazine and simazine, oats are the most sensitive. Barley is next sensitive followed by wheat, and rye is the most tolerant. If you are considering planting small grains in a field treated with atrazine, you may want to do a bioassay. Collect soil cores to a depth of 6 inches throughout the field. Mix the soil, put it in a pot and plant oats or collard seeds into the pots. At the same time, pull some soil from a flowerbed or garden with no herbicide, put into a pot, and plant the same seeds. Plants should start to show symptoms within one to two weeks after emerging from the soil.
Beet Armyworm (BAW):
Corn Earworm
(CEW):
Week of August 15
to
|
|
Rainfall: NONE.
|
|
|
|
Air Temperature: |
|
Highs Ranged from 96°F on August
18 & 19 to 85°F on August 21. |
|
Lows Ranged from 77°F on August
16 to 64°F on August 21. |
|
Soil Temperature: |
|
90 °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:
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, Robin Morgan, Dean and Director.
Distributed in furtherance of the Acts of Congress of
May 8 and
