Volume 12, Issue 11
June 4, 2004
Volume 12, Issue 11
June 4, 2004
Vegetables
Vegetable Crop Insects -
Cucumbers.
All fields should be scouted for cucumber beetles
and aphids. Fresh market cucumbers are susceptible to bacterial wilt, so
treatments should be applied before beetles feed extensively on cotyledons and
first true leaves. Pickling cucumbers have more tolerance to wilt, but a
treatment may be needed if you find 2 or more beetles per plant and significant
damage can be found on the cotyledons. A treatment should be applied for aphids
if 10 to 20 percent of the plants are infested with aphids with 5 or more
aphids per leaf. Fulfill, Thionex or Lannate will provide
aphid control. Be sure to watch for bees foraging in the area and avoid
insecticide applications on blooming crops. A pyrethroid, Lannate, Sevin
or Thionex are labeled for cucumber beetle control in cucumbers.
Melons.
Continue to scout all melons for aphids, cucumber beetles, and spider
mites. We continue to see an increase in the number of fields with spider mite
infestations. If populations are high at the time of treatment, 2 sprays spaced
5 days apart may be needed. The threshold for mites is 20-30% infested crowns
with 1-2 mites per leaf. Acramite, Capture, Danitol, Agri-Mek or Kelthane will provide
control, but should be rotated to avoid the development of resistance. The
treatment threshold for aphids is 20% infested plants with at least 5 aphids
per leaf. Continue to watch
fields carefully for cucumber beetles. Be sure to look under the plastic where
beetles can often hide until disturbed. Be sure to watch for bees foraging in
the area and avoid insecticide applications on blooming crops.
Peppers.
Fields should be sampled for thrips
and corn borers. Although corn is
growing rapidly and should be more attractive to corn borer moths, you should
still watch for corn borer egg masses in isolated fields ( i.e. not near corn
fields). You should also check local moth catches in your area (http://www.udel.edu/IPM/traps/latestblt.html
). A treatment with a pyrethroid
may be needed if corn borer moth catches exceed 10 moths per night, especially
if corn planting is delayed in your area or you are using rye strips as
windbreaks. In general, 2 applications will be needed to achieve
effective control. Thrips
can cause damage in peppers by vectoring tomato spotted wilt virus and by
causing direct plant damage. There have been reports of tomato spotted wilt in
tomatoes in
Potatoes.
Colorado potato beetle (CPB) adults and larvae
can be found in many fields, even where at planting treatments were used. The
treatment threshold for adults is 25 beetles per 50 plants and defoliation has
reached the 10% level. Once larvae are detected, the threshold is 4 small
larvae per plant or 1.5 large larvae per plant. The threshold for each should
be reduced if all stages of larvae are present. Avaunt + PBO, Actara, cryolite, Spintor or Provado will provide
control. Corn borer sprays will now be needed 3-5 days after an increase in
trap catches. Be sure to check our website http://www.udel.edu/IPM/traps/latestblt.html)
for the most recent moth catches in your area. Avaunt, Ambush, Baythroid, Furadan, Penncap, Pounce or Spintor will
provide control. If you are scouting for infested terminals, the first
treatment should be applied when 20-25% of the terminals are infested. Furadan or Monitor will provide the best control if you are
waiting until you see infested terminals. Economic levels of potato
leafhopper adults and nymphs can be found in many fields. As a general
guideline, controls should be applied if you find ½ to one adult per sweep
and/or one nymph per every 10 leaves. Dimethoate, a pyrethroid, Actara or Provado will provide
control.
Snap Beans.
All fields should be scouted for leafhopper and thrips activity, especially seedling stage beans. The thrips threshold is 5-6 per leaflet and the leafhopper
threshold is 5 per sweep. If both insects are present, the threshold for each
should be reduced by 1/3. Dimethoate, Lannate, Asana, Capture, or Warrior will provide control of
both insect pests. As soon as the earliest fields have buds present, a
treatment will be needed for corn borer control once moth catches are above 2 per night in your
area. Be sure to check our website (http://www.udel.edu/IPM/traps/latestblt.html)
for the most recent moth catches in your area.
Sweet Corn.
Flea beetles and cutworms are still active in
seedling stage sweet corn. The treatment threshold for flea beetles is 5%
infested plants. The cutworm threshold is 3% cut plants or 10% leaf feeding. We are also seeing cereal
leaf beetle adults in seedling and whorl stage corn. A treatment may be needed
if you find 10 beetles per plant and 50% of the plants exhibit damage.
Continue to sample any corn in the whorl stage to pretassel stage for European
corn borer larvae. A treatment should be applied if 15% of the plants are
infested. In recent years, Avaunt (whorl stage only), Baythroid,
Mustang, Penncap, Spintor or Warrior has provided effective control. If economic levels of corn
borers are present in pretassel to tassel stage corn, two sprays spaced 3-4
days apart are often needed. The first silk sprays will be needed for corn
earworm as soon as ear shanks are visible. Treatment will be needed on a 5-day
schedule.
Bee Kills in Watermelons –
Bee
kills in watermelons is a serious problem. Everyone loses when it happens. The
bee keeper loses his bees and the grower loses the pollination service. Unfortunately, materials act
differently. Some kill the worker bees
in the field during spraying. Others can
be carried by the field workers from the field to the hive. Larvae are then killed. If the brood larvae are affected, you are
looking at a 21 day set back before the queen will lay new eggs and new workers
are available to care for the hive. It is economically important for growers to
protect the bees that are in your field.
We recently looked at a field where most of field
force was killed off. We think the hives will recover, but it will take time to
replace the field force and build up the colony strength. As a grower, you can help reduce the problem
of bee kills by informing the bee keeper of when you are going to apply bee
killing materials. Spray late in day when there are fewer bees in the
field. Alert the applicator to hive
location to avoid direct spraying of hives.
Select the safest material that works. You can provide additional
protection for the bee hives by sitting your overhead irrigation system over
the hive and run the system while the field is being sprayed. Another trick is
to soak burlap with water and cover the hives to keep them in and cool. This would probably be the only way to
protect hives sitting in the field. You have to remove the burlap right after
spraying to prevent them from getting too hot and being killed by the heat. In
the past, we used to just use local bee keepers. They could come protect their
hives. Commercial bee keepers cannot
make it around to all of the sites to protect their bees. A lack of bees will
cost growers quality and yield. Can you afford not to help protect them?
Vegetable Crop Diseases
-
Late
Blight Advisory
Disease
Severity Value (DSV) Accumulation as of June 2, 2004, is as follows:
|
Date |
Daily DSV |
Total DSV |
Spray Recommendation |
|
4/25-
5/2 |
4 |
4 |
none |
|
5/3 |
8 |
12 |
none |
|
5/9 |
2 |
14 |
none |
|
5/13 |
1 |
15 |
none |
|
5/17 |
2 |
17 |
none |
|
5/18 |
1 |
18 |
none |
|
5/19 |
4 |
22 |
7-day |
|
5/20 |
2 |
24 |
7-day |
|
5/21 |
2 |
26 |
7-day |
|
5/25 |
5 |
31 |
7-day |
|
5/27 |
3 |
34 |
7-day |
|
5/30 |
8 |
42 |
7-day |
|
5/31 |
1 |
43 |
7-day |
|
6/1 |
1 |
44 |
7-day |
All potatoes in DE have accumulated 18 DSV’s or
more by now. The threshold of 300 P-days was also exceeded yesterday, which
would recommend initiating sprays for early blight. This will be important for
growers with early blight susceptible varieties. This 300 P-day threshold was
exceeded for potatoes that emerged on or before April 25.
Growers who do not want to rely only on the DSV
calculations for scheduling fungicide applications should apply mancozeb
(Dithane, Pencozeb, Manex II) or Bravo before plants canopy down the row and
repeat on a 7-day schedule. Late blight has not been a problem here in
Management Strategies for Phytophthora Fruit
Rot Control in Pickling Cucumbers -
and Ed Kee, Extension Vegetable Specialist,
Phytophthora
fruit rot can be a devastating disease of pickles on Delmarva. Last year’s wet
season was a very favorable year for Phytophthora
capsici on many crops. The fungus is soilborne and the overwintering oospores
can remain viable in the soil for 10 years or more. Cultural practices that
help control Phytophthora are (1) as long a rotation away from susceptible
crops (tomatoes, peppers, eggplants, lima beans, cucurbits including pumpkins,
summer and winter squash, watermelon, and cantaloupe) as possible, (2) plant
only well-drained fields, (3) use as
wide a row spacing as possible to allow drying and reduce humidity. Properly constructed raised beds can also
be helpful as they keep vulnerable plants from saturated soil conditions. The
most effective control measure that growers have available is to avoid planting
in infested soil and limit the spread of the disease to clean fields.
Fungicides have also been shown to provide some control if applied at the right
time and good coverage is achieved. A combined approach of all available
control methods is more effective than using just one control measure.
Recent work done in Michigan by Dr. Mary
Hausbeck and her team over the past several seasons to control Phytophthora
fruit rot has promise for us here in Delaware. We have relied on applications
of Ridomil Gold or Ultra-Flourish in a band at planting followed by several
applications of Acrobat or Gavel combined with a copper fungicide such as Champ
or Kocide for
fruit rot control. Their research is
showing the best control under their conditions with three applications of
Acrobat or Gavel when fruit are
1, 3, and 5 inches long. Under our
conditions, fruit may size so quickly that only two sprays at
1 and 3 inch long fruit would be used here.
Application of the fungicides is also very important. All the fungicides for
fruit rot control which includes Acrobat, Gavel (zoxamide plus mancozeb),
mancozeb (Dithane DF, Manzate, Penncozeb) and copper hydroxide (Champ, Kocide)
are not systemic, so coverage of the fruit is very important if control is to
be effective. It is not enough to just spray until the leaves are wet, you need
enough pressure and/or air to drive the fungicide to the fruit. They have had
good success with conventional spray rigs equipped with 8003 nozzles, spaced 20
in. apart operating at 60 psi, delivering 30 gal/A. Air-assisted sprayers with
4 nozzles spaced 60 in. apart, delivering 10 gal/A have also been demonstrated
to be very effective.
Fungicide test plots and large
demonstration plots have shown that several treatments have proven effective
under varying amounts of disease pressure. As mentioned before, Acrobat 50 WP
(6.4 oz/A) or Gavel 75DF (2 lb/A) are applied with 2 lbs. of Kocide or Champ when
they are applied. They are getting slightly better control compared to the
untreated check by alternating Gavel with Acrobat. Since Gavel contains
mancozeb it has a 5 day pre-harvest interval (phi) which limits its use close
to harvest. They were applying Gavel at the 1 and 3 in. stage and ending with
Acrobat at the 5 in. size. There was no significant difference between all
three sprays of either Acrobat or Gavel.
All
that being said, we would recommend for Delaware growers that they choose their
fields wisely following the non-chemical guidelines addressed earlier and
applying preventative sprays of Acrobat 6.4 oz/A or Gavel at 2 lbs/A plus Champ
DF or Kocide 2000 at 2 lbs/A when the fruit are 1 in. long and again at 3 in.
long. If weather conditions are such that a spray at 5 in. is possible, it
would be recommended as well. Mefanoxam (Ridomil Gold or UltraFlourish) could
also be used in a band over the row at planting when planting fields with a
history of fruit rot and no or very little mefanoxam use in the past. We
identified several populations of Phytophthora
capsici in DE last season that are resistant or insensitive to mefanoxam.
It would be logical to assume that if mefanoxam has been used to control Phytophthora capsici on pickles or any
other susceptible crop in a field that the fungus may develop insensitivity
over time. But, that does not always happen as we have seen in NJ where
mefanoxam has been used exclusively for crown rot control in peppers and
insensitivity has not developed. Resistance usually occurs over time, but not
always. Rotating mefanoxam with other fungicides with different modes of action
like Acrobat and Gavel will delay or prevent insensitivity from occurring.
.jpg)
Phytophthora Fruit Rot.
Economics of
Phytophthora Control in Pickling Cucumbers –
Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Bob’s article suggests two applications, perhaps
three of an Acrobat 50WP (6.4 oz./A) or Gavel 75DF (2 lbs./A) plus
Kocide or Champ (2 lbs./A) during the fruit enlargement stage has
provided good control of Phytophthora in
On a per bushel basis, again using 180 bushels as
the estimated yield, two applications of the Acrobat/Kocide combination would
cost $0.16 per bushel. Two applications
of the Gavel/Kocide combination would cost $0.18 per bushel. Three applications of each combination would
be $0.24 per bushel for Acrobat/Kocide; or $0.27 per bushel for Gavel/Kocide.
Adding the highest cost scenario, i.e., three
applications of Gavel/Kocide, adds $48 of cost to the $209 basic variable costs
mentioned in the first paragraph, for a total of $257 per acre, or $1.42 total
variable costs per bushel.
If belly rot control (rhizoctonia) is required,
adding two applications of Amistar at 5 oz/acre would add an additional $56 per
acre, or $0.31 per bushel; and bring total variable costs to $313 per acre, or
$1.73 per bushel for a 180 bushel crop.
We have also calculated fixed costs (equipment,
harvesting, labor, etc.) to range from $0.60 to $1.00 per bushel, bring the
maximum costs of production up to somewhere between $2.33 to $2.73 per bushel.
Growers know their margin between price received
and their costs. Fungicide investment is
critical to profit, but often hard to predict which plantings will benefit the
most from this investment, due to weather fluctuations, crop history, and other
variables. The above discussion also
presents decisions on the number of applications and whether to include belly rot
control measures in addition to phytophthora control measures.
The various choices can add $0.16 to as much as $0.55 cents per bushel. At a price of anywhere between $3.75 to $4.25 per bushel, a well-conceived approach to disease control can be a worthwhile investment. This is especially true when wet, warm weather conditions can trigger outbreaks of Phytophthora that cause acreage to be by-passed.
Field Crop Insects -
Alfalfa.
Continue to sample all fields on a weekly basis for leafhopper adults
and nymphs. Once fields are yellow, stand and yield loss has already occurred.
We are starting to see an increase in nymphs which often cause damage very
quickly. The treatment thresholds are 20 per 100 sweeps on alfalfa 3 inches or
less in height, 50 per 100 sweeps in 4-6 inch tall alfalfa and 100 per 100
sweeps in 7-11 inch tall alfalfa. Baythroid, dimethoate, Mustang or Warrior will provide effective
control.
Field
Corn.
Continue to scout corn up to V-5 stage for cutworms. We continue to find
cut plants and larvae feeding below the ground level. Under these conditions, a rescue treatment
will only be effective if applications are made late in the day, you use 30
gallons of water per acre and materials are directed to the base of
plants. A pyrethroid or Lorsban will
provide control.
There
have also been reports of grasshoppers feeding on small plants. A grasshopper
treatment should be considered if you find 5-8 grasshoppers per square yard.
Asana, Dimethoate, Lorsban, Furadan and Warrior will provide control, but
multiple applications may be needed.
Continue to scout whorl stage corn for cereal leaf
beetle, true armyworms and European corn borer. Be sure to carefully sample no-till
fields for true armyworm where a grass cover or volunteer small grains were
burned down at planting. The treatment threshold for armyworms in corn is 25%
infested plants with larvae less than one-inch long. No controls will be needed for cereal leaf
beetles until you find 10 beetles per plant and 50% of the plants exhibit
damage. European corn borer control will not be needed until 50% of the planted
are infested in irrigated fields and 80% of the plants are infested in dry land
fields. Since corn is growing quickly, the best time for control will be just
at pre-tassel or tassel emergence as long as larvae have not bored into the
midribs of leaves.
Small
Grains.
Continue to scout all fields for grass sawfly and armyworms. In both
wheat and barley, the treatment threshold for sawflies is 2 per 5 foot of row innerspace or 0.4 per foot of row. The armyworm threshold
is one per foot of row in barley and two per foot of row in wheat. If multiple
pests are present in barley, your only control option is Lannate.
In wheat, your options include Lannate, Mustang, or Warrior.
Soybeans.
Grasshopper and bean leaf beetle feeding continue to be found in
seedling stage soybean fields. A treatment for bean leaf beetle will be needed
from plant emergence to the second trifoliate when you find 2 beetles per foot
of row and a 25% stand reduction. A pyrethroid, dimethoate or Lorsban will
provide control. The treatment threshold for grasshoppers is 1 per sweep and
30% defoliation. Asana, Furadan, Lorsban,
or Warrior will provide grasshopper control.
Field Crop Diseases -
Wheat.
Several samples were received and I have had
several phone calls about wheat that has turned almost white in the field. The
affected areas are on knolls and other dry parts of the field in areas of the
state that have had little rain. It appears that the problem is the dry
weather. One sample had some Rhizoctonia eyespot as well on the lower stems.
In
.jpg)
Tanspot on Wheat
Postemergence Grass
Control in Corn - Mark
VanGessel, Extension Weed Specialist; mjv@udel.edu
There are a number of herbicides to control grasses postemergence in corn. These herbicides include the active ingredients nicosulfuron – Accent or Celebrity Plus; nicosulfuron plus rimsulfuron - Basis Gold, Steadfast, or Steadfast ATZ; or foramsulfuron – Option or Equip. Accent or Celebrity Plus will not control crabgrass, while the other products will only control small crabgrass (labels specify 1 to 2 inches).
Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu
General Comments.
Corn,
soybean and wheat old crop and new crop futures rallied limit moves on Tuesday
morning this week, the first day back form the Memorial Day weekend. The rally was due to three primary reasons.
First,
Second,
Weather - currently, the primary problem in the
Third,
Funds - the funds amassed a huge liquidation of soybean futures contracts going
into the holiday weekend, predisposing the likelihood that the soybean market
is now oversold. It is reasonable to expect that the funds will come back into
the market buying both corn and soybean futures contracts.
Market Strategy.
Bear
in mind that we are in volatile times, with the commodities markets being of no
exception. Reports of too much rain, nitrogen leeching on acres planted and
intended for corn, the possibility that some corn acres may be abandoned for
soybeans (although not all that likely depending upon ground preparation that
had occurred), and the likelihood that yield reductions are forthcoming in the
production forecasts all portend to higher prices yet to come. We need to find
out more about the extent of crop damage in the
White Head
Syndrome and Head Scab in Wheat
- Richard W. Taylor, Extension Agronomist, University of
Delaware; rtaylor@udel.edu
and
Now is a good time to scout your fields for the
amount of head scab that has developed.
One caution is that when the entire head is infected, scab can be easily
confused with white head syndrome caused by damage to the main stem either by
insect feeding or other agents. Photo 1
below may help you distinguish between the two.
In scab that affects the entire head, the glume structures that enclose
the wheat kernel appear more uniformly white or bleached of color than when the
head has been partially clipped by insect feeding. In the latter case, if you closely examine
the glumes, you will see green striations since at least some nutrients and
food is usually able to move to the head through the injured stem.
.jpg)
Photo 1. Head scab (Fusarium head blight) on the left
and two white heads caused by injury (insect feeding) to the wheat stem on the
right (Photo by R. Taylor).
Another way to distinguish the two problems is to
pull on the plant and see if the head easily snaps off (usually at a node where
the injury occurred). To estimate the
percentage of damage from each, walk across your field and check 50 to 100
random heads that are completely white to see if the head easily snaps off the
plant. Keep track of the numbers to
determine the percentage of white heads cause by scab or by white head
syndrome. At the same time, you could
stop in several areas and estimate the percentage of heads affected by scab,
counting only those heads that have a portion of the head affected (See Photo
2). By estimating both the percentage of
seed heads affected and the percentage of an individual head that is affected,
you could come up with a rough estimate of the amount of damage to your field.
.jpg)
Photo 2.
Head scab in wheat affecting the upper third of the panicle (Photo by R.
Taylor).
When
Calibration Goes Awry -
Richard W. Taylor,Extension Agronomist,
The rash of storms that have rumbled across our
area in recent days combined with rapidly maturing barley and wheat has made it
easier to diagnose when your sprayer is not delivering a product as uniformly
as you would like. Take for example the
field shown below in Photos 1 to 3. One
side of the boom used to apply nitrogen (N) was not working properly in this
field. The result was an
over-application of N that resulted in a distinct lodging pattern. When regular patterns appear in fields as
seen in Photos 1 and 2, you can be pretty sure that the problem relates to
something manmade, in this case a sprayer uniformity problem.
Although N is required for good grain yields, too
much N can actually cost you in lost yield.
When the crop severely lodges early in grain fill, many tillers are
shaded so that they no longer can intercept the maximum available light and
convert it into sugars, starches, and protein that becomes the grain you
harvest. Seed size and yield are not the
only factors affected since test weight and grain quality can be hurt.
If you see patterns in your field, be sure to check
them out to see what may be causing the problem. Then, correct the problem so subsequent crops
will have optimal management.
.jpg)
Photo 1.
Lodging in soft red winter wheat caused by excessive application of
nitrogen from a miscalibrated sprayer (Photo by R. Taylor).
.jpg)
Photo 2.
Distinct patterns of lodging indicating a manmade causal agent (Photo
by R. Taylor).
.jpg)
Photo 3.
Although lodging is not severe at this point, indications are that
additional lodging may occur due to a high N application rate (Photo by R.
Taylor).
PESTICIDE
APPLICATOR TRAINING & TESTING
June 21 - 22, 2004, Kent Co.
The first day is training -- 8:30 am - 4:30 pm. Training continues the morning of the
second day, 8:30 am - noon.
Be sure to
bring your Workbook! You don't have to register for training, but you must
register for the exam. Call DDA (302-698-4500) one week in advance to
register for the exam. The exam
starts at 1:00 pm the second day. All exams are closed book!!
Bring your calculator for the calibration questions.
Access the link below for everything you wanted to know about
pesticide applicator training, certification, and recertification in
http://www.udel.edu/pesticide/howto.htm#whocert
Pesticide Container
Recycling
In cooperation with the
Agricultural Container Research Council (ACRC), the Pesticides Section provides
an empty pesticide container recycling program in the State of
Each container is
closely inspected for cleanliness (they must be triple rinsed or equivalent),
chipped and bagged for storage and transport. Container chips are combined with
those collected in similar programs across the country and processed into
pallets, park benches, new pesticide containers, or converted into fuel.
Containers are collected
at the Sussex Conservation District, Maintenance Yard, Shortly Road,
Collection hours are from 9:30 a.m. – 1:30 p.m
Week of May 27
to June 2, 2004
|
|
Rainfall: |
|
0.38
inches: May 28 0.30
inches: May 31 0.03
inches: June 1 |
|
|
|
Air Temperature: |
|
Highs
Ranged from 83°F on June 2 to 72°F on May 29 & 30. |
|
Lows
Ranged from 67°F on May 28 to 53°F on May 30. |
|
Soil
Temperature: |
|
73°F
average. |
|
(Soil
temperature taken at a 2 inch depth, under sod) |
Web
Address for the U of D Research & Education Center: http://www.rec.udel.edu
Compiled and
Edited By:
Tracy Wootten
Cooperative
Extension Education in Agriculture and Home Economics, University of Delaware,
Delaware State University and the United States Department of Agriculture
cooperating. Distributed in furtherance
of the Acts of Congress of May 8 and June 30, 1914.