Volume 12, Issue 8
May 14, 2004
Volume 12, Issue 8
May 14, 2004
Vegetables
Foliar Fertilizers
and Vegetable Crops – Ed
Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Foliar
fertilizers are often considered for use in vegetable crops. While they have a utility, if a certain
nutrient becomes unavailable or deficient during the growing season, building a
total fertilizer program around foliar fertilizers is expensive and inefficient. To quote from our five-state Commercial
Vegetable Recommendation Book: “Properly managed soils are usually able to
supply the essential nutrients the crop will need during its development. If one or more soil-supplied nutrients become
deficient or unavailable during the development of the crop, foliar nutrient
applications may be beneficial.”
Trickle Irrigation
Guidelines – Ed
Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Trickle
irrigation systems have gone from essentially none used to the dominant method
of irrigation on several vegetable crops on Delmarva. These include watermelons, cantaloupes,
peppers, and tomatoes. Strawberries,
squash and other crops are also irrigated by trickle systems.
Excellent,
tried and proven recommendations for fertigation of these crops are discussed
in the five-state publication, Commercial Vegetable Production Recommendations.
Of course, the publication offers a wide range of recommendations on every aspect
of production of 42 vegetable crops and strawberries. This is available from your County Extension
Office
Vegetable Crop Insects -
Asparagus.
We continue to find asparagus beetle egg laying
activity on spears. A treatment is recommended if 2% of the spears are infested
with eggs. Since adults will also feed on the spears, a treatment is
recommended if 5% of the plants are infested with adults. Sevin,
Lannate, Ambush, or Pounce will provide control.
Cabbage.
With the warmer weather, be sure to watch for an increase in
diamondback activity. Imported cabbageworm and diamondback larvae can both be
found feeding on cabbage. Treatments should be applied when 5% of the plants
are infested with larvae and before larvae move to the heart of the plants. Avaunt, Bt insecticides, Proclaim,
or Spintor will provide effective control of both
species. Be sure to rotate between these classes of insecticides to avoid
the development of resistance.
Melons.
The predominant insect pest continues to be aphids. However, in most cases,
these aphids have moved off of rye strips and should be controlled by
beneficials. We are finding predominantly English grain aphids and green peach
aphids – very few melon aphids. Be sure to watch carefully for cucumber
beetles. The first beetles have been found and the warmer weather often results
in spikes in populations. We have also found extremely low levels of spider
mites. As soon as plants are set in the field, you should begin scouting for
all three insect pests. The treatment threshold for aphids is 20% infested plants with at least 5 aphids
per leaf. Actara, Fulfill, Lannate and Thionex are labeled on melons and will provide melon aphid
control. Dimethoate will not control melon
aphids. These materials should be applied before aphids explode. The
treatment threshold for cucumber beetles in watermelons is 2 per plant. Since
cantaloupes are very susceptible to bacterial wilt, sprays should be applied as
soon as beetles are observed and you find feeding on the cotyledons and first
true leaves. If a foliar treatment is used, dimethoate provided good control of
high populations in 2003. The spider mite threshold is 20 - 30% of the crowns
infested with 1-2 mites per leaf.
If populations of mites explode and adult mites are the predominant life
stage, Capture or Danitol should be used. If the
population is a mixture of eggs, immature mites and lower levels of adult
mites, Agri-Mek should be used at 8 oz/acre. A second
miticide application may be needed in 3-7 days
depending on the population level at treatment time. Acramite (new label for
2004) can also be used for spider mite control. It provided good control in our research trials
in 2002. However, the label states apply
in a minimum of 50 gallons of water per acre and you are limited to one
application per season. We are working with the manufacturer (Crompton) to get
a 24C to allow aerial application. We will keep you posted on the progress.
Potatoes.
Colorado potato beetle adults,
egg masses and the first small larvae can be found in earliest emerged
fields. A treatment should not be needed for adults until you find 25 beetles
per 50 plants and defoliation has reached the 10% level. Once larvae are
detected, the threshold is 4 small larvae per plant. Avaunt + PBO, Actara, cryolite, Spintor or Provado will provide
control. Although corn borer catches have increased, we have not seen a peak in
populations. A corn borer spray may be needed 3-5 days after an increase in
trap catches or when we reach 700-degree days (base 50). With the warmer
weather, we should reach this level some time next week. 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, Monitor or Spintor
will provide corn borer 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.
Sandea on Watermelons - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
Gowan has an expanded label for Sandea use on
watermelons for preemergence application.
Sandea has been labeled for row middles of watermelons, this allows for
an application under the plastic.
Application needs to be made after the beds are shaped, but prior to
laying plastic. Use rate is 0.5 to 0.75
oz/A. A copy of this label as well as
Reflex on snap beans, and Sinbar on watermelons are available by contacting
Vegetable Diseases –
Dr.
Dan Egel, Purdue University, wrote the following article for
10
USEFUL RULES FOR FUNGICIDE APPLICATION- (Dan Egel)- Below I have listed 10 rules
that will help vegetable growers apply fungicides effectively and safely. Rules 1 through 7 are listed in no particular
order; however, I saved the most important three for last.
1.
Apply fungicides prior to
the development of disease. Most fungicides do not have
a “kick back” action. That is, they do
not effectively eradicate diseases after they have started. And by the time a single disease lesion is
observed in the field, many more lesions too small to observe are already
working at your crop.
2.
Use shorter spray intervals
during weather conducive to plant disease. Each
plant disease has its own “personality” and thus prefers different
weather. However, most plant diseases
require leaf wetness. Therefore, during
periods of rain and heavy dews, more frequent fungicide applications are a good
idea. The normal range of spray
applications is every 7 to 14 days.
Muskmelon and watermelon growers have the guesswork taken out of this
process with a
3.
Apply fungicides before
a rain if possible. Water is necessary for most
fungal spores to infect a leaf or stem and for the splash dispersal of many
spores. Therefore apply fungicides
before a rain if it appears that the fungicide will have a chance to dry before
the rain. It is not necessary to apply
fungicides again after every rain. Most
modern fungicides have a good sticker and will persist through rains pretty
well.
4.
Avoid applying fungicides
in the heat of the day. It is possible for any
foliar applied chemical to cause some plant damage if applied under conditions
of heat and direct sunshine. Also
remember that if fungicides and insecticides are applied together, make the
applications so that bees are unharmed.
5.
Timing of fungicide
applications is more important than nozzle type and spray pressure. Studies here in southern
6.
Some diseases cannot be
managed by foliar sprays. Problems caused by soil
borne fungi or nematodes cannot be controlled with foliar fungicides. Examples of these types of problems would be
Fusarium wilt of watermelon or root-knot nematodes of tomatoes. Also, be certain that the problem you observe
is really a disease. No amount of
fungicide will improve a problem caused by soil fertility.
7.
Do not apply foliar
fungicides to the soil. Although fungicides may
kill or inhibit the growth of fungi which cause plant diseases, the application
of those same fungicides to the soil will be wasteful and off label. Foliar fungicides are designed to protect the
surfaces of plants.
8.
Make certain the fungicide
matches the crop and disease. That is,
READ THE LABEL. The label is the
law. Plus, considerable time and money
was spent to test each fungicide with a particular crop and disease. Off label applications also waste your time
and money.
9.
Double – check the label for
the current rate per acre. Rates may
vary widely based on label changes and different formulations. While you are checking the rate, also check
to make sure your application method is labeled. (Can this fungicide be applied in the
greenhouse?) Did you get the rate from
the Mid-Atlantic Commercial Vegetable Production Recommendations (http://www.rce.rutgers.edu/pubs/pdfs/e001t.pdf)? Check
the label anyway.
10.Play it safe. Always adhere to the Post-Harvest Intervals,
Re-Entry Intervals and Worker Protection Standards listed in the label. No one wants an accident or lawsuit. Besides, the label is the law.
Field Crop Insects -
Alfalfa
Weevil.
In many cases, fields have been cut or will be cut within 5-7 days.
Before cutting, we could find late instar larvae as well as pupae in many
fields. If economic levels of weevils were present before cutting and you did
not treat, be sure to check the regrowth for larvae as well as adults within
one week of cutting. If bailing is delayed, adults and larvae feeding in the
crowns can delay normal green-up. A
treatment should be considered if you find 2 or more adults and/or larvae per
crown.
Field
Corn.
We continue to find cutworm leaf feeding and cut plants mainly in
no-till fields, so continue to sample for cutworms through V-5 stage corn. We have also received a number of questions
about flea beetles feeding on corn. In some cases, it has been a combination of
frost damage and springtails (most are scavengers that feed on decaying plants,
fungi, molds, or algae), In other cases,
folks have observed flea beetles and small holes in plants. In these cases,
cutworms have been the culprit – remember that small cutworms can produce small
holes in leaves. If flea beetles are present, they physically damage seedling
corn by chewing long lesions in the leaves. These feeding lesions run parallel
to the leaf veins and they first appear as thin, silvery or white streaks.
Heavily injured leaves can turn brown and wilt; however, this generally occurs
during periods of cool, wet weather. Flea beetles can also transmit Stewart's
wilt; however, most all commercial field corn hybrids are resistant to this
disease. In general, only susceptible inbreds or sweet corn will need a flea
beetle treatment to manage Stewart’s wilt. A treatment should only be
considered before growth stage V-5 if growth is being held back , 50% of the
plants show extreme injury and you find 5 or more beetles per plant.
Small
Grains.
With the warmer weather, we have seen an increase in
cereal leaf beetle larval numbers and feeding damage. We are also just starting to find extremely
low levels of grass sawfly and true armyworm larvae. A treatment for armyworm
should be considered if you find one per foot of row in barley, or 2 per foot
of row in wheat. The treatment threshold for grass sawfly is 2 per 5 foot of
row innerspace or 0.4 per foot of row. If both are present, the threshold for
each insect should be reduced by one-half.
Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu
Supply and Demand Highlights
Corn.
USDA
issued the May crop report on Wednesday giving an initial assessment of
Global
ending stock estimates for world corn supplies increased by about 20 million
metric tons over the April estimate due mainly to an adjustment made in
Soybeans.
The
May 12th crop report was viewed as somewhat friendly, from a fundamental
perspective, with USDA leaving old crop ending stocks unchanged at 115 million
bushels. New crop production was estimated at record levels, while the South
American old crop estimate was lowered.
USDA's
Brazilian production estimate was reduced to 53.5 million metric tons, with
Even
though this report was not viewed as negative, commodity price bidding in the
soybean pits yesterday experienced a 'technical meltdown', with soybean futures
declining in double digit market limit fashion for the nearby contracts and
double digits for the new crop. Apparently, news broke about possible tenders
for South American soy oil and soy meal by large American firm(s), coupled with
settlements occurring in the May futures contracts. These factors and the fact
that we are already in a volatile situation resulted in a sell-off in the
soybean pits yesterday of an estimated 11,000 to 12,000 contracts.
Wheat.
Domestic
and global ending stocks were reduced. U.S. carry out for the '04/'05 marketing
year is now estimated at 499 million bushels, a 27 million bushel reduction
from the 526 million bushel carry over projected for the '03/'04 marketing
year. Adverse weather conditions in the hard red winter wheat areas resulted in
a lowering of the production estimate. New crop wheat production in the
Market Strategy.
With
the sell off occurring in yesterday's market this is likely to be viewed by
commodity speculators as a good time to buy the market, particularly for new
crop corn and wheat. Assuming that statement is true,then advancing forward
pricing sales should be placed on hold until the markets have had a chance to
work higher. Crop planting progress will soon be taking the back seat to
weather conditions and crop development. It will take ideal weather conditions
to produce 145 bushel per acre corn and 40 bushel per acre soybeans, on 79
million and 75.4 million acres planted, respectively. These markets remain
extremely volatile.
Soil-Applied Herbicides Need To Be
Moved Into the Soil - Mark
VanGessel, Extension Weed Specialist; mjv@udel.edu
Herbicides applied to the soil surface require
rainfall or irrigation or mechanical incorporation to move them into the soil
where the plants will absorb them. The
amount of water needed to “activate” these herbicides depends on the water
solubility of the herbicide and moisture content of the soil. Even with good soil moisture like we have, it
still will require some rain or irrigation to move the herbicide into the soil. Most soil-applied herbicides require 0.5 to
0.75 inches to be moved in the soil if the soil is “dry” (less water if the
soil is moist). Princep requires 0.75 to
1.0 inches of water to become “activated”.
If you have irrigation and your corn herbicides have been applied, but
you have not received at least 0.5 inches of water, you should consider
applying that amount with your system.
Mechanical incorporation with a field cultivator, set no more than 3 to
4 inches deep, will physically move the herbicide into the root zone. Field cultivators set any deeper will cause
the herbicides to become too diluted. A
field cultivator will mix the soil to half the depth it is set (set to 4 inches
– soil mixes to 2 inches). This is one
situation where spending a little money now could save money later. For instance, if your residual grass
herbicide is not moved into the soil and grass control is poor, you are looking
at a postemergence application of Option, Steadfast, or Accent-containing
pre-mix, and control of crabgrass with
postemergence herbicides is only fair.
Spending the money to irrigate and activate the herbicides could save a
high herbicide bill later.
Be Sure To Scout Early Planted Corn - Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
It is important to start to get over the early
planted corn ground to check if there are weed breaks. Crabgrass is also one that worries me since
it is very difficult to control with a postemergence spray. Most of the postemergence grass herbicides
(Basis Gold, Steadfast, or Option) will not control crabgrass over 1 to 2
inches tall. Herbicide-resistant corn
(Liberty Link or Roundup Ready) gives you a wider window for crabgrass
control. Be sure to check your fields
early.
2004
The
2004