Volume 10, Issue 20
August 9, 2002
Volume 10, Issue 20
August 9, 2002
Vegetables
Vegetable Insects
-
Cabbage.
Be sure to sample fall planted fields for diamondback and cabbage looper larvae. We can find both insects in recently planted fields. If both species 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.
Lima
Beans.
Be sure to sample fields carefully for corn earworm, 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. Lannate, Mustang or Capture can be used to control all 3 insects on lima beans.
Peppers.
At the present time, all peppers should be sprayed on a 7-day schedule for corn borer, corn earworm, beet armyworm and pepper maggot control. Remember, Orthene or Address will not provide satisfactory earworm control. A pyrethroid or Lannate will be needed for earworm control. Dimethoate should still be added to the mix for pepper maggot control if a pyrethroid or Lannate are used. If beet armyworms are present, Avaunt, Spintor, Confirm or Lannate 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. After the pin stage, Lannate, Capture or Mustang should be used. Sprays will be needed on a 6-7-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 on a 7-day schedule from the pin stage until harvest. Lannate, Capture or Mustang should be used.
Sweet
Corn.
Fresh market silking sweet corn
should be sprayed on a 2-3-day schedule in the Bridgeville,
(http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html ). Economic levels of fall armyworm can be found in most late-planted sweet corn. Insecticides must be directed into the whorls with at least 25-30 gallons of water per acre to achieve control. In addition, at least 2 applications may be needed. Lannate, Avaunt or Warrior have provided effective fall armyworm control in whorl stage corn.
Maintain Fungicide
Sprays on Watermelons -
Several growers have asked about discontinuing fungicide sprays on watermelons in light of the dry weather. If growers expect to keep harvesting, fungicide coverage needs to be continued. You are protecting new tissue resulting from leaf and fruit growth. Fungicides do breakdown and new coverage is necessary. Additionally, heavy dews can provide enough moisture to support the disease causing organism. Sprays need to protect until the last harvest is finished.
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 6 0 8 0 5 0
Collins Farms 0 3 2 4 2 1 1
Vincent Farms 0 3 2 4 5 3 1
White Marsh 0 6 0 3 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
-
Soybeans.
It is still important to monitor fields for spider mite infestations. If left uncontrolled, this pest can cause 40-60% yield loss. Although it is tempting to give up on drought stressed fields, treated fields can recover when miticides are applied in a timely manner. Although diseased mites have been detected, the amount of natural mortality varies from field to field. In some fields we have seen populations crash from both diseases and natural enemies, and in others populations continue to increase. The treatment threshold for mites is 20 mites per leaflet or 10% of the new growth exhibiting stippling damage with mites present on leaves. The only available materials for treatment are dimethoate 4E (1 pt/A) or Lorsban (1 pt/A). Although Lorsban has provided good control, it only provides contact activity. If dimethoate is used, an acidifying-penetrant similar to LI-700 or AD-100 should be used. In most cases, it may take 2 applications to achieve satisfactory control. Also, edge treatments are not advised at this time because mites have already dispersed into the main part of the field. Edge treatments are only effective if infestations are caught early in the season before significant damage is noticed on field borders.
It will also be important to watch all soybean fields carefully for potential earworm outbreaks this year. Since the drought has resulted in open canopy situations in many fields, both full season and double crop beans will be attractive to egg-laying moths. Our experiences from the 1999 season indicate that it is important to scout for this insect on a weekly basis. As many recall, populations increased very rapidly resulting in wide spread economic losses. In addition, drought stressed fields received later season rains and many fields were very attractive to earworm egg laying. A combination of factors indicates that conditions may be favorable for an earworm outbreak in soybeans this year:
(1) Since corn has either already or is rapidly drying down, emerging earworm moths will be attracted to late planted vegetables and any open canopy, blooming soybean fields.
(2) Results of the 2002 Virginia Field Corn Survey used to predict the potential for earworm outbreaks in soybeans indicate that the potential is very high, especially compared to 2001. This could result in migratory populations heading our way in mid to late August.
(3) Although results of our field corn survey are generally lower than last season, we are seeing a significant increase in moth catches in blacklight and pheromone traps.
(4) Weather conditions in August will determine if egg laying results in economic larval damage. Last year, humid, wet weather caused populations to crash quickly. If the weather remains hot and dry, we may not see a crash this season. It has been our experience that you need to see at least a week of rainy weather combined with warm, humid days to get fungal pathogens to develop and spread between larvae.
So, all fields should be scouted for earworms as soon as blossoms are present. Earworms can also act as defoliators during bloom so a treatment may be needed if 15% of the plants are defoliated. The treatment threshold for pod feeding is 3 per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields ( 20-inches are greater). If a sweep net is not used, 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. When possible, treatment should be delayed until at least 1/3 of the worms are at least 3/8-inch long. In addition, watch for diseased worms since the same diseases that attack green cloverworm can also help to reduce earworm populations.
The following materials will provide corn earworm control in soybeans: Ambush, Asana, Mustang, Pounce, Warrior (all pyrethroids) or Larvin. Larvin acts by ingestion on both small and large larvae. Remember that if you are using a pyrethroid, the primary mode of action on large larvae will be ingestion. Earworms will need to feed to cause death so you will not see much activity from the contact action. Once they ingest the product, they immediately stop feeding. Therefore, fields should not be evaluated for control until 4 days after application. Small larvae are generally killed by contact as well as ingestion. It is important that you do not look at fields 1-2 days after spraying and assume control failure if large worms are present. This could result in unnecessary re-sprays.
Grain Marketing Highlights -
Commodity Markets Braced for Higher Prices
Commodity markets appear to be poised for a move higher
based upon a continuing decline in
The spring wheat crop condition estimate now
rates only 32% of the crop in the good/excellent category, the lowest in
thirteen years.
Marketing Strategy
For reasons discussed above, advancing a portion of
remaining new crop corn sales ahead of the crop report at $2.60 per bushel or
better is advisable. Local basis bids of 20 over Dec. (
Late Herbicide
Applications to Soybeans
- Mark VanGessel,
Extension Weed Specialist; mjv@udel.edu
The rains we have had lately have resulted in reconsidering postemergence herbicide applications. In most situations these are rescue treatments, but there is some concern about herbicide injury. The trade-off is herbicide injury versus yield loss due to weeds. Weed competition will be a much greater factor in reducing yields than the herbicide application, even if the plants are blooming. However, most herbicides will not kill large weeds in conventional soybeans (non-Roundup Ready soybeans), so be careful in your herbicide selection that it will provide an acceptable level of control or suppression.
Late-Summer Pasture and Hay Seedings -
Richard W. Taylor,Extension Agronomist, rtaylor@udel.edu
As mid-August
approaches, many of us may begin thinking about planting new forage seedings for pastures or hay production. We might also be thinking about reseeding
some of last spring’s fields due to poor establishment this summer because of
the continuing drought conditions.
Late summer or early
fall is a good time to establish forage plantings since many annual weeds that
emerge with the crop will be controlled by the first frost of the winter. Fall is also an advantage in that the crop is
able to complete much of the establishment process during the off-season so
there is less down time than with a spring seeding. This can be especially true in summer drought
years when late summer production is minimal if available at all. Below are some tips to remember during the
process of seeding forages.
n Remember a forage establishment
if successful will be for many, many years so be sure to soil test ahead of
time and make lime and fertilizer (phosphorus and potassium) additions prior to
seeding. This will allow you to work the
materials into the plow layer. After
establishment, all fertilizer and lime applications will be on the soil
surface. Only nitrogen moves quickly
through the soil. For example, lime
effects move downward only about 1 inch per year.
n Calculate a budget for the
seeding and weigh the benefits and costs of seeding at the high end (or 1.5
times) of the recommended seeding rate.
I often see more consistent success at the higher seeding rates although
long-term yield levels may not be any higher.
n Avoid the use of companion
crops such as oats. Although a companion
crop does provide a minimal amount of early cash flow from the sale of either
grain or straw, forage establishment is often greatly delayed and can even lead
to poorly established stands that continue to yield below expectation.
n Much of the demand for hay now
is for grass hay. If the market moves
back to demanding grass: legume mixtures, legumes such as red clover and white
clover can easily be introduced into pure grass stands using no-till or even
frost-crack seeding.
n Do not proceed with new seedings until we receive enough rain to wet not only the
surface soil, but also the deeper subsoil.
New seedings do not have well established root
systems so moisture stress can be particularly harsh on establishment. Being certain that the surface and subsoil
layers have enough moisture to carry the new seedlings into the winter will be
important for long-term success of your planting.
n After the end of September, the
risk of establishment failure increases dramatically especially if the
temperatures turn cold early in the fall or we experience a harsh winter.
n If you prefer to renovate your
grass pasture or hay field instead of replanting it, consider doing weed
control this fall to clean out broadleaf weeds.
Additional grass seed or even a compatible legume can be overseeded early next spring to thicken the stand. We often see producers overseeding
with a minimal amount of grass or legume-grass seed each spring or every other
spring to help maintain hay or pasture stands.
Corn Silage Harvest Concerns -
Richard W. Taylor,Extension Agronomist, rtaylor@udel.edu
In the last week,
I’ve observed farmers beginning to chop corn fields to make silage. In a drought year, one of the major concerns
with using drought-damage corn is the potential for the corn to accumulate
nitrate to a degree that is toxic to livestock.
Corn is not the only plant that should concern growers when it comes to
harvesting fields for silage. In
addition to corn, soybeans, grain sorghum, sudangrass,
millet, and the sorghum sudangrass hybrids have been
shown to accumulate nitrates. Also,
weeds including jimsonweed, johnsongrass, lambsquarter, nightshade, pigweed,
Drought does not
always lead to high nitrate levels in plants since some moisture must be
present in the soil for the plant to absorb and accumulate nitrate. Late-planted corn that has produced little
top growth because of severe drought conditions may not be as much of a risk as
an almost normal corn crop (with respect to height) where moisture was
available for early season growth and nitrate uptake. Crops that were fertilized with surface
applications of manure may also not be as great a risk if inadequate soil
moisture were available for the normal mineralization of the organic nitrogen
in the manure.
Nitrate is not in
and of itself toxic to animals, but when ingested at high levels it can cause a
disease known as nitrate poisoning. In
ruminant animals, the nitrates normally found in forages are converted by
digestion into nitrite, and then this in turn is converted into ammonia. The bacteria in the rumen convert the ammonia
into protein. If cattle ingest large
quantities of a crop containing high levels of nitrate-nitrogen, an
accumulation of nitrite can occur in the rumen.
Nitrite is ten times as toxic to cattle as nitrate. Toxicity occurs when the nitrite is absorbed
into red blood cells and combines with the hemoglobin to form methemoglobin. This
latter compound is not near as efficient at transporting oxygen to cells as the
hemoglobin is. An animal’s heart rate
and respiration increases as oxygen starvation of the cells and tissues
occurs. The blood and tissues turn blue
to chocolate brown, muscle tremors develop, the animal begins to stagger, and
eventually the animal can suffocate.
What can you do to
lower the potential for the problem?
First, since nitrates tend to accumulate in the lower stem of plants
(the plant parts closest to the ground), raise your height of cut to at least 8
to 12 inches above the soil surface for corn and to at least 6 to 8 inches
above the soil for millets, sorghums, and sorghum sudangrass
hybrids. Stalks contain the highest
concentration of nitrate followed by leaves and then grain. Younger plants contain more than mature
plants although even mature plants can contain excessive amounts of nitrate if
environmental and soil conditions are favorable. Nitrates remain high for several days
following the first rain and decline thereafter only if the plant is able to
resume growth.
Secondly, when in doubt test all drought-affected
forage before it is fed to or grazed by animals. For forage or silage marginal in nitrate
accumulation (but below the toxic level cited below), you may have success
mixing the material with other forage testing low in nitrates and then feeding
the mixture. If you test forage, be sure
you understand the test results that you get back. Some labs report results in parts per million
of nitrate while others report parts per million nitrate nitrogen. Forages containing 0 to 1,500 parts per
million nitrate nitrogen are generally considered safe for livestock. To obtain the corresponding range for parts
per million nitrate, multiply parts per million
nitrate nitrogen by 4.5 so the safe range in parts per million nitrate is 0 to
6,500. If the level of nitrate nitrogen
is 1,500 to 4,500 parts per million, you must use caution in feeding this
forage as problems have occurred at these levels. You can mix, dilute, or limit feed forage in
this range. If levels are greater than
4,500 parts per million nitrate nitrogen (>20,000 parts per million
nitrate), consider the forage dangerous and do not feed as it is potentially toxic.
When grazing, first
feed either a dry roughage first or graze low nitrate
forage to reduce the amount of affected plants ingested by hungry animals. When in doubt, test all forage and have your
veterinarian or other consultant help calculate the correct ratios of high and
low nitrate forages to blend to develop a safe ration for a particular class of
livestock. Additional management
guidelines for grazing are listed below.
n Frequent intake of small
amounts of high nitrate feed helps animals adjust to high nitrate feeds and
increases the total amount of nitrate that can be ingested daily without
adverse effects.
n Allow cattle time to adapt to
increased nitrate in the diet if levels are moderate (<9,000 ppm nitrate or about 2,000 ppm
nitrate nitrogen).
n Do not overstock pastures as
overstocking forces animals to consume plant parts closer to the ground and
that are higher in nitrate.
n Do not strip graze or use high
intensity grazing systems on pastures at risk for high nitrates as this also
increases the amount of stem and stalk material consumed.
n Feed supplements to dilute the
nitrate.
n Graze high nitrate pastures
during the day and remove animals at night especially for the first week or two
of grazing on high nitrate pastures.
This helps acclimate the animals.
n Consider harvesting and feeding
high nitrate forages as silage. The
fermentation process can reduce nitrate levels during the ensiling
process. Also, test forage for silage
after the ensiling process is completed.
n Do not feed green chop if it
goes through a heat as nitrite accumulation can occur.
Ag Fact
The Amish Community in
UPCOMING EVENTS:
Wicomico Farm & Home Show
RT
50 &
Week of August 2
to
|
|
Rainfall: August 6 -0.24 inches |
|
|
|
Air Temperature: |
|
Highs Ranged from 96°F on August
2 to 80°F on August 6 & 7. |
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Lows Ranged from 73°F on August
5 to 56°F on August 7. |
|
Soil Temperature: |
|
86 °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