Volume 12, Issue 15
July 2, 2004
Volume 12, Issue 15
July 2, 2004
Vegetables
Vegetable Crop Insects -
Lima Beans.
Be sure to watch for spider mites on
seedling stage lima beans, especially in areas of the state that have not been
receiving adequate rainfall. Both field interiors as well as field edges should
be examined for mites. Look for the white stippling along the veins on the
underside of the leaves. A treatment should be considered when you first notice
the stippling and you find 10-20 mites per leaflet. Kelthane or Capture (6.4
oz/A) have provided the best control in lima beans. The earliest planted fields
should be scouted for lygus bugs and stinkbugs. Treatment should be considered
if you find 15 adults and/or nymphs per 50 sweeps. Lannate, Capture or Mustang
can be used if both species are present. The higher labeled rates of Capture (4
oz/A) and Mustang (4.3 oz/A) will be needed if stinkbugs are the predominant
insect present.
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 and aphid infestations. If spider
mite populations are high at the time of treatment, 2 sprays spaced 5 days
apart will be needed. The threshold for mites is 20-30% infested crowns
with 1-2 mites per leaf. Acramite (only one application per season), 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. Be sure to check runners
carefully for aphids. For a treatment to
be effective, fields should be sprayed before you see significant leaf
curling. Be sure to watch for bees
foraging in the area and avoid insecticide applications on blooming crops.
Peppers.
Although corn borer catches are still generally light, we are starting to
see an increase in moth catches. In
areas where corn borer trap catches are above 2 per
night and pepper fruit is ˝ inch in size or larger, fields should be sprayed on
a 7-10 day schedule for corn borer control.
You will also need a treatment for pepper maggot. If Orthene is used, it
will also provide pepper maggot control. Otherwise, dimethoate should be added
to the mix. High beet armyworm (BAW) moth catches have been reported from VA.
Consultants have also found the first larvae in pepper fields. You will first
notice the “shot-hole” feeding signs in the terminals. No threshold is
available, so you need to watch for the first small larvae as well as their
feeding signs. You will also need to use a product like Confirm, Spintor,
Avaunt or Intrepid which provide good BAW control.
Potatoes.
Continue to scout fields on a weekly
basis for Colorado potato beetle (CPB) adults and
larvae. The larval threshold is 4 small larvae per plant or 1.5 large larvae
per plant. The threshold for each should be reduced by ⅓ to ˝ if all stages of larvae are present. Avaunt +
PBO, Actara, cryolite, Spintor, Provado or newly labeled Rimon will provide control of
larvae. We continue to see an increase in the emergence of summer adults.
Unfortunately, most of our labeled products are most effective on larvae. The
higher labeled rates of Spintor and cryolite have provided some level of adult
suppression this season; however, have not been adequate under high population
pressure. Actara, Leverage and Provado provide adult control, but should not be
used where Admire, Platinum or Gaucho were used at planting to avoid
development of resistance. We continue to find economic levels of green
peach aphids in fields that did not receive Admire, Platinum or Tops MZ Gaucho
at planting. A control will be needed if you find 2 aphids per leaf pre-bloom,
4 aphids per leaf post bloom and 10 aphids per leaf at 2 weeks from vine
kill/harvest. If melon aphids are found,
the threshold should be reduced by ˝. If
green peach aphid is the predominant species, Fulfill, Lannate, Monitor,
Provado, or Vydate will provide control. If Fulfill is used, a penetrating
surfactant is needed to achieve good coverage and achieve optimum control.
Snap
Beans.
Continue to scout all
seedling stage beans for leafhopper and thrips
activity. 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 ⅓. Dimethoate, Lannate, Asana, Capture, or Warrior will provide control of
both insect pests. Once corn borer catches reach 2 per night, fresh market and
processing snap beans in the bud to pin stages should be sprayed for corn
borer. Acephate should be used at the bud and pin
stages on processing beans. Once pins are present on fresh market snap beans
and trap catches are above 2 per night, a 7-10 day schedule should be
maintained for corn borer control. Lannate, Asana,
Capture, Warrior or Mustang are labeled. Acephate has a 14-day wait 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 decision in
processing snap beans (http://www.udel.edu/IPM/traps/latestblt.html
and http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html).
Sweet
Corn.
All fresh market silking
sweet corn should be sprayed on a 5-day schedule except in the
Potato Maturity,
Skinning, and Bruising: Vine Killing and Harvester Operation –
Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu
Moderate temperatures, especially with the relatively
cool nights we have experienced, favor potato tuber bulking. The sugars or carbohydrates formed during the
day in the leaves through photosynthesis are not “burned up” as much through
the respiration process. In other words,
a higher amount of carbohydrates can be accumulated in the tubers, rather than
being used by the plant to keep it functioning.
While I’ve never done it, I often said our potato yields could be
correlated with the average temperatures in June and early July.
Soon potato vine growth will slow and leaf
senescence will increase, with the vines reaching the maximum size and then
begin to decline. Early maturing
varieties will die back soon, while later maturing varieties will die back if
the season is long enough, which is usually the case in
Vine killing not only hastens tuber maturation,
often called hardening. The outer skin,
or periderm, forms from the outermost three or four cell layers of the
tuber. The collapsed walls of these
cells form a barrier which prevents water loss from the tuber, protects it
against pathogens, and helps limit bruising.
Tuber bruising costs potato growers across the
country millions of dollars because it reduces raw product quality for
processing. In
There are several types of Bruises. Skinning
occurs when the tubers are not completely mature. A corky layer will form on the bruised
area. Cuts and scrapes result when potatoes strike a sharp edge or object
during harvest, packing or handling. Pressure bruise from the weight of the
potatoes on themselves, especially when relative humidity is low. Blackspot
appears as a dark, semispherical spot in the tuber flesh beneath the skin 24-48
hours after impact on a hard surface.
Blackspot is a physiological disorder resulting from a serious of
biochemical reactions leading to the production of a black pigment in the
bruised flesh. The injury may not be
detected until the potato is peeled.
Potato varieties will differ in their susceptibility to Blackspot, but
all varieties are more susceptible when soil moisture at harvest is low and the
tubers are dehydrated. Inadequate
potassium may also increase the risk of Blackspot.
Allowing potatoes to reach full maturity helps
reduce bruising injury. Proper vine
killing to speed maturity when an advanced harvest is desired is also
important. If the vine killing is done
10 to 14 days in advance, there will be enough time for increased skin
development on the tubers.
There are three materials recommended for vine
killing in
ü
Desicate
II (endothall) Apply 1.5 to 2 quarts/A 10 to 14 days
before harvest. Ammonium sulfate may be
added.
ü
Diquat
2SC at 1 pint/acre with a nonionic surfactant may be
used. It can be repeated in five days,
if necessary. Do not harvest for 7 days
after treatment.
ü
Paraquat
at 1-2 pints per acre with a non-ionic surfactant may be
used. Do not harvest until 3 days after treatment. This may be the fastest kill, which could be
problematic as to good hardening or “skin set.”
There are important directions and recommendations
on the labels of each of these products.
Read and follow the directions carefully.
With all of these, the proper adjustment, operation and
maintenance of all parts of the harvester may be the most critical component of
reducing injury. Forward speed,
chain speeds, and belt speeds should be adjusted to manufacturer’s
recommendations. Often, these
adjustments need to be modified according to soil moisture conditions, crop
maturity, and other field factors.
Vegetable Crop Diseases - Bob Mulrooney,
Extension
Plant Pathologist, bobmul@udel.edu
IMPORTANT NOTICE
- Late Blight.
I just received a reliable report that late blight
was confirmed on tomatoes in
Lima
beans.
The State Department of Agriculture recently
granted a section 24(c) label for the use of Phostrol in
Late Blight Advisory.
Disease Severity Value
(DSV) Accumulation as of
|
Date |
Daily DSV |
Total DSV |
Spray Recommendation |
|
4/25- 5/18 |
4 |
18 |
7-day |
|
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 |
|
6/4 |
17 |
61 |
5-day |
|
6/7 |
2 |
63 |
5-day |
|
6/8 |
1 |
64 |
5-day |
|
6/10-6/13 |
9 |
73 |
7-day |
|
6/14-6/15 |
3 |
76 |
7-day |
|
6/16 |
3 |
79 |
7-day |
|
6/17 |
3 |
82 |
7-day |
|
6/22 |
1 |
83 |
7-day |
|
6/23 |
1 |
84 |
10-day |
|
6/25 |
3 |
87 |
7-day |
|
6/26-30 |
0 |
87 |
10-day |
What is driving the spray recommendation at the present
time is the need for fungicides for early
blight control. Conditions are not favorable for late blight.
Application rates for protectant fungicides
(Dithane, Bravo, etc.) should be at the high end of the rate with the amount of
foliage present.
For specific fungicide recommendations, see pages
F132-33, 2004 Delaware Commercial Vegetable Production Recommendations Book. EB
137.
Field Crop Insects -
Alfalfa.
Continue to sample all
fields on a weekly basis for potato leafhopper (PLH) adults and nymphs.
Although we have seen an increase in the number of lygus bug nymphs, controls
are rarely needed for this insect. Weather conditions are favorable for PLH
population increases. Remember, controls are most critical on small plants. 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.
Field Corn.
Although European corn
borer (ECB) populations have been light in most non-Bt fields, especially
compared to VA, be sure to check mid and later planted fields one last time if
they are just starting to shoot tassels.
This will be the best time to achieve control, as long you do not see
more than 1/3 of the population bored into the mid-ribs of leaves or the stalk.
The treatment threshold is 50% infested plants in irrigated corn and 80%
infested plants for dry land corn.
Soybeans.
Continue to scout all seedling stage
beans for leafhopper and thrips, especially drought stressed fields.
Grasshopper levels continue to increase and control is best when grasshoppers
are small. In addition, multiple applications are often needed for grasshoppers
since they migrate in and out of fields. You can use the following thresholds
as a treatment guideline: (a) Grasshoppers -- 1 per sweep and 30% defoliation,
(b) Thrips -- 8 per leaflet with plant growth being held back and significant
leaf cupping, and (c) Leafhoppers --- 4 per sweep in drought stressed fields
and 8 per sweep in non-stressed fields.
Continue to watch for spider mites, especially in
no-till fields where a heavy weed cover was present before planting. We are starting to see an increase in fields
with visible spider mite damage, especially drought stressed fields. There are
also reports of economic levels in irrigated fields, especially in fields where
no burn down was used at planting and weed pressure was heavy before planting.
Although an edge treatment can be effective when you are trying to protect
fields from mites moving in from weedy edges, this may not be effective if weed
pressure is heavy throughout a field before planting. We continue to find that
weeds provide an ideal habitat for overwintering mites. It will be important to scout the entire
field before deciding if an edge treatment is enough. A treatment is
recommended if you find 20-30 mites per leaflet or 10% of plants with 1/3 or
more leaf area damaged. At this point, the only materials available for mite
control in soybeans are dimethoate and Lorsban.
If dimethoate is used, the addition of a penetrating surfactant will
improve control, especially in drought stressed fields.
We are also starting to see an increase in green
cloverworm populations. No controls will be needed until you find 30%
defoliation pre-bloom and 15% during bloom. As a general guideline, you should
also find 10-15 cloverworms per foot of row. Unfortunately, we do not have a
threshold for the number per sweep.
Although soybean aphid
populations are still light in most areas of the
Mites on Soybeans Warning – Derby
Walker, Sussex County Extension Ag Agent, derby@udel.edu
Warning: Growers should be
checking soybean fields for mite damage.
There have been several calls this week on soybeans that have died
and/or are declining. After examining
the field, drought stress and mites are the culprits. Be sure to check areas of the field that you
know will be the first area of the field to be affected by drought. Mites are attracted to stressed plants, and
therefore will show up in these areas first.
Many times we see mites starting on field edges and moving into the
field. One area investigated was located
in the middle of the field. Damage did
not start along the field edge. Some plants were dead. Mites starting in the
middle of the field is not typical activity.
At first glance you may suspect nematode damage or some other problem. Be sure to investigate these areas
further. For spider mite controls, refer
to Joanne’s article above.
Two spotted spider mite
Spider mite damage
on soybeans
(Photos
taken from the University of Delaware Integrated Pest Management Website)
Field Crop Diseases - Bob Mulrooney,
Extension
Plant Pathologist, bobmul@udel.edu
Soybeans.
Soybean cyst nematode damage shows up as stunting of the
soybean plants in irregularly shaped areas of the field. Anytime after about
32-34 days the white or yellow females can be seen on the roots of infected
plants. Carefully dig up suspected plants with a shovel or trowel and examine
the roots. They are smaller than the
nitrogen fixing nodules and can be difficult to see especially if the soil is
dry. Traditionally we see severe stunting of young plants when we have high SCN
populations in the soil and conditions are dry early in the growing season.
Abundant rainfall that we had last season can mask increasing soil populations
of SCN resulting in stunting early in the season. Take a soil sample with a few
root systems of the plants and submit for testing at your County Extension Office.
Be sure to sample soil from around the roots. Usually sampling between the
plants in the row works best.
Numerous SCN cysts
and N fixing nodule (large tan in picture) for comparison.
Magnified view of
lemon-shaped SCN cyst.
Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu
General Comments.
The
June Grain Stocks and Acreage reports came in close to trader expectations,
although there is some concern as to whether the impact of diverse weather, in
some parts of the Corn Belt, are truly reflected in USDA's planted and
harvested acreage estimates. Nevertheless, the reported acres will go into the
July 12th Supply and Demand revisions. Farmer certification for '04 planted
acres of corn and soybeans in the
The
two primary driving forces impacting commodity prices the next month will be
weather in the
Export
sales reported for the week were larger than anticipated for corn and soybeans.
They were also reported to be at the high end of trader expectations for wheat.
Corn Analysis.
Soybean Analysis.
Soybean
planted acreage, pegged at 74.81 million acres, is down from the
75.41
million acres reported in the March intentions and up from '03 acres of 73.4
million. Soybean stocks were reported at 410 million bushels, slightly above
the average trade guess of 395 million bushels. Last year's
Wheat Analysis.
All
wheat acreage, reported at 59.87 million acres was up slightly from March at
59.46 million acres, and down from the 61.7 million acres a year ago. Wheat
stocks, pegged at 546 million bushels are up from June '03 of 491 million
bushels and slightly above pre-report trade guesses.
Market Strategy.
Considering
the drenching that new crop corn, soybean, and wheat prices have taken this
week, the short supply situation for old crop soybeans coupled with the need to
ration supply, and the fact that we are now entering the most critical period
for '04 corn and soybean crop development farmers are advised to hold sales
positions at current levels.
Manganese
Deficiency is Showing Up in Soybeans - Sean
Scanlon, Cooperative Extension Intern and Richard W. Taylor,Extension
Agronomist, rtaylor@udel.edu
In touring the state, it is quite evident that
manganese (Mn) deficiency (or in some cases possibly Mn toxicity) of soybeans
is rather widespread this growing season.
Usually, the symptoms appear in localized areas of a field rather than
as a general problem throughout the field (See Photo 1).
Photo 1. The front part of this field showed moderate
to severe manganese deficiency but the back half (different soil type) was
still green and growing. (Photo by R.
Taylor)
In a number of locations, this problem is a
reoccurring one in that Mn deficiency symptoms appear each year that soybeans
are grown. This can be due to slightly
high soil pH from liming activities, low native Mn soil levels, or differences
in soil type within a field. In locations
where the problem reoccurs, it’s not likely necessary to confirm deficiency
with a tissue or soil analysis if the symptoms are similar to those in Photo
2. If, however, you have not noticed
symptoms in a particular field or area of a field, then you should test the
soil for pH to be certain the problem relates to Mn deficiency and not a
toxicity related to low pH. This year a
number of fields are showing severe to moderate problems associated with low
soil pH so it will be important to accurately diagnose the problem before
applying Mn as a foliar spray (see article on causes of low pH in next week’s
issue of Weekly Crop Update).
Photo
2. Manganese deficiency is characterized
by leaves with green veins and yellow to white tissue between the veins and
with symptoms appearing on the youngest growth.
(Photo by R. Taylor)
Symptoms of Mn deficiency
include:
Treatment options include:
Best Wishes to You and Your
Family for a Safe and Happy July 4th
Week of June 25
to
|
|
Rainfall: |
|
0.13
inches: June 26 0.11
inches: July 1 |
|
|
|
Air Temperature: |
|
Highs
Ranged from 87°F on July 1 to 79°F on June 28. |
|
Lows
Ranged from 65°F on June 25 to 57°F on June 27 &
30. |
|
Soil
Temperature: |
|
78°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