May 26, 2005 Volume 4 Number
1. View from the Field
2. Alfalfa Weevil Biological Control, Continued
3. How Do You Monitor Alfalfa Weevil
4. Seed Corn Maggot in Soybeans
5. Fusarium Head Blight May be Coming to a Field
6. Growing Degree Days in NYS
7. Clipboard Checklist
8. Contact Information
From the Field
Stavisky, NYS IPM
SMALL GRAINS MANAGEMENT FIELD DAY
ROBERT MUSGRAVE RESEARCH FARM
Poplar Ridge Road, Aurora, NY
Thursday, June 2, 2005
Coffee at 9:30 AM
Program 10 AM to Noon
This last week I found a few alfalfa weevil larvae. There were a
few signs of feeding on the leaves. The field I was looking in
is right about 310 growing degree days (base temperature 480F).
This is when about when you start to see larvae in the fields.
How do you monitor for alfalfa weevil? Read on… more information
in this issue….
Alfalfa weevil larvae have been seen, but they are few and far
between. Occasional cereal leaf beetle eggs are present, but I
haven’t seen any larvae yet.
Carl Albers has seen the first signs of alfalfa weevil feeding
in Steuben County this year. Also in forage news from the
Southern Tier, Carl reports confirmed cases of brown root rot in
alfalfa and trefoil. Rough stalked bluegrass and henbit are
abundant in alfalfa.
Weevil Biological Control, Continued
Stavisky, NYS IPM
addition to the parasitoids we talked about a couple of weeks
ago, another biological control friend in alfalfa is an entomophagous
fungus. Yes, it’s an insect-feeding fungus. Its only choice
for breakfast, lunch, and dinner is the alfalfa weevil. The
rain that has been falling on and off for the last week may
provide a big advantage for keeping alfalfa weevil larva numbers
in check. With the cool temperatures keeping alfalfa growth
slow so far this spring, we’ll take all the help we can get
for protecting alfalfa.
fungal pathogen, Zoophthora phytonomi, is always present
in low levels in and around alfalfa fields. Under the right
cool, wet conditions, an epizootic, or outbreak, of the fungal
pathogen can occur. Infected larvae lose their normal light
green color. The pale yellow infected larvae become less active
and usually die within a few days.
phytonomi first appeared in Ontario, Canada in 1973, and
now commonly occurs throughout the weevil’s range in the Midwest
and northeast. Although there are several theories about where
the fungus might have come from, its origin remains a mystery.
a photo showing
what you may see.
do you Monitor Alfalfa Weevil.
Wise, NYS IPM
alfalfa weevil weekly from mid to late-April through June. Because
weevil populations can build up over the life of the alfalfa
stand, monitoring fields that are two or more years in production
is critical to determine infestation levels. Start weekly field
sampling in fields at about 350 degree-days (base temperature
48F) which is about mid to late April in most years, but not
50 alfalfa stems at random throughout the field.
for the small "shot holes" in the leaves that indicate
that larvae are feeding.
the percentage of alfalfa stems that show the "shot hole"
feeding damage in the top 3 inches of the canopy.
the first cutting, if 40% of the stem tips show feeding damage,
you are at the "action threshold". The good thing
is that alfalfa weevil can generally be controlled by harvesting.
If you reach an action threshold within a week of your normal
1st cutting date, early harvesting will help avoid economic,
yield, and forage quality losses. Alfalfa weevils only have
one generation per year and are typically not a problem after
first harvest. Occasionally, weevil can damage alfalfa re-growth
after harvest. This damage may be more evident in the windrow
areas, and can be more noticeable under cool or droughty weather
conditions. If you find that 50 percent of the new growth is
damaged, with many small larvae present, a chemical control
may be warranted. For more information on alfalfa weevil checkout
our online publication: http://www.nysipm.cornell.edu/publications/alfweevil.pdf
Corn Maggot in Soybeans
Stavisky, NYS IPM
corn maggots occasionally attack soybean seeds and seedlings
before plants emerge from the soil. Generally, stand reduction
does not impact soybean yield potential as directly as corn
yield potential is impacted because of the ability of the remaining
soybean plants to compensate and fill in gaps. Rarely is damage
severe enough to warrant re-planting.
of fresh organic matter draw in the adult female flies. The
adults look like a small, slender version of a house fly (they’re
about half the size of the house fly). They lay eggs in fresh
organic matter, including weeds on the soil surface (or recently
incorporated into the soil), recently applied manure, or debris
left on the soil surface in a no-till situation.
seedcorn maggot is a small, yellowish-white, headless, legless
larva. The body is tapered in the front with two small black
mouth hooks. The maggots seek out seed, then feed directly on
the seed before it germinates, and may additionally attack stems
on seedlings before they push through the soil. These seedlings
seldom survive. Delays in germination resulting from cool weather
give seed corn maggot more time to find a seed and do damage
before the plant is vigorously growing.
an image of seed corn maggot
in a soybean seed
is our job now? It’s time to scout newly planted fields as seedlings
emerge. Look first for gaps in the stand. Then, focus on plants
at several locations in a field, and assess the color and growth
stage of the plants. Plants that have a yellowish coloration
or appear stunted or wilted may be injured. If cotyledon-stage
plants show signs of damage, dig up the soil around the plants
to detect the presence of the maggots.
Head Blight (Scab) May be Coming to a Wheat Field Near You
Stavisky, NYS IPM
of the most devastating diseases of wheat is Fusarium head blight,
or scab. The disease reduces yield by decreasing the number
of viable kernels, but the more significant impact is that a
mycotoxin may be produced by the fungus in diseased kernels.
is caused by airborne spores of the fungus Fusarium graminearum
that dwell in nearby crop debris, including corn stalks and
wheat straw. This is the same fungus that can cause root, stalk,
and ear rots of corn. Since the fungus is very widespread, likelihood
of exposure is generally not reduced by crop rotation or other
cultural practices. Extended periods of warm, moist weather
at crop flowering can cause the anthers to be infected just
after their emergence, killing the florets so kernels do not
develop. Symptoms of scab become visible on emerged heads soon
after flowering. During early grain fill, the disease shows
up as pink to salmon orange on infected kernels. As kernel fill
progresses, the infected kernels appear bleached. Spikes that
are infected later than flowering will produce diseased kernels
that are shriveled in appearance.
tuned for more information on Fusarium and prediction models
Degree Days for NYS
Waldron, NYS IPM
1 - May 24, 2005
field records: variety, planting date/rate, pesticides used,
nutrient inputs including manure, other important field observations,
hay harvesting equipment ready to go in next 2 weeks?
any repairs to corn planters, other spring machinery, and harvesting
equipment as they are cleaned and lubricated.
forage harvest equipment as needed
weevil, weeds, crown rot, leaf spot diseases
Wheat: Cereal leaf beetle, virus diseases, weeds, powdery mildew
Grains: Cereal leaf beetle, seedling diseases, weeds
corn for weeds, note presence of triazine resistant annual broadleaf
weeds. Cultivate or treat if necessary.
corn emergence, take stand counts/plant populations, check for
signs of damping off / seedling blights, seed corn maggot
Grain Management Field Day, Robert Musgrave Research Farm, June
Stavisky:IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Waldron: NYS Livestock
and Field Crops IPM Coordinator
(315) 787 - 2432
Wise: Eastern NYS IPM
Area Educator: Field Crops and Livestock