July 28, 2005 Volume 4 Number 15
1. View from the Field
2. Pea Aphids Come in Red and Green: Ever Wonder
3. Do You Know How to Scout for Corn Rootworm?
4. Downy Mildew in Soybean
5. European Corn Borer, Armyworm and Corn Earworm
6. Soybean Rust Update
7. Soybean Aphid Management Guidelines
8. Clipboard Checklist
9. NYS Growing Degree Days
10. Contact Information
View From the Field
Soybeans: This week at the Cornell University
Farm in Valatie soybean aphids ranged for 10 to 200 per plant.
The average was about 75 aphids per plant. There were several
ladybeetles (Adults, and larvae) feeding on the aphids. There
were several lady beetle pupae on the leaves also. There were
also green lacewing adults and larvae in the field. There are
a few pictures of the good beasts:
Alfalfa: Alfalfa fields at the Cornell University Farm in
Valatie were far about threshold for potato leafhopper. In three
samples I counted 255 potato leafhopper nymphs and adults. The
alfalfa was showing the traditional yellowing of the leaves
that potato leafhoppers can do. Here is a picture of the alfalfa:
I've seen downy mildew in all the soybean fields I've visited
(Wayne, Ontario, Seneca, and Cayuga Counties).
Nancy Glazier (NWNY Team) continues to observe soybean aphid
mites, particularly on drought-stressed beans, as she scouts
Orleans County soybean TAg program. This week she also saw phytophthora
root rot on beans in an area where there is heavy soil. The
indicated that there was standing water this spring.
Reports from wheat harvest have been favorable so far. Neither
sprouting has been of concern.
Jeff Miller and Kevin Ganoe both reporting soybean fields
with soybean aphids approaching 250+ per plant. Yellow alert
for these fields.... time to increase SBA monitoring frequency
to see if populations maintain, increase or decrease. Natural
enemies are present but variable in number, some fields with
winged aphid forms.
Mike Hunter reports fall and armyworms in corn field causing
damage. Mike says the field had an obvious giant foxtail and
large crabgrass that attracted the moths to the site.
Pea aphids come in red and green… Ever wonder why?
Keith Waldron, NYS IPM
NY alfalfa fields are home to resident populations
of pea aphids. Close observation will detect red and green color
morphs of this aphid species in the same field. What’s that
Because the aphids reproduce parthenogenically,
the color morphs remain distinct through the summer months.
Pea aphids experience high levels of parasitism by the wasp
Aphidius ervi and heavy predation by several predators,
including ladybird beetles, especially Coccinella septempunctata.
Both the parasitoid and the predator can have a major impact
on pea aphid populations and may be important selective agents.
Research by John Losey (Entomologist now at Cornell) determined
that for these aphids there was an advantage of one color over
another but it varied… Think predators, think escape…
Losey and his colleagues sampled 100 alfalfa stems in eight
similar locations every 6 days. They counted the number of red
and green aphids, ladybugs, and the mummified remains of aphids
parasitized by wasp larvae. They discovered that the predators
had distinct preferences--ladybugs being partial to red aphids,
and wasps to green aphids.
The result is that the two predators keep the colors balanced.
With ladybugs eating the red aphids and wasp larvae parasitizing
the green, neither form dominates the population and both survive.
Believe it or don’t…. More information see: Nature 388, 269
- 272 (17 July 1997).
Do you know how to scout for Corn Rootworm? Ken Wise,
You will need to scout all corn fields that
will be kept in corn next year from emergence of the tassel
until pollination is complete. Pollination occurs for three
weeks and monitoring takes about 20 minutes per field. You will
need to monitor each field once a week until you reach a threshold
or until pollination is over. Look for gravid, (i.e. mature,
egg laying) corn rootworm female beetles--the ones that, when
you squeeze their bodies, release white eggs from their posteriors.
Here’s how you scout:
Are female beetles present? Mature and capable of egg
laying? Conduct the squeeze test (see above) to determine
if they are ready to lay eggs.
Approach a corn plant carefully because the beetles
will fly off if they disturbed too much.
Grasp the silk with one hand.
Count the beetles on the entire plant.
Start counting at the top working down.
Gently pull leaves away from the stalk so you count
any beetles that may be hiding in the whorls.
For each corn plant monitored, record the total number
of beetles observed. See the sequential sampling chart below.
Since western corn rootworms are potentially more damaging
than their northern cousins, count each western (yellow
striped) beetle observed as “one” and each northern (green
type) as “1/2”.
Check several plants at random (not next to each other!)
in several parts of the field.
Continue sampling at seven-day intervals until the ear
silks are brown, approximately 3 weeks after tassels are
first visible, pollination is complete or an above threshold
number of beetles are found.
Using the Sequential Sampling Card for Corn Rootworm(For
fields with uniform physiological crop age, for variable age
fields see the CU Guide for FCrop Management “www.fieldcrops.org”)
Keep a running total (RT) of the number of corn rootworm
beetles you have counted on each plant. Each northern corn
rootworm has half the value of each western corn rootworm.
The western corn rootworm does twice the damage to corn
than does the northern. So if you count 3 westerns and 4
northern (2 western equivalent) on a plant you would have
a total of 5 beetles.
If the number of corn rootworm beetles observed is smaller
than the “N” (“Not at threshold”) number stop and scout
7 days later.
If the number of corn rootworm beetles observed is larger
than the “T” (“At threshold” or “Treat”) number then you
need to manage rootworms next year.
If the number of corn rootworm beetles observed fall
between “N” and “T”, continue sampling additional plants
until you finally go over or under.
In a very low or very high rootworm population a sampling
decision can be made in sampling as few as 3 to 8 plants.
For moderate populations more samples may be necessary to
Sequential Sampling for Corn Rootworm
Downy Mildew in Soybean
Downy mildew is showing up on soybean foliage
in New York State. I’ve observed this fungal disease frequently
on leaves in the upper canopy. Downy mildew can be identified
by the pale yellow or greenish irregular areas on upper leaf
surfaces. These spots show through to the lower leaf surface,
where the affected areas are grayish. Under humid conditions,
grey tufts of the fungus are apparent on these spots on the
underside of leaves (see photo below). Soybean productivity
is generally not affected by downy mildew.
On a severely infected plant, downy mildew also can affect
soybean seed. While pods show no symptoms, seeds inside can
be covered with white fungal mycelia. If this infected seed
were planted, stunted seedlings with mottled leaves would result.
The fungus that causes downy mildew can survive on infected
leaves and seed. A key management strategy for downy mildew
is to not plant contaminated seed. Rotation to a crop other
than soybean or tillage that deeply buries infected crop residue
effectively control downy mildew.
European Corn Borer, Fall Armyworm, Corn Ear Worm Trap
Keith Waldron, NYS IPM
Two calls this week about potential
armyworm / fall armyworm issues in corn and mixed alfalfa grass
stands. Positive identification still pending. Either species
could be possible this time of year. Trapping networks reporting
such data indicate low FAW counts. ECB counts have been moderate.
If you are looking for the latest information on trap catches
for these lepidopteran pests in NY check the Sweet Corn PheromoneTrap
Network for Western NY, Report for 7/12/05
This trapping network is gathered by Abby Seaman of the NYS
For information on trap catches for these insects in the
states to our south go to the
Soybean Rust Update
Keith Waldron, NYS IPM
rust on soybeans has been reported in Florida , some adjacent
counties in Alabama and Georgia as well as Mississippi. The
most recent finds in Mississippi and Georgia were in sentinel
plots. The most recent find in Alabama was the first detection
in a commercial field in 2005. Scouting and spore trapping continues
throughout the soybean production areas of the U.S. Scouting
of sentinel plots in New York State continues this week and
to date no soybean rust has been found. The risk of soybean
rust infection in New York is currently considered to be low
and no fungicide application for soybean rust is advocated at
this time. Septoria brown spot is the most prevalent foliar
disease in all 10 of the research protocol sentinel plots in
New York State over the past two weeks. Bacterial blight has
also been observed and soybean aphid populations are increasing.
Growth stages in New York State sentinel plots range from V5
to R2 stages and several are flowering. (Last updated 7/27/05)
Soybean Aphid Management Guidelines
Expect soybean aphid populations to rise over
the next week or so as “cooler” temperatures (in the 80’s F)
occur over our region.
Guidelines for management? A short review of guidelines.
Adapted from: http://www.plantpath.wisc.edu/soyhealth/aglycine.htm
Pay particular attention to late-planted fields, or fields
under moisture stress. Examine the entire plant, particularly
the new growth at the top and side branches.
Use an action threshold of 250 aphids per plant if
populations are actively increasing. This action threshold
should be based on an average of 250 aphids per plant
over 20-30 plants sampled throughout the field. Regular
field visits are required to determine if soybean aphid populations
In replicated research trials, in the Midwest , this threshold
have worked well in R1 (right at first bloom) to R4 soybeans.
This threshold incorporates an approximate 7-day lead-time between
scouting and treatment to make spray arrangements or handle
weather delays. Spraying at or beyond R6 has not been documented
to increase yield.
Like more discussion? See
“Soybean Aphid Management Recommendations (Consensus recommendations
developed by Ontario and U.S. researchers, Jan. 2004)”
Research to enhance Soybean aphid management guidelines continues.
Data (SBA counts, growth stage, yield, etc.) from Treat No
treat fields is in “short supply”. If you have a situation that
will be treated and have the ability to collect information
including yield checks please consider doing trial. More SBA
data will help us all. For more information contact
Keith Waldron, NYS IPM
• Maintain crop production
activity records by field, including harvest date, pesticides
used, nutrient inputs including manure, etc.
Alfalfa & Hay:
• Continue monitoring for potato leafhopper- harvest early
or spray on basis of need.
• Monitor for diseases record information on type and location
for future cropping decisions.
• Monitor for foliar and stalk diseases, nitrogen and other
nutrient deficiencies, European corn borer, weeds.
• Monitor corn rootworm adults at silking.
• Monitor for soybean aphid, soybean rust, foliar diseases.
• Continue livestock facility sanitation management (manure,
feed bunks and storage areas, waterers, etc.). Cleaner, less
• Mow around facilities to minimize rodent habitat.
• Monitor young stock for cattle lice and mange mites
• Check condition of pastures and animals on pastures
- Evaluate need for face fly and stable fly control measures
- Check and clean pasture water supplies.
NYS Growing Degree Days
Keith Waldron, NYS IPM
March 1 - July 27, 2005
Base 50 F
Julie Stavisky: IPM Area Educator, Livestock
and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360
Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316