July 22, 2005 Volume 4 Number 14
1. View from the Field
2. Know Your Corn Rootworms
3. Pea Aphids in Alfalfa
4. Common Smut on our Corn or Plate?
5. Pollen Islands Will Attract CRW
6. Corn Rootworm Scouting Tip: Are they Gravid?
7. Soybean Rust Update
8. Clipboard Checklist
9. Growing Degree Days in NYS
10. Contact Information
From the Field
In a field in Wyoming County, I found zero potato leafhopper
(PLH) but I observed many pea aphids. See Keith’s notes and
an article below regarding aphids in alfalfa. From Seneca County,
Mike Dennis reports that very low numbers of PLH nymphs are
present in a 10-inch tall new seeding, and no PLH were found
in an established alfalfa stand.
In Ontatio County, northern corn rootworms are emerging in droves
from a field of continuous corn. Western corn rootworms were
observed to be over threshold in a continuous corn field in
Seneca County, though in other fields in Seneca County, numbers
Aphids were seen in all fields I observed this week (Wayne County,
Seneca County, Ontario County, and Cayuga County). About half
of the fields I visited continue to have relatively low numbers
(well below the threshold of 250 aphids per plant), while other
fields have plants with over 1,000 aphids. In two heavily infested
fields I scouted, plants are sticky and sooty mold is present,
and some leaves are cupped. Given that lady beetle larvae and
adults are abundant (and doing a great job of cleaning up aphids)
and that the damage is already done, growers have made the decision
to not use an insecticide. (For treatment with insecticide to
be advisable, aphid numbers must be 250 per plant and increasing).
Nancy Glazier (NWNY Team) reports that soybean aphid numbers
continue to grow in the northern part of Orleans County, especially
in areas where rainfall is lacking. Spider mites are a threat
in soybean fields that have not had adequate rainfall (Orleans,
Cayuga, and Ontario Counties).
week at the SUNY Cobleskill Farm potato leafhoppers (PLH) on
alfalfa were hard to find. There were many pea aphids which
generally is not a problem on alfalfa in NYS. Alfalfa fields
at the Cornell University Farm in Valatie were farm over threshold
and showing PLH damaged leaves.
few fields at the SUNY Cobleskill Farm were over threshold for
corn rootworm. All of the beetles I observed were western corn
rootworm. Generally, you see western corn rootworm before you
see northern corn rootworm.
beetles were feeding on the silks of field corn at the Cornell
University Farm in Valatie. There was silk clipping going on
and as many as 5 to 6 beetles could be on a silk. Over all it
appeared that about 1 in 10 ears of corn had Japanese beetles
feeding on the silks. Here are a few photos of what I was seeing:
Beetles Clipping Silks
aphids still remain relatively low at the Cornell University
Farm in Valatie. There was about an average of 50 aphids per
plant. The soybeans were in the R-1 to R-2 stage of growth.
resistant alfalfa comparison trial in Ithaca showing visible
differences in color and plant height. Oneida VR planted as
one of the PLH susceptible varieties showing classic “V-pattern”
leaf symptoms. Some pea aphid presence and many natural enemies
abundant. Easily found adult and young growth stages of lady
bird beetles (lady bugs), syrphid flies, lacewings, nabids,
aphid damage? Pea aphids are the common alfalfa aphid species
found in NY. These aphids can be found in light green and rosy/peach
color morphs. Aphids typically suck juices from the plants they
feed on. Unlike some aphid species, pea aphids do not secrete
toxins while feeding. Their primary damage is related to the
amount of fluid removed from the plant. For this reason large
numbers (several hundred per plant) are typically needed before
plants are affected. In NY, pea aphid populations are largely
controlled by natural enemies. Also given our usually adequate
rainfall, pea aphids are typically not an economic problem for
us. I.e. the plants are able to compensate for the moisture
removed by the aphids. More pea aphid info and things to look
for follow in an article by Julie Stavisky.
your corn rootworms
Stavisky, NYS IPM
adults are emerging in droves from corn fields. They are most
often observed in the silks of developing ears. Here’s a review
of how to identify the adult rootworms:
corn rootworm (WCRW) adults are black and yellow beetles that
are approximately º inch long. The female is yellowish with
3 black stripes on its back, while the male is solid black with
a pale yellow area at the tip of its abdomen (see photos). Northern
corn rootworm is slightly smaller than the western, and it is
bright green in color (see photo).
northern corn rootworm (NCRW) used to be the predominant species
in New York State, but since the arrival of the western in the
1980’s, the western has become the dominant species. When scouting,
1 western corn rootworm equals 2 northern corn rootworm adults.
During pollination, developing ears can tolerate many rootworms
feeding on silks without suffering economic losses.
Female WCRW Male
Aphids in Alfalfa
Stavisky, NYS IPM
there any such thing as too many?
week when I was sweeping alfalfa in Wyoming County to check
for potato leafhopper, I should have had a measuring cup with
me! Every time I took 10 sweeps, I estimate that the sweep net
contained approximately a cup and a half of aphids. To continue
my PLH searching, I resorted to taking a single sweep at a time.
Can this many aphids be tolerated? Well, aphid numbers might
not be our best indicator. Instead, answering several questions
from observations that accompany a pea aphid infestation will
be more useful. To have a significant economic impact, some
of the following conditions would have to exist:
the plants drought stressed?
stunted plants observed?
heavy honeydew and/or sooty mold present?
leaves becoming curled, cupped or otherwise misshapen?
natural enemies absent?
in doubt, cutting within the next week will help prevent a growing
pea aphid outbreak from reaching economic proportions.
a photo of a plant showing a heavy (but non-economic) population
of pea aphids:
smut on corn or on your plate?
found a little bit of common smut on corn this week. Common
smut forms white, soft galls that can be found on most any plant
part on the corn plant above the ground. It is suggested that
the galls form where hail or machinery have injured the plant.
As the smut galls age they fill with dark brown to black spore
masses. The good thing is that smut rarely kills the plant,
and typically causes little if any yield loss. For pictures
view this website: Common
smut is also edible at the right stage of growth. It is called
the maize mushroom (Cuitlacoche) or the Mexican truffle. Many
people in Mexico eat the immature smut galls as a delicacy known
as Cuitlacoche. Some sweet corn growers produce smut galls as
a high value crop and sell them to Mexican restaurants. If you
like mushrooms you should like common smut. Check out this website
if you think you would like to try maize mushrooms: Common Smut Recipes
Islands will Attract CRW
those corn fields that had troubles with uneven emergence, ponding,
compaction, fertilizer, herbicide, or other planting time issues?
Drive by many of these fields this week and their up and down
plant height patterns look more like a side view of a crazy
roller coaster ride than the ideal production field… And now
watch the pattern of tassel emergence. Whatever the reason for
the uneven stand its effect on corn rootworm (CRW) populations
can be very predictable. CRW beetles are pollen feeders and
will zero in on plants producing pollen. So in fields with large
differences in corn maturity expect that CRW beetles will “head
to the islands” of pollinating corn. In fields of uniform crop
growth stage, CRW egg laying is reasonably well distributed.
(Recall that CRW females are capable of producing eggs about
3 weeks after they emerge…) In the case of the pollen island
fields, CRW egg laying may be expected to be more concentrated
in the areas where the pollen (food source) is. You can also
expect that the highly mobile CRW beetles will follow the pollen
sources from clump to pollinating clump…. Watch these areas
closely for signs of potential silk clipping as hungry CRW populations
build up in them high numbers of CRW beetles could interfere
with pollination and grain fill.
these areas can be at higher risk for egg laying make a note
of their location(s). Record any scouting information. Should
egg laying be high enough in those “islands”, it is a good bet
that they would be at higher risk for lodging from CRW larval
feeding next year should corn be replanted into the same field.
Better yet? If cropping schedules allow, this field may be a
good candidate for rotation next year.
The sequential sampling method for sampling CRW assumes the
field is uniform in physiological development. This
sampling procedure is dependent on an even distribution of corn
rootworm beetles across the field. Fields with uneven development
from uneven germination or water stress should not be sampled
using this sequential sampling procedure since the beetles will
be clumped on pollinating plants.
If sampling for CRW in fields with “uneven growth development”
follow the method recommended in the Cornell Field Crops Guide.
CRW counts are taken from 55 corn plants sampled at random.
The threshold is 55 CRW beetles. When determining fields at
risk recall that the Western corn rootworm beetles count as
one and northern CRW beetles count as 0.5. For more information
see: http://www.fieldcrops.org/ field corn
insect (CRW) management (18.104.22.168).
Rootworm Scouting Tip (Are They Gravid?)
Wise, NYS IPM
when taking beetle counts you are monitoring to assess the potential
that CRW's will lay enough eggs in the field to cause damage
to next year's corn crop. Taking beetle counts is important
but make sure you stop to check a portion of the female western
CRW's for the actual presence of eggs. Squeeze the abdomens
of the yellow and black striped CRWs and look for the small
yellow - white eggs. It takes CRW about three weeks from the
time the adult beetles emerge from the soil and mate until the
time the females are gravid. In this time period you may find
high CRW numbers in a field but since the females are not yet
capable of laying eggs they are not causing an economic problem.
This is the reasoning behind sampling the same field 2-3 times
before making the management decision. Being pollen feeders
and highly mobile, CRW's may relocate to another pollinating
field during the 3 week period. Comparing the two types of fields,
the second field is at greater risk from subsequent CRW damage
since females (and their eggs) will have matured and are ready
is the best time to control corn rootworm if a field exceeds
the action threshold?
there is a field over the action threshold what are the options
for control next season?
best option to control corn rootworm is crop rotation. Corn
after corn is prime habitat for corn rootworm and will increase
infestations from year to year.
rotation is not always possible so ....... The second management
option is the use of a soil-applied insecticide at planting.
To select an insecticide registered for corn rootworm, please
consult the Cornell Guide for Integrated Field Crop Management.
CRW management technologies are now available. You can use
insecticide treated seed to control moderate populations of
corn rootworm infestations
can also use Bt hybrids now for CRW.
to Monitor for Corn Rootworm
Waldron, NYS IPM
brown spot and bacterial blight have been observed in NY, but
fortunately still no reports of SBR.
the NYS soybean rust website: 2005 Soybean Rust
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. 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. Scientists are intensively monitoring soybeans
in the path of recent tropical storms and are following the
paths of Hurricanes Dennis and Emily for their potential to
move soybean rust spores to wider areas of the U.S. (Last updated
7/19/05). For more see: http://www.ppath.cornell.edu/soybeanrustny/default.htm
Maintain crop production activity records by field, including
harvest date, pesticides used, nutrient inputs including manure,
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.
Watch wheat grain moisture. Combining underway when moisture
at 18 percent.
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 fly
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.
Degree Days in NYS
1 - July 20, 2005
Stavisky: IPM Area Educator, Livestock and Field Crops, Western
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