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Weekly Field Crops Pest Report 2008

May 29, 2008                 Volume 7 Number 7

1. View from the Field

2. Weather Outlook 5.29.08

3. Seed Corn Maggot Threatens Corn and Soybeans

4. Insect Pests of Canola

5. Soybean Seed Rot and Seedling Blight

6. NYS Soybean Rust Update

7. Growing Degree Days in NYS

8. Clipboard Checklist

9. Upcoming Events

10. Contact Information

View from the Field

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Eastern NYS-Ken Wise

This week I scouted the Cornell University Research Farm in Valatie and found my first 2 potato leafhoppers this season! I also found 1st through 3rd instar alfalfa weevil larvae. Tip feeding was still less than 5%. I also found clover leaf weevil in alfalfa. They look similar to alfalfa weevil larvae but often have the white stripe edged with pink that runs the down the back and are larger with a light brown head.

1. Alfalfa Weevil Larvae, 2. Clover Leaf Weevil Larvae

There was also a lot of white cockle in alfalfa fields at the Cornell University Research Farm in Valatie

White Cockle In Alfalfa

Western NYS-Julie Dennis

Although most alfalfa fields are not suffering from alfalfa weevil damage, Mike Stanyard reports on at least one field in Ontario County in which every plant has weevil feeding injury! Damage is so severe that the whole field has a frosted appearance. The best solution in this circumstance is to harvest ASAP. Even though we have a lot of biological control agents on our side for alfalfa weevil control, it remains very important to scout for this pest.

Weather Outlook 5.29.08

Art DeGaetano
NOAA Northeast Regional Climate Center

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Generally cool and dry characterized the weather last week. Temperature did climb to above 80 on Monday, but overnight lows on Tuesday and Wednesday dropped below freezing in many places. Temperatures for the week averaged 4 degrees below normal in the west and about 1-3 degrees below normal in the east. Across the state precipitation amounts were less than half an inch, except for as much as an inch in the Adirondacks.

Most of upstate New York accumulated between 25 and 50 growing degree days (base 50) last week. For the season growing degree days totals are around 200, with around 300 in the lower Hudson Valley and about 150 across the Southern Tier. These accumulations are very close to normal for late May, but around 3-7 calendar days behind last year’s late May accumulation.

High pressure will dominate through Friday before giving way to a low pressure system that will track through the Great Lakes Friday night and Saturday. The system should produce a widespread 1 inch precipitation accumulation through much of upstate NY through Saturday. Western parts of the state may see as much as 1.5 inches, while the city will be drier with about a half inch of rain. The cold front will linger Saturday night and lead to a cool dry period Sunday through Tuesday. Expect highs in the upper 50s and low 70 in this period and lows in the upper 40s and low 50s. The next weather system will bring the chance of precipitation late Tuesday or Wednesday. Beyond this a weak ridge will establish to our west bringing warmer and drier conditions.

Seed Corn Maggot Threatens Corn and Soybeans

Julie Dennis

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When temperatures remain cool in May as they have this year, large seeded crops including corn and soybean are at risk from seed corn maggot (SCM). Sources 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 weeds recently incorporated into the soil), recently applied manure, or debris left on the soil surface in no-till fields. Maggots hatch from the eggs and find nearby swollen seeds to burrow into and feed on. SCM 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 cause damage before the plant is vigorously growing. These maggots are tapered, legless, appear to be headless, pale yellowish-white, and reach a length of about a 1/4 inch long. They feed using two small black mouth hooks. Here’s an image of seed corn maggot in a soybean seed.

Symptoms of SCM damage are not readily apparent until skips in the rows are observed. Rarely are enough seeds damaged to necessitate replanting of a corn crop, especially since use of seed treatments is very common. Seed corn maggots may attack soybean seeds and seedlings before plants emerge from the soil, too. Generally, soybean 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 soybean.

What is our job now? It’s time to scout 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 soybean plants show signs of damage, dig up the soil around the plants to detect the presence of the maggots.

Prevention is the key to control this insect pest. Recommendations for management include minimizing the common risk factors and using pretreated seed, especially in the case of corn. For more information check out Early Season Insect Pests of Corn (1016k pdf file).

Insect Pests of Canola

Ken Wise

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This is the second of 2 articles on canola pests. I have selected 3 of the more devastating insect pests of canola. These are cabbage seedpod weevil, flea beetles, and tarnished plant bug. Please note that in this article I have focused on the biology and damage of what these insect pests can do to canola. We DO NOT have any researched economic thresholds for these pests in NYS. I have added how they are monitored and what a threshold would be in other states just as a potential guideline to measure the severity of the issue that might occur in your field. Please refer to the websites listed below for more specific information.

Cabbage Seedpod Weevil

Adults migrate into fields from over-wintering sites in the spring. This is a pest of both winter and spring canola. Adults are about 1/6 inch long and have a light-grayish color. Adults will feed on pollen produced by the canola flowers. The female weevil will deposit eggs inside a seed pod after its formation on the plant. Normally only one small, oval, and white egg is placed in one 1/2 to 3/4 inch seed pod. When there are high rates of infestation there may be 2 to 3 eggs/ seed pod in some cases. Depending on the temperature eggs will hatch in about a week. The larvae are white, grub-like and have no legs or eyes. The larvae have 3 instars and will eat up to 5 seeds in the pod. For NYS we have no established economic thresholds for this insect pest. This insect pest can be monitored with sweep net. These samples are to be taken at ten locations across a field with ten 180 degree sweeps per location. University of Idaho suggests that their economic threshold is an average of 2 weevils/sweep. There is no known cultural control for Cabbage seedpod weevil. There are some naturally occurring biological control agents like parasitoids, predators and diseases that can help give minimal control of this pest. For more information please view this website from Alberta Canada: Cabbage Seedpod Weevil

Crucifer Flea Beetle and Striped Flea Beetle

Both Crucifer Flea Beetle and Striped Flea Beetle can be very serous pests of canola. Both are primarily insect pests of spring canola but can still damage fall planted canola. When adult flea beetle emerges in the spring and if in large numbers they can quickly destroy a spring canola field by feeding on the cotyledons and true leaves. To see typical damage of these two pests view the following pictures: Canola seedlings, damaged & undamaged.

Crucifer flea beetle is all black with a metallic bluish sheen. Striped Flea Beetle has two yellow strips that run down the elytra! They lay up to 25 eggs in the soil near a canola plant in June. Larvae will emerge in about 10 to 12 days depending on the soil temperature and start feeding on the roots of the canola plant. Generally, they do not cause yield losses due to larvae feeding on the roots. About mid July the larvae pupate and in late July adults will emerge to feed on the leaves of the canola. For NYS we have no known economic thresholds for this insect pest. To detect the early presences of flea beetle, use of yellow sticky card traps on the edges of fields is recommended. In other states like North Dakota the economic threshold is around 25% defoliation on canola cotyledons in the spring. To see what defoliation levels looks like view the following website: 10 - 25% defoliation.

For more information on these insect pests view this website: Crucifer Flea Beetle Biology

Tarnished Plant Bug (TPB)

Tarnished plant bug (sometimes referred to as Lygus bugs) can be a serous insect pest of canola. This is a pest of both winter and spring canola. This brownish-yellow adult plant bug is around 1/4 inch in length. Behind the shoulders is a distinctive white triangle. The nymph stage of this pest is yellow-green and on its back it has 4 distinctive black dots. Like all plant bugs it has a needle-like mouthpart, which it uses to draw plant sap from developing flower buds and seeds, thus causing lesions to form on the stems, buds, flowers and pods. When this insect pest feeds on buds, flowers and young pods it causes new buds to turn white and not develop. It also causes new forming flowers to abort and not form a seed pod. If the seed inside the pod is fed on it will shrink or collapse and turn dark, thus losing quality. For NYS we have no known economic thresholds for this insect pest. This insect pest can be monitored with sweep net. A suggested threshold from the North Dakota State University is an “average of 15 to 20 tarnished plant bugs (nymphs or adults) are captured per 10 sweep net sample taken in ten locations in the field (150 to 200 bugs per 100 sweeps)”. For more information in this insect pest please view the following website: Insect Pests of Canola

Soybean Seed Rot and Seedling Blight

Ken Wise

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Many different organisms cause seed rot and seedling blights. Most of these organisms are soil-borne and a few are seed-borne. Most seed rots and seedling blights proliferate in poorly drained, cold (less than 58 degrees) and wet soils.

Seed Rot: Many times the infected seed will not germinate. If the seed does germinate the radicle will become infected and rot. The rot can be tan, brown, gray or black and the seed or radicle will appear wet and mushy. Some of the organisms that infect seed are Pythium, Fusarium, and Rhizoctonia.

Seedling blight: It is difficult to determine which pathogen causes seedling blight in any one field. Many times it can be a complex of Pythium, Rhizoctonia and Phytophthora. Pythium can cause the seedlings to have a wet, rotted appearance, while Phytophthora generally appears as a dry, dark rot on the roots. Sunken, reddish-brown lesions on the hypocotyls are most likely a Rhizoctonia infection. The Rhizoctonia lesions are small when they first appear. As these lesionsgrow they cangirdle the stem, causing the soybean plant to die. If the Rhizoctonia infected seedlings do not kick the bucket the infection will weaken the stem and may cause the plant to lodge after the pods form.

Make sure you use a fungicide seed treatment to protect seed from these pathogens at planting. Do not plant soybeans too early when soil temperatures are low. If soil temperatures are low the seed will take longer to germinate and grow, thus allowing the pathogens more time to enter the seed.

NYS Soybean Rust Update

Gary Bergstrom
Department of Plant Pathology, Cornell University

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Rust continues to be found in the southern U.S. Active disease is still being reported on kudzu in six counties in Florida and one county in Texas. Efforts continue in the Gulf Coast Region to establish soybean rust sentinel plots.

Coordination of soybean rust sentinel plots in New York State is currently underway. Many of last year’s cooperators will be volunteering their time again to establish and scout these plots. Please visit us again for future updates.(Updated May 14, 2008 )

NYS Soybean Rust Website

USDA Soybean Rust Website

Growing Degree Days in NYS

Ken Wise

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March 1 - June 4, 2007

Base 48 F
Base 50 F
Clifton Springs
*Missing data 
Source: Network for Environment & Weather Awareness
(Note: for alfalfa weevil predictions use Base Temp of 48F)

click to enlarge

Growing degree Days for peak (50%) Occurrence of Alfalfa Weevil growth stage:

Stage or Event
Accumulated growing degree days (48F base temperature)
Eggs hatch
Instar 1
Instar 2
Instar 3
Instar 4
Adult Emergence

Clipboard Checklist

Keith Waldron

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• Emergency contact information (“911”, local hospital, Chem. Spill emergency contact, other?) posted in central posting area

• Review EPA Worker Protection Standard training and posting compliance needs

• Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.

• Watch for winter annual and other early season weeds, any patches of herbicide resistant weeds?

• Storage areas cleaned and ready to accept hay harvest?


• Determine plant populations, make notes on emergence problems, growth stage

• Gaps in row? Check for seed corn maggot, wireworm, cutworm, armyworm, seedling blights, birds, seed placement issues

• Check no-till fields/fields with high residue or weeds for slug damage

• Monitor for weeds, note presence of “who”, “how many” and “where”

• Adjust post emergence weed control actions

Small Grains:

• Monitor winter grains for crop stage (flag leaf?), insect (cereal leaf beetle, armyworm) and disease problems

• Check wheat for powdery mildew and soil borne wheat mosaic virus (susceptible varieties such as Harus and Jensen)

• Evaluate crop for adequate stand and plant vigor

Alfalfa & Hay:

• Monitor alfalfa seedings for weeds, insects & diseases.

• Check established alfalfa stands for alfalfa weevil, potato leafhopper, weed and disease problems.

• Check windrows / regrowth of recently harvested alfalfa for signs of alfalfa weevil feeding damage and weevil life stage (instar cocoon).

• Timothy stands: check fields for symptoms of cereal rust mite

• Storage areas cleaned and ready to accept upcoming harvest?


• Field preparations, planter ready, Rhizobium inoculum?

• Evaluate stand emergence – seedling blights, seed corn maggot, weed assessment, soybean aphid

Dairy Livestock Barn Fly Management:

• Sanitation, sanitation, sanitation – clean animal resting areas, feed troughs, minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard

• Check waterers, drainage, roof gutters for leaks and potential overspill

• Begin fly monitoring: install “3X5” index card fly speck monitoring cards through out barn

• Order fly management materials: fly tapes, insecticide baits, natural enemies (parasitoids)


• Check storage areas (bunk silos, etc.) for readiness to accept first cutting

• Check forage allocation and anticipate feed program adjustments as forages are used up from previous year

• Plan where forages should be stored for optimum allocation for feeding

• Keep areas around storage bins and silos clean and mowed


• Note any repairs needed for recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.

• Service corn planter as needed. alfalfa harvesting equipment, and tillage implements

• Soybean planter and alfalfa harvesting equipment ready?

• Calibrate manure spreaders - maintain records on amount spread per field

Emergency responder information on pesticide spills and accidents CHEMTREC: 800-424-9300

For pesticide information:
National Pesticide Information Center: 800-858-7378

To Report Oil and Hazardous Material Spills in New York State_NYS Department of Environmental Conservation Spill Response:_800-457-7362 (in NYS)_518-457-7362 (outside NYS)

Poison Control Centers: Poison Control Centers nationwide: 800-222-1222

If you are unable to reach a Poison Control Center or obtain the information your doctor needs, the office of the NYS Pesticide Coordinator at Cornell University, 607-255-1866, may be able to assist you in obtaining such information.

Upcoming Events

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Small Grains Field Day

*June 5, 2008

Robert B. Musgrave Research Farm

Aurora, NY ( Poplar Ridge Road, connects 90 and 34B)

Corn and Alfalfa Field Day

*June 18 at 12:30pm – 3:30pm

At the SUNY Cobleskill Farm

Warnerville Cutoff Road, between Rt 7 and Rt 10 just West of Cobleskill, NY

Seed Growers Field Day

*Tuesday July 8

NYSIP Foundation Seed Barn

Cornell University, Ithaca, NY

Weed Science Field Days

*Wednesday, July 9, 2008

Valatie Research Farm

9:30 am - Noon

Valatie, NY ( State Farm Road off Route 9 just north of Valatie)

*Wednesday, July 16, 2008

Robert B. Musgrave Research Farm

1:30 pm - 5 pm

Aurora, NY ( Poplar Ridge Road, connects 90 and 34B)

Aurora Field Day

Wednesday, July 23, 2008

Robert B. Musgrave Research Farm

Aurora, NY ( Poplar Ridge Road, Connects 90 and 34B)

Contact Information

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Julie Dennis: IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 252-5440

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