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Weekly Field Crops Pest Report 2006

June 9, 2006 Volume 5 Number 8

1. View from the Field

2. Soybean Aphid Season Opener

3. Soybean Emergence and Stand Counts

4. Does Biological Control Work for Reducing Alfalfa Weevil Survival

5. Lady Beetles in Alfalfa

6. Pest Management in Pastures: White grubs

7. Soybean Rust Update

8. Growing Degree Days in NYS

9. Clipboard Checklist

10. Upcoming Meetings

11. Contact Information

View From The Field
Eastern NYS

Julie Stavisky, NYS IPM

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Ken Wise, NYS IPM

At this time last year, soybean aphids started showing up on seedling soybeans.  Once again, they are here early!  Mike Stanyard, Nancy Glazier, and a soybean TAg team in Genesee County saw winged soybean aphids on buckthorn on Tuesday.  Mike, Nancy, a soybean TAg team, and I observed low populations of soybean aphid on V-1 soybean in Ontario County on Wednesday.  The infested plants were close to a large buckthorn plant in a hedgerow.  In a V-C soybean field several miles away, I did not observe any aphids. We will need to keep the eagle eye out for our soft-bodied foes! Read on for Keithís review of soybean aphid biology and the new national soybean aphid reporting network.

Reports from the Midwest indicate that corn rootworm larvae have begun hatching.  Rootworm hatch in NY usually begins around the same time that fireflies are first seen.  I have yet to spot any of our favorite night-time summer signalers. Maybe this weekend!

This week, Mike Stanyard reported that black cutworm has been seen in Wayne County in a corn field with muck soils and a history of cutworm.  Small larvae were seen at under-threshold levels, but now is the time to watch fields carefully! Black Cutworm larvae vary in color from light gray to black with a pale brown to black head. Larvae have a greasy, shiny appearance with coarse granules present over their body. During the day larvae burrow into the soil next to the corn plant. These larvae curl into a C shape when disturbed. Symptoms of damage are leaf feeding, irregular holes in stems, notched and cut or missing plants.  For more information on the biology and thresholds, visit the NYS IPM Black Cutworm brochure.

This week while scouting alfalfa at the Cornell Research Farm in Valatie, I found several potato leafhoppers in alfalfa fields. While they are not at threshold there seems to have been an increase over the last week. While numbers potato leafhopper populations are below threshold they  can build very quickly with warm weather. Do you know what potato leafhopper looks like? Remember adults are bright lime green, 1/8 inch long and can fly. Potato leafhopper nymphs are yellowish-green and look similar to the adult but do not have wings.

Alfalfa fields had been cut week at the Cornell Research Farm and alfalfa weevil damage on re-growth was only at 5 to 10 percent. While tip feeding was low I was still finding 1st to 3rd instar larvae in fields. The threshold for alfalfa weevil on re-growth is 50% of the of the steams show tip feeding. A new seeding at the farm was very weedy. There was a lot of common lambsquarter, and common ragweed.

Soybean Aphid Season Opener

Keith Waldron, NYS IPM

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Soybean fields are beginning to green up with 2 leaf stage rows of seedlings visible in many areas of the state. NYS Agricultural Statistics Service estimates 220 thousand acres of soybeans will be planted in New York this season.
Soybean rust has been in the news lately and this week soybean aphids (SBA) were reported in the Midwest signaling the beginning of the 2006 SBA season. For the national perspective on soybean aphid see the USDA soybean rust / soybean aphid web site

Over the last three weeks we have surveyed a limited amount of local buckthorn for signs of over-wintering soybean aphids in the Finger Lakes region of upstate NY. As of Monday of this week, we had not observed SBA's on any buckthorn surveyed. We have, however, detected low amounts of the aecial stage of the crown rust Puccinia coronata. A possible variant from oat, rye, or some other grass. Would be interested to hear SBA observations from other NY readers as the season continues.

Nationally, SBA activity was reported in Minnesota and Indiana this week by university field crop extension entomologists. Closer to home Julie Stavisky observed SBA on unifoliate soybean seedlings in central New York. These observations are a little earlier than last year. It is too early to tell if this will turn into a bad aphid year for soybean aphid, but initial colonization has begun.

Since their initial detection in 2001,soybean aphids have been observed widely across the state, generally at low, sub-economic populations. In some instances SBA populations have, however, exceeded treatment guidelines. Now would be a good time to review SBA management basics. First of all - "Don't Panic".

How will we know when soybean aphids are present in NY soybeans?  Look carefully at the undersides of the uppermost soybean leaves in the canopy.  If present, the aphids are usually seen in small clusters near the leaf veins. They are tiny, 1/16" long at their largest, with distinctive black cornicles (tail pipes).  Soybean aphids are the only aphids to successfully colonize soybean plants.

During early to mid-vegetative stages of soybean growth, economic benefit from insecticide application is not likely.  Plus, using an insecticide too early in the season may jeopardize the establishment of natural enemies in the field. When scouting the early vegetative stages of soybeans for soybean aphid, it is just as important to watch for the aphid's natural enemies, including ladybugs, syrphid fly larvae, parasitic wasps, and fungal pathogens. During late vegetative stages and early R stages, the economic threshold is 250 aphids per plant, though this only holds true if aphid populations are still on the rise.

More information on managing soybean aphid will be the subject of future Weekly Pest report articles.

Soybean Emergence and Stand Counts

Julie Stavisky, NYS IPM

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In addition to watching for soybean aphid, it is time to assess soybean stands. Information gathered this year will help guide decisions about management that may be warranted in future years. The to-do list includes estimating plant populations and investigating the cause of skips in the rows. These activities were done at soybean TAg Team meetings this week.

To estimate plant population, see the following table. Count the number of plants in the given length of row based on the row spacing, then add 3 zeros. (For example, if 165 plants are counted, your estimated plant population is 165,000). Repeat this for the number of rows in your planter or drill, and repeat in 2 more areas of the field.

If your row width is:

 Measure this length of row:

7"

74 feet 8 inches

15"

34 feet 10 inches

30"

17 feet 5 inches

When skips are seen in the rows, it is time to do some digging. Are seeds planted too deep such that plants are still emerging? Is the planter or drill acting up? Are damaged seeds or seedlings seen? If seeds are mushy or rotten, a seed or seedling blight might be the problem. Review Kenís article from last week

If seeds, stems, or roots show signs of feeding injury, the usual suspects are seedcorn maggot, wireworm, or white grub. Risk from seedcorn maggot is greatest if there is high organic matter on the soil surface, from crop residue or manure, for example. Wireworm and grub threats are usually greatest following a grass or pasture sod.

Does biological control work for reducing alfalfa weevil survival?

Ken Wise, NYS IPM

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There are a number of natural enemies that have a taste for alfalfa weevil. Protecting the diversity of these biological control agents is important for reducing weevil induced losses. Data collected by Paula Davis, Ted Erkilla, and Keith Waldron in 1993 can offer some insights. Alfalfa weevil populations were high that year in Ithaca and Aurora, NY. Alfalfa weevil larvae and pupae were collected from alfalfa fields and reared in the laboratory to determine presence of parasitoids and fungal diseases. Larval parasitism by Bathyplectes spp and fungal disease infection was detected at all locations. Weevil cocoons showing signs of Bathyplectes wasp parasitism were specifically collected to determine species. B. anurus and B. curculionis were found in almost equal proportions that year. Alfalfa weevil larvae were collected and reared to detect fungal infection. Results are shown below.

 

Bathyplectes spp.
Min. % parasitism

 Zoopthora phytonomi (fungus)

Location

 B. anurus

B. curculionus

mortality
at collection

mortality
 post rearing

Aurora

24.2%

7.1%

5.2%

87.5%

Ithaca

7.4%

0.7%

38.8%

90.7%

Mt. Pleasant a

18.9%

22.5%

1.8%

32.4%

Mt Pleasant b

0%

4.2%

4.7%

32.7%

Fields sampled had not been monitored earlier during the alfalfa weevil season. Field monitoring and an early harvest or insecticide treatment could have avoided the nearly 60% tip feeding and the resulting yield and quality losses observed at first harvest. The presence of natural enemies did, however, reduce the number of alfalfa weevil available to over winter and attack those alfalfa fields the following year.

Ladybeetles in Alfalfa

Ken Wise, NYS IPM

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This year I have seen a wide range of lady beetle predators in alfalfa. Many of these lady beetles feed on aphids and other pests that feed on alfalfa. Because of these predators aphids are generally not a problem in alfalfa in NYS like they are in other parts of the country. Here is a list and photos of lady beetles I have found in alfalfa this year.

While Multicoloured Asian Lady Beetle (Harmonia axyridis)has been an annoyance to home-owners by getting in their houses in the fall, they are an effective predator of aphids. An adult is capable of consuming 100 to 270 aphids per day, and each larva can consume 600 to 1,200 aphids during its development. This lady beetle is oval and convex and is about 6 millimeters.  Coloration varies from light orange to red, and number of spots vary.

Seven-spotted Lady Beetle (Coccinella septempunctata), while introduced from Europe, is also an effective predator of aphids. A single larva can consume 800 to 1,000 aphids and an adult will eat from 3,000 to 4,000 aphids during its lifetime. This is a large lady beetle and is 7-8 millimeters.

Pink-spotted Lady Beetle (Coleomegilla maculata) is native to North America and is very abundant in the Northeast. Adults can consume 50 aphids per day, while larvae can eat 10 to 25 per day. The pink-spotted lady beetle will consume plant pollen that may constitute up to 50% of the diet. This is a medium sized lady beetle at 5 to 6 millimeters.

Spotted Amber Lady Beetle (Hippodamia variegate) was introduced from Europe. Depending on the Hippodamia spp. and the larval instar, this beetle may consume about 25 aphids per day. Adults can eat as many as 50 per day depending on Hippodamia spp. This lady beetle is small and only 4 or 5mm.

Parenthesis Lady Beetle (Hippodamia parenthesis) is native to North America. Larvae may consume about 25 aphids per day. Adults can eat as many as 50 per day depending on Hippodamia spp. This small beetle is only 4 to 5 millimeters.

Fourteen Spotted Lady Beetle or the Cream Spotted Lady-beetle (Propylaea quatuordecimpunctata) is a European lady beetle. This lady beetle was accidentally introduced to North America. Some people think it was transferred on a ship in the St. Lawrence Seaway sometime in the late 1960s. This lady beetle does feed on aphids but I found no information on the amount they can consume. This is a small beetle that is only 4 to 5 millimeters.

Next week I will cover the other predators in alfalfa.

Pest Management in Pastures: White grubs

Julie Stavisky, NYS IPM

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Well-managed pastures (those under management intensive grazing) are generally low-maintenance and require few inputs for pest management.  Selection of grass and forage species for pasture are generally the most important decisions.  Due to the diversity of habitat within a pasture, insect and disease pests are generally kept in natural check.  Once pastures are established, little ground is exposed and weed invasion is minimized until pastures are exposed to stresses, including over-grazing, continuous grazing, or weather extremes.

But a few pests can cause real headaches, including white grubs, armyworms, and several weeds, including poisonous weeds.  Watch the weekly report for periodic highlights for pasture pest management throughout the season.

Pasture grasses are growing vigorously with warm temperatures and well-timed rains, but now is the time to begin watching for weakened areas where white grubs are feeding.  White grubs feed on the roots of pasture grasses.  Grub feeding may weaken the roots of plants, leaving the plants loosened.  Grazing animals can easily harm or uproot grub-damaged plants.  High-risk areas for grub damage include pastures with manure applied as fertilizer and pastures on sandy or light soils.  There is an increased threat of weeds taking over in areas where grass is damaged or killed by grub feeding.  Under drought conditions, recovery of pasture from severe grub feeding is impeded.

White grubs are the larval forms several scarab beetles, including Japanese beetles, May or June beetles, and European chafers.  White grubs spend their life in the soil, feeding on roots.  They are thick, white, soft-bodied insects from ľ - 1 inch long.  They are typically observed in a C-shape when they are dug up. Sampling in a pasture involves digging up the soil in the suspected area, and sifting through for grubs. 

One of the challenges of managing grubs in pasture is that the various species present have different life cycles.  While Japanese beetle grubs live in the soil for a 1-year life cycle, May and June beetles may survive for several years in the soil.  Therefore, re-seeding or over seeding after a problem has been discovered may need to be repeated for several years.  Risk from grubs in pasture can be minimized with a legume mix, given that most grubs rarely feed on our clovers, alfalfa, or trefoil.

Soybean Rust Update

Gary Bergstrom, Cornell University Department of Plant Pathology

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The current risk of soybean rust infection in New York is extremely low. Future risk in New York will depend on rust build-up in the southern U.S., especially in commercial soybean fields. The 2006 North American epidemic is starting from over-wintered rust on kudzu in a somewhat broader and more northerly area than in spring 2006, yet early pockets of rust from Florida to Alabama are scattered and of low severity.  Rust development is basically in a holding pattern along the Gulf Coast. Despite recent rains across the South, the region is again in an overall pattern of hot, dry weather.  To date, in 2006, soybean rust has been reported on kudzu in five counties in Alabama, 11 counties in Florida, and four counties in Georgia.  While soybean rust was found in a mature field of soybean in far southern Texas in February, the infected field has since been destroyed and no new rust has been found in Texas.  Scouting continues on kudzu patches from Florida northward to southern Illinois, and westward to Texas and Nebraska. Many of the soybean sentinel plots have been planted throughout the country with the most advanced ones in the south starting to fill pods. We are finalizing plans for approximately 20 sentinel soybean plots in New York to be scouted in cooperation with soybean producers and Cornell Cooperative Extension Educators. Sentinel plots are planned for locations in Cayuga, Chautauqua, Chemung, Chenango, Genesee, Jefferson, Montgomery, Oneida, Onondaga, Ontario, Orleans, Seneca, Steuben, Tompkins, and Wayne Counties. Last updated (May 26, 2006).

For more information, consult:

Alfalfa Weevil and Growing Degree Days in NYS

Ken Wise NYS IPM

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Accumulated Growing Degree Days for March 1 to June 7

Location

Base 48 F

Base 50 F

Batavia

518

435*

Chazy

491

416

Clifton Park

714

618*

Geneva

539

452

Ithaca

463

384*

Mexico

471

402*

Prattsburg

434

362*

Redhook

755

656

*indicates missing data

Source: NEWA

Clipboard Checklist

Keith Waldron-NYS IPM

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General:
* Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
* Watch for early season weeds, any patches of herbicide resistant weeds?
* Storage areas cleaned and ready to accept upcoming hay harvest?

Corn:
* Determine plant populations, make notes on germination problems
* Gaps in row? Check for seed corn maggot, wireworm, cutworm, seedling blights, birds, seed placement issues?
* Monitor for weeds, note presence of "who", "how many" and "where"
* Adjust post emergence weed control actions

Small Grains:
* Monitor winter grains for crop growth stage, insect and disease problems
- Note flowering date

Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, insects & diseases.
* Check established alfalfa stands for alfalfa weevil, weed and disease problems
* Harvest alfalfa - first cutting, check windrows for signs of alfalfa weevil feeding

Soybeans:
* Check stand establishment, weed control
* Gaps in row? Check for seed corn maggot, wireworm, seedling blights, birds, planter problems, drainage issues?

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 water sources, 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)

Equipment:
* Note any repairs needed for recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.
* Hay harvesting equipment ready?
* Calibrate manure spreaders - maintain records on amount spread per field

Upcoming Meetings

2006 CORNELL SEED GROWERS FIELD DAY
6 July 2006

For Seed Growers, Seed Treaters, and other Seed Professionals
Place: NYSIP Foundation Seed Barn, 791 Dryden Rd., Rt. 366, Ithaca, NY, Time: 9:00 AM-12.00 noon (registration and refreshments available at 8:30 AM)

Contact Information

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Julie Stavisky: IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Email: js38@cornell.edu

Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360
Email: jkw5@cornell.edu

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316
Email: klw24@cornell.edu