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Weekly Field Crops Pest Report 2007

June 6, 2007                Volume 6 Number 7

1. View from the Field

2. Are slugs a threat to corn and soybeans this year?

3. Soybean Emergence and Stand Counts

4. Soybean Seed Rot and Seedling Blight

5. Soybean aphids - expected soon?

6. 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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Western NY and Finger Lakes Region

Julie Dennis, NYS IPM

I have seen fireflies the past several nights.  Remember the anecdotal link between fireflies and field crop pest management? Once fireflies are active, corn rootworm eggs are said to be hatching.

Mike Stanyard reported that he saw potato leafhoppers last Thursday, May 31st. This tiny lime-green insect arrives each spring in late May on storm fronts.  They begin laying eggs in alfalfa soon after their arrival.  It is definitely time to begin potato leafhopper scouting in alfalfa!  Mike also saw cereal leaf beetles in wheat and oats in several fields in Ontario County.  He saw some plants with up to 3 larvae per flag leaf, but they were not widespread in fields.

Mike Dennis (Seneca County CCE) reported on the occurrence of loose smut in wheat this week.

Gary Bergstrom, Cornell Plant Pathologist reports that loose smut is very common in NY, but incidence is usually low except where farmers save their own seed (bin run) and don't treat it or treat it inadequately.  “This is a disease that would be controlled if everyone planted certified seed with commercially applied seed treatment.  It is a disease that is on a comeback as farmers cut corners and use bin-run seed.  Hopper box treatments should be effective but the coverage is unlikely to be as good as with professionally applied treatments,” says Gary.

Eastern NYS-Ken Wise

This week I found potato leafhoppers over threshold in a field at the Cornell Research Farm in Valatie. The alfalfa was 25 inches tall and in 4 samples (10 swings/sample) using sweep net collection I had 105 potato leafhoppers. The following picture is the typical damage I was seeing to the alfalfa in the field.

The best thing to do now is to CUT and harvest the field over threshold. If you are within a week of your harvest date the best management practice is to harvest the alfalfa, thus you save the yield and quality of the forage. If the alfalfa was NOT within a week of harvest, an insecticide application may be warranted in a pure stand of alfalfa.

I made my first visit to the Columbia County soybean sentinel plot this week near Kinderhook, NY. The beans are all out of the ground and in the V1 to V2 growth stage. I did not find evidence of any diseases or soybean aphids yet. I did see a few thrips on the leaves of the plants.

Are slugs a threat to corn and soybeans this year?

Julie Dennis
NYS IPM

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Usually we worry about the threat from slugs as soon as corn and soybeans begin emerging.  The dry conditions across much of NY have eased this concern so far.  Mike Stanyard with the NWNY Team reports that 50 slug traps had zero slugs so far in no-till soybean fields.  Mike and some growers were hoping to test various slug baits this year….

Slugs spend the winter as eggs. The overwintering eggs are usually laid in the general area where slugs were feeding the previous spring, summer, and fall. Thus, if they were a problem in an area last year, there’s a good chance of a slug risk this year. Slugs will attack seedlings and lower leaves, leaving coarse, irregular holes and characteristic “slime trails” in their wake. Feeding may result in serious injury and even stand reduction under severe infestations.

Slugs prefer cool and moist conditions, and they thrive when there are hideouts in the field, such as in the cover provided by debris on the soil surface. Slugs tend to feed most when temperatures are in the mid 60’s. Stand reduction problems have typically been worst during wet, cool springs.  No-till corn and soybean fields are at highest risk from slugs.

A change in moisture conditions is bound to happen; therefore growers with a history of slug troubles in corn and soybeans will want to keep an eye out for slugs for the next several weeks.

Soybean Emergence and Stand Counts

Julie Dennis
NYS IPM

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I’ve seen a lot of fields where soybeans are emerging nicely, so it will soon be time to assess soybean stands. The to-do list includes estimating plant populations and investigating the cause of missing plants in the rows. These activities will be conducted at soybean TAg Team meetings occurring over the next couple of weeks.

The following table shows how to estimate plant populations. Count the number of plants in the given length of row based on the row spacing, and 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 the row width is:(inches)

Then measure this length of row:

7

74 feet, 8 inches

15

34 feet, 10 inches

20

26 feet, 2 inches

30

17 feet, 5 inches

32

16 feet, 4 inches

36

14 feet, 6 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? Was 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. If seeds, stems, or roots show signs of feeding injury, the usual suspects are seedcorn maggot, wireworm, or white grub. See Ken’s article below for detailed descriptions of disease problems in soybean seedlings, and stay tuned for an article in next week’s Pest Report on a description of insect problems. 

Stand assessment information gathered this year will help guide decisions about management that may be warranted in future years.

Soybean Seed Rot and Seedling Blight

Ken Wise
NYS IPM

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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 Phytophtora. Pythium can cause the seedlings to have a wet, rotted appearance, while Phytophtora 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 lesions grow they can girdle 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.

Soybean aphids - expected soon?

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 210 thousand acres of soybeans will be planted in New York this season. Soybean aphids (SBA) were reported in the midwest and Canada this week signaling the beginning of the 2007 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 last 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 pathogen Puccinia coronata on buckthorn foliage. This organism is a possible variant that can attack oat, rye, or some other grasses.

Nationally, SBA activity was reported in late May on V1 stage soybeans in Wisconsin, Ohio and Ontario by field crop extension entomologists. The sighting near London, Ontario is nearly a month ahead of what they normally see for that location. Midwestern entomologists have predicted 2007 will be a big year for SBA. Our NY soybean crop is just starting to emerge and it is too early to tell what SBA issues may lie ahead for us this season. So far there have been no reports of SBA in this years NY soybean crop. Recent reports from the midwest and Canada, however, serve as a reminder to check our emerging soybeans for SBA as early as possible. This could be particularly important for soybean fields planted adjacent to areas containing buckthorn.

To check plants for soybean aphids carefully look at the undersides of the uppermost leaves in the soybean canopy - pretty easy to do at this early stage of development.  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. As always, we are interested to hear from our NY readers regarding any SBA and other soybean field observations as the season continues.

Soybean Rust Update

Gary Bergstrom
Department of Plant Pathology, Cornell University

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National Soybean Rust Commentary (updated: 06/04/07)

Soybean rust was detected on a small patch of kudzu in eastern Texas in Liberty County. This is currently the only known active rust site in Texas. The disease was also found on kudzu in south Louisiana on May 8, but there have been no new reports of soybean rust in that state. Tropical depression Barry and the end of the high pressure system that was centered over Florida have resulted in a dramatic change in weather conditions in that state. Barry deposited several inches of rain across peninsular Florida last week. Current forecasts suggest that more typical rain patterns will continue in Florida which will favor soybean rust development and spread. There are currently eight counties in Florida with active rust sites. Scouting for soybean rust has intensified and soybean sentinel plots are now being monitored throughout most of the soybean growing states, and north into Canada. No active sites of soybean rust have been reported in Alabama or Georgia. Soybean rust has been detected in 10 counties in Florida, five counties in each of Georgia and Alabama, two counties in Texas and one in Louisiana.

USDA soybean rust / soybean aphid web site

Growing Degree Days in NYS

Ken Wise
NYS IPM

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

Stage or Event

Accumulated growing degree days (48F base temperature)

Eggs hatch

280

Instar 1

315

Instar 2

395

Instar 3

470

Instar 4

550

Cocooning

600

Pupa

725

Adult Emergence

815

(Note: for alfalfa weevil predictions use Base Temp of 48F)


CURRENT Accumulated Growing degree days (48F Base)
March 1 -June 4, 2007

Location

Base 48 F

Base 50 F

Batavia

566

486

Chazy

464

399

Clifton Springs

757

666

Geneva

579

497

Ithaca

535

460

Prattsburg

500

429

Clipboard Checklist

Keith Waldron
NYS IPM

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Clipboard Checklist
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, wire worm, 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
        - evaluate crop for adequate stand and plant vigor
        - evaluate crop for Fusarium head blight (Scab) and other grain head diseases
* Check, clean, prepare storage bins to accept upcoming harvest?
* Mow around storage bins to remove rodent habitat, remove spilled grain
* Clean grain handling equipment (conveyors, wagons, tucks, combines, elevators, etc.) for signs of leftover grain - remove potential sources of stored grain insect infestations..

Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, potato leafhopper and diseases.
* Check established alfalfa stands for alfalfa weevil, potato leafhopper, weed and disease problems.
* Timothy stands: check fields for symptoms of cereal rust mite

Soybeans:
* Field preparations, planter ready, Rhizobium inoculum?

* Initial stand assessment: plant populations, seedling diseases and insects

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)

Equipment:
* Note any repairs needed for recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.
* Service soybean planter as needed. alfalfa harvesting equipment, and tillage implements
* Calibrate manure spreaders - maintain records on amount spread per field
* Check, clean, adjust and service small grain harvesting equipment as needed.

Upcoming Events

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SMALL GRAINS MANAGEMENT FIELD DAY
ROBERT MUSGRAVE RESEARCH FARM
Poplar Ridge Road, Aurora, NY
Thursday, June 7, 2007
Coffee at 9:30 AM
Program 10 AM to Noon

SEED GROWERS FIELD DAY

NYSIP Foundation Seed Barn
Thursday, July 5, 2007
Ithaca, NY (761 Dryden Road, Route 366)
Registration and Coffee at 9:00 AM
Tour Begins at 9:30 AM

WEED SCIENCE FIELD DAYS

Valatie Research Farm – July 6
(Stage Farm Road just off Route 9, North of Valatie)
Registration and Coffee at 9:00 AM
Tour Begins at 9:30 AM to 12 Noon
(Field Crops)

Robert B. Musgrave Research Farm- July 11
(Popular Ridge Road, connects 90 and 34B)
11:00 am to 1:00 pm-Chicken BBQ
1:00 pm Registration
1:30 pm to 5:00 pm Tour
(Field Crops)

H.C. Thompson Research Farm- July 12
Freeville, NY 10 miles north of Ithaca, Fall Creek Road Rt. 366 extension)
8:00 am Registration ($8 Informational Packet)
8:30 am to Noon-Vegetable Weed Control

AURORA FIELD DAY

ROBERT MUSGRAVE RESEARCH FARM
Thursday July 26, 2007
Poplar Ridge Road, Aurora, NY (connects 90 and 34B)
Coffee at 9:30 AM
Tour Plots 10 AM to 3 PM

Contact Information

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Julie Dennis: 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