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Weekly Field Crops Pest Report 2012

August 20, 2012, Volume 11 Number 18

  1. View from the Field
  2. Weather Outlook
  3. New Disease: Soybean Vein Necrosis Virus
  4. Sclerotinia Stem Rot/White Mold: in Soybeans
  5. Western Bean Cutworm Update
  6. Clipboard Checklist
  7. Mark Your Calendars
  8. Contact Information

View from the Field


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White mold has been found on soybeans in eastern NY. One of the fields of soybeans I (Ken Wise) scouted this week looked healthy and very tall. Because the plants were so tall much of the beans had lodged. Under the lodged beans white mold is starting to develop. White mold does well when itís humid and moist, developing quickly and under a canopy of lodged soybeans. See article below for more information on white mold.

A soybean vein necrosis virus has been reported in soybeans Cayuga, Ontario, Orleans and Yates counties this week. This disease was first discovered in NY last year. See article below for more information. If you see symptoms, itís important to let your local extension educator know so they can start the process of confirming whether thatís what it is.

Minor amounts of several foliar diseases of soybeans are also reported, including downy mildew, Septoria leaf spot, bacterial leaf blight, and bacterial pustule.

Soybean aphids are being reported at low levels on soybeans in eastern and western NY. †In some fields there is an average about 50 aphids or less per plant.† Many aphid predators such as lady beetles are also reported. The economic threshold: 250 aphids per plant, with populations rising prior to the R5 stage. After the R5 stage, thereís no advantage in spraying; youíre just wasting the spray.

Spider mites are still damaging soybeans. Mites really proliferate and thrive when the weather is hot and very dry. Often soybeans are under some drought stress when mites cause damage. Economic damage happens during R4 and R5 growth stages. Because the mites interfere with photosynthesis, thus promoting drought stress, a loss of 10 to 15% of leaf surface causes damage. Pod set, seed size and number of seeds are all reduced, and pods are more prone to shattering. If mites reach economic threshold at the R4 to R5 stages, an insecticide should be used to avoid economic loss.

Alex Wright with Carolina Eastern-Vail Inc. reports spider mite damage on corn. The symptoms first show on the leaves closest to the soil. The symptoms are a white to yellow stippled appearance.

spider mite damage on corn
Spider mite damage on corn; photo by Alex Wright

Alex also reports a field of corn with a severe infestation with northern corn leaf blight. She says theyíre finding a lot of this disease in cornfields this growing season.

Weather Outlook

August 16, 2012
Jessica Rennells, Northeast Region Climate Center, Cornell University

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Last week temperatures ranged from 0 to 6 degrees above normal for most of the state.† Rainfall amounts ranged from one to two inches for most of the state. The Base 50 growing degree-days ranged from 100 to 175.

Today will be mostly sunny and dry with temperatures in the low to mid 80ís as high pressure builds over the state.† Overnight temperatures will be in the low to mid 60ís with showers and thunderstorms possible. Friday temperatures will be in the upper 70ís to mid 80ís with rain and thunderstorms likely moving west to east as a cold front moves through.† Isolated storms could be severe.† Lows will be in the mid 50ís to low 60ís. Saturday should clear and become mostly sunny with highs throughout the 70ís.† Some leftover showers from Fridayís passing front may linger in the southeast, but then will be a mostly dry day.† Lows will be in the low to mid 50ís. Sunday will be mostly sunny with highs throughout the 70ís and lows in the 50ís. Monday will be mostly sunny with highs again throughout the 70ís; some scattered showers are possible.† Overnight temperatures will be in the mid to upper 50ís. Tuesdayís temperatures will be in the 70ís with showers possible.† Lows will be in the mid to upper 50ís. Wednesday temperatures will be in the upper 70ís and low 80ís.† Lows will be in the mid 50ís to low 60ís.

The five-day precipitation amounts will range from a tenth to three-quarters of an inch. The 8-14 day outlook is showing normal temperatures and above normal precipitation.

National Weather Service Climate Prediction Service Maps of 8-14 day outlooks

National Weather Service Eastern Region Headquarters watch/warnings map

NRCC Drought Page which features the US Drought Monitor map (updated every Thursday)

New Disease: Soybean Vein Necrosis Virus

Gary Bergstrom, Professor Plant Pathology-Cornell University

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A new soybean disease was confirmed in New York this week. The pathogen is Soybean vein necrosis virus (SVNV). It was first described in Tennessee in 2008, and in Arkansas, Illinois, Kansas, Kentucky, and Missouri in 2009.

The symptomatic plants in New York came from a soybean field in Ontario County. Symptoms are vein-clearing followed by browning veins and 'scalded' reddish areas around the veins, especially on lower leaf surfaces. Dr. Ioannis Tzanetak at the University of Arkansas is a leading researcher on SVNV; she positively identified RNA of SVNV in samples from Ontario County.

In the same time frame as our New York discovery, SVNV has been confirmed in Delaware and Maryland, and with pending diagnoses in Virginia and Pennsylvania. This morning I viewed photographs with symptoms from a field in Herkimer County that also appear to be caused by SVNV; the symptoms were predominantly on the upper, youngest leaves. 

soybean vein necrosis virus
Soybean vein necrosis virus; photo by Mike Stanyard

What is known about SVNV? The answer: not much. It might be transmitted from soybean to soybean by thrips (soybean thrips and perhaps others). The virus has been placed in the Tospovirus group of plant RNA viruses (stands for Tomato spotted wilt virus); all are transmitted by thrips.

Finding SVNV this year doesn't mean we will find it next year. We don't know if the virus can also be transmitted through seed or other means. We don't know if it will have an impact on yield. Perhaps the virus is transported long distances by thrips; perhaps the virus could survive locally in weed hosts (no one has demonstrated this yet) and then be transmitted locally by thrips when their population increases within a season. Tospoviruses are both circulative and propagative in their association with thrips, so if thrips survive our winters, SVNV might well survive in the living thrips.

Insecticidal seed treatments could have a role to play in killing thrips on young soybean plants and reducing the incidence of early virus infection. Resistant varieties appear to be the main path to sustainable management and several investigators are assessing varieties in other parts of the country. Right now we have no basis to recommend that farmers do anything substantially different in their cropping practices just because we found this new virus. For now, I would classify it as a potential problem worth keeping an eye on.

We encourage growers and consultants to inspect any still-green soybean plants for possible SVNV and to inform your local Cornell Cooperative Extension field crops educator if you find symptoms that are similar to soybean vein necrosis.

Some links from PRO-MED Plant Digest:

Pictures of SVNV symptoms:

Leaf

Leaf2

Leaves

Disease Progression

Information and updates on SVNV:

Soybean vein necrosis: old disease, new virus

Epidemiology of soybean vein necrosis virus

New virus found in Arkansas soybean fields

Management Strategies to Control Major Soybean Virus Diseases in the North Central Region

Management of soybean viruses:

Potential for Integrated Management of Soybean Virus Disease

Sclerotinia Stem Rot/White Mold: in Soybeans

Ken Wise, NYS IPM

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The white mold fungus (Sclerotinia sclerotiorum)can be a very serious and problematic disease of soybeans. This fungus has a wide host range including: alfalfa, beans, canola, clover, peppermint, potato, sunflower and tomato. White mold can also attack certain weeds like amaranth, castor beans, dandelions, lambsquarter, ragweed and velvetleaf.† In total there are about 400 different plant species that are susceptible to this disease.

The whole field can look very healthy with one or 2 plants apparently dead. The leaves will remain on the plant but the main stem will turn brown and then die.† This disease thrives in dense stands where there is not much room between plants. If you combine a thick healthy stand of soybeans and cool damp weather can create prime conditions for white mold to take hold.

This soil-borne fungus overwinters in soil in a special structure called sclerotia. The structure looks like a dark hard mouse dropping. Sclerotia can survive up to 7 years in the soil when there are no hosts present in the field.† When the soil temperature is below 650 F, excess moisture and the sclerotia is within an inch of the surface small mushroom like structures grow. These are called apothecia and are 1/8” to ĺ” in diameter. The top of the apothecia is cup like and is where spores are produced. The spores are ejected out of the cup area of the apothecia.

White mold spores infect the soybean plants at flowering. The spores land on the flower and germinate. Once spores germinate they can infect the plant through the dead or dying flower tissue near the node. After entering the plant the fungus consumes plant nutrients. In the end this will girdle the tissue around the stem killing all the tissue above that point.†

Look for white, cottony growths and small, dark, round or elongated sclerotia on or within the stem. Some sclerotia can be about the same size as a soybean seed and may enter the bin with the seed at harvest. Most of the sclerotia fall to the surface to complete a cycle again in the future.

white mold on soybean
White mold on soybean stem

The infected stems and pods are pale brown and look water soaked.

When conditions are right white mold can be very difficult to manage. Some research suggests that using a corn planter and leaving 30 inches between the rows allows for air to move around the plants. This helps keep plants drier at flowering. It also helps keep the soil surface drier and humidity to remain lower. This reduces the development of the apothecia or spores from being released.

Rotation is an important factor when dealing with white mold. NEVER plant soybeans directly after dry beans, soybeans or other susceptible plant species. This is like playing with fire when it comes to white mold.† Always try to rotate with a non-host like corn, wheat, barley, grass hay, and so on.

If you do get an infection of white mold in a field it is important to not plant soybeans or dry beans back to the field for 7 years. If a field does get infected try to harvest this last. You can move sclerotia from field to field if you are not careful. If you do harvest a field with white mold before the others make sure to clean your combine very well before entering a non-infected field.

There are soybean cultivars now that have moderate resistance to white mold. When selecting a cultivar make sure it is one that is well adapted to the region where you live.

The population density of apothecia was greatest in moldboard plow systems compared to no-tillage systems. Fewer apothecia in no-tillage systems is a partial explanation why lower incidence of white mold is observed in no-till fields compared to fields receiving some degree of tillage.
Some fungicides help provide some suppression of white mold. Good canopy penetration and proper timing are essential to get a limited amount of control. It seems that the fungicide works best when infection is moderate.

New biological fungicides are available and being developed. These are small microorganisms, sprayed on the soil, attack the sclerotia and feed on itóand in time, killing it.

To manage white mold in soybeans, combine rotation, row spacing, resistant cultivars, tillage, and possibly fungicides where conditions are favorable.

Western Bean Cutworm Update

Keith Waldron, NYS IPM

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Western Bean Cutworm captures continued to drop off again this week. As of this writing, a total of 157 WBC moths were caught in the 48 traps reporting this week, down from 335 WBC moths caught in 59 traps last week. Trap catches ranged from 0 to 25. The majority of our NY trap catch numbers are relatively low and do not indicate any cause for concern. Interestingly, 13 traps have caught less than a total 10 WBC moths so far this season. High counts this week came from: Chautauqua (25).
Average number of western bean cutworm moths captured per trap.

western bean cutworm chart

WBC larvae were collected in Penn Yan, NY (Yates county) this week.
In the weeks ahead be on the lookout for signs of WBC larval feeding in corn ears. WBC infested ears may contain more than one larva. Larvae may enter through the silk channel at the ear tip or can bore through the husk or ear shank.  Excessive bird activity and damage may indicate insect larvae are in the ears. Damage caused by larval feeding can open ears up to potential risk of ear molds.

Accumulated western bean cutworm moths per location as of 8.16.12

County Location Total WBC County Location Total WBC

Broome

Whitney Point

0

Livingston

Caledonia

28

Cattaraugus

Olean

16

Livingston

Lima

57

Cayuga

King Ferry

1

Madison

Kirkville

34

Cayuga

Sherwood

0

Monroe

Hamlin

49

Cayuga

Aurora

29

Monroe

Spencerport

23

Cayuga

Auburn

59

Monroe

Churchville

34

Chautauqua

Kennedy

132

Niagara

Lockport

21

Chenango

Sherburne

19

Oneida

Clinton

21

Chenango

Afton

14

Oneida

Clinton

21

Clinton

Chazy

24

Onondaga

Baldwinsville

16

Clinton

Beekmantown

50

Onondaga

Tully

16

Cortland

Preble

77

Ontario

Farmington

2

Cortland

Marathon

2

Ontario

Geneva

45

Delaware

Oneonta

19

Ontario

Hopewell

8

Delaware

Walton

34

Ontario

Stanley

26

Dutchess

Millbrook

39

Orleans

Waterport

21

Erie

Eden Z

115

Otsego

Garrattsville

13

Essex

Willsboro

13

Schoharie

Middleburg

22

Essex

Westport

19

Schuyler

Burdett

1

Franklin

Malone

134

Schuyler

Valois

9

Genesee

Batavia

30

St.Lawrence

Madrid

301

Genesee

Leroy

35

Steuben

Avoca

16

Genesee

Batavia

23

Steuben

Wayland

34

Genesee

Stafford

16

Suffolk

Riverhead

1

Genesee

Alexander

17

Tioga

Owego

12

Genesee

Stafford

82

Tioga

Owego

1

Green

 

27

Tompkins

Varna

27

Herkimer

Little Falls

47

Washington

 

7

Jefferson

Ellisburg

192

Wayne

Williamson

24

Jefferson

Sacketts Harbor

340

Wayne

Macedon

13

Jefferson

Plessis

41

Wyoming

Pike

0

Lewis

Martinsburg

322

Wyoming

Attica

276

Livingston

Avon

46

Yates

Bellona

26

Livingston

Cuylerville

8

Yates

PennYan

30

 

More WBC monitoring information is available at:
Western Bean Cutworm identification card Ė including larval stages.

Cornell Sweet Corn Monitoring Network
Penn State Pest Watch (Includes WBC data from NY, New England and other state)
Ontario WBC Trap Network
Cornell Field Crop Extension Homepage: “field crops.org” "blog" section. 
Western Bean Cutworm - Corn scouting videos:
Ontario
Wisconsin
The NY WBC trapping program will continue through August.

Clipboard Checklist

Keith Waldron
NYS IPM

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General:
* Emergency contact information ("911", local hospital, Chem.Spill emergency contact, other) posted in central posting area
* Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
* Watch for any patches of herbicide resistant weeds, weed escapes
* Storage areas cleaned and ready to accept hay, wheat harvest

Corn:
* Monitor fields for plant vigor, growth stage, late season pest issues (European corn borer, armyworm, foliar diseases, nutritional deficiencies, vertebrate damage)
* Monitor for weeds, note presence of "who", "how many" and "where"
* Monitor reproductive stage corn fields for corn rootworm beetles and other insect pests and diseases
* Prepare storage areas to accept upcoming silage harvest

Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, insects & diseases.
* Check regrowth of established alfalfa stands for potato leafhopper, weed and disease problems.
* Storage areas cleaned and ready to accept incoming harvest

Soybeans:
* Evaluate stand growth, development and condition
* Monitor fields for soybean aphid, foliar diseases, white mold, natural enemies, defoliating insects, spider mites, bean leaf beetles and weed escapes

Dairy Livestock Barn Fly Management:
* Sanitation, sanitation, sanitation - clean animal resting areas, feed throughs, 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
* Continue fly monitoring: install "3X5" index card fly speck monitoring cards through out barn
* Install/refresh/replenish as needed: fly tapes, insecticide baits, natural enemies (parasitoids)

Dairy Livestock Pasture Fly Management:
* Monitor animals for presence of pasture fly pests. Treatment guidelines: Horn flies (50 per dairy animal side, 100 per side for beef cattle), face flies(10 per animal face), stable flies (10 per 4 legs). See IPM'sLivestock page.
* Consider installing biting fly traps to reduce horse, deer and stable fly populations.

Storage:
* Check temperature, moisture, pest status of recent bin stored small grains
* Keep areas around storage bins and silos clean and mowed
* Check areas around storage bins and silos for vertebrate tunneling
* Check temperature of recently baled hay in hay mow

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


PESTICIDE EMERGENCY NUMBERS
Emergency responder information on pesticide spills and accidentsÖ
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.

Mark Your Calendars


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Corn Foliar Disease In-Field Workshop.
When: Tuesday, August 21, 2012, 10:30am
Where: Meet at Dandy Mini-Mart, 305 County Road 509, Nichols, NY (just off of (I-86/17) at 10:30 AM Visit French and Lloyd Farms to view gray leaf spot and results of fungicide application; learn how to rate foliar disease.

Hosted by Mark Ochs and French and Lloyd Farms
Organized by Gary Bergstrom, Mary McKellar, Jaime Cummings

RSVP to Mary McKellar (mem40@cornell.edu) if you plan to attend.

Contact Information


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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