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Weekly Field Crops Pest Report 2007

August 9, 2007                Volume 6 Number 15

1. View From the Field

2. What pest problems to consider when planting winter wheat?

3. The Outlook for White Mold in Soybeans

4. Check For Stalk Rots!

5. Bean Leaf Beetles in NY

6. Soybean Rust Update

7. Soybean Aphid Update

8. Clipboard Checklist

9. Contact Information

View From the Field

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This week was pasture fly week! We had a pasture fly meeting in Essex County where 20 beef, dairy and a few horse producers attended. Keith Waldron discussed the biology, thresholds and management of horn flies, face flies and stable flies on pasture. Julie Dennis led a similar meeting in Cayuga County for dairy and beef producers. 

As you can see from a few photos we were able to demonstrate the use of certain fly traps.

“Horse Pal” trap targets horse and deer flies

Alsynite trap targets stable flies

I discussed the importance of dung beetles in decomposing cattle manure in pastures. Dung beetles compete with other organisms like flies within the cattle pat for resources within the manure, thus limiting pasture fly development. There are three types of dung beetles in a cattle pat:

Rollers (telecoprids)
Geotrupes species, form balls of manure which they push from the pat to bury as brood balls

Tunnelers (paracoprids)
Onthophagus species are tunnelers that consume the pat and burrow beneath it to bury brood balls. 

Dwellers (endocoprids)
Aphodius species, consume the manure as they tunnel within the dung pat and oviposit eggs in the manure or surrounding soil.  Most dung beetles found in NY are dwellers.

Currently, we are conducting a project under the leadership of Dr. Don Rutz in Veterinary Entomology at Cornell University where we are looking at the diversity of dung beetles in cattle pats in NYS. Many cattle are given an insecticide for fly control on pasture that are not always completely metabolized in the body and is dispelled into the manure pat, thus killing some dung beetles. This summer we are collecting samples of manure on pastures from organic and conventional dairy and beef farms and are looking at the difference in diversity and numbers of dung beetles.

What pest problems to consider when planting winter wheat?

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There are several factors to consider when planting winter wheat. The first is to never plant wheat in the same field two years in a row. By rotating you reduce the risk of several diseases like eyespot foot rot, powdery mildew, leaf rust, stagonospora nodorum blotch, glume blotch and more. The second item to consider is what winter wheat variety to plant. Of course you will look at potential grain yield, grain test weight and straw quality. It is also important to consider resistance to diseases in the varieties you select. Diseases of particular concern are wheat spindle streak mosaic virus, soil borne mosaic virus, yellow dwarf virus (formally called “barley yellow dwarf virus”), powdery mildew, leaf & stem rust and/or other disease problems your farm has had in previous years.  For a list of potential wheat varieties consult your Cornell Guide for Integrated Field Crop Management (available online at www.fieldcrops.org). Next, remember to plant AFTER the Hessian fly free date. By doing so, not only are you avoiding infestations of Hessian fly but also certain aphids that can transmit yellow dwarf virus. The following figure shows the “Hessian Fly Free Dates” in NYS:

The use of certified wheat seed should be considered. When seed is certified you can be confident of the quality and it is void of diseases and weed seed. Next is to remember to always use a fungicide seed treatment to protect the crop from certain seed and seedling related diseases. Another core consideration is having a sound fertility program. When a plant is healthy it can complete with weeds and may tolerate more insect pest pressure and still maintain good yield.

The Outlook for White Mold in Soybeans

Julie Dennis
NYS IPM

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Many of the soybean growing areas of the state have experienced dryer than normal conditions this growing season, leading to a lot of stressed stands.  The generally dry conditions during the early to mid stages of flowering in soybeans might have helped to curb outbreaks of the dreaded disease white mold, or Sclerotinia.  But it will be helpful to watch for disease symptoms from now until the plants reach maturity.

Highly productive, dense stands of soybeans favor white mold development. The fungus survives from year to year in the soil as hard black pellets called sclerotia. Sclerotia of white mold must be present to cause the disease, though a small number of sclerotia on the soil surface can lead to significant outbreaks if wet, cool conditions are present while plants are flowering. Under these favorable conditions, sclerotia will germinate and mushroom-like structures (apothecia) will form. The apothecia produce ascospores which spread by wind and splashing rain. Ascopsores require a nutrient source to grow, and soybean flowers serve as ideal locations. The fungus colonizes dead flowers and the characteristic thick white moldy covering on stems and pods develops (see photo below). Mixed in with the white mold on stems are the black sclerotia. Plants may wilt and die as a result of infection. If white mold infection occurs late in the season, yield loss will not be as severe. Temperatures over 90 degrees will typically stop disease development. During harvest, the sclerotia on stems and pods may end up in the soil or residue, or may stay with harvested seed.  Fields where white mold has occurred in the recent past are where it will most likely occur, so these are the fields to scout the most closely for disease development.

The following photo shows the white mold infection on a plant that is starting to wilt.

Photo taken by Mike Stanyard

A key to white mold management is to find strategies to prevent the build-up of the pathogen in a field. Rotation to crops other than soybean for at least 1 year (ideally 2 or more years) is recommended. Additionally, weed management practices that reduce weeds that serve as alternate host for white mold (for example lambs quarters and pigweed) will help to decrease build-up of the pathogen. It is also essential to avoid the planting of contaminated or infected seed, and to avoid the movement of infected soil with equipment. A strategy for preventing movement of infected soil is to harvest fields infected with white mold last. Varieties of soybeans that are tolerant or moderately resistant to white mold should be selected. Yield protection by spraying fungicides has not been documented in New York.

Check For Stalk Rots!

Ken Wise
NYS IPM

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It is important to monitor your fields for stalk rots as you start thinking of your corn harvest. If you have an infection of stalk rot it can cause the plant to die early losing grain or silage yields. Stalk rots are caused by many different fungi that enter the plant. They occur when the plant is under stress or when it may be injured by insect pests, hail, deer and bird damages, drought or soil saturation, lack of sunlight, extended cool weather, and the lack of fertility. The following are symptoms of specific stalk rots:

Anthracnose stalk rot symptoms may appear after tasselling as vertical, tan to reddish brown, water-soaked lesions (streaks) in the stalk rind. Lesions become large, dark brown to shiny black. Fields with high amounts of anthracnose leaf blight (both diseases have the same causal agent) should be checked for indications of anthracnose stalk rot.

Diplodia stalk rot symptoms may appear as numerous black pycnidia in the lower internodes of the stalk. The black dots are the size of a pinhead or smaller. When conditions are wet a white mold may develop on the stalk surface.

Fusarium stalk rot normally starts just after pollination and symptoms appear later in the season. When you cut open the stalk, the pith appears as a whitish to pink (salmon) color. There are also distinctive brown streaks on the lower internodes.

The first symptom of gibberella stalk rot is the onset of grayish-green color of the leaves. The stalk will turn dark green to tan near the base of the plant. The pith of the stalk becomes soft and will appear as a red to pinkish color.

Pythium stalk rot normally appears as a decay of the first internode above the soil. The pith will become soft, turn brown and appear water-soaked. Many times the stalk can twist and/ or lodge. Even though it may have lodged the plant will stay green for several weeks because the vascular tissue is not destroyed.

If you discover certain stalk rot diseases make notes of the hybrid, tillage methods, rotation history, and planting date. By doing this you be able to avoid the disease occurrence in the future. The following is the effectiveness of specific management practices for stalk rots:

Corn Disease
(Stalk Rots)
Resistant Variety
Crop Rotation
Clean Plow
Down of Residue
Fungicides
Anthracnose
1
1
1
4
All Other
2
3
3
4
1= highly effective, 2= moderately effective, 3=slightly effective, 4= not effective, 5 = not usually economical,
Reference: Purdue University Field Crops Pest Management Manual

As with most diseases that attack corn, if you can reduce stress on the plants you most likely can reduce the occurrence of certain stalk rots. Having a sound fertility program based on soil testing is important for keeping a corn plant healthy. Select a hybrid with resistance to certain diseases and good standability that is adapted to your region. Some of these stalk rots can produce mycotoxins that can be toxic to livestock. You should consider having silage tested for certain mycotoxins if you had fields with stalk rots this season. For more information on corn diseases checkout our online publication: IPM for Corn Diseases

Bean Leaf Beetles in NY

Julie Dennis
NYS IPM

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In August of 2006, bean leaf beetles were seen for the first time on soybeans in New York State.  We need to add this insect to our list of pests to watch for when we’re scouting.

What do bean leaf beetles look like?  They are usually yellow, and the characteristic markings are 4 black rectangular spots on the wing covers.  But there also is a red phase of the beetle, and sometimes the spots are indistinct.  They always have a small black triangle at the top of the wing covers.  There is a helpful photo showing the different color phases at the Iowa State website.

In the Midwest, bean leaf beetles (BLB) often are a significant economic threat.  The first generation of BLBs appear in early July, and if the populations build sufficiently, the second generation of BLB, appearing in August, can cause substantial pod damage. Yields may be reduced 20-50%.

While BLB will feed on soybean leaves, the primary economic injury results from feeding on pods. Pods may be clipped from plants, or injured areas on pods may serve as entry points for fungal pathogens, thus causing reductions in seed quality.

Thresholds in the Midwest vary based on soybean price and insecticide costs, but they range from 3.5 to 12 beetles per foot of row.  Last year, only a few beetles were observed per field, and minimal feeding injury occurred as a result of their presence.

Are there bean leaf beetles in the soybeans in your area??  Let us know!

Soybean Rust Update

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New York State Soybean Rust Information Center

Weekly scouting is being conducted in twenty New York State sentinel plots located in the following counties: Cayuga, Chautauqua, Chemung, Chenango, Columbia, Cortland, Jefferson, Monroe, Oneida, Onondaga, Ontario, Oswego, Otsego, St. Lawrence, Seneca, Steuben, Suffolk, Wayne, and Wyoming. Plant stages in these plots reported to date range from V-6 to R-3. Low to moderate levels of Septoria Brown Spot, Bacterial Pustule and Downy Mildew have been detected this week in some of these plots.

Nine counties in Texas were confirmed to have soybean rust this week as well as two counties in Oklahoma and one county in Arkansas.  To date in 2007, soybean rust has been detected in ten counties in Florida, five counties in Georgia and Alabama, six Parishes in Louisiana, twenty-three counties in Texas, one county in Mississippi and two counties in Oklahoma and Arkansas. There also has been a confirmed report of soybean rust earlier this year in Mexico in the state of Veracruz on yam bean (Pachyrhizus erosus). Weather conditions remain favorable for rust development in the southern U.S. as well as just north of the gulf states. (Updated August 3, 2007)

Soybean Aphid Update

Keith Waldron
NYS IPM

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NY sentinel site soybean fields 8.4-9.07.  Sentinel fields reporting R2-R3 growth stages, generally 15-24 inches or more.

Reports have documented an increase in SBA populations in Cayuga, Chemung, Columbia, Cortland, Monroe, Oneida and Seneca counties.  Numerous fields have exceeded the recommended threshold. Cayuga and Ontario counties report some fields treated earlier this season for SBA are again at or over threshold. North country soybean fields have had very little SBA activity this season, however numbers have begun to increase in the last 2 weeks. St. Lawrence county reported some fields reaching SBA threshold. Reports indicate SBA populations in Jefferson, Ontario and Wyoming counties still below the 250 SBA / plant threshold. While SBA populations have been increasing in a number of fields, we have also heard of SBA population crashes, most recently in Onondaga county. This week we received the first report of a soybean aphid in the Long Island soybean sentinel plot. Overall very few winged aphids have been reported. A few sites have indicated the presence of "white dwarf" soybean aphid types.

A number of those providing SBA information have reiterated the value of field by field monitoring as the most reliable means to identify local SBA problems. SBA populations have been found to vary, at times considerably, in fields on the same farm, neighborhood or county. I.e. More than one field observed to be above threshold has been found to have an adjacent field well below threshold, and visa versa. Bottom line? It's worth checking individual fields on regular basis...

Natural enemy populations vary across monitored fields. Beneficial insect numbers generally appear to be increasing since last week. High numbers of lady bugs, parasitized aphids, are syrphid fly larvae beginning to more numerous. Orius spp and predaceous stink bugs also being found.

Producers are advised to continue monitoring soybean fields closely for crop condition and growth stage, soybean aphids, other insects and natural enemies, foliar diseases, Phytopthora root rot and white mold.  Indications of a soybean aphid infestation can include stunting of plants, yellowing and misshaped or contorted leaves, an obvious presence of natural enemies such as ladybugs or ants in the uppermost canopy, and a charcoal gray discoloration of leaves indicating presence of sooty mold. During the period when the soybean crop is reproductive (i.e. flowering) in the R1 to R5 growth stages, the recommended SBA management guideline is: 250 or more aphids per plant and approximately 80% of the field is infested and populations are increasing. If fields reach the 250 SBA / plant threshold, resample fields within a week to re-evaluate the population level before taking action.

Thanks to: B. Aldrich/S. Woodard, P. Barney, J. Degni, J. Dennis, M. Dennis, K. Ganoe, N. Glazier, J. Lawrence, M. Hunter, J. Miller, M. Seagraves, M. Stanyard, B. Tillapaugh and K. Wise for sharing their soybean aphid observations.

For more on the current national Soybean aphid perspective see the USDA Public PIPE website.

Clipboard Checklist

Keith Waldron
NYS IPM

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General:
* Maintain crop production activity records by field, including harvest date, pesticides used, nutrient inputs including manure, etc.

Established Alfalfa & Hay:
* Monitor for crop growth and condition, potato leafhopper and nutrient deficiencies.
* Monitor for diseases, particularly Verticillium wilt, record information on type and location for future cropping decisions.

Alfalfa Seedings:
* Continue monitoring for potato leafhopper, weeds and diseases.
* Monitor fields for weeds and diseases: record information on type and location for future cropping decisions.

Small Grains:
* Watch grain moisture. Be ready to combine at 18 percent.
* Adjust combine in preparation for winter grain harvest (late-July) or spring grain Harvest (early to mid-August). Contract custom-operation if necessary.
* Clean grain storage areas.

Field Corn:
* Monitor for crop growth and condition, European corn borer, armyworm, foliar and stalk rot diseases, vertebrate damage, nutrient deficiencies.
* Monitor corn rootworm adults at silking.
* Observe corn for weeds and fertility

Soybeans:
* Monitor for crop growth and condition, soybean aphids, and other insects, including bean leaf beetle and natural enemies such as ladybird beetles, vertebrate damage, nutrient deficiencies.
* Monitor for diseases including white mold, Phytopthora root rot, foliar and stem diseases.
* Check droughty fields for presence of spider mites

Livestock:
* Continue confinement areas sanitation activities and release of biological control agents (parasitic wasps) for house fly and stable fly management in dairy facilities
* Monitor young stock for cattle lice and mange mites
* Check condition of pastures and animals on pastures
* Evaluate need for face fly, horn fly and stable fly control measures for animals on pasture
* Check and clean pasture water supplies.

Equipment:
* Note any repairs to harvesting equipment as they are cleaned and lubricated.
* Repair forage harvest equipment as needed
* Ready combine for small grains or finalize arrangements for custom harvest

Contact Information

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