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Weekly Field Crops Pest Report 2008

April 24, 2008                 Volume 7 Number 2

1. View from the Field

2. NYS Weather Outlook

3. “New” Corn Herbicides for 2008

4. Potato leafhopper (PLH)-Resistant Alfalfa Varieties - To Plant or Not to Plant - Spring 2008

5. Hessian Fly in Winter Wheat

6. Foliar Early Season Fungal Diseases of Wheat and Other Cereal Grains

7. Looking for Cornell Pest Management Guidelines on-line?

8. National Asian Soybean Rust Report (April 20th)

9. Clipboard Checklist

10. Up-coming Events

11. Contact Information

View from the Field

Eastern NYS-Ken Wise

Western NYS- Julie Dennis

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Eastern NYS
Farming is moving right along in Eastern NYS. Many fields have been plowed since the weather has been ideal! In Tom Kilcer's triticale plots I have seen what appears to be a foliar disease, possibly Septoria tritici or Stagonospora nodorum blotch. More information on wheat foliar diseases appears in the article below. In clover and alfalfa I picked up a few pea aphids and tarnished plant bugs in the sweep net. There were also several alfalfa and clover plants heaved out of the ground due to a combination of root diseases and frost heaving. Elson Shields reports alfalfa snout beetle emergence has begun in some northern counties including southern and northern Jefferson county. ASB emergence is expected this week in St Lawrence & Franklin counties, although emergence may be delayed a couple of weeks due to cooler soil temperatures. Joe Lawrence in Lewis County reports alfalfa snout beetle emergence and an alfalfa field showing symptoms of brown root rot.

Western NYS
Mike Stanyard reports many northwestern NY growers are applying herbicides for weed control to their wheat and alfalfa. He states the henbit, chickweed and purple deadnettle are now blooming. Nate Herendeen discovered adult alfalfa weevils in western NY alfalfa this week. He suggests watching closely for alfalfa weevil eggs laid in new alfalfa growth over the next week or so.

NYS Weather Outlook

Art DeGaetano - Director, NE Climate Center

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A large high pressure system dominated the weather across NY last week, steering precipitation south of the state and boosting temperatures to well above normal levels.  For the week most locations saw no rain (up to 0.5 inches fell in scattered thunderstorms across central NY Wednesday evening), while temperatures across the state averaged 15 -18 degrees above normal.  Over the last 30 days precipitation has been 50-70% of normal across upstate.  Farther south (Long Island and NJ) only 25-50% of the normal precipitation has fallen

Big changes are in store for next week as a trough sets up over the Northeast and a persistent upper level low will dominate the weather through Tuesday .  A rainy day on Saturday will be followed by a dry Sunday, before a showery period follows Sunday night through Tuesday.  As much as an inch of rain will fall through the weekend.
Temperatures will turn sharply colder Monday through Wednesday (about 10 degrees below the normal high of 60).  Snow showers will be a good possibility Monday and Tuesday as nighttime temperatures fall below freezing.

Beyond Wednesday temperatures will slowly return to normal by early the following week as the trough departs and a ridge moves east from the Ohio Valley.  This later period is also expected to be dry under the influence of the high pressure.

“New” Corn Herbicides for 2008

Russ Hahn, Department of Crop & Soil Sciences, Cornell University

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NY field corn producers should be aware of several “new” herbicides they may want to consider for the 2008 growing season and beyond:

Impact from AMVAC is registered for use on both field and sweet corn.  Corn growers are likely familiar with another herbicide, Callisto, with the same site-of-action.  While Callisto can be used both preemergence and postemergence (POST), Impact is for POST use only from the spike stage of corn up to 45 days prior to harvest.  Impact has excellent activity against many annual broadleaf weeds including velvetleaf, pigweed, common ragweed, common lambsquarters, and wild mustard.  It also provides significant burndown against annual grasses like giant foxtail and large crabgrass.  The normal application rate is 0.75 fl oz/A, and the spray solution must include MSO (methylated seed oil) or COC (crop oil concentrate) and a nitrogen fertilizer source such as UAN (urea ammonium nitrate) or AMS (ammonium sulfate).  For best performance, Impact should be tank mixed with 0.25 to 1 lb ai/A of atrazine.  Small grains can be planted 3 months after application while alfalfa, soybeans, and several other crops can be planted after 9 months.  The rotational interval for many other crops is 18 months.

Status from BASF is registered for field corn but not sweet corn.  Dicamba, one of the active ingredients in Status, is also the active ingredient in Banvel and Clarity.  Each of these products has activity against a wide variety of broadleaf weeds.  Dicamba is rapidly absorbed by foliage and roots and readily moved throughout plants.  It accumulates in growing points causing uncontrolled growth and plant death.  A second active ingredient in Status, diflufenzopyr, blocks movement of dicamba away from growing points and increases the activity of the dicamba.  Status also includes a safener for dicamba on corn.  This safener should minimize concerns about the types of adjuvants and tank-mix partners used with Status.  Status can be applied to field corn from 4 to 36 inches tall at rates of 5 to 10 oz/A.  Adjuvants must be used with Status.  Best results are achieved by combining a NIS (non-ionic surfactant), MSO, or COC with UAN or AMS.  If at least 1 inch of rainfall is received following application of 5 oz/A or less, alfalfa, small grains, and soybeans can be planted 30 days after the rainfall event.  Results from comparisons we’ve made in NYU suggest that Status may not consistently provide better weed control than Banvel or Clarity.  In addition, Status is more costly than Banvel or Clarity and requires the use of spray additives.  Unless corn injury is a concern, growers should proceed with caution until additional research is completed with Status.

Halex GT from Syngenta combines residual herbicides with glyphosate in a single product for use in glyphosate-resistant corn.  This new product, which is available in bulk only, combines glyphosate for control of emerged weeds with Dual Magnum and Callisto for residual annual grass and broadleaf control.  In addition to providing residual activity against a broad spectrum of weeds, this premix provides three different site-of-action (ways of killing weeds) classifications.   The label shows that Halex GT contains herbicides from Groups 15 (Dual Magnum), 9 (glyphosate), and 27 (Callisto).  With multiple sites-of-action, this product simplifies efforts to prevent development of herbicide-resistant weed populations.  The label allows for the addition of atrazine with a fourth site-of-action (Group 5).  In fact, Halex GT use guidelines encourage the addition of atrazine if broadleaf weeds are greater than 4 inches tall.  Halex GT should be applied at 3.6 to 4 pt/A from corn emergence up to 30 inches in height and should be applied with NIS and AMS.  Small grains may be planted after 4 months, and alfalfa and soybeans after 10 months.

Potato leafhopper (PLH)-Resistant Alfalfa Varieties - To Plant or Not to Plant - Spring 2008

Julie Hansen, J. Keith Waldron, and Don Viands

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Potato leafhoppers (PLH) are perhaps the most widespread and damaging insect pests of alfalfa in the NE, causing risk to new seeding establishment and survival, and to established stands during mid-to-late summer.  When high populations of PLH are not controlled during the establishment year, large reductions in alfalfa yield and quality can occur.

Risk from this migrating insect pest can vary greatly year to year but it is reasonable to assume that an alfalfa field could be at significant economic risk at least once during it's years in stand. To minimize risk and avoid economic impacts growers are encouraged to monitor crops frequently and, when PLH populations warrant, harvest the forage early or treat with a properly labeled insecticide.

PLH resistant alfalfa varieties are very effective at minimizing risk of PLH induced damage. A common question remains: Do the PLH-resistant alfalfa varieties yield as much as conventional alfalfa varieties when PLH are not a problem?

It is certainly true that the PLH resistant alfalfa varieties initially released a decade ago did not yield as much as conventional alfalfa when PLH were not at damaging levels.  This has been attributed to 'yield drag', where the PLH resistance trait from an unimproved, wild alfalfa species when bred into conventional alfalfa brought along some other traits of the wild alfalfa species such as more fall dormant and winter hardy, less upright growth habit, yellow flowers, less disease resistance, and lower yield.  Plant breeders now have 10+ years of selection behind them for alfalfa that is resistant to PLH that does not have the 'yield drag' characteristics.  Thus, the new PLH-resistant alfalfa varieties are now very similar to conventional alfalfa in all aspects other than PLH-resistance including disease resistance.  However, while breeders were doing 'catch up' breeding with PLH-resistant alfalfa, they were also continuing their selection programs with conventional alfalfa to improve yield, forage quality, persistence, etc.  Thus it is not unreasonable to think that some of the conventional alfalfa varieties on the market would out yield the PLH-resistant varieties in tests where PLH were controlled.

Decisions to plant PLH-resistant or conventional alfalfa should consider how the crop will be managed for this insect pest. Is the alfalfa being grown as organic? If so PLH resistant alfalfa is an obvious choice. For the conventional grower, will your alfalfa fields be scouted every year for PLH and sprayed in a timely fashion when PLH damage reaches an economic threshold?  If the answer is yes, then that producer should plant the highest yielding conventional alfalfa variety he or she can find.  If the answer is no and the fields are not managed to reduce losses from PLH damage, then planting a conventional alfalfa variety will result in lower yields and reduced profit.

Both conventional alfalfa and PLH-resistant alfalfa varieties will yield more when insecticides are applied to control threshold levels of PLH than when insecticides are not applied. The PLH-resistant alfalfa varieties still support a population of PLH, although this population is smaller (a third to a half) than for a conventional alfalfa variety.  This smaller population of PLH adult and nymph insects still feed on the PLH-resistant alfalfa and reduce yield somewhat although the plants do not readily turn yellow and are not stunted.
There are some other tidbits of information that may help when deciding whether to plant PLH-resistant alfalfa or conventional alfalfa. Seed costs of PLH-resistant and conventional alfalfa varieties are comparable.  If a producer prefers an aggressive cutting schedule, such that the PLH populations do not have time to build up between harvests (life cycle of PLH is about 1 month), then a PLH-resistant variety may not be that advantageous.  However, in the seeding year, the field would certainly need to be sprayed with insecticide because the new seeding would likely not be cut until sometime in July, well after PLH arrive in NY each year.  It has been documented that if is severely damaged by PLH in the seeding year, the alfalfa will yield less at first harvest the following year.

With current high costs of pesticides, fuel, and all petroleum based products, economics may tend to favor PLH-resistant alfalfa even more now than in the past.  A producer would avoid expense of extra passes across the field and pesticide.  In a bad PLH year or a year with heavy PLH damage to alfalfa crops.  In a year with high PLH population pressure it may pay to spray such that extra yield would be gained, but fortunately here in NY we don't have heavy PLH damage every year and sometimes yield loss can be avoided by early harvests.  Avoiding insecticide applications through the use of PLH-resistant alfalfa varieties will also allow beneficial insects, including bees, to thrive in fields.

Some recommendations include spraying PLH-resistant alfalfa in the seeding year, however if the new alfalfa fields are planted by early May, the PLH-resistant alfalfa plants will have developed the resistance traits by the time PLH arrive in NY in early to mid June.  Late planting of alfalfa fields is risky, and will likely need to be sprayed with insecticide to protect both conventional and PLH-resistant alfalfa seedlings from severe PLH damage.

First decide how you plan to manage your forage crop, and then decide what variety best fits that management system.

Hessian Fly in Winter Wheat

Julie Dennis, NYS IPM

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The careful observance of Hessian fly-free dates combined with the planting of resistant varieties has put this once destructive pest on the list of difficult to spot insects, thankfully. However, Hessian flies have been detected in Indiana, Missouri, and Oklahoma in the past couple of years.

If wheat was infested last fall, scouting this spring will reveal stunted, dark green plants.  Another tell-tale sign is that stems of infested plants are thickened. Look for larvae or pupae tucked in to the tight leaves around the base of the plant.  The pupa has the characteristic “flax seed” appearance.

Hessian fly pupae spend the summer in the stubble of the current year’s wheat crop.  The “fly free date” is based on when, historically, most adult flies will have emerged and died. If there is not yet a fall wheat crop emerging, egg laying females will not find host plants on which to lay eggs. 

Keeping track of when and where infestations of Hessian fly occur is of interest to researchers and other farmers. Please alert your local cooperative extension educator if you find an infestation.

Planting winter wheat crops after the Hessian fly free date is common practice, especially since this practice also decreases the risk for other disease and insect pests, particularly aphids which may transmit yellow dwarf.  When planting winter wheat as a cover crop, Hessian fly free dates may be overlooked given that growing a harvestable grain crop is not the priority.  However, planting cover crop wheat after the fly free date remains important.  In some areas of the country, entomologists speculate that Hessian fly populations may be building up in areas because of the planting of wheat as a cover crop before the Hessian fly free date.

Foliar Early Season Fungal Diseases of Wheat and Other Cereal Grains

Ken Wise, NYS IPM

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Stagonospora nodorum blotch: I have seen what appears to be Stagonospora nodorum blotch on triticale at the Cornell Research farm in Valatie this spring. Splashing rain or thunderstorms can move spores from soil surface on to the plant. This fungal pathogen may also reside in residue on the field surface. In wheat, greatest yield losses occur when the flag leaf and the next two lower leaves become infected by the time the wheat flowers in late May. Leaf lesions begin as very dark brown flecks or spots, sometimes with a yellow halo. These small irregular lesions expand into oval light brown lesions with dark brown centers. As lesions enlarge, they become dark brown and the centers turn grayish-white in color as tiny brown or black dots (pycnidia) develop within them.

Powdery Mildew: While I have not seen powdery mildew this year, it is a common disease of cereal grains in NYS. Powdery mildew forms a white to gray, fungal coating on the above-ground parts of the wheat plant. Lower leaves are usually the most severely infected because of the high humidity in the lower canopy. As disease lesions age, small black fruiting bodies (cleistothecia) develop with in white infected areas. Powdery mildew is favored by wet and humid days with moderate temperatures of 600 F or above. Powdery mildew is disseminated by airborne spores.

Leaf Rust: Leaf rust does occur in NYS and is commonly found in Late April through June.  Rust lesions are small, circular, and vivid orange in color. They may occur on stems, but are most common on the upper surface of leaves. Leaf rust is favored by warm and humid weather with thunderstorms in June. Leaf rust is disseminated on by winds which carry the airborne spores great distances. Temperatures between 600 and 800 F are optimal for disease development.

Thresholds and Management

Thresholds for foliar fungal diseases of wheat are based on potential yield and the level of infection of the disease in the field. For Economic Thresholds and making decisions on fungicides please refer to the 2008 Cornell Guide For Integrated Crop Management On-line, or more specifically: 5.7.4 Guidelines for Wheat Fungicide Decisions.

Looking for Cornell Pest Management Guidelines on-line?

Keith Waldron

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See Cornell Guidelines for Pest Management for your one stop Cornell guidelines information connection. This website has links to all Cornell Pest Management Guidelines On-Line including: Berry Crops, Field Crops, Floral and Greenhouse Crops, Grapes, Herbaceous Perennials, Livestock, Pests Around the Home, Tree Fruit, Trees and Shrubs, Vegetable Crops and Wildlife Damage Management.

Cornell Guide to Integrated Field Crop Management

National Asian Soybean Rust Report (April 20th)

Gary C. Bergstrom-Cornell University

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On April 19th, a trace amount of soybean rust was found on the new growth of kudzu at a kudzu sentinel site in Polk County in eastern Texas. The disease was first detected at this site in January, but was no longer found in late March. Outside of Texas the disease is still active on kudzu in six counties in Florida. Soybean sentinel plots are being established throughout the Gulf Coast region. Kudzu is also greening-up rapidly in this area of the country.

NYS Soybean Rust Information Center

National Soybean Rust Website

Clipboard Checklist

Keith Waldron

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*Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks.
*Observe wet areas and plot on aerial photo of farm for future drainage considerations and crop decisions
*Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
*Watch for early season weeds: winter annuals: chickweed, henbit, purple deadnettle, field penny cress, shepherd's purse; annuals: giant ragweed, lambsquarters, Pennsylvania smartweed, common sunflower

Alfalfa and Small Grains:
*Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)
*Monitor alfalfa for alfalfa weevil as weather continues to warm
Evaluate established legume stands for winter damage (thinning stand, frost heave, Brown Root Rot), determine average alfalfa stand count, adjust crop plans if necessary
*Monitor winter grain fields for over wintering survival, virus disease symptoms, weed pressure, goose damage

*Pre-plant weed evaluation
*Prepare land for corn if it is dry enough and begin planting the last week of April if it is dry (even if it is cold!)

*Check and mend fences as needed.
*Check crop growth
*Review/Plan rotation system

*Arrange for custom weed control or check your own application or cultivator equipment for repairs.
*Check nozzles, pumps, etc., recalibrate pesticide application equipment regularly before use.
*Check/tune up corn planting equipment
*Calibrate planting equipment - maintain records on crop planting rate per field
*Calibrate manure spreaders - maintain records on amount spread per field

*Check forage allocation and anticipate feed program adjustments as forages from previous year are used up
*Plan where forages should be stored for optimum allocation next feeding season

Upcoming Events

Small Grains Field Day
June 5, 2008
Cornell Research Farm at Aurora, NY

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

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