Weekly Field Crops Pest Report 2008

View from the Field

Ken Wise
NYS IPM

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Joseph Lawrence ( Lewis County) and Mike Dennis ( Seneca County) report corn rootworm root pruning and goose-neck lodging damage in corn. REMEMBER, pollination is the prime time to scout for corn rootworm in field corn.

Potato leafhopper populations appear to remain low statewide. I have seen a lot of pea aphids in alfalfa. The good thing is that pea aphids generally are not a problem on alfalfa in NY. We have a lot of biological control agents that keep the population in check. There are several diseases, predators and parasitoids that all attack aphids in alfalfa.

Most of the soybean fields I have scouted this week look good. One exception is a field in Columbia County that has drainage issues and possible round-up herbicide damage. I have seen a few foliar diseases including bacterial blight, bacterial pustule and frogeye leaf spot in the lower portion of soybean canopies. I also saw on a few upper leaves what appears to be Cercospora leaf blight.

Weather Outlook

Leon Nguyen
NOAA NE Climate Center, Cornell

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Temperatures last week were slightly below normal across much of the state of NY.  A significant amount of rain fell across the state, with more than 4 inches falling in the mid-Hudson Valley.  The New York City and Long Island areas received anywhere from 2-3 inches of rain, while Central NY remained relatively dry with less than an inch.

Across Southeastern NY and Long Island, over 150 base 50 GDD accumulated last week.  About 125-150 GDD accumulated over much of Central NY, while the Adirondacks picked up less than 100 GDD.  Since March 15th, over 1600 GDD have accumulated over Southeast NY and Long Island, while only 800-1000 GDD have accumulated over the Adirondacks.  The rest of the state ranged from about 1100-1500 GDD.  Much of the state has accumulated more GDD than last year.  The 2008 accumulation is about a week ahead of the long-term normal.

A low-pressure system located in southern Quebec will give much of New England a chance of rain and thunderstorms today.  Once this system passes, a dry day will be in store Friday before the next storm arrives on Saturday, bringing another chance of thunderstorms.  The best chance for heavy rainfall amounts appears to be in parts of Northern New England, although thunderstorms will result in areas of locally heavy rainfall amounts in NY.  There may be a few lingering showers on Sunday, especially in the eastern half of the state, but Monday should be a dry, tranquil day for all of New York.  The next storm system appears to move in on Tuesday, bringing yet another chance of thunderstorm activity.

Temperatures should be generally slightly below normal over the weekend, warming to slightly above normal heading into Tuesday and Wednesday of next week.   Beyond mid-week, a trough is expected to persist across the Northeast, bringing generally below-average temperatures and some rainfall chances.

What pest problems to consider when planting winter wheat?

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Planting winter wheat is just around the corner. 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.

Corn Silks and Beetles

Ken Wise
NYS IPM

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Every year I see two kinds of beetles feeding on corn silks: corn rootworm beetles and Japanese beetles.  I have been asked many times “Does this feeding by beetles reduce pollination of corn?” Generally, these beetles do not affect pollination of corn. Corn rootworm beetles prefer to eat pollen. The corn plant can produce enough pollen to pollinate the ear of corn and still have plenty left over for the corn rootworm beetles.

In New York, the feeding of the adult beetles on silks can occasionally be a problem. Clipping of the silks can prevent pollination, resulting in poorly filled ears. If 10 or more adults are found per plant at silking, less than 50 percent of corn silks are brown, and silks <0.5 inch long, treatments to control adults may be warranted, and pollination has not yet occurred, apply an insecticide (see: www.fieldcrops.org, Table 3.6.1).

The good thing is that even a damaged silk can still receive pollen and will fertilize the ear. Reduced fertilization can only occur when the silk is clipped to less than a ˝ inch long before pollination.

Japanese beetles also like to feed on the silks of corn. I have seen up to 8 or 9 on one ear of corn. The thing with Japanese beetles is that they prefer to feed on browning silks. When the silk has turned brown the ear of corn has already been pollinated. Japanese beetles also clump in certain areas of the field. Many times this is along edges and not the rest of the field.

Japanese Beetles on Feeding on Silks

Soybean Rust Update

Gary Bergstrom
Cornell University

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Sentinel plots in New York State have been established in the following counties: Cayuga, Chautauqua, Chemung, Columbia, Cortland, Jefferson, Lewis, Madison, Niagara, Oneida, Ontario, Schoharie, Seneca, Steuben, Wayne and Yates. Plant growth stages in these plots range from V-2 to R-3. Low levels of bacterial pustule, downy mildew and Septoria brown spot were detected in a few of the sentinel plots last week.

Soybean rust was reported on soybean in Baldwin County, Alabama late last week. This is the first detection of rust on soybean in Alabama in 2008. Previous detections in this state were on kudzu.

Since the beginning of 2008, soybean rust has been reported on kudzu in two counties in Alabama; one county in Georgia, sixteen counties in Florida (two of these counties had reports on coral bean and snap bean and one had a report on soybean); three counties in Louisiana; one county in Mississippi, and three counties in Texas. Reported infected kudzu sites in many counties have been destroyed. Rust was also reported in three states (5 municipalities) in Mexico on yam bean and soybean. These too have been destroyed or are no longer active. (Updated July 28, 2008)

Soybean Aphid Update

Keith Waldron
NYS IPM

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No soybean aphid issues have been reported in NY so far this season.

Crop Growth Stage - V-10 to R-4

Soybeans are in reproductive growth stages in most areas reporting. Soybean heights vary from 12 inches to 30 plus inches tall.

Observation and Outlook - Insect

Soybean aphid (SBA) populations remain low across areas reporting in NY. SBA's are present in many (but not all) locations reporting from across the state, generally averaging 0 to less than 5 SBA's per plant. Occasionally individual plants may have higher numbers. All fields reporting well below threshold. Natural enemy populations, such as ladybird beetles, are present and increasing in many areas. Field monitoring continues to be hampered by frequent storms.

The national soybean aphid commentary (7.28.08) mentions southern Minnesota fields are nearing or over threshold. The production and emigration of winged migrants from this area is likely. Possible impacts on soybean aphid populations in NY remains to be seen.

Scouting and Management - Growers are encouraged to monitor for presence of soybean aphids, other insects and diseases. Fields entering the blooming stages should be monitored closely for SBAs, foliar diseases and white mold.

While localized soybean aphid problems have occurred in recent years, the low numbers of aphids being reported across NY so far this season continues to support close inspection of fields as a source of objective information on which to base potential insecticide use decisions. There have been some recent reports of fields being treated with insecticides for soybean aphid, some fields sprayed had also been planted with an insecticide applied to the seed. Some insecticides have been added to herbicide or fungicide applications.

As soybean fields enter their reproductive phase of development, growers should evaluate the actual need for the insecticide based on a soybean aphid population assessment. Fortunately, soybean aphid population assessment is fairly easy. The national soybean aphid management recommendations, including the recommended soybean aphid action threshold, follow.

National Soybean Aphid Management Guidelines

Emergence to Vegetative

During the period when the soybean crop is in the emergence to vegetative (not reproductive, i.e. no flowers) growth stages, current research data has shown that spraying will not result in an economic return. Although uncommon, soybean aphids have reached threshold during the vegetative stage in some regions.

R1 to R5 growth stages

- During the period when the soybean crop is reproductive (i.e. flowering) in the R1 to R5 growth stages, an insecticide application may be necessary when 250 or more aphids occur per plant and approximately 80% of the field is infested and populations are increasing. Sequential scouting in the same field is necessary in order to determine if populations are increasing. Comparing SBA counts over a week or more is necessary.

- The data scale chosen also potentially corresponds with input of speed scouting information. For more information on the University of Minnesota speed scouting program visit http://www.soybeans.umn.edu/crop/insects/aphid/aphid_sampling.htm . The speed scouting protocol differs from the soybean aphid sentinel plot protocol, but collection of this mobile data is also possible.

- Always read, understand, and follow pesticide label recommendations.

- Please follow your state's insecticide guidelines for more information on pesticide use.

- Insecticide applications should only be considered when needed according to the pest population status.

- Tank mixing with fungicides is not recommended unless soybean aphids have reached threshold requirements mentioned above and spraying for soybean rust treatment is also recommended by your state extension plant pathologist.

- Unnecessary pesticide applications may increase pest problems by adversely affecting beneficial insect natural enemy populations.

R6 growth stage

A higher threshold is required for economic return during the R6 growth stage, but no threshold data is available at this time. If treatment options are considered, ensure pre-harvest intervals of the insecticidal product chosen are met prior to application.

R7 growth stage and later

During the R7 and R8 growth stages, there is no economic return on insecticidal applications.

(For more information see: Management Toolbox - Guidelines - USA)

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, yields, etc.

* Watch for weed escapes, any patches of herbicide resistant weeds?

Field Corn:

* Check crop growth stage and condition

* Check for European corn borer, armyworm, foliar diseases, vertebrate injury (birds / deer), weed escapes, herbicide injury, nutritional deficiencies, etc.

* Pollinating corn - check corn rootworm populations

* Monitor weed populations noting presence of "who", "how many" and "where"

* Check herbicide resistant corn fields for herbicide resistant soybean

* Adjust post emergence weed control actions

* Note any differences between Bt hybrids and non-Bt refuge portions of fields

Small Grains:

* Evaluate standing crop for timing grain and straw harvest, evidence of sprouting (wheat)

* Storage areas cleaned and ready to accept next harvest?

Alfalfa & Hay:

* Monitor alfalfa seedings for weeds, potato leafhopper & diseases.

* Check established alfalfa stands for potato leafhopper, weed and disease problems.

* Storage areas cleaned and ready to accept next harvest?

Soybeans:

* Check crop growth stage and condition

* Evaluate stand for soybean aphid, spider mites, deer, weed assessment, foliar disease incidence

* Check herbicide resistant soybean fields for herbicide resistant corn

Dairy Cattle: Livestock Barn Fly Management:

* Monitor animals and facilities for house fly and stable fly populations

* Check facilities for favorable fly breeding conditions: (organic matter + moisture): leaks in watering systems, roof gutters for leaks and potential overspill, drainage,

* 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 * Continue fly monitoring: install "3X5" index card fly speck monitoring cards through out barn

* Order fly management materials: fly tapes, insecticide baits, natural enemies (parasitoids)

* Continue release of purchased natural enemies (fly attacking parasitoids)

Dairy Cattle: Pasture Fly Management:

* Monitor animals for presence of face flies, horn flies and stable flies.

* Check feed bunk / water source locations for signs of stable fly breeding (moist undisturbed organic matter (spilled feed, round bales, etc.) , minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard

* Check paddocks for forage quality / quantity, rotate as appropriate

* Check paddocks for vegetation poisonous to livestock

* Consider use of fly traps to help reduce deer, horse and stable fly populations

Storage:

* Pre-clean in and around grain bins before adding newly harvested wheat.

* Keep areas around storage bins and silos clean and mowed

Equipment:

* Note any repairs needed for recently used equipment: tractors, tillage implements, harvesting equipment, etc. as they are cleaned and serviced.

* Calibrate manure spreaders - maintain records on amount spread per field

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