Weekly Field Crops Pest Report 2006

View From The Field

Eastern NYS
Ken Wise, NYS IPM

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Western NY and Finger Lakes
Julie Stavisky, NYS IPM

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This week at the Cornell University Research Farm in Valatie potato leafhopper population were very high. In a second year field I got 120 potato leafhoppers in 3 sets of 10 sweeps. The alfalfa plants are showing the typical v-shaped yellowing at the tips of the leaflets that indicates PLH damage. By contrast, PLH populations at the SUNY Cobleskill Farm remain very low, i.e. 1 or 2 leafhoppers/10 sweep sample in 24 inch alfalfa.

While scouting the soybean sentinel plot in Columbia County I found a few plants with soybean aphids (SBA) on them. The aphids were hard to find and only 5 of 50 plants inspected had aphids (1-8 sba’s per plant) on them. I scouted the rest of the field and found a few more plants with aphids but still well below economic threshold of 250 SBA’s/plant. I did find this plant (see photo) with ants tending the aphids. The ants protect the aphids from predators and in turn the ants eat the aphid’s honeydew secretion.

There were also some Japanese Beetles feeding on the soybean leaves. While beetle feeding can be conspicuous, plants can generally tolerate up to 40 % damage and not affect the yield. (See article below)

Jeff Miller (Extension Educator: Oneida County) discovered a field infected with Glume Blotch which is the same disease that is called Stagonospora Nodorum Blotch on the leaves. On wheat heads the lesions begin as either grayish or brownish spots on the chaff, usually on the upper third of the glume. 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.

Across western NY and the Finger Lakes, it has been a dull week for soybean aphids and an active week for potato leafhoppers.  Fortunately, soybean aphid numbers have been below 75 aphids for plants from all reports that I have heard and observations that I have made.  These encouraging observations come from soybeans (mostly at or close to R1 growth stage) in Wyoming, Wayne, Seneca, Ontario, and Onondaga counties.

Potato leafhopper (PLH) is a different story.  Last Friday in Cattaraugus County, we swept an alfalfa field at a TAg team meeting, and the field was close to threshold.  Some yellow V-shaped areas on leaf tips were already visible.  Harvest was just a day or 2 away, so treatment with an insecticide was not necessary.  Nancy Glazier made similar observations at the farms participating in the Yates County TAg team.  In particular, new seedings were under severe threat from PLH.  One field that was 18 to 24 inches tall and close to being cut had over-threshold numbers of PLH.  On the same farm, two alfalfa fields - one planted to PLH resistant alfalfa, the other non-resistant.  Interestingly, the same numbers of PLH were observed, but visual symptoms of damage were considerably less in the PLH resistant alfalfa.  In other PLH news, Nancy observed only very few PLH in alfalfa (first re-growth) in Livingston County. In Onondaga County, I also saw few PLH in a mixed alfalfa/grass stand.  For a review of PLH thresholds and the sequential sampling plan, check out our brochure Potato Leafhopper on Alfalfa Management Guide.

One field in Livingston County had numerous leaf blotch miners, approximately 30-40% of the tips mined. Generally this insect pest does not do much damage to alfalfa. Much of the recommendation for other states suggest that the economic threshold for this insect pest is right around 50% of the leaflets showing the serpentine trails where the larvae has feed on the cells just under the epidermis of the leaf. See picture below:

Fusarium Head Blight of Wheat - Considerations for Harvest-time

Julie Stavisky, NYS IPM

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Last week at the Cornell Seed Growers Field Day, Gary Bergstrom reviewed for us the serious situation of wheat scab infestation occurring across the wheat-growing areas of NY.  We reviewed scab in an article earlier this season, and you may want to visit the Wheat Scab Prediction Model website.

Wheat scab reduces yield by decreasing the number of viable kernels and reducing test weight, but the more significant impact is that the fungus in diseased kernels may result in the production of a mycotoxin known as DON, or vomitoxin. A wheat head showing the salmon/orange colored spores that indicate Fusarium head blight (scab) infection is shown below.

Gary reminds us that it is critical for farmers to be scouting their fields now, before harvest, to determine if wheat is heavily infested. An infected head of wheat will have “tombstoned” kernels (those that are small and shriveled), or chalky white kernels.  Seeing a salmon-pink color on the heads is another sign of infection.  Free testing of wheat for the vomitoxin is available at The Star of the West Mill in Churchville, near Rochester.  If scab is present in a wheat field, Gary recommends turning up fans on the combine to blow out small, lightweight kernels, and taking measures to clean the wheat.

Why use Potato Leafhopper Resistant Alfalfa?

Ken Wise, NYS IPM

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Have you had problems with potato leafhoppers (PLH) in your alfalfa? You know that large infestations of PLH in alfalfa can reduce the plant protein by 5% and yield by a half ton per acre per cutting. If you see V-shaped yellowing on the tips of the leaves you have a good chance potato leafhopper has been in your alfalfa. If V-shaped yellowing has appeared you have already lost protein and yield, plus the alfalfa will have slower re-growth after harvest and increased chance of winter kill. A good option for reducing losses to this insect pest is to plant PLH resistant alfalfa. Research has shown that potato leafhopper resistant alfalfa is consistently higher in quality than susceptible cultivars with or without potato leafhopper pressure. The benefits of PLH resistance are particularly obvious in years with high PLH infestations, a situation that can be expected at least once or more during the life of the typical alfalfa stand. Some of the most recent releases of PLH resistant alfalfa are as high as 85 percent resistant. (Note: a “ highly resistant” cultivar is 50% or more of the plants are resistant.) The newer potato leafhopper resistant varieties have comparable yields as susceptible alfalfa. You will still need to monitor this alfalfa because resistant does not mean that it is immune to the pest. In the first 3 to 4 weeks the young plants have not developed their resistance to PLH. The resistance is the granular hairs that grow in the surface of the leaflets. In the young plants these hairs do not become fully functional until about a month of growth. For management information check out our on-line IPM guide IPM for Potato Leafhopper in Alfalfa.

Soybean Aphid Update

Keith Waldron, NYS IPM

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Statewide monitoring for soybean aphids is being conducted through volunteer efforts by many individuals participating in New Yorks’ Soybean rust sentinel site network. These individuals provide weekly summaries of their findings. These reports and input from other cooperative extension, crop consultant and agricultural professionals working with soybean producers are summarized and posted to the USDA soybean rust / soybean aphid website.

Soybean aphid populations have been slowly increasing but have typically been at low to trace levels at most locations reporting across the state. No economically significant populations have been reported in any NY soybean fields so far this season. SBA populations can be expected to increase in the next weeks should warm temperatures continue. A few reports indicate finding winged soybean aphids. Natural enemy populations such as lady bird beetles have begun to increase in many areas. Fields are generally at the V6 to early reproductive stages.

Soybean Defoliators: Do They Do Damage?

Ken Wise, NYS IPM

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Japanese beetle and Mexican bean beetle are the main defoliators of soybeans in NYS. While they are minor pests, defoliation of soybeans sends up many red flags by growers. The question normally is how much leaf defoliation is too much in soybeans? The good thing is that soybeans can withstand much defoliation without losing yield. The soybean defoliation threshold is 35 percent of leaf are eaten or missing from V1 to just before bloom. During blooming through pod-filling stages, the threshold is 20 percent defoliation. The following pictures are a guide that depict 10, 20, 30 and 40 percent defoliation:

(Source: Purdue University Field Crops Pest Management Manual, 1/92)

Barn Fly Populations on the Increase

Keith Waldron, NYS IPM

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Warm temperatures and summer rains provide two ingredients that can lead to a rapid increase in house and stable fly populations - heat and moisture. Add undisturbed organic matter such as spilled feed / silage, straw or soiled bedding and conditions are quite favorable for a potential booming increase in house and stable fly populations.

The Cornell Veterinary Entomology summer research crew (Colleen Strong, Joy Tomlinson, Kay Russo, and Meaghan Pimsler) reports house fly numbers appear to have dropped this week, although stable fly counts rose significantly demonstrating the highest populations they have seen on and around herds in the central NY (Finger lakes) region yet this summer.  The continued storm fronts seem to be bringing in the stable flies.  Trends in the stable fly populations are being monitored on three local dairy farms (within 1 hour drive of Ithaca) using adhesive fly traps strategically placed throughout the pastures.  On one of the farms during the week of 6/26 there was an average of 16 stable flies caught by the traps.  On the following week, the week of 7/3, the average jumped up to 127 stable flies, representing a significant increase in stable fly populations.  This same drastic increase was observed on the other two dairy farms as well.  It is speculated that the large stable fly populations will persist for the next couple of weeks at least.  Horse flies on a local horse farm peaked about a month ago and seem to be causing fewer problems now.

Now would be a good time to walk barns with an eye for evaluating fly populations and the effectiveness of sanitation efforts.

Recall that each female house fly can lay between 100 and 150 eggs in each of the 4 - 6 batches of eggs produced over her 3+ week lifetime. At a constant temperature of 86 F, house fly eggs can hatch in 10 hours, go through their maggot stages in 5-6 days, pupate and emerge as adults in another 4-5 days. Total time egg to adult as few as 9 - 11 days.

Potential for population growth? One study showed that 25,000 to 40,000 stable and house flies could develop from bedding of a single calf hutch during the summer. Under favorable environmental conditions it is easy to see how fly populations can explode in a very short amount of time.

Shutting down fly production relies heavily on cultural practices that eliminate conditions favorable to fly breeding. Since house flies and stable flies both breed in moist undisturbed organic matter such as spilled feed, moist hay, wet grain, and manure-soiled bedding eliminating these conditions on a regular schedule reduces fly population growth by minimizing conditions favorable to successful fly breeding. Cornell's Veterinary Entomology program reminds us that sometimes innocuous routines such as dragging the hose between water buckets in a calf greenhouse can create great fly breeding spots.  Especially in the calf greenhouses and coveralls, try to keep the area in front of pens clean and dry.  Sweep up spilled grain regularly.

Likely Fly Breeding Locations. Calf rearing areas, near water sources and feed troughs / bunks, adult animal resting areas, maternity and hospital pens, manure traps / conveyor systems. Outside areas adjacent to barns prone to fly breeding include the water and feed troughs in the animal loafing yard, base of stored big bales, and edges of bunk or standing silos. Hard to clean corners and other areas where organic matter can accumulate.

Evaluating Fly Populations: spot cards and direct observation. Spot cards provide an objective means to monitor relative fly activity over time. White index cards (3X5 inches) serve as a clean surface to collect fly "specks" left by resting flies. Cards can be mounted on posts, beams, walls, etc. Select areas 10 areas throughout the barn where flies are seen resting. Do not put cards in windy areas or within reach of curious "critters" and children. Draw a map to indicate card location and save as part of your fly management record.  Date and number the cards and change them weekly. After 1 week remove the cards and replace them with a fresh set. Count the number of spots found on each index card. One hundred (100) spots per card can be used as a guide to indicate a fly problem. Spot cards provide an objective means to monitor relative fly activity over time. Each farm can adjust this number to their individual tolerance threshold.

Check areas surrounding spot cards with high counts for fly breeding. Stable fly (the biting flies) monitoring involves direct observation to check the legs and bellies of 10 animals and count number of resting flies. Check calf legs for patches of thin hair which can indicate a reaction to stable fly feeding. Ten stable flies per animal are considered a high number. Keep records of spot card and stable fly counts for reference. More information can be found in the Cornell IPM Factsheet: Integrated Management of Flies in and around Dairy and Livestock Barns.

Soybean Rust Update

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Weekly scouting is occurring on 19 sentinel plots located in Cayuga, Chautauqua, Chemung, Chenango, Columbia, Genesee, Herkimer, Jefferson, Montgomery, Oneida, Onondaga, Ontario, Seneca, Tompkins, Wayne, and Wyoming Counties. Plant growth stages in NY state have been reported to range from V2-R1. Low levels of Septoria brown spot continues to be found in several of the sentinel plots. The current risk of soybean rust infection in New York is extremely low. Future risk in New York will depend on rust build-up in the southern U.S., especially in commercial soybean fields. To date, in 2006, soybean rust has been reported in five counties in Alabama, 12 in Florida, one in Texas, five in Georgia, and two in Louisiana. Currently, there are no known reports of rust on commercially planted soybean in 2006. Last updated ( July 12, 2006 )

For more see the New York State Soybean Rust Information Center website.

Growing Degree Days in NYS

Ken Wise NYS IPM

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Accumulated Growing Degree Days for March 1 to July 12

*indicates missing data

Source: NEWA

Clipboard Checklist

Keith Waldron-NYS IPM

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General:

* Maintain crop records by field, including crop condition, inputs, observations, issues, concerns, etc.

* Storage areas cleaned and ready to accept wheat harvest? Check and disinfect inside, under and around grain bins.

* Mow around barn and farm facilities

* Clean and store weed sprayers. Flush tanks, booms, nozzles.

Established Alfalfa & Hay:

* Monitor for potato leafhopper- harvest early or spray on basis of need.

* Monitor for diseases, particularly Verticillium wilt, record information on disease species 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.

Summer Forages:

* Plant birdsfoot trefoil by end of July.

Small Grains:

* 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.

* Watch wheat grain moisture. Be ready to combine at 18 percent.

Corn:

* Monitor corn rootworm adults at silking.

* Observe corn for crop growth and condition, weeds, foliar diseases and fertility

Soybeans:

* Monitor for crop condition and growth stage, soybean aphids, natural enemies, foliar diseases, soybean rust

Livestock:

* Continue manure management and release of biological control agents (parasitic wasps) for house fly and stable fly control in barns

* Monitor young stock for cattle lice and mange mites

* Check condition of pastures and animals on pastures

- Evaluate need for face fly and stable fly control measures, adjust paddock rotation as needed.

Equipment:

* Provide annual maintenance to fertilizer and pesticide application equipment,

* Note any repairs to harvesting equipment as they are cleaned and lubricated.

* Ready combine for small grains or finalize arrangements for custom harvest

Contact Information

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Julie Stavisky: 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