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Weekly Field Crops Pest Report 2006

June 2, 2006 Volume 5 Number 7

1. View from the Field

2. Barn Fly Natural Enemies

3. Alfalfa Weevil Biological Control Continued

4. Soybean Seed Rots and Seedling Blight

5. Soybean Rust Update and USDA Soybean Rust Website Now Includes Soybean Aphid Reports

6. Growing Degree Days in NYS

7. Clipboard Checklist

8. Contact Information

View From The Field
Eastern NYS

Julie Stavisky, NYS IPM

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Ken Wise, NYS IPM









Keith Waldron, NYS IPM

At a TAg team meeting in Onondaga County in the Skaneateles Lake Watershed this week, corn that was planted in early May was finally starting to green up and grow.

When we conducted stand counts in corn field during a TAg meeting in Cattaraugus County this week, many skips were observed in the rows.  In most places where we did a little digging, we found seeds still trying to poke through the soil surface. One persistent TAg team member unearthed a white grub larva feeding on the roots of a seedling, and some instances of kernel damage were seen nearby.  This is a first year corn field following an alfalfa/grass stand (mostly grass by the last year), and it isn’t a surprising circumstance in which to see an occasional white grub.

On May 27th in Monroe County, I saw my first potato leafhopper of the year.  I would not be surprised if they are widespread in NY by now.  Once some new growth starts to show following the first cutting, it’s time to start scouting for PLH in alfalfa!

This week I scouted the SUNY Cobleskill farm and found my first potato leafhopper…just one! I did find a lot of aphids and ladybeetles. Next week I will have an article on ladybeetles in alfalfa. Here is a photo of an aphid mummy! An aphid mummy is really an aphid that had been parasitized by a parasitoid. The parasitoid lays its eggs inside the aphid and once it develops into a larva, it feeds on the inside of the aphid, thus, killing it.

Most of the alfalfa was severally lodged from the thunderstorm we have been receiving the last few days. In fields that are 2 plus years old alfalfa weevil tip feeding was 30 to 40 percent. Remember threshold for first cutting of alfalfa is 40 percent tip feeding.

In a new seeding there were many weeds competing with the new alfalfa plants. There are yellow nutsedge, lambsquarter, crabgrass and velvetleaf weed seedlings in abundance.

I found one lonely PLH found while sweeping and established alfalfa field at NYSAES farm. The alfalfa at 26 inches and should be harvested soon. I observed many alfalfa weevil larvae and extensive feeding injury this week. These established fields are very close to the economic threshold for AW.

Again I found no soybean aphids on buckthorn. I'm thinking it would be better to check buckthorn in an area that had soybeans recently. NYSAES farm has not had any appreciable acreage of soybeans planted in years.
Gary Bergstrom confirms a sample I left with him recently found on buckthorn as aecia of the crown rust Puccinia coronata.  It could be the variant from oat, rye, or some other grass.  See photo.

Barn Fly Natural Enemies

Keith Waldron, NYS IPM

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Look closely in areas of spilled silage, soiled calf bedding and moist organic matter in the barn and chances are you’ll be able to find one of several species of natural enemies of house and stable flies. Beetles and mites devour fly eggs and larvae. Fly pupae are attacked by small parasitoids (wasp spp). Fungi can cause disease to adult flies. Generally unnoticed and unaided by us, these natural biocontrol agents can take a heavy toll on the fly population.

Sanitation and other cultural practices minimize fly breeding habitats and interfere with the successful completion of the fly life cycle. In addition to reducing fly populations and minimizing the need for insecticide use, these practices protect natural enemy survival and help insure that they will be available to assist in fly management.

This time of year we get a number of requests for information on enhancing biological control of barn flies. Parasitoids have been well studied by Veterinary Entomologists in NY for their effectiveness at reducing house and stable fly populations in and around animal facilities. Research has shown that some species perform better in different climates, and some prefer different kinds of manure and other fly breeding materials. The species that is best adapted, occurring naturally on many dairy farms in the Northeast, is Muscidifurax raptor. This species attacks fly pupae inside barns as well as outside.

Much of the following information is adapted from the Cornell IPM Factsheet: Integrated Management of Flies in and around Dairy and Livestock Barns.

Parasitoids are like "smart bombs"-they live only to find and kill fly pupae. Although the female parasitoid has a stinger, the only purpose she can use it for is to kill flies. When she finds a fly pupa, she stings and feeds on it. This kills the fly. She then uses her stinger to lay an egg inside the pupa. The egg hatches, and the parasitoid larva feeds on the dead fly. The young adult parasitoid then chews its way out of the fly's pupal case and searches for new pupae to kill. Development from egg to adult parasitoid is completed in about 3 weeks. This extended development time compared to a house fly life cycle from egg to adult fly in as little as 5 days under ideal conditions is the reason why one would consider purchase and release of these parasitoids. If we think of them as competitors in a race that happens each summer, the fly has certain advantages that help it to win unless we intercede. For example, the fly develops twice as fast from egg to adult, lives longer, and lays more eggs than Muscidifurax raptor parasitoids. As fly populations begin to grow in late May and early June, the parasitoid populations lag behind.

The parasitoid also lags behind the fly in developing resistance to insecticides. Many insecticide treatments for flies therefore have the undesirable side effect of killing large numbers of parasitoids. Each subsequent insecticide treatment kills more beneficial insects and creates conditions that require repetitive treatments to keep flies in check.

Parasitoid populations can be conserved by using insecticides that are compatible with these important biocontrol agents. Baits and pyrethrin space sprays are good examples of compatible insecticides. Residual premise sprays are highly toxic to parasitoids and should be used only as a last resort.

Parasitoid Releases

Along with conserving natural enemies, it is possible to go one step further and release parasitoids to "jump-start" their population growth in the early summer. Such releases can be effective in managing fly populations if certain conditions are met:

  • Sanitation (waste management) is a must; parasitoid releases complement manure management but cannot replace it – i.e. there are No Silver Bullets….

  • When insecticidal treatment is necessary for supplemental fly control, only use insecticides that are compatible with parasitoids (space sprays and baits).

  • Parasitoids are sold in containers as immature insects in killed fly pupae. If most fly breeding on the farm occurs inside the barn, two or three tablespoons of the parasitoids should be distributed in areas where fly breeding is a problem. If calves are housed in hutches, about three heaping teaspoons of pupae (approximately 1,000) placed in each hutch weekly.

  • Many companies that sell parasitoids advertise their products in farm magazines, but not all of them sell the right species or provide parasitoids that are adapted for the northeastern climate. Muscidifurax raptor is the species recommended for use in the Northeast. Nasonia parasitoids are inexpensive but are inappropriate for use in dairies.

  • Parasitoid releases should be started early, preferably in middle to late May, and continue weekly until the middle of August.

  • How many parasitoids should be released? Weekly releases of either 200 parasitoids per milking cow or 1,000 parasitoids per calf have proven effective in research trials. But every farm is different, and release rates and schedules may require adjustment to achieve a level that is both effective and affordable for an individual farm.

  • In research trials, the cost of releasing parasitoids has been more than offset by reductions in insecticide treatments. On average, dairy farmers who use biocontrol in fly IPM programs make 80 percent fewer insecticide treatments than farmers who rely solely on insecticides for fly control. In addition, fly populations on IPM farms are about 50 percent lower than on conventionally managed farms. It is important to understand, however, that no single fly management strategy such as parasitoid releases alone will provide long-term control.

  • Check locally for producers of distributors of parasitoids. IPM Laboratories, Inc. (Locke, NY. 315-497-2063, Email -  ipminfo@ipmlabs.com ) is one source of M.raptor  parasitoids.

For more information:

Pdfs of the dairy cattle recommendations, factsheets and more can be found at Veterinary Entomology at Cornell and NYS IPM for Livestock.

Alfalfa weevil Biological Control, Continued

Julie Stavisky, NYS IPM

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Large numbers of 1st through 3rd instars have been seen in localized areas.  For example, take a look at this photo of a handful of alfalfa weevil larvae collected by Mike Stanyard in Yates county!  The field where these were collected was showing heavy, over-threshold injury in one area.  Insecticide treatment will not be necessary because the field will be cut within a few days.

In addition to the parasitoids we talked about in last week’s pest report, another biological control friend in alfalfa is an entomophagous fungus.  Yes, it’s an insect-feeding fungus.  Its only choice for breakfast, lunch, and dinner is the alfalfa weevil.

Light (but widespread) rains at the end of last week may provide a big advantage for keeping alfalfa weevil larval numbers in check.  Given that most alfalfa weevil larvae have not reached the 4th instar (the most damaging stage), but many fields are being cut, larvae could pose a threat to early re-growth. So we’ll take all the help we can get from biological control agents for protecting alfalfa.

The fungal pathogen, Zoophthora phytonomi, is always present in low levels in and around alfalfa fields. Under the right cool, wet conditions, an epizootic, or outbreak, of the fungal pathogen can occur. Infected larvae lose their normal light green color. The pale yellow infected larvae become less active and usually die within a few days.

Zoopthora phytonomi first appeared in Ontario, Canada in 1973, and now commonly occurs throughout the weevil’s range in the Midwest and northeast.  Although there are several theories about where the fungus might have come from, its origin remains a mystery.

Here’s a photo showing what you may see if you find infected alfalfa weevil larvae. 

Soybean Seed Rot and Seedling Blight

Ken Wise, NYS IPM

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Many different organisms cause seed rot and seedling blights. Most of these organisms are soil-borne and a few are seed-borne. Most seed rots and seedling blights proliferate in poorly drained, cold (less than 58 degrees) and wet soils.

Seed Rot: Many times the infected seed will not germinate. If the seed does germinate the radicle will become infected and rot. The rot can be tan, brown, gray or black and the seed or radicle will appear wet and mushy. Some of the organisms that infect seed are Pythium, Fusarium, and Rhizoctonia.

Seedling blight: It is difficult to determine which pathogen causes seedling blight in any one field. Many times it can be a complex of Pythium, Rhizoctonia and Phytophtora. Pythium can cause the seedlings to have a wet, rotted appearance, while Phytophtora generally appears as a dry, dark rot on the roots.  Sunken, reddish-brown lesions on the hypocotyls are most likely a Rhizoctonia infection. The Rhizoctonia lesions are small when they first appear. As these lesions grow they can girdle the stem, causing the soybean plant to die. If the Rhizoctonia infected seedlings do not kick the bucket the infection will weaken the stem and may cause the plant to lodge after the pods form.

Soybean Rust Update

Keith Waldron, NYS IPM

USDA Soybean rust website now includes soybean aphid reports

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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. The 2006 North American epidemic is starting from over-wintered rust on kudzu in a somewhat broader and more northerly area than in spring 2006, yet early pockets of rust from Florida to Alabama are scattered and of low severity.  Rust development is basically in a holding pattern along the Gulf Coast. Despite recent rains across the South, the region is again in an overall pattern of hot, dry weather.  To date, in 2006, soybean rust has been reported on kudzu in five counties in Alabama, 11 counties in Florida, and four counties in Georgia.  While soybean rust was found in a mature field of soybean in far southern Texas in February, the infected field has since been destroyed and no new rust has been found in Texas.  Scouting continues on kudzu patches from Florida northward to southern Illinois, and westward to Texas and Nebraska. Many of the soybean sentinel plots have been planted throughout the country with the most advanced ones in the south starting to fill pods. We are finalizing plans for approximately 20 sentinel soybean plots in New York to be scouted in cooperation with soybean producers and Cornell Cooperative Extension Educators. Sentinel plots are planned for locations in Cayuga, Chautauqua, Chemung, Chenango, Genesee, Jefferson, Montgomery, Oneida, Onondaga, Ontario, Orleans, Seneca, Steuben, Tompkins, and Wayne Counties. Last updated (May 26, 2006)

We have been reprinting Gary Bergstrom’s soybean rust updates and a link to the NY Soybean Rust (SBR) website. The NY website provides NY producers with our best recommendations regarding risk of the disease and help producers better time scouting and apply preventative fungicide applications. The NY SBR site will also provide updates on observations of sentinel plot activities.

The USDA also has a soybean rust web site which presents the national perspective for SBR observations and recommendations. Information on that site documents SBR detections in soybean sentinel plots and on kudzu, an alternate rust host. Specialists also present their individual state’s commentary.

This summer the USDA site is adding information on soybean aphid (SBA) detections across the US. State commentaries for SBR and SBA observations will follow a standard format highlighting:

Crop Growth Stage, Observation and Outlook – Insect, Observation and Outlook – Disease, Scouting and Management – Insect, and Scouting and Management – Disease.

For SBA information enter the website, and go to the drop down menu in the top right corner,. Under the date, select soybean aphid. Two maps appear on the right side of the screen. The top map shows “SB Aphid Observations.” As of this writing (June 1) this map is blank (it isn’t active yet), but once reports of soybean aphid come in, dots will appear. Commentary is currently available for the states colored.  Unlike the rust map, which only has two colors (green for no detection, red for detection), the color of the dots on the aphid map will reflect the number of SBA per plant with purple dots indicating fields or plots over the 250 per plant threshold. The second map has the “SB Aphid State Update,” commentary by state specialists. Note that the color of the state reflects when the commentary was last updated. USDA is funding the sampling of sentinel plots in some states for aphids. NY is voluntarily participating both SBR and SBA data input contributing to this data set with observations from sentinel plots and other locations across the state. We welcome you to share your SBR and SBA observations. Please share these observations with the fcrops bb and with either Gary Bergstrom (gcb3@cornell.edu) or Keith Waldron (jkw5@cornell.edu)

A note of caution about the soybean aphid web site – (some comments and material adapted from a 5.25.06  article by Chris DiFonzo in the Michigan Field Crop CAT Alert.) Entomologists agree this map should not be used to make spray decisions in your individual fields. This is different from how the rust maps are used. Detections of rust near your location will help to time preventative fungicide applications across a region. Watch Gary Bergstrom’s SBR website for recommendations appropriate for NY. However, detecting soybean aphid in your area and even having fields go over threshold does not necessarily indicate individual fields should be treated. SBA populations have been very variable across NY. Field to field variations even on the same farm may be dramatic. Only a relatively few fields in NY have exceeded the 250 SBA / plant threshold and required treatment. We also know from our limited experience that natural enemies can have a significant impact on aphid populations. It is also known that optimal timing of insecticide applications, when warranted, can protect yield. These factors argue for scouting as needed and making field-by-field decisions. Use the soybean aphid maps to get information about aphid populations in general, but do not use the maps to make a decision about whether or not to treat your own fields.

For more information, consult:

Alfalfa Weevil and Growing Degree Days in NYS

Ken Wise NYS IPM

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Growing degree Days for peak (50%) Occurrence of Alfalfa Weevil growth stage:

Stage or Event

Accumulated growing degree days (48F base temperature)

Eggs hatch


Instar 1


Instar 2


Instar 3


Instar 4






Adult Emergence


(Note: for alfalfa weevil predictions use Base Temp of 48F)

Accumulated Growing Degree Days for March 1 to May 24


Base 48 F

Base 50 F







Clifton Park














187* (Many days not recorded)




*indicates missing data

Do you know the number of growing degree-days in your region today? Check this website: NY Growing Degree-Day Tracker Base Temp. 50F.

Clipboard Checklist

Keith Waldron-NYS IPM

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• Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.

• Watch for early season weeds, any patches of herbicide resistant weeds?

• Storage areas cleaned and ready to accept upcoming hay harvest?


• Determine plant populations, make notes on germination problems

• Gaps in row? Check for seed corn maggot, wireworm, cutworm, seedling blights, birds, seed placement issues?

• Monitor for weeds, note presence of “who”, “how many” and “where”

• Adjust post emergence weed control actions

Small Grains:

• Monitor winter grains for crop growth stage, insect and disease problems

      - assess crop for adequate stand and plant vigor

Alfalfa & Hay:

• Monitor alfalfa seedings for weeds, insects & diseases.

• Check established alfalfa stands for alfalfa weevil, weed and disease problems.

• Storage areas cleaned and ready to accept upcoming harvest?


• Check stand establishment of early plantings

• Gaps in row? Check for seed corn maggot, wireworm, seedling blights, birds, seed placement issues?

Dairy Livestock Barn Fly Management:

• 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

• Check water sources, drainage, roof gutters for leaks and potential overspill

• Begin fly monitoring: install “3X5” index card fly speck monitoring cards through out barn

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


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

• Hay harvesting equipment ready?

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

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