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Weekly Field Crops Pest Report 2006

May 18, 2006 Volume 5 Number 5

1. View from the Field

2. Barn Fly Management Not Too Early to Start…

3. How do You Monitor Alfalfa Weevil

4. Important Alfalfa Diseases to Know Now

5. Start Watching for Slugs In Corn and Soybeans

6. Growing Degree Days for NYS

7. Clipboard Checklist

8. Contact Information

View From The Field
Eastern NYS

Ken Wise, NYS IPM

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This week alfalfa weevil larvae were out in force in 4 plus year old alfalfa fields at the Cornell University Research Farm in Valatie. The larvae ranged for 1st to 3rd instar in their development. I was getting 10 to 15 larvae per 10 sweeps of the net. Tip feeding was below threshold in these 4 plus year old fields and ranged from 20 to 30 percent. In a 2nd year alfalfa field there were many alfalfa weevil adults and tip feeding was less than 5 percent. This should increase as larvae start to hatch from the eggs laid on the inside of the alfalfa stem. There were many dandelions in the 4 plus year old field.

Russ Hahn’s corn trials are out of the ground and a few inches tall all already. I did not see any real pest issues in the corn. I did see a few crows and deer tracks in the fields.

Tom Kilcer’s triticale plots are already in the boot to heading stage of development. Again there were no major pest issues with the triticale.

Potato Leafhopper Challenge! Every year it is fun to see who finds the first potato leafhopper in alfalfa. I have not yet found one which is late for me… so has anyone else discovered this pest yet this year or if not who will be the first?

Barn Fly Management – Not too early to start…

Keith Waldron, NYS IPM

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Arthropods (Insects and their allied groups) comprise more than 82% of all species of animals found on earth. Fortunately, the number of arthropods of affecting dairy animals is New York is relatively few: a cadre of fly species, chorioptic and sarcoptic mange mites, and four species of cattle lice. This season we will be adding a new feature to the weekly pest report inserting information on IPM for flies affecting cattle in and around barns and on pasture. Since many field croppers also raise dairy and beef animals, including cattle pests with other field crop issues should be of interest. For those that are strictly cash croppers, the additional information may at least be entertaining…

This week – Who’s who in the barn? Management of pest problems begins with proper identification. Knowing what the pest is allows us to use knowledge about their biology, growth and development, feeding habits, habitat preferences, and more as information for management. For example, one basic concept to know is that different fly species affect animals in confinement than attack animals on pasture. These fly species are different, as is their biology, and the specific strategies typically used to manage them.

This week we’ll introduce two species of flies commonly found in and around dairy facilities: the housefly and stable fly. Houseflies are generally considered nuisance flies, while stable flies are blood feeders that bite animals and humans on the lower legs. These pests can affect animal health and farm profitability by annoying and irritating animals and farm workers, and stress animals which can lead to animals going off feed, reducing weight gain and milk production. Severe house fly populations may increase bacterial counts in milk. In addition, off-farm emigration of flies can spark the interest and concerns of non-agricultural neighbors.

The following information is adapted from the Cornell / Penn State Pest Management Recommendations for Dairy Cattle.


Both house fly and stable fly have similar biology and habitat preferences. These similarities enable them to be managed using similar tactics, primarily through the use of sanitation and other cultural practices to destroy their breeding sites and disrupt their life cycle. While similar in many respects, differences between the two species are worth noting, in particular subtle differences in life cycle, fecundity (number of eggs produced per female) and habitat preference,

House flies, Musca domestica, are non-biting insects that breed in animal droppings, manure piles, decaying silage, spilled feed, bedding, and other organic matter. They can complete their life cycle from egg to adult in 10 days under ideal conditions in summer months. Each female can produce 150 to 200 eggs, which she lays in batches at 3- to 4-day intervals. Females may lay between 2 – 7 batches of eggs over their lifetime. Eggs hatch in less than 24 hours. The young larvae, called maggots, feed on microorganisms which cause fermentation and decay that live in moist organic matter. The maggot goes through three instars gradually increasing to it’s maximum length of 1/3 to 1/2 inch in length over a 3 to 10 day period depending on temperature. As the maggots mature they move to drier regions of their habitat to pupate. The pupa is a red to chestnut-mahogany brown colored capsule-like oblong structure.  Adult flies emerge from the pupae 3 – 10 days later. Although house flies may be of only minor direct annoyance to animals, their potential for transmitting diseases and parasites is considerable.

The stable fly, Stomoxys calcitrans, is about the size of a house fly but is dark gray. Its abdomen has seven rounded dark spots on the upper surface. The adult’s piercing mouthparts protrude spear-like from under the head. Stable flies breed in wet straw and manure, spilled feeds, silage, grass clippings, and in various other types of decaying vegetation. Each female fly lives about 20 to 30 days and lays 200 to 400 eggs during her lifetime. Under optimum conditions, an egg develops to an adult in about 3 weeks. Stable fly breeding habitat is similar to that used by house flies. Stable flies may have more of a relative preference towards manure/straw, and can be found at the soil interface with big bales stored outside, and in poorly managed compost piles. Cattle are most irritated by these pests during the warm summer months. Both male and female stable flies feed on blood several times each day, taking one or two drops at each meal. Stomping of feet is a good indication that stable flies are present, since they normally attack legs and bellies. Production performance declines in infested herds because of the flies’ painful biting activity and animal fatigue from trying to dislodge flies.

Compare the heads of the two flies shown above. Note the sponging (non-biting) mouth part of the house fly compared to the spear-like piercing-sucking (biting) mouth part of the stable fly.

In the weeks to come we’ll discuss monitoring, thresholds, management strategies, and the very real issue of insecticide resistance.

Next week – Fly breeding hot spots – where to watch, what to do.

If you are still wondering what the insect is that you find in the feed storage room window, circling the calf pen, or sitting on the trash can, check out the factsheet: Common Pest Flies Found in the Urban/Rural Environment and Their Biological Control Agents available at the websites cited below. Pdfs of the dairy cattle recommendations, factsheets and more can be found at: Veterinary Entomology  and IPM for Livestock

How Do You Monitor Alfalfa Weevil?

Ken Wise, NYS IPM

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Monitor alfalfa weevil weekly from mid to late-April through June. Because weevil populations can build up over the life of the alfalfa stand, monitoring fields that are two or more years in production is critical to determine infestation levels. Start weekly field sampling in fields at about 350 degree-days (base temperature 48F) which is about mid to late April in most years, but not this year!

  • Pick 50 alfalfa stems at random throughout the field.

  • Look for the small "shot holes" in the leaves that indicate that larvae are feeding.

  • Record the percentage of alfalfa stems that show the "shot hole" feeding damage in the top 3 inches of the canopy.

Before the first cutting, if 40% of the stem tips show feeding damage, you are at the "action threshold". The good thing is that alfalfa weevil can generally be controlled by harvesting. If you reach an action threshold within a week of your normal 1st cutting date, early harvesting will help avoid economic, yield, and forage quality losses. Alfalfa weevils only have one generation per year and are typically not a problem after first harvest. Occasionally, weevil can damage alfalfa re-growth after harvest. This damage may be more evident in the windrow areas, and can be more noticeable under cool or droughty weather conditions. If you find that 50 percent of the new growth is damaged, with many small larvae present, a chemical control may be warranted. For more information on alfalfa weevil checkout our online publication: IPM for Alfalfa Weevil.

Important alfalfa diseases to know Now!

Ken Wise, NYS IPM

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Anthracnose is a disease that occurs in warm and wet weather.  Stems of infected plants wilt and stem tips bend over to form a Shepherds crook. Diamond-shaped lesions can appear on the lower parts of the stem about 1-3 inches above the soil line. Anthracnose may advance from infected stems into the crown tissue. The infected crowns appear bluish-black near the base of stems. Plants can appear straw colored and are scattered throughout the field. For pictures of anthracnose see: Anthracnose Photos

Verticillium wilt can be a serious disease, limiting yield and stand life. An early symptom includes a characteristic V-shaped yellow foliar discoloration similar to potato leafhopper (PLH) injury. One way to tell the difference between PLH injury and verticillium wilt is by using a sweep-net. If you see the yellow V-shaped foliar discoloration and there are no PLHs in the net it is most likely verticillium wilt. As the disease progresses, leaflets wilt, turn yellow or pink, and often curl or twist. Stems of infected plants can remain green for long periods of time. Taproots appear healthy and sound, but in cross section appear to have a dark ring indicating damage to the water-conducting tissues, causing wilt symptoms. Verticillium wilt symptoms may be more obvious in the second cutting. For pictures of verticillium wilt see: Verticillium Wilt Photos

For more information on alfalfa wilts and crown rots see our online publication: Wilt and Rot Diseases in Alfalfa

Start watching for slugs in corn and soybeans

Julie Stavisky, NYS IPM

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The Ohio “CORN” report this week indicates that slugs are hatching!  Slug problems were not widespread in corn and soybeans in NY last year, but if the cool, wet conditions continue, the threat for this year’s crops may be just around the corner.  It is time to start monitoring.

Slugs spend the winter as eggs. The overwintering eggs are usually laid in the general area where slugs were feeding the previous spring, summer, and fall. Thus, if they were a problem in an area last year, there’s a good chance they will be back for more. Slugs will attack seedlings and lower leaves, leaving coarse, irregular holes and characteristic “slime trails” in their wake. Feeding may result in serious injury and even stand reduction under severe infestations.

Slugs prefer cool and moist conditions, and they thrive when there are hideouts in the field, such as in the cover provided by debris on the soil surface. Slugs tend to feed most when temperatures are in the mid 60’s. Stand reduction problems have typically been worst during wet, cool springs.  No-till corn and soybean fields are at highest risk from slugs.

Alfalfa Weevil and Growing Degree Days in NYS

Ken Wise and Keith Waldron-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 17


Base 48 F

Base 50 F







Clifton Park


















*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, 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 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.

• Timothy stands: check fields for symptoms of cereal rust mite

• Storage areas cleaned and ready to accept upcoming harvest?


• Field preparations, planter ready, Rhizobium inoculum?

• 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 waterers, 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.

• Service corn planter as needed. alfalfa harvesting equipment, and tillage implements

• Soybean planter and alfalfa 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