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Weekly Field Crops Pest Report 2006

June 15, 2006 Volume 5 Number 9

1. View from the Field

2. Powdery Mildew on Wheat

3. Predators in Alfalfa II

4. Sampling for Potato Leafhopper in Alfalfa

5. Clipboard Checklist

6. Growing Degree Days in NYS

7. Up Coming Events

8. Contact Information

View From The Field
Eastern NYS

Julie Stavisky, NYS IPM

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Ken Wise, NYS IPM

Alfalfa weevil injury is showing up in alfalfa re-growth!  I’ve heard reports from fields in Ontario county where feeding is close to threshold.  In Seneca County, a field was showing 50% tip feeding, and 2nd and 3rd instar larvae were observed.  Let’s review the alfalfa weevil (AW) guidelines following first harvest: If more than 50% of the AW are in the cocoon stage, the population is maturing to a non-feeding stage and will no longer be a problem for this year. If the larvae are predominantly young, however, damage may be expected, especially if the weather is cool and dry. In addition to watching for cocoons of the AW, watch for the cocoons of the parasitic wasps that keep AW populations in check. After the first harvest, control measures are recommended when either 50% or more of the stems show signs of AW feeding, or there are two or more larvae per crown.

Soybean rust sentinel plot sampling has begun across NY.  For regular NY updates, visit New York State Soybean Rust Information Center, and for national updates, visit the USDA Public PIPE website.

During an “Early Season Corn Pests” meeting led by Dean Sprague in Chautauqua County this week, black cutworm was the star of the show.  Close to 5% of plants had been cut, but the larvae we found were all larger than 1 inch.  In an adjacent alfalfa seeding, a lone potato leafhopper was observed.

Nancy Glazier conducted scouting for the Ontario County soybean TAg team this week, and observed soybean aphid in only 1 field (where they were originally observed last week).   One soybean field she is scouting was half grain corn and half silage corn last year, and Nancy saw slug damage on 60-70% of plants in the area that was previously grain corn.  Little slug damage was present in the silage area, where there was of course less soil debris. 

This week at the Cornell University Research Farm in Valatie there could be a possible issue with alfalfa weevil on alfalfa re-growth. The larvae are still small (1st to 3rd instar) and tip feeding is at about 10 to 20 percent. Remember that the 4th instar eats 80% of the all the alfalfa an individual will ever eat. Since larvae are still small, as they approach the 4th instar they could still cause some economic loses to the field. Remember the threshold on 2nd cutting alfalfa is 50% of the plants show tip feeding.

Potato leafhopper infestation remains low at both the Cornell University Research Farm in Valatie and the SUNY Cobleskill farm. I found only a few individual potato leafhoppers in several fields.

There are plenty of weeds present in the Cornell University alfalfa trials at the SUNY Cobleskill Farm. As you can see from the photograph yellow nutsedge and velvetleaf are thriving very well. I think Julie Hanson plans to spray these soon.

Peter Carey in Sullivan County is finding some black cutworm damage in field corn.  He indicated that damage was below the economic threshold. Cutworm damage can appear as plants have been cut off just above the soil surface. Most likely you would not see cutworms during the day since they are a nocturnal pest. Black Cutworm larvae vary in color from light gray to black with a pale brown to black head. Larvae have a greasy, shiny appearance with coarse granules present over their body. During the day larvae burrow into the soil next to the corn plant. For more information on black cut worm you can view an article I had prepared earlier in the season for the pest report

During an organic soybean/winter and spring wheat meeting last Friday, we observed Stagonospora nodorum blotch on the lower leaves and on some of the flag leaves. Rainy weather conditions in the area were expected to be favorable to disease development. After close field inspection, we found only one small powdery mildew infection on one plant. Fortunately, no scab (Fusarium head blight) problems were detected.  I will continue to collect samples from this field for Gary Bergstrom to check for possible scab as the heads mature. The organic soybean stands look very uniform, although weed emergence has also been good. Growers were not able to use blind cultivation because the ground was too wet and the weeds greened up. Growers plan to row cultivate as soon as it is dry enough. No soybean diseases were observed.

Powdery Mildew on Wheat

Julie Stavisky, NYS IPM

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With as much wet weather as we’ve seen in many areas of NY, powdery mildew has the potential to really take off in wheat fields.  If powdery mildew shows up, the first symptoms include white powdery patches on upper surfaces of lower leaves.  With continued cool, wet temperatures, the white powdery patches can spread to stems and upper leaves.  Patches may turn to a dull gray color, peppered with tiny black specks as the disease continues to develop. A dense, lush stand that does not dry from dew and rain is at the highest risk from powdery mildew.  The greatest chance for yield loss occurs when the flag leaf is infected. Follow this link for photos of powdery mildew symptoms.

Management of powdery mildew depends on planning ahead.  Varieties that are moderately resistant are recommended, as are systemic seed fungicides.  Avoiding excess nitrogen will prevent the growth of an excessively dense stand.  Foliar fungicide sprays are generally not economical, though many factors including plant stage of development must be considered.  Although it is likely too late this year to consider foliar fungicide sprays, now is a good time to review the Managing Diseases of Small Grains section and the Guidelines for Wheat Fungicide Decisions section in the online version of The 2006 Integrated Guide for Field Crop Management.

Predators in Alfalfa II

Ken Wise NYS IPM

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Lady Beetle Larvae

I have been asked many times if this is a pest!  I have also been asked if they bite! If you have never seen a lady beetle larva they look rather intimidating. Some people think they look like tiny alligators. So – to answer the questions above – they are a very effective beneficial insect and beware if you are a food source like aphids and other small insects – they do bite!

Lacewing (several species)

Adults feed in the evening or night on nectar, pollen, and aphid honeydew. Larvae are very active predators of aphids and other small insects in many agricultural crops. Adults are light green with long, slender antennae, golden eyes and have large lace-like wings that are 1/2 to 1/3 inches long. Larvae are called antlions, and look like a little green-gray alligator. Antlions have sickle-shaped jaws, that penetrate the prey, inject a paralyzing venom, and then suck out the body fluids of the victim. The larvae will reach about 1/2" long before they pupate.

Damsel Bugs (Nabidae)

Damsel bugs, also known as “nabids”, eat small insect eggs as well as aphids and mites. This insect uses a needle like mouth-part to insert into its prey and suck out the insides. They are slender, often yellowish-brown and about 8 -12 mm (3/8 to 1/2 inch) long. The wings lie flat across the back, crossing at the tips. The abdomen is slightly swollen and the body tapers toward a narrow, elongated head. The adult female inserts white colored eggs into the stem of the plant --only the egg cap shows. Damsel Bug nymphs are a little smaller than their parents, do not have fully developed wings, but otherwise resemble wingless adults in shape and color. Be a little careful with damsel bugs because they are predators and can give a painful bite to big and small alike.

Syrphid Flies

Adult syrphid flies, also known as flower flies,  like to feed on nectar and pollen of several kinds of flowers. Many species of adult syrphid flies look like bees. After the adults feed they lay 100’s of white 1mm long eggs in the mist of aphid colonies. Syrphid fly larvae are good predators of aphids and other soft-bodied insects. Larvae are legless maggots that are green, yellow or gray with a yellow or white stripe down their back. For pictures of syrphid flies view this website: Syrphid Flies

Fourteen Spotted Lady Beetle or the Cream Spotted Lady-beetle (Propylaea quatuordecimpunctata) is a European lady beetle. This lady beetle was accidentally introduced to North America. Some people think it was transferred on a ship in the St. Lawrence Seaway sometime in the late 1960s. This lady beetle does feed on aphids but I found no information on the amount they can consume. This is a small beetle that is only 4 to 5 millimeters.

Sampling for Potato Leafhopper in Alfalfa

Ken Wise, NYS IPM

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Scouting alfalfa fields is the key to early detection of potato leafhopper infestations. Use a 15-inch diameter sweep net to determine the potential risk a potato leafhopper infestation may pose to your alfalfa. Scouting for potato leafhopper starts after the first cutting of alfalfa (about the first part of June – i.e. NOW) till the first fall frost. You will want to use a potato leafhopper sequential sampling plan to determine if an infestation requires management or not. The first thing to do is determine the height of your alfalfa. Smaller plants are more vulnerable to potato leafhopper; thus there are different action thresholds for different heights of alfalfa. The second thing you will need to know is how to sample for potato leafhopper. A sample consists of a set of 10 sweeps of the net. A sweep is one pass in front of you as you walk through the alfalfa. The return swing is counted as another sweep. Sequential sampling reduces the time spent in each field and tells you whether to treat (management action) or not treat (no management action). Sequential sampling is particularly helpful in minimizing time required to make a management decision in situations where PLH populations are very high or very low. Use the following chart to determine potato leafhopper infestation levels.

N= No management needed at this time

T= Management needed as soon as possible

Write down the number of potato leafhoppers for each sample taken on the card. Add each sample to the next, keeping a running total of potato leafhoppers. You will need to take at least 3 samples using the sequential sampling method. On the sequential sampling card “N” is defined as no treatment (no management) needed at this time and “T” is defined as treatment (management) needed within in a week. If the sample is smaller than the “N” number stop and scout 7 days later. If the number of leafhoppers is larger than the “T” number then management action needs to be taken within a week. If the number of potato leafhoppers fall between “N” and “T” then continue and take the next sample till a decision can be determined. A guide with a printable version of the sequential sampling chart.

Growing Degree Days in NYS

Ken Wise NYS IPM

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Accumulated Growing Degree Days for March 1 to June 14


Base 48 F

Base 50 F







Clifton Park


















*indicates missing data

Source: NEWA

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)

Weevil season nearly over for 2006. The accumulated growing degree model for alfalfa weevil predicts weevil 50% of populations are at cocooning stage in many areas of NYS, signaling the end of weevil season. In areas where alfalfa weevil populations were high this season, continue to monitor windrow areas for indications of weevil feeding. Recall the post-harvest threshold recommendation is: 50% of alfalfa stems showing signs of weevil feeding, larvae are < 3/8 in, and three are few or no weevil cocoons.

Clipboard Checklist

Keith Waldron-NYS IPM

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Clipboard Checklist

* Update crop records by field, including pesticides used, nutrient inputs including manure, growth and development observations, other comments, etc.
* Watch for weed escapes, herbicide resistant weeds, growth stage for cultivation opportunities
* Storage areas cleaned and ready to accept 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", "where", growth stage
* Adjust post emergence weed control actions

Small Grains:
* Monitor winter grains for crop growth stage, insect and disease problems
- Note flowering / heading date

Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, insects & diseases.
* Check established alfalfa stands for potato leafhopper, weed and disease problems
* Harvest alfalfa - first cutting, check windrows for signs of alfalfa weevil feeding

* Check stand establishment, weed control
* Gaps in row? Check for seed corn maggot, wireworm, seedling blights, birds, planter problems, drainage issues?
* Check for soybean aphid on young soybean seedling

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
* Collect and evaluate "3X5" index card fly speck monitoring cards. Record results for future comparisons. Replace with new cards
* Evaluate animals for stable fly harassment (10 stable flies per animal)
* Replace fly tapes as needed, check insecticide bait traps

* Note any repairs needed for recently used equipment: tractors, harvest equipment and wagons, etc. as they are cleaned and serviced.
* Calibrate manure spreaders - maintain records on amount spread per field

Upcoming Events

For Seed Growers, Seed Treaters, and other Seed Professionals
Place: NYSIP Foundation Seed Barn, 791 Dryden Rd., Rt. 366, Ithaca, NY, Time: 9:00 AM-12.00 noon (registration and refreshments available at 8:30 AM)

Aurora, NY (Poplar Ridge Road, connects 90 and 34B)

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