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Weekly Field Crops Pest Report 2007

June 28, 2007                Volume 6 Number 10

1. View from the Field

2. Be Ready for Potato Leafhopper before the damage occurs!

3. Monitor soybean fields closely for soybean aphids

4. Is corn under threat from European corn borer yet?

5. NYS 2007 Asian Soybean Rust Status

6. Which is Corn Rootworm?

7. Clipboard Checklist

8. Upcoming Events

9. Contact Information

View from the Field


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Eastern NYS
Ken Wise

Soybean aphids in the Columbia County soybean sentinel plot increased from an average of 20 aphids/plant to 60 aphids/plant over the past week. While this is a large increase it still falls short of the 250 aphids/plant economic threshold. I saw several lady beetles, lacewing larvae and aphid mummies. It seems as if biological control is also starting to increase: Good news!

The lower leaves of the soybean plants in the sentinel plot showed symptoms of Septoria Leaf Spot (brown spot). Fungus inoculum is common from infected leaf and stem debris on the soil surface. Infection is favored by warm, moist weather, which promotes sporulation of the pathogen. Conidia spores can be distributed by wind and splashing rain. Infection and defoliation proceed from lower to upper portions of the plant. Dry weather tends to halt the spread of the disease. The lesions are dark brown and irregular shaped.

Septoria on a soybean leaf:

Speaking of aphids I am seeing many of them in alfalfa. Pea aphid populations have also increased over the past week. These tiny insects are not typically an economic concern for NY forage alfalfa. One reason these aphids are not a problem for NY alfalfa is because they are considered “lunch” by many natural enemies including a variety of predators, parasitoids, and fungal pathogens. Anyone see the lady beetle?

While I did not detect any fields over threshold for potato leafhopper this week the populations in fields are increasing. With the warm weather potato leafhopper populations can explode in a very short period of time. The lack of rainfall can add a second stress to the plant on top of the potato leafhopper pressure. I would really start to look closely at alfalfa fields for potato leafhopper. Especially watch new alfalfa seedings for PLH as their small size makes them more susceptible to PLH injury.

Western NY and Finger Lakes
Julie Dennis

You’ll notice that our “View from the Field” section is growing longer lately. We have our TAg Team scouts to thank for this! Pest observations made by Erin Hull, scout for the Skaneateles Lake TAg, and by Sarah Woodard, scout for the Cayuga County Soybean TAg, are highlighted this week.

If you see an important pest outbreak that it would be helpful for other people to hear about, drop us a line, or better yet, a photograph!

Soybean aphids seem to be having a big year in parts of NY so far. Wayne County: Mike Stanyard reported that a field in southeastern Wayne County was plagued by up to 1,000 aphids per plant! The plants in the affected areas were stunted and sticky, and natural enemies were few and far between. Thanks, Mike, for the following photos:

Winged aphids, however, were not hard to find. For more information about the implications of winged aphids, see Keith’s article below. Cayuga County: Soybean aphids were as high as 100 per plant, and all stages of ladybugs were plentiful (eggs, larvae, pupae, and adults!) Onondaga County: Soybean aphids averaged 5-10 per plant in one field, while there were still none in another field. Ontario County: Last week, I saw many winged aphids in the Ontario County sentinel plot, but overall aphid numbers were very low. Seneca County: Mike Stanyard and Mike Dennis report that serious hail damage to beans and corn in the east-central part of the county has temporarily suspended all interest in pests!

Be Ready for Potato Leafhopper before the damage occurs!

Ken Wise
NYS IPM

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As temperatures increase and weather fronts roll through NY, so does the risk of potato leafhopper populations reaching levels damaging to alfalfa yields and quality. Do you know what to do if a field reaches an action threshold for potato leafhopper in alfalfa? Here are the management options for potato leafhopper in alfalfa!

Option 1: Early Harvest

You can harvest the alfalfa early to control potato leafhoppers if the field is within a week to ten days of a scheduled harvest. By harvesting the alfalfa early, you’ll prevent potato leafhopper from reaching infestation levels that can cause yield and quality loss to the forage. Make sure that the whole field is harvested at the same time. If a field is not clean harvested then the alfalfa that has not been cut will serve as a refuge for potato leafhoppers and can re-infest; thus severely damaging alfalfa re-growth.

Option 2: Use an Insecticide

To protect yield and health of new seedings and established alfalfa, insecticide control can be warranted when a field is not within a week of harvest. For selection of an insecticide consult the current issue of Cornell Guide for Integrated Field Crop Management. Remember to read the label and be aware of blooms, bees and the days until harvest restrictions.

Option 3: Plant Potato Leafhopper Resistant Alfalfa

A third option for control is planting potato leafhopper resistant alfalfa. Obviously, it is a little late for this season’s crop but something to consider for future seedings. Research has shown that potato leafhopper resistant alfalfa is consistently higher in quality than susceptible alfalfa varieties with or without potato leafhopper pressure. PLH resistant varieties yields are comparable and generally better than susceptible varieties when PLH are present. A bonus benefit is that currently available alfalfa varieties with PLH resistance have come down in price over the past several years.

For management information check our on-line IPM guides: IPM for Potato Leafhopper in Alfalfa

Monitor soybean fields closely for soybean aphids

Keith Waldron
NYS IPM

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Soybean aphids (SBA) have been reported in most NY soybean sentinel site locations this season. Fortunately, most fields appear to have low SBA populations (0 - 49/SBA plant) at this time. There are a few exceptions, however. Several central NY locations have reported up to 100 SBA's per plant on young soybeans. In central NY there are reports of fields with an excess of 1000 SBA's per plant (well above threshold the 250 SBA / plant threshold). These fields are also stunted, have areas leaf curling and the sticky "honey dew" residue associated with a high aphid population and relatively low numbers of natural enemies. Above threshold SBA numbers at this early a stage of soybean development raises concerns. Some fields have been sprayed with insecticide. If treated, these fields should be monitored closely for a potential resurgence in aphid populations later in the season. The treatment that controlled the SBA's also took out the beneficials as well.

Dry weather conditions reduce the efficiency of insect attacking disease epidemics that help keep soybean aphids in check. Dry conditions can also favor the development of spider mite populations.

Given the recent reports on young seedlings it would be prudent for soybean producers to check fields as soon as possible. Aphids are capable of explosive population growth if given favorable conditions. Last season several locations reported SBA populations on V2 soybeans. Fortunately, SBA populations at these locations did not reach threshold levels. How much of an issue will SBA's be in NY this year remains to be seen. Frequent monitoring will provide the information needed to avoid problems.

SBA threshold guideline - 250 soybean aphids per plant at or near R1 is the guideline for SBA management. This information comes from research trials conducted over the past several years by entomologists at a number of midwestern universities.

The 250 SBA / plant action threshold is based on an average of aphids per plant over 20-30 plants sampled throughout the field. Regular field visits are required to determine if aphid populations are increasing. Midwestern research has found that treating earlier than this threshold in most cases does not pay for itself. But if you have aphids at flowering, the SBA population is increasing compared to the previous weeks count, no or insufficient numbers of natural enemies are present, or other limiting factors are present such as drought, the treatment of SBA may be warranted. Yield loss is due to pod abortion and once pods are gone, there is no recovery of yield other than getting seed a bit bigger. This recommendation has held up well over the past 5 years.

When scouting the early vegetative stages of soybeans for soybean aphid, it is just as important to watch for the aphid's natural enemies, including ladybugs, syrphid fly larvae, parasitic wasps, and fungal pathogens. How many SBA's are present? What's 60 or 250 SBA per leaflet look like? Count, estimate and perhaps check out the
"Visual Guide For Soybean Aphid Scouting" brochure developed by the U. of WI. (http://www.plantpath.wisc.edu/soyhealth/pdf/sba_scout.pdf.). Remember the SBA threshold guideline is 250 SBA's per plant

We are still gaining knowledge regarding this insect. Your observations will help document SBA presence, abundance, and help identify locations with potential concerns. Individuals monitoring NY soybean rust sentinel sites have been asked to report presence and abundance of soybean aphids. This information is being added to the NY information for soybean rust / soybean aphid available on the National USDA PIPE website (www.sbrusa.net). If you wish to share your SBA observations send comments to Keith Waldron (jkw5@cornell.edu). Information on date, location, average SBA population number, plant growth stage, and aphid form (winged or wingless) will be helpful. Feel free to include additional commentary such as presence of natural enemies, crop condition, other pests observed.

The USDA recommends the following protocol to monitor soybean aphids.

1. In soybean rust/soybean aphid sentinel plots, note the latitude and longitude with a GPS unit.
2. Select 20 plants at random, each from a different location (not consecutive down the row) so that the 20 plant-sample is representative of the entire plot. Identify the growth stage of 5 of the 20 plants.
3. Examine the entire plant beginning with the growing point (newest trifoliate) for soybean aphids. If plants are in vegetative growth (no pods or flowers) generally only the growing point needs to be examined. As flowering and pod set occur, examine the entire plant, including pods. Spend no more than 30 sec to examine an individual plant.
4. Count aphids per plant when they are below 250 and estimate aphid density when aphid numbers exceed 250. Apterous (wingless) aphids are assumed to be present. Note whether alate (winged) aphids were also observed. Notes could also be used to indicate if any predators or parasitized aphids (mummies) are present or other such noteworthy observations on crop growth and field condition.

Is corn under threat from European corn borer yet?

Julie Dennis
NYS IPM

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European corn borer (ECB) adults were plentiful in trap catches across New York State since the middle of June, but numbers are now declining. ECB egg masses and newly hatched larvae have been found on sweet corn in scouted fields for several weeks now. The trapping network in western NY is managed and reported on by Abby Seaman, NYS IPM’s WNY extension educator for vegetables. You can check out her weekly updates online at: Sweet Corn Pheromone Trap Network for Western New York

What does it mean for us in field corn when ECB adults, eggs, and larvae are present? The first generation of caterpillars generally only causes minor leaf feeding injury. A healthy corn crop in the whorl stages will outgrow any feeding damage that may happen. The greater potential for economic loss from ECB will happen later in the season when they bore into the stalks. Feeding on whorl stage corn looks like this: ECB damage

Full-grown ECB larvae are up to 1 inch long. The larvae are creamy-white to pink in color with a dark brown head capsule. There is a ring of dark colored spots on each segment of the caterpillar.

NYS 2007 Asian Soybean Rust Status

Gary Bergstrom
Cornell Univeristy Plant Pathology

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http://www.ppath.cornell.edu/soybeanrustny/

Scouting has begun in the twenty New York State sentinel plots located in the following counties: Cayuga, Chautauqua, Chemung, Chenango, Columbia, Cortland, Jefferson, Oneida, Onondaga, Ontario, Orleans, Oswego, Otsego, St. Lawrence, Seneca, Steuben, Suffolk, Wayne, and Wyoming. Updates on scouting efforts in these sentinel plots will be posted weekly on the NY State Soybean Rust Information Center.

Soybean rust was reported in three new locations on June 21, 2007. Two reports come from sentinel plots located in Avoyelles and Rapides Parishes in Louisiana. Additionally, soybean rust was reported in a commercial field in Cameron County, Texas. This is the second detection of soybean rust in a commercial field in Texas in the month of June. On June 14th, a commercial field in Hidalgo County, Texas was confirmed to have soybean rust. Soybean rust was found on volunteer soybeans in this county earlier this year as well as last year on late planted soybeans. Soybean rust has been detected to date in 10 counties in Florida, five counties in each of Georgia and Alabama, and four Parishes in Louisiana and three counties Texas.(Updated June 26, 2007 )

Which is Corn Rootworm?

Ken Wise
NYS IPM

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Have you ever gotten western corn rootworm confused with the striped cucumber beetle? Do you know the difference between corn rootworm and striped cucumber beetle? Striped Cucumber Beetle and Western Corn Rootworm look similar but are two different species of insects.

Striped Cucumber Beetle, Acalymma vittatum
The Striped Cucumber Beetle adult is about 1/4 inch long and the upper body surface is about equal black and yellow, the folded wing covers forming three longitudinal black stripes. The adult beetle starts appearing on several vegetable crops starting in mid-June.

Western Corn Rootworm, Diabrotica virgifera virgifera
Female Western Corn Rootworm is 5/16 inches long with three black strips alternating with yellow. Male Western Corn Rootworm is mostly black with a small area on the poster end that is yellow-green. Adults start appearing in mid to late July

Female Western Corn Rootworm

Insect Markings:
Stripes are less distinctive and do not extend to the tip of the abdomen
Insect size:
5/16 inches long
Host range:
Primarily Corn, Secondary Cucurbits
Emerge:
July
Life cycle:
1. Over-winter as eggs in the soil in the field
2. Eggs hatch and larvae feed on the corn roots starting in late May
3. Adults emerge at time of corn pollination. Males emerge first
4. Adults lay eggs in cornfields mid to late pollination
5. Adults die, eggs overwinter

Striped Cucumber Beetle

Insect Markings:
Both sexes have stripes, are clearly defined, and extend to the tip of the abdomen.
Insect size:
1/4 inch long
Host range:
Primarily Cucurbits, Secondary beans, corn, potatoes and other crops
Emerge:
June
Life cycle:
1. Over-winter as adults in woodland litter or in the soil.
2. Lay eggs at the base of the plant in mid-June through mid-July
3. Larvae develop for 2 to 4 weeks on the roots, pupate in the soil.
4. Adults appear in early to mid-August
5. Adults produced this season overwinter

Learn more about the differences between Western Corn Rootworm and Striped Cucumber Beetle:
Cucumber Beetles, Corn Rootworms, and Bacterial Wilt in Cucurbits

Clipboard Checklist

Keith Waldron
NYS IPM

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General:
* Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
* Watch for early season weed escapes, any patches of herbicide resistant weeds?

Corn:
* Determine plant populations, make notes on emergence, drought, and other problems
* Check for cutworm, armyworm, European corn borer, leaf blights, slugs, bird and deer damage
* Monitor for weeds, note presence of "who", "how many" and "where"
* Adjust post emergence weed control actions as appropriate

Small Grains:
* Monitor winter grains for crop growth stage, insect and disease problems
- evaluate crop for adequate stand and plant vigor
- evaluate crop for Fusarium head blight (Scab) and other grain head diseases
* Check, clean, prepare storage bins to accept upcoming harvest?
* Mow around storage bins to remove rodent habitat, remove spilled grain
* Clean grain handling equipment (conveyors, wagons, trucks, combines, elevators, etc.) for signs of leftover grain - remove potential sources of stored grain insect infestations.

Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, potato leafhopper and diseases.
* Check established alfalfa stands for potato leafhopper, weed and disease problems
Soybeans:
* Monitor for soybean aphids, and other insects, including natural enemies such as lady bird beetles.
* Check droughty fields for presence of spider mites

Dairy Livestock Barn Fly Management:
* Check confined animals and barns for house and stable fly populations
* 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)

Dairy Livestock Pasture Fly Management:
* Monitor animals for face, horn, and stable fly populations
* Check feed troughs, around waterers for signs of stable fly breeding.
* Consider use of traps if horse and stable fly populations are a problem

Equipment:
* Note any repairs needed for recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.
* Service planters, alfalfa harvesting equipment, and tillage implements as needed.
* Calibrate manure spreaders - maintain records on amount spread per field
* Check, clean, adjust and service small grain harvesting equipment as needed.

Upcoming Events


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SEED GROWERS FIELD DAY
NYSIP Foundation Seed Barn
Thursday, July 5, 2007
Ithaca, NY (761 Dryden Road, Route 366)
Registration and Coffee at 9:00 AM
Tour Begins at 9:30 AM

WEED SCIENCE FIELD DAYS

Valatie Research Farm – July 6
(Stage Farm Road just off Route 9, North of Valatie)
Registration and Coffee at 9:00 AM
Tour Begins at 9:30 AM to 12 Noon
(Field Crops)

Robert B. Musgrave Research Farm- July 11
(Popular Ridge Road, connects 90 and 34B)
11:00 am to 1:00 pm-Chicken BBQ
1:00 pm Registration
1:30 pm to 5:00 pm Tour
(Field Crops)

H.C. Thompson Research Farm- July 12
Freeville, NY 10 miles north of Ithaca, Fall Creek Road Rt. 366 extension)
8:00 am Registration ($8 Informational Packet)
8:30 am to Noon-Vegetable Weed Control

AURORA FIELD DAY
ROBERT MUSGRAVE RESEARCH FARM
Thursday July 26, 2007
Poplar Ridge Road, Aurora, NY (connects 90 and 34B)
Coffee at 9:30 AM
Tour Plots 10 AM to 3 PM

 

Contact Information


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Julie Dennis: 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