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NY Weekly Field Crop Pest Report, 2005

July 14, 2005 Volume 4 Number 13

1. View from the Field

2. Potato Leafhopper-Feeling Heat Stressed?

3. Why Use Potato Leafhopper Resistant Alfalfa?

4. Wild Buckwheat, Field Bindweed and Hedge Bindweed

5. Spider Mite Update

6. Soybean Aphid Predators-The Flower Fly

7. Soybean Rust Update

8. Clipboard Checklist

9. Growing Degree Days in NYS

10. Contact Information

View from the Field

Eastern NYS

Ken Wise

Western NYS

Julie Stavisky

Keith Waldron, NYS IPM

Potato leafhoppers are on the rise. I was in a few older alfalfa fields at the Valatie Cornell Farm where potato leafhoppers were over threshold, while the new seeding fell far under the threshold. Most of the leafhoppers were nymphs.

Soybeans were in the V4 to V5 stage of development. Soybean aphids remain at low infestation levels. I was finding 0 to 15 aphids per plant. I did find some seven-spotted ladybeetles in the field.

Field corn looked very good and just a few plants with European corn borer damage. Field corn was also pollinating but no signs of adult corn rootworms.

Large infestations of spider mites were observed in soybeans in Orleans County this week. Numbers were highest at field edges near drought stressed weeds and on plants threatened by other stresses.

Western corn rootworm adults have been observed in tasselling corn in several counties.

Potato leafhopper numbers continue to stay fairly low in new alfalfa re-growth.

Soybean aphids are present in every field observed, though they vary in abundance from less than 20 per plant to hundreds per plant. Insecticide test plots with untreated check strips have been sprayed in Seneca county and Orleans county. The more check strips that we evaluate this year, the more confidence we will gain in our threshold of 250 aphids per plant. Contact Keith, Ken, or Julie for more information on putting in a test plot.

PLH numbers are on the increase. Populations are spotty in the Ithaca area. Judging by the signs of insect injury, the PLH resistant alfalfa variety trial appears to have a nice population of PLH. We look forward to more good data from Julie Hansen and Cornell’s Forage Project Team

Potato Leafhopper-Feeling Heat Stressed?

Keith Waldron, NYS IPM

Potato leafhoppers appear to be well distributed across the state this season. Fortunately for many of us PLH populations have been below economic injury levels. What’s up with Potato leafhoppers lately?

Part of what’s affecting population build up might be our hot summer heat. The optimum temperature for PLH egg laying is 76F with no egg laying above 90 F or below 62 F. Recall that PLH eggs are about 1 mm in length and hatch in approximately 10 days. PLH moms can lay 2-3 eggs per day over their lifetime. Temperatures can also affect nymph development. PLH young go through 5 nymph stages over a period of 12-35 days. Development is most rapid at 86 F, no development occurs below 54 F, and development is inhibited above 88 F. The total period from egg to reproductive maturity is about 28 days, under favorable conditions. Approximately 815 F degree days (base 54 F) are needed for development from the first nymph stage to adult hood. PLH factsheet see: Insect management section potatoes http://www.nysaes.cornell.edu/recommends/24frameset.html

Why use Potato Leafhopper Resistant Alfalfa?

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. Some of the most recent releases of PLH resistant alfalfa are as high as 70 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 our on-line IPM guides: IPM for Potato Leafhopper in Alfalfa.

Wild Buckwheat, Field Bindweed and Hedge Bindweed?

While scouting this week I stumbled over some wild buckwheat in a corn field. As you know they can easily trip a person up! After brushing off the dust I did have to go and check my weed guide to make sure it really was wild buckwheat. It's fairly easy to get Wild Buckwheat, Field Bindweed and Hedge Bindweed mixed up. Some call them all bindweed. The following table is a guide to help distinguish between the weed species:

Plant Characteristic

Field Bindweed

Hedge Bindweed

Wild Buckwheat

Leaves

Leaves are 1 to 2” long, smooth and shaped like an arrowhead. The leaf sides are generally parallel. Single point basal lobe.

Generally triangular shaped and somewhat pointed. Double point basal lobe.

Heart-shaped leaves with a pointed tip.

Flower

White or pale pink, about 1” across

White or pinkish,

1.5 to 2” across

Very small and green

Roots

Deep rooted

Roots are relatively shallow but very extensive

Root are shallow

Life Cycle

Perennial

Perennial

Annual

Other features

 

 

Wild buckwheat has an ochrea(membranous sheath) at each node.

Spider Mite Update

Julie Stavisky, NYS IPM

Spider mites have become a significant pest in areas of western New York state. The following photos, taken Monday, July 11th in Orleans County show 1) high number of spider mites and webbing at the leaf tip; 2) spider mites on the underside of a leaf; and 3) the stippling injury on the upper leaf surface.

Spider mites 1 Spider mites 2

Spider mites 3

Soybean aphid predators - the flower fly

Julie Stavisky, NYS IPM

The widespread reports of heavy soybean aphid infestations in many places in New York has led to an impressive number of people scouting their soybean fields. Almost everyone keeps on the lookout for lady beetles in their observations, but there is another stealthy predator who often escapes notice - the larva of the flower fly.

With black and yellow stripes on their abdomen, the adults of the flower fly often mimic bees in their appearance (see photo below). Flower fly adults play an important role in pollinating many plants as they feed on nectar and pollen in flowers. These flies are often observed hovering near flowers, and thus are sometimes referred to as hover flies. Eggs, which are 1mm in length, are laid singly in the vicinity of aphids. Larvae are legless with a tapered head (see photo below). Coloration of larvae varies from green with a white stripe to yellowish or brownish. Newly hatched larvae may be as small as 1 mm, and fully developed larvae may be up to 12 mm in length. The larvae are slow-moving and they are often difficult to see, but they voraciously consume aphids. During its development, a flower fly larva may consume between 200 and 800 aphids!

Flower flies are one of many predators that provide naturally occurring defense against soybean aphids, but they are also susceptible to insecticides used for aphid control.

(Photos from IPM Images, http://www.ipmimages.org)

Soybean Rust Update

Keith Waldron, NYS IPM

Septoria brown spot and bacterial blight have been observed in NY, but fortunately still no reports of SBR.

From the NYS soybean rust website: 2005 Asian Soybean Rust Status

Soybean rust on soybeans has only been reported in Florida and some adjacent counties in Alabama and Georgia. The most recent Alabama and Florida finds were in sentinel soybean plots, while the Georgia find was on volunteer soybeans. Scouting and spore trapping continues throughout the soybean production areas of the U.S. Scouting of sentinel plots in New York State continues this week and to date no soybean rust has been found. The risk of soybean rust infection in New York is currently considered to be low and no fungcide application for soybean rust is advocated at this time. Septoria brown spot is the most prevalent foliar disease in all 10 of the research protocol sentinel plots in New York State over the past two weeks. Bacterial blight has also been observed and soybean aphid populations are increasing. Growth stages in New York State sentinel plots range from V5 to R2 stages and several are flowering. Scientists are intensively monitoring soybeans in the path of recent tropical storms and are following the paths of Hurricanes Dennis and Emily for their potential to move soybean rust spores to wider areas of the U.S. (Last updated 7/14/05)

For more see: http://www.ppath.cornell.edu/soybeanrustny/default.htm.

Clipboard Checklist

Keith Waldron, NYS IPM

General:

• Maintain crop production activity records by field, including harvest date, pesticides used, nutrient inputs including manure, etc.

Alfalfa & Hay:

• Continue monitoring for potato leafhopper- harvest early or spray on basis of need.

• Monitor for diseases record information on type and location for future cropping decisions.

• Prepare for summer seedings of alfalfa. Test soils. Lime as needed.

Small Grains:

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

Corn:

• Monitor for foliar and stalk diseases, nitrogen and other nutrient deficiencies, European corn borer, weeds.

• Monitor corn rootworm adults at silking.

Soybeans:

• Monitor for soybean aphid, soybean rust, foliar diseases.

Livestock:

• Continue livestock facility sanitation management (manure, feed bunks and storage areas, waterers, etc.). Cleaner, less fly production

• Initiate integration of biological control agents into house fly and stable fly management program.

• Mow around facilities to minimize rodent habitat.

• 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

- Check and clean pasture water supplies.

Growing Degree Days in NYS

Keith Waldron, NYS IPM

March 1 - July 5, 2005

Location

Base 50 F

Batavia

1126.2

Chazy

919.2

Clifton Park

1346.3 * * Missing data

Geneva

1109.165*

Ithaca

1023.6

Prattsburg

978.6

Source: http://newa.nysaes.cornell.edu/

Contact Information

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