Weekly Field Crops Pest Report 2006

View From The Field

Western NY and Finger Lakes

Julie Stavisky, NYS IPM

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Eastern NYS

Ken Wise, NYS IPM

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Potato leafhopper numbers are variable across the region.  Among the growers in the Yates County TAg team, regrowth following 2nd cutting is all over threshold.  From the Livingston County TAg team, some fields have high numbers and some are staying low.  In Wyoming county, I observed low numbers of PLH in Julie Hansen’s variety tests the day after a heavy rainstorm. 

Corn rootworm adults are beginning to emerge.  Keep on reading the rest of this week’s report to learn more!

Soybean aphid numbers have remained low, except for an occasional plant with 100-plus aphids.  Let’s bear in mind that soybean aphids can be deposited by storms, so the aphid situation could change overnight.  Let’s keep up the vigilant scouting.

During a soybean TAg meeting in Ontario county last week, Mike Stanyard saw several Mexican bean beetle adults.  Although they are a common pest in dry beans and snap beans, Mexican bean beetles do not often visit soybeans.  Here’s a link with a photo of this “ladybug gone bad.” http://entweb.clemson.edu/cuentres/cesheets/soybean/ce55.htm

Downy mildew is prevalent in soybeans that I have observed in Seneca, Ontario, and Genesee counties.  See the article and photos below.

This week at the Cornell University Research Farm in Valatie, potato leafhopper infestations were very high. In a second year field I counted 300 potato leafhoppers in 3 sets of 10 sweeps in 22 inch alfalfa.  But at the SUNY Cobleskill farm potato leafhopper populations were very low with less than 10 per 10 sweeps with the net in 24 inch alfalfa.

I did find some corn rootworm damaged plants at the SUNY Cobleskill Farm. The larvae had eaten 90 percent of the roots of the plant, thus the plant had fallen over. When a corn plant falls over it attempts to grow back up toward the sun causing a curve in the lower part of the plant. This is called goose necking or J necking. See photos below.

The soybeans that I monitor weekly in Columbia County look very good. There are very few aphids at this point this year.

Know your corn rootworms

Julie Stavisky, NYS IPM

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Corn is beginning to tassel, and the first rootworm adults are being spotted in western NY. Corn rootworm beetles will be feeding on the pollen for the next few days, and then they are most likely to be observed in the silks of developing ears. Here’s a review of how to identify the adult rootworms:

Western corn rootworm (WCRW) adults are black and yellow beetles that are approximately 1/4 inch long. The female is yellowish with 3 black stripes on its back, while the male is solid black with a pale yellow area at the tip of its abdomen (see photos). Northern corn rootworm is slightly smaller than the western, and it is bright green in color (see photo).

The northern corn rootworm (NCRW) used to be the predominant species in New York State, but since the arrival of the western in the 1980’s, the western has become the dominant species. When scouting, 1 western corn rootworm equals 2 northern corn rootworm adults. During pollination, developing ears can tolerate many rootworms feeding on silks (10+ per ear) as long as silks are not trimmed to less than 0.5 inches without suffering economic losses.

Pollen Islands will Attract CRW

Keith Waldron, NYS IPM

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Remember those corn fields that had troubles with uneven emergence, ponding, compaction, fertilizer, herbicide, or other planting time issues? Drive by many of these fields this week and their up and down plant height patterns look more like a side view of a crazy roller coaster ride than the ideal production field…  And now watch the pattern of tassel emergence.  Whatever the reason for the uneven stand its effect on corn rootworm (CRW) populations can be very predictable.  CRW beetles are pollen feeders and will zero in on plants producing pollen. So in fields with large differences in corn maturity expect that CRW beetles will “head to the islands” of pollinating corn. In fields of uniform crop growth stage, CRW egg laying is reasonably well distributed. (Recall that CRW females are capable of producing eggs about 3 weeks after they emerge…) In the case of the pollen island fields, CRW egg laying may be expected to be more concentrated in the areas where the pollen (food source) is. You can also expect that the highly mobile CRW beetles will follow the pollen sources from clump to pollinating clump…. Watch these areas closely for signs of potential silk clipping as hungry CRW populations build up in them – high numbers of CRW beetles could interfere with pollination and grain fill. 

Since these areas can be at higher risk for egg laying – make a note of their location(s). Record any scouting information. Should egg laying be high enough in those “islands”, it is a good bet that they would be at higher risk for lodging from CRW larval feeding next year should corn be replanted into the same field. Better yet? If cropping schedules allow, this field may be a good candidate for rotation next year.

NOTE: The sequential sampling method for sampling CRW assumes the field is uniform in physiological development. This sampling procedure is dependent on an even distribution of corn rootworm beetles across the field.  Fields with uneven development from uneven germination or water stress should not be sampled using this sequential sampling procedure since the beetles will be clumped on pollinating plants.

If sampling for CRW in fields with “uneven growth development” follow the method recommended in the Cornell Field Crops Guide.  CRW counts are taken from 55 corn plants sampled at random. The threshold is 55 CRW beetles. When determining fields at risk recall that the Western corn rootworm beetles count as one and northern CRW beetles count as 0.5. For more information see the Cornell Guide for Integrated Field Crop Management field corn insect (CRW) management (3.6.2.2).

Corn Rootworm Scouting Tip (Are They Gravid?)

Ken Wise, NYS IPM

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Remember, when taking beetle counts you are monitoring to assess the potential that CRW's will lay enough eggs in the field to cause damage to next year's corn crop. Taking beetle counts is important but make sure you stop to check a portion of the female western CRW's for the actual presence of eggs.  (Gravid CRW females have eggs). Squeeze the abdomens of the yellow and black striped CRWs and look for the small yellow - white eggs. It takes CRW about three weeks from the time the adult beetles emerge from the soil and mate until the time the females are gravid. In this time period you may find high CRW numbers in a field but since the females are not yet capable of laying eggs they are not causing an economic problem. This is the reasoning behind sampling the same field 2-3 times before making the management decision. Being pollen feeders and highly mobile, CRW's may relocate to another pollinating field during the 3 week period. Comparing the two types of fields, the second field is at greater risk from subsequent CRW damage since females (and their eggs) will have matured and are ready for deposit.

When is the best time to control corn rootworm if a field exceeds the action threshold?

• The following year!

• If there is a field over the action threshold what are the options for control next season?

• The best option to control corn rootworm is crop rotation. Corn after corn is prime habitat for corn rootworm and will increase infestations from year to year.

• Crop rotation is not always possible so ....... The second management option is the use of a soil-applied insecticide at planting. To select an insecticide registered for corn rootworm, please consult the Cornell Guide for Integrated Field Crop Management.

• Additional CRW management technologies are now available.  You can use insecticide treated seed to control moderate populations of CRW infestations

Well adapted hybrids are now available that contain Bt specific for CRW.

Downy Mildew in Soybean

Julie Stavisky, NYS IPM

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Last week, reports of downy mildew on soybean foliage in New York State started coming in. This fungal disease is generally observed on leaves in the middle and upper canopy. Downy mildew can be identified by the pale yellow or greenish irregular areas on upper leaf surfaces. These spots show through to the lower leaf surface, where the affected areas are grayish. Under humid conditions, grey tufts of the fungus are apparent on these spots on the underside of leaves (see photos below). Soybean productivity is generally not affected by downy mildew.

On a severely infected plant, downy mildew also can affect soybean seed. While pods show no symptoms, seeds inside can be covered with white fungal mycelia. If this infected seed were planted, stunted seedlings with mottled leaves would result.

The fungus that causes downy mildew can survive on infected leaves and seed. A key management strategy for downy mildew is to not plant contaminated seed. Rotation to a crop other than soybean or tillage that deeply buries infected crop residue effectively control downy mildew.

	Downy mildew on the upper leaf surface
	Downy mildew on the lower leaf surface

Soybean Rust Update

Gary Bergstrom, Cornell University

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Weekly scouting is occurring on 19 sentinel plots located in Cayuga, Chautauqua, Chemung, Chenango, Columbia, Genesee, Herkimer, Jefferson, Montgomery, Oneida, Onondaga, Ontario, Seneca, Tompkins, Wayne, and Wyoming Counties. Plant growth stages in NY state have been reported to range from V5-R3. Low levels of Septoria brown spot continue to be found in several of the sentinel plots.  In addition, we have found low levels of downy mildew and bacterial pustule.  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. To date, in 2006, soybean rust has been reported in five counties in Alabama, 12 in Florida, one in Texas, five in Georgia, and two in Louisiana. Currently, there are no known reports of rust on commercially planted soybean in 2006. Dry to very dry conditions prevail in the spore source regions and movement to new areas has been slow. There is virtually no chance that rust will cause yield loss to soybean in New York in 2006. Last updated July 19, 2006.

For more see the New York State Soybean Rust Information Center website.

Growing Degree Days in NYS

Ken Wise NYS IPM

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Accumulated Growing Degree Days for March 1 to July 12

*indicates missing data

Source: NEWA

Clipboard Checklist

Keith Waldron-NYS IPM

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General:

* Maintain crop records by field, including crop condition, inputs, observations, issues, concerns, etc.

* Storage areas cleaned and ready to accept wheat harvest? Check and disinfect inside, under and around grain bins.

* Mow around barn and farm facilities

* Clean and store weed sprayers. Flush tanks, booms, nozzles.

Established Alfalfa & Hay:

* Monitor for potato leafhopper- harvest early or spray on basis of need.

* Monitor for diseases, particularly Verticillium wilt, record information on disease species and location for future cropping decisions.

* Monitor for Phytopthora root rot in fields recently flooded or subject to ponding.

Alfalfa Seedings:

* Continue monitoring for potato leafhopper, weeds and diseases.

* Monitor fields for weeds and diseases: record information on type and location for future cropping decisions.

* Monitor for Phytopthora root rot in fields recently flooded or subject to ponding.

Summer Forages:

* Plant birdsfoot trefoil by end of July.

Small Grains:

* Adjust combine in preparation for winter grain harvest (late-July) or spring grain Harvest (early to mid-August). Contract custom-operation if necessary.

* Clean grain storage areas.

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

Corn:

* Monitor corn rootworm adults at silking.

* Observe corn for crop growth and condition, weeds, foliar diseases and fertility

Soybeans:

* Monitor for crop condition and growth stage, soybean aphids, natural enemies, foliar diseases, soybean rust

* Monitor for Phytopthora root rot in fields recently flooded or subject to ponding.

Livestock:

* Continue manure management and release of biological control agents (parasitic wasps) for house fly and stable fly control in barns

* 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, adjust paddock rotation as needed.

Equipment:

* Provide annual maintenance to fertilizer and pesticide application equipment,

* Note any repairs to harvesting equipment as they are cleaned and lubricated.

* Ready combine for small grains or finalize arrangements for custom harvest

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