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Weekly Field Crops Pest Report 2008

July 24, 2008                 Volume 7 Number 15

1. View from the Field

2. Weather Outlook

3. Corn Rootworm Scouting TIP!

4. White Mold in Soybeans

5. Pollen Islands will Attract CRW

6. Partial Alfalfa Field Harvest Increases PLH risks

7. Soybean Rust Update

8. Soybean aphid update

9. Clipboard Checklist

10. Contact Information

View from the Field

Ken Wise & Keith Waldron
NYS IPM

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No reports this week of major field crop pest activity across the state.

Most observations reported this week include mention the impact frequent rain showers are having on field activities such as wheat and forage harvests, crop growth and development and apparent nutrient uptake. Moisture can help encourage epizootics of fungal diseases of insects that can help curb populations of such pests as soybean aphid. Moist conditions can also favor various field crop diseases. While moisture is needed for healthy crop growth, moderation and timing is appreciated!

Potato leafhopper (alfalfa) and soybean aphid (soybeans) counts appear to be low this week.  Both insects, however, can be transported with weather fronts and may become more noticeable in the weeks to come. Only by scouting will we know for sure. Stable flies, a pest of dairy animals, other livestock and humans can also be transported on weather fronts. As noted in last week‚s pest report, numbers of this pest have noticeably increased over the last several weeks.

There have been some reports of Japanese beetle defoliation injury in soybean fields across the state. The good news is that soybeans can withstand a lot of feeding before any yield losses can occur. The soybean defoliation threshold is 35 percent of leaf area eaten or missing from V1 to just before bloom. During blooming through pod-filling stages, the threshold is 20 percent defoliation.

Corn tasselling and silking is more obvious in many areas across the state this week. Make sure to monitor any corn field that will remain field corn next year for corn rootworm beetle assessments. For no-till corn or fields with high previous crop residue, watch for early signs of foliar diseases.

Weather Outlook

Art DeGaetano
NOAA Northeast Regional Climate Center, Cornell University

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Temperatures averaged slightly above normal last week across NY.  The Southern Tier, Great Lakes and Hudson Valley saw temperatures about 4-5 degrees above normal.  In northern NY, temperatures were a degree or two above normal.  Precipitation was again plentiful with the majority of central, eastern and Northern New York receiving between 1 and 2 inches of rain.  In central New York a few 2-3 inch totals were also observed.  The Lower Hudson Valley, New York City, southwestern NY and the Mohawk Valley were relatively dry with some places, particularly in the south receiving less than 0.5 inches.  This was before the heavy rains that are currently occurring in these areas.

Last week approximately 150 base 50 GDD accumulated across central and Eastern NY, with a few spots picking up as many as 175 GDD.  In the Adirondacks only 100-125 GDD accumulated.  Since March 15, the majority of the state has accumulated 1400 GDD, with as many as 1600 in the Lower Hudson Valley and only 900 in the Adirondacks.  These accumulations are slightly ahead of last year‚s values except in the southwest part of the state.  The 2008 accumulation is about a week (125 GDD) ahead of the long-term normal.

The pesky upper air low that has given us our fair share of rainfall this week, will start to depart today and finally exit the region on Friday, The next front approaches the state on Saturday and will bring NY another showery weekend.  By Monday the region should see another 1 inch plus rain event with locations in the extreme eastern parts of the state, including NY City and Long Island and much of New England picking up as much as 2-3 inches of rain.  The trough will persist over the Northeast through mid week bring daily chances of showers and thunderstorms.  However, most days will be at least partly sunny with temperatures very near the normal for late July (highs in the 80s and lows in the upper 50s and low 60s).

Beyond mid-week, a trough is expected to persist in the east continuing the pattern of frequent showers and generally normal temperatures.

Corn Rootworm Scouting TIP!

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. Squeeze the abdomen of the yellow and black striped female CRWs and look for the small yellow ˆ 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 corn rootworm infestations.

CRW resistant (Bt hybrids) are also available for use to manage CRW. If you choose to use them, don‚t forget to plant the non-Bt refuge portion of the field.

<http://nysipm.cornell.edu/publications/crw_bro/default.asp>How to Monitor for Corn Rootworm

White Mold in Soybeans

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Highly productive, wet and dense stands of soybeans favor white mold development. The fungus survives from year to year in the soil as hard black pellets called sclerotia. Sclerotia of white mold must be present to cause the disease, and a small number of sclerotia on the soil surface can lead to significant outbreaks if wet, cool conditions are present while plants are flowering. Under favorable conditions, sclerotia germinate and form small mushroom-like structures (apothecia). The apothecia produce ascospores which can be spread by wind and splashing rain. Ascopsores require a nutrient source to grow, and soybean flowers serve as ideal locations. The fungus colonizes dead flowers and the characteristic thick white, cotton-like moldy covering on stems and pods develops (see photo below). Close inspection should reveal the black („rat feces‰-like) sclerotia mixed in with the white mold on stems. Infected plants can show wilt symptoms and stems will have a soft rot. Infection leads to premature death of plants. If white mold infection occurs late in the season, yield loss will not be as severe. Temperatures over 90 degrees will typically stop disease development. During harvest, the sclerotia on stems and pods may end up in the soil or residue, or may stay with harvested seed.  Fields where white mold has occurred in the recent past are where it will most likely occur, so these are the fields to scout the most closely for disease development.

The following photo shows the white mold infection on a plant that is starting to wilt.

Photo taken by Mike Stanyard

A key to white mold management is to find strategies to prevent the build-up of the pathogen in a field. In addition to soybean, common bean and sunflowers can serve as favorable hosts for this disease. . Rotation to nonhost crops such as corn, wheat or other grass for at least 1 year (ideally 2 or more years) is recommended. Additionally, weed management practices that reduce weeds that serve as alternate host for white mold (for example lambs quarters and pigweed) will help to decrease build-up of the pathogen. It is also essential to avoid the planting of contaminated or infected seed, and to avoid the movement of infected soil with equipment. A strategy for preventing movement of infected soil is to harvest fields infected with white mold last. Varieties of soybeans that are tolerant or moderately resistant to white mold should be selected. Yield protection by spraying fungicides has not been documented in New York.

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 ˆ high numbers of CRW beetles could interfere with pollination and grain fill. 

Since these areas can be at higher risk for egg laying ˆ 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 an average of 1 western corn rootworm beetle / plant  (or 2 northern CRW beetles / plant). 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). (see field corn insect management section)

Partial Alfalfa Field Harvest Increases PLH risks

Keith Waldron
NYS IPM

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Are PLH in your alfalfa fields? If so, avoid partial field harvests to best manage PLH populations. Clean harvest of whole alfalfa fields is optimal, however our recent stretch of rainy weather has surely messed up more than one harvest schedule sometimes stopping a hay harvest in mid-stride. These partially harvested fields can set the stage for future PLH problems.  In situations where edges or portions of alfalfa fields have been harvested but other areas of the field are left intact watch closely for PLH populations and potential injury.

Adult PLH in the standing portion of the field can easily relocate to the shorter portion of the field and attack the vulnerable regrowth. The shorter alfalfa has a lower threshold for PLH than taller alfalfa so is at much higher risk for injury.

Harvesting remaining portions of the field as soon as is practical is recommended to minimize PLH population buildup and their easy movement to adjacent portions of the field.

Soybean Rust Update

Gary Bergstrom
Plant Pathology, Cornell University

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Sentinel plots in New York State have been established in the following counties: Cayuga, Chautauqua, Chemung, Columbia, Cortland, Jefferson, Lewis, Madison, Niagara, Oneida, Ontario, Schoharie, Seneca, Steuben, Wayne and Yates. Plant growth stages in these plots range from V-2 to R-2. Samples from two of the sixteen plots showed symptoms of Septoria brown spot last week.

Since the beginning of 2008, soybean rust has been reported on kudzu in one county in Alabama; one county in Georgia, thirteen counties in Florida (two of these counties had reports on coral bean and snap bean and one had a report on soybean); three counties in Louisiana; one county in Mississippi, and three counties in Texas. Reported infected kudzu sites in many counties have been destroyed. Rust was also reported in three states (5 municipalities) in Mexico on yam bean and soybean. These too have been destroyed or are no longer active.(Updated July 21, 2008 )

Soybean aphid update

Keith Waldron
NYS IPM

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No soybean aphid issues have been reported in NY so far this season.

Crop Growth Stage - V-1 to R-2

Variations in planting dates have soybean growth stages ranging from early vegetative (V2-V4 to R1, some fields in western NY just beginning to enter R2 stage). Soybean heights also vary from 12 inches to nearly 30 inches tall.

Observation and Outlook - Insect

Soybean aphid (SBA) populations continue to remain low across areas reporting in NY. SBA's are present in many (but not all) locations reporting from across the state, generally averaging 0 to less than 5 SBA's per plant. Occasional individual plants may have higher numbers. All fields reporting well below threshold. Natural enemy populations, such as lady bird beetles, are present and increasing in many areas.

Field monitoring has been hampered by frequent storms. It is not clear whether the storms have been helping to physically knock down SBA numbers from populations that may have been in fields or if the storms will be a source of new SBA from other regions. It is also possible, though not yet substantiated by direct observation, that the moist conditions brought by storms may be enhancing the biological control of SBA by entomopathogenic fungi. As mentioned earlier, only by scouting will we know for sure.

Scouting and Management - Growers are encouraged to monitor for presence of soybean aphids, other insects and diseases. Fields entering the blooming stages should be monitored closely for SBAs, foliar diseases and white mold.

For more on the current national Soybean aphid perspective see: www.sbrusa.net.

Clipboard Checklist

Keith Waldron
NYS IPM

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General:

* Emergency contact information ("911", local hospital, Chem. Spill emergency contact, other?) posted in central posting area

* Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, yields, etc.

* Watch for weed escapes, any patches of herbicide resistant weeds?

Field Corn:

* Check crop growth stage and condition

* Check for European corn borer, armyworm, foliar diseases, vertebrate injury (birds / deer), weed escapes, herbicide injury, nutritional deficiencies, etc.

* Tasselling / Pollinating corn check corn rootworm populations

* Monitor weed populations noting presence of "who", "how many" and "where"

* Check herbicide resistant corn fields for herbicide resistant soybean

* Adjust post emergence weed control actions

Small Grains:

* Evaluate standing crop for timing grain and straw harvest, evidence of sprouting (wheat)

* Storage areas cleaned and ready to accept next harvest?

Alfalfa & Hay:

* Monitor alfalfa seedings for weeds, for potato leafhopper & diseases.

* Check established alfalfa stands for potato leafhopper, weed and disease problems.

* Storage areas cleaned and ready to accept next harvest?

Soybeans:

* Check crop growth stage and condition

* Evaluate stand for soybean aphid, spider mites, deer, weed assessment, foliar disease incidence

* Check herbicide resistant soybean fields for herbicide resistant corn

Dairy Cattle: Livestock Barn Fly Management:

* Monitor animals and facilities for house fly and stable fly populations

* Check facilities for favorable fly breeding conditions: (organic matter + moisture): leaks in watering systems, roof gutters for leaks and potential overspill, drainage,

* 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 * Continue fly monitoring: install "3X5" index card fly speck monitoring cards through out barn

* Order fly management materials: fly tapes, insecticide baits, natural enemies (parasitoids)

* Continue release of purchased natural enemies (fly attacking parasitoids)

Dairy Cattle: Pasture Fly Management:

* Monitor animals for presence of face flies, horn flies and stable flies.

* Check feed bunk / water source locations for signs of stable fly breeding (moist undisturbed organic matter ć spilled feed, round bales, etc.) , minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard

* Check paddocks for forage quality / quantity, rotate as appropriate

* Check paddocks for vegetation poisonous to livestock

* Consider use of fly traps to help reduce deer, horse and stable fly populations

Storage:

* Pre-clean in and around grain bins before adding newly harvested wheat.

* Keep areas around storage bins and silos clean and mowed

Equipment:

* Note any repairs needed for recently used equipment: tractors, tillage implements, harvesting equipment, etc. as they are cleaned and serviced.

* Calibrate manure spreaders - maintain records on amount spread per field

Contact Information

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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