Corn flea beetle and Stewart's wilt predictions for 2004

Mike Hoffmann & Jeffrey Gardner, Dept. of Entomology, Cornell University, Ithaca.

John Gibbons, Ontario Co. CCE

Abstract: 2004 forecast:
 In general, the risk for 2004 is mostly "absent" across much of the state with some areas showing "moderate" risks. Risk maps generated using two different models can be accessed at 
http://www.nrcc.cornell.edu/grass/stewart_maps.html. The predictive models do not account for the insulating effect of snow cover. However, despite relatively heavy snow cover in 2002-2003, 
overwintering beetles suffered high mortality.

Stewart's wilt is an important disease of sweet corn in New York. The disease is caused by a bacterial pathogen that is vectored almost exclusively by the corn flea beetle. The bacteria overwinter in the gut of adult flea beetles. In the spring, beetles infest early plantings of corn and transmit the pathogen to the plant by feeding and defecating on leaves. Stewart's wilt is characterized by development of conspicuous streaks on the leaves and stalk due to plugging of vascular tissue. Early wilt infections cause reduction of yield in susceptible varieties by reducing stands due to death or stunting of infected seedlings. Seedlings, which survive early infections, remain stunted, tassel prematurely, and frequently produce no ears or nubbins. Disease severity is aggravated by high temperatures, which causes faster development and movement of the bacteria through the infected plants.

Corn flea beetles spend the winter as adults near the soil surface in grassy areas in and around cornfields. Severe winter temperatures can kill most of the population and result in a very low incidence of Stewart's wilt disease the following summer. Thus, a winter temperature index is used to predict the likelihood of Stewart's wilt problems. One forecast (modified Stevens-Boewe) is based the sum of the mean monthly temperatures for December, January, and February. The Stewart's wilt index (likelihood of wilt problems) is as follows:

Modified Stevens-Boewe

Index (winter temperature)	Likelihood of early season Stewart’s wilt
> 100	High
85 to100	Moderately High
75 to 84	Moderate
Below 75	Absent

2004 forecast:

This is the second cold winter in a row. Last winter (2002-2003) killed many of the overwintering corn flea beetles but we did observe an increased number of beetles in August of 2003. We don’t know if that represented a significant population heading into the 2003-2004 winter. In general, the risk for 2004 is mostly “absent” across much of the state with some areas showing “moderate” risks. Risk maps generated using two different models can be accessed at http://www.nrcc.cornell.edu/grass/stewart_maps.html. The predictive models do not account for the insulating effect of snow cover. However, despite relatively heavy snow cover in 2002-2003, overwintering beetles suffered high mortality.

Management options for Stewart's wilt disease control include:

1) planting resistant varieties

2) planting with treated seed for susceptible varieties

3) applying a foliar insecticide spray if needed to protect seedling corn

Below we have tabulated risk of Stewart’s wilt for many locations in NY (using the modified Stevens-Boewe method).

County	Site	Index	Risk
Albany	ALCOVE DAM	63	Absent
Albany	ALBANY COUNTY AP	68	Absent
Allegany	WELLSVILLE	63	Absent
Allegany	ALFRED	64	Absent
Allegany	ANGELICA	65	Absent
Broome	WHITNEY POINT DAM	62	Absent
Broome	BINGHAMTON EDWIN A LINK FIELD	65	Absent
Cattaraugus	FRANKLINVILLE	60	Absent
Cattaraugus	LITTLE VALLEY	63	Absent
Cattaraugus	NEW ALBION 2	64	Absent
Cattaraugus	OLEAN	68	Absent
Cattaraugus	ALLEGANY STATE PARK	68	Absent
Cayuga	LOCKE 2 W	68	Absent
Cayuga	AURORA RESEARCH FARM	72	Absent
Cayuga	AUBURN	73	Absent
Chautauqua	JAMESTOWN 4 NE	70	Absent
Chautauqua	DUNKIRK CHAUTAUQUA CO AP	78	Moderate
Chautauqua	Fredonia*	80	Moderate
Chautauqua	SILVER CREEK 2 NE	80	Moderate
Chautauqua	FREDONIA	83	Moderate
Chemung	CHEMUNG	61	Absent
Chemung	ELMIRA CORNING REGIONAL AP	67	Absent
Chenango	NORWICH	62	Absent
Clinton	ELLENBURG DEPOT	44	Absent
Clinton	DANNEMORA	48	Absent
Clinton	PERU 2 WSW	55	Absent
Columbia	COPAKE	69	Absent
Columbia	VALATIE 1 N	72	Absent
Cortland	TULLY HEIBERG FOREST	57	Absent
Delaware	WALTON 2	58	Absent
Delaware	EAST SIDNEY	61	Absent
Delaware	DELHI 2 SE	62	Absent
Delaware	ARKVILLE 2 W	63	Absent
Delaware	DEPOSIT	70	Absent
Dutchess	RHINEBECK 4 SE	66	Absent
Dutchess	POUGHKEEPSIE	74	Absent
Dutchess	STORMVILLE	77	Moderate
Dutchess	POUGHKEEPSIE DUTCHESS CO AP	79	Moderate
Erie	WALES	67	Absent
Erie	BUFFALO NIAGARA INTL AP	76	Moderate
Essex	NEWCOMB	39	Absent
Essex	LAKE PLACID 2 S	47	Absent
Essex	WILLSBORO 1 N	55	Absent
Franklin	TUPPER LAKE SUNMOUNT	41	Absent
Franklin	MALONE	42	Absent
Genesee	Elba	68	Absent
Genesee	Batavia	71	Absent
Genesee	BATAVIA	74	Absent
Greene	EAST JEWETT	58	Absent
Greene	PLATTE CLOVE	60	Absent
Greene	CAIRO 4 NW	72	Absent
Hamilton	INDIAN LAKE 2 SW	44	Absent
Hamilton	PISECO	44	Absent
Herkimer	OLD FORGE	41	Absent
Herkimer	BIG MOOSE 3 SE	48	Absent
Herkimer	LITTLE FALLS CITY RE	58	Absent
Jefferson	WATERTOWN AP	54	Absent
Jefferson	WATERTOWN	57	Absent
Jefferson	WELLESLEY ISLAND	61	Absent
Kings	NEW YORK	98	Moderately high
Lewis	HIGHMARKET	37	Absent
Lewis	LOWVILLE	47	Absent
Lewis	HOOKER 12 NNW	49	Absent
Livingston	HEMLOCK	71	Absent
Livingston	AVON	72	Absent
Livingston	DANSVILLE	74	Absent
Livingston	Groveland	76	Moderate
Madison	MORRISVILLE 6 SW	53	Absent
Monroe	ROCHESTER GREATER ROCHESTER IN	74	Absent
Niagara	NIAGARA FALLS INT'L	73	Absent
Niagara	NORTH TONAWANDA	77	Moderate
Niagara	North Appleton	79	Moderate
Oneida	BOONVILLE 2 SSW	46	Absent
Oneida	UTICA ONEIDA COUNTY AP	59	Absent
Oneida	CAMDEN 2 NW	61	Absent
Onondaga	SYRACUSE HANCOCK INT'L ARPT	68	Absent
Ontario	HONEOYE	72	Absent
Ontario	GENEVA RESEARCH FARM	72	Absent
Ontario	Farmington	75	Moderate
Ontario	CANANDAIGUA 3 S	76	Moderate
Orange	WALDEN 1 ESE	73	Absent
Orange	PORT JERVIS	74	Absent
Orange	MIDDLETOWN 2 NW	81	Moderate
Orange	WEST POINT	83	Moderate
Orleans	Albion	64	Absent
Orleans	LYNDONVILLE 4 ESE	75	Moderate
Orleans	ALBION 2 NE	78	Moderate
Oswego	OSWEGO EAST	72	Absent
Otsego	CHERRY VALLEY 2 NNE	59	Absent
Otsego	COOPERSTOWN	59	Absent
Otsego	MARYLAND 6 SW	59	Absent
Putnam	CARMEL	75	Moderate
Rensselaer	TROY L & D	68	Absent
Rensselaer	WEST SAND LAKE 2 S	74	Absent
Schoharie	LANSING MANOR	58	Absent
Schoharie	COBLESKILL 2 ESE	62	Absent
St. Lawrence	MASSENA AP	42	Absent
St. Lawrence	GOUVERNEUR 3 NW	47	Absent
St. Lawrence	CANTON 4 SE	47	Absent
St. Lawrence	LAWRENCEVILLE 3 SW	49	Absent
St. Lawrence	COLTON 2 N	54	Absent
Steuben	HORNELL ALMOND DAM	62	Absent
Steuben	ADDISON	65	Absent
Steuben	Wayland	69	Absent
Steuben	Arkport	70	Absent
Steuben	BATH	71	Absent
Steuben	CORNING	71	Absent
Suffolk	BRIDGEHAMPTON	93	Moderately high
Suffolk	RIVERHEAD RES FARM	96	Moderately high
Sullivan	CLARYVILLE	63	Absent
Sullivan	LIBERTY 1 NE	65	Absent
Sullivan	ROCK HILL 3 SW	68	Absent
Sullivan	BLOOMINGBURG 2 SW	73	Absent
Tioga	SPENCER 1 NE	63	Absent
Tioga	OWEGO 3 WSW	65	Absent
Tioga	WAVERLY	71	Absent
Tompkins	FREEVILLE 1 NE	60	Absent
Tompkins	ITHACA CORNELL UNIV	67	Absent
Tompkins	Freeville	67	Absent
Tompkins	Ithaca	70	Absent
Ulster	SHOKAN BROWN SLIDE MOUNTAIN	56	Absent
Ulster	MOHONK LAKE	77	Moderate
Warren	GLENS FALLS AP	48	Absent
Warren	NORTH CREEK 5 SE	50	Absent
Washington	WHITEHALL	59	Absent
Wayne	Sodus	75	Moderate
Wayne	Savannah	75	Moderate
Wayne	Williamson	75	Moderate
Wayne	SODUS CENTER	76	Moderate
Westchester	YORKTOWN HEIGHTS 1 W	79	Moderate
Westchester	DOBBS FERRY ARDSLEY	92	Moderately high
Wyoming	WARSAW 6 SW	61	Absent
Wyoming	Gainesville	65	Absent
Yates	Potter	70	Absent
Yates	Branchport	73	Absent
Yates