Corn flea beetle and Stewart's wilt predictions for 2003

Mike Hoffmann, Dept. of Entomology, Cornell University, Ithaca.

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. The forecast 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:

Refined forecasting system for Stewart’s wilt of sweet corn

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

2003 forecast:

According to the Stewart's wilt index forecasting model, the 2002-2003winter temperatures were cold and sufficient to kill much of the corn flea beetle population in New York. For most of the state, the Stewart's wilt index falls into the ‘absent’ category (cumulative monthly temperatures below 75). Notable exceptions include some southerly areas where the Stewart's wilt forecast is considered to be moderately high. This year, there is little potential for Stewart's wilt problems in sweet corn for most of the state (See following table).

Management options for Stewart's wilt disease control include:

1) planting resistant varieties

2) planting with Gaucho-treated seed for susceptible varieties

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

NEWA Sites:

Station	County	Sum	Risk
Arkport	Steuben	63.3	Absent
Batavia	Genesee	65.1	Absent
Branchport	Yates	67.4	Absent
Dresden	Yates	69.2	Absent
Elba	Elba	61.5	Absent
Fredonia	Chautaqua	74.3	Absent
Gainesville	Wyoming	58.6	Absent
Groveland	Livingston	69.2	Absent
Himrod	Yates	72.6	Absent
Ithaca	Tompkins	68.8	Absent
Lansing	Tompkins	74.4	Absent
Lyndonville	Orleans	72.7	Absent
North Appleton	Niagara	74.9	Moderate
South Appleton	Niagara	71.2	Absent
Pavilion	Wyoming	62.8	Absent
Potter	Yates	65	Absent
Savannah	Wayne	69.8	Absent
Sodus	Wayne	69.1	Absent
Valois	Yates	72.9	Absent
Wayland	Livingston	64.1	Absent
Williamson	Wayne	71.5	Absent
Farmington	Ontario	69.1	Absent

National Weather Service Cooperative Observer Sites

TOWN	COUNTY	SUM		RISK
ALBANY	ALBANY	63.6	ABSENT
ALCOVE DAM	ALBANY	57.3	ABSENT
ANGELICA	ALLEGANY	57.3	ABSENT
BINGHAMTON	BROOME	60.3	ABSENT
FRANKLINVILLE	CATTARAUGUS	55.2	ABSENT
OLEAN	CATTARAUGUS	62.4	ABSENT
AUBURN	CAYUGA	65.1	ABSENT
DUNKIRK	CHAUTAUQUA	70.8	ABSENT
JAMESTOWN	CHAUTAUQUA	62.7	ABSENT
ELMIRA	CHEMUNG	63.9	ABSENT
NORWICH	CHENANGO	59.1	ABSENT
COPAKE	COLUMBIA	65.7	ABSENT
TULLY	CORTLAND	54.3	ABSENT
WALTON	DELAWARE	57	ABSENT
POUGHKEEPSIE	DUTCHESS	72.6	ABSENT
STORMVILLE	DUTCHESS	73.5	ABSENT
BUFFALO NIAGARA INTL	ERIE	68.4	ABSENT
WALES	ERIE	60.3	ABSENT
NEWCOMB	ESSEX	36.6	ABSENT
MALONE	FRANKLIN	41.4	ABSENT
GLOVERSVILLE	FULTON	52.2	ABSENT
EAST JEWETT	GREENE	54.9	ABSENT
PLATTE CLOVE	GREENE	56.7	ABSENT
INDIAN LAKE	HAMILTON	42	ABSENT
PISECO	HAMILTON	40.5	ABSENT
WATERTOWN	JEFFERSON	49.5	ABSENT
HIGHMARKET	LEWIS	38.4	ABSENT
HOOKER	LEWIS	49.2	ABSENT
LOWVILLE	LEWIS	45.3	ABSENT
AVON	LIVINGSTON	65.1	ABSENT
ROCHESTER	MONROE	67.5	ABSENT
OCEANSIDE	NASSAU	94.8	MOD-HIGH
NIAGARA FALLS	NIAGARA	66	ABSENT
CAMDEN	ONEIDA	56.1	ABSENT
UTICA	ONEIDA	57.9	ABSENT
SYRACUSE	ONONDAGA	69.3	ABSENT
GENEVA	ONTARIO	64.8	ABSENT
HONEOYE	ONTARIO	66	ABSENT
PORT JERVIS	ORANGE	68.4	ABSENT
STEWART AP	ORANGE	72.6	ABSENT
WALDEN	ORANGE	69.9	ABSENT
COOPERSTOWN	OTSEGO	57.9	ABSENT
CARMEL	PUTNAM	71.7	ABSENT
TROY LOCK AND DAM	RENSSELAER	65.7	ABSENT
COBLESKILL	SCHOHARIE	57	ABSENT
CANTON	ST. LAWRENCE	47.4	ABSENT
MASSENA	ST. LAWRENCE	41.1	ABSENT
ADDISON	STEUBEN	61.2	ABSENT
CORNING	STEUBEN	66	ABSENT
BRIDGEHAMPTON	SUFFOLK	90.3	MOD-HIGH
ISLIP	SUFFOLK	87.9	MOD-HIGH
SPENCER	TIOGA	59.4	ABSENT
WAVERLY	TIOGA	67.2	ABSENT
ITHACA	TOMPKINS	63	ABSENT
SLIDE MOUNTAIN	ULSTER	52.8	ABSENT
GLENS FALLS	WARREN	51	ABSENT
WESTCHESTER	WESTCHESTER	81	MODERATE
WARSAW	WYOMING	54.6	ABSENT