Corn flea beetle and Stewart's wilt predictions for 2002
Mike Hoffmann and Jeff Gardner
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 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 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:
>100 = severe
90-100 =
moderate - severe
85-90 = moderate
80-85 = light
<80 = absent
2002 forecast: The Stewart's wilt index
for several New York locations can be found below.
According to the Stewart's
wilt index forecasting model, the 2001-2002 winter temperatures were relatively
mild and not 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 either the 'moderate to severe' or 'severe'
category (cumulative monthly temperatures above 90). Notable exceptions include some northerly areas where the
Stewart's wilt forecast is considered to be 'light' or 'absent'.
Management options for Stewart's wilt
disease control include:
1) planting
resistant varieties
2) planting with insecticide-treated seed for susceptible varieties
3) applying a
foliar insecticide spray if needed to protect seedling corn
We recommend
the use of treated seed for susceptible varieties.
|
COUNTY* |
CITY |
SUM |
WILT PREDICTION |
|
CAYUGA |
LOCKE |
92.6 |
MODERATE-SEVERE |
|
CHAUTAUQUA |
JAMESTOWN |
97.7 |
MODERATE-SEVERE |
|
CHENANGO |
NORWICH |
92.3 |
MODERATE-SEVERE |
|
DUTCHESS |
POUGHKEEPSIE |
102.6 |
SEVERE |
|
FRANKLIN |
MALLONE |
76.5 |
ABSENT |
|
FULTON |
GLOVERSVILLE |
86 |
MODERATE |
|
GENESEE |
ELBA |
95 |
MODERATE-SEVERE |
|
GENESEE |
BATAVIA |
97.8 |
MODERATE-SEVERE |
|
JEFFERSON |
WATERTOWN |
87.9 |
MODERATE |
|
LIVINGSTON |
WAYLAND |
96.5 |
MODERATE-SEVERE |
|
LIVINGSTON |
AVON |
99.9 |
MODERATE-SEVERE |
|
NIAGARA |
BUFFALO |
98.5 |
MODERATE-SEVERE |
|
ONEIDA |
CAMDEN |
90.1 |
MODERATE-SEVERE |
|
ONTARIO |
GENEVA |
99 |
MODERATE-SEVERE |
|
ORLEANS |
WATERPORT |
103.1 |
SEVERE |
|
RENSSELAER |
MELROSE |
93.5 |
MODERATE-SEVERE |
|
SCHOHARIE |
COBLESKILL |
93.8 |
MODERATE-SEVERE |
|
ST.
LAWRENCE |
CANTON |
83.8 |
LIGHT |
|
STEUBEN |
ARKPORT |
95.2 |
MODERATE-SEVERE |
|
SUFFOLK |
ISLIP |
115.2 |
SEVERE |
|
SULLIVAN |
BLOOMINGBURG |
101.2 |
SEVERE |
|
TOMPKINS |
ITAHCA |
98.2 |
MODERATE-SEVERE |
|
WASHINGTON |
WHITEHALL |
91 |
MODERATE-SEVERE |
|
WAYNE |
SODUS |
100.5 |
SEVERE |
|
WAYNE |
SAVANNAH |
101.5 |
SEVERE |
|
WAYNE |
WILLIAMSON |
102.6 |
SEVERE |
|
WAYNE |
ONTARIO |
103.5 |
SEVERE |
|
WESTCHESTER |
YORKTOWN
HTS. |
108.5 |
SEVERE |
|
WYOMING |
WARSAW |
88 |
MODERATE |
|
WYOMING |
GAINESVILLE |
91.7 |
MODERATE-SEVERE |
|
YATES |
POTTER |
100 |
MODERATE-SEVERE |
*If a particular county is not listed, it is
reasonable to use estimates from a nearby county.