Corn flea beetle and Stewart's wilt predictions for 2006
Mike Hoffmann & Jeffrey Gardner, Dept. of Entomology,
Cornell University, Ithaca.
John Gibbons, Ontario Co.
CCE
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.
For several years we have used a forecast system that used the sum of the
average temperatures for the months of December, January and February to
predict the risk of Stewart’s wilt. However, based on recent research in the
Midwest (Iowa) a different approach is apparently more accurate at predicting
the risk of Stewart’s wilt and it uses the number of months (December, January, February) with average temperatures
above 24F. So if the average
temperature for each of the three months is above 24F, the predicted risk is 3
(high). This new method of predicting risk is somewhat more conservative (more
likely to indicate a higher level of risk) then the old method. The Stewart's
wilt index (likelihood of wilt problems) using this system is as follows:
|
Number of months ³ 24 F |
Predicted risk |
|
0 |
Negligible |
|
1 |
Low
to moderate |
|
2 |
Moderate
to high |
|
3 |
High |
2006 forecast:
The
winter of 2005-2006 was a warm winter.
Last winter (2004-2005) was moderate with some mortality of the
overwintering corn flea beetles, but we did observe an increased number of
beetles in August of 2005. Thus, we anticipated a significant population
heading into the 2005-2006 winter.
Because of our mild winter, the Iowa model predicts moderate to high
risk throughout much of NY. Risk maps
can be accessed at http://www.nrcc.cornell.edu/grass/stewart_maps.html.
The model does not account for the number of beetles entering the winter
season, the number of surviving beetles that actually carry the pathogen, or
the effect of varietal susceptibility.
Despite these knowledge gaps the model has done well in predicting
relative incidence of Stewart’s wilt.
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.
Tabulated risk of
Stewart’s wilt for locations in NY:
*Locations in the
NEWA network are appended in separate table below*
|
LOCATION |
|
Dec Average |
Jan Average |
Feb Average |
Risk |
|
ADDISON |
STEUBEN |
23.8 |
32.0 |
27.3 |
mod-high |
|
ALBANY
COUNTY AP |
ALBANY |
26.7 |
31.5 |
27.9 |
high |
|
ALCOVE
DAM |
ALBANY |
25.0 |
29.6 |
26.7 |
high |
|
ANGELICA |
ALLEGANY |
23.9 |
31.6 |
25.4 |
mod-high |
|
AUBURN |
CAYUGA |
26.5 |
32.0 |
28.2 |
high |
|
BAINBRIDGE
2 E |
CHENANGO |
23.5 |
29.9 |
25.7 |
mod-high |
|
BATH |
STEUBEN |
24.4 |
31.0 |
26.3 |
high |
|
BINGHAMTON
LINK FIELD |
BROOME |
23.7 |
30.8 |
25.1 |
mod-high |
|
BLOOMINGBURG
2 SW |
SULLIVAN |
26.6 |
32.5 |
27.7 |
high |
|
BRIDGEHAMPTON |
SUFFOLK |
34.9 |
38.6 |
33.7 |
high |
|
BUFFALO
NIAGARA INTL AP |
ERIE |
27.1 |
34.8 |
27.8 |
high |
|
CAIRO
4 NW |
GREENE |
25.4 |
30.4 |
28.9 |
high |
|
CAMDEN |
ONEIDA |
24.6 |
29.2 |
23.3 |
mod-high |
|
CANTON
4 SE |
ST. LAWRENCE |
20.9 |
25.3 |
21.2 |
low-mod |
|
CARMEL
4 N |
PUTNAM |
27.3 |
32.4 |
29.5 |
high |
|
CENTERPORT |
SUFFOLK |
33.8 |
37.9 |
34.2 |
high |
|
CHEMUNG |
CHEMUNG |
24.8 |
31.7 |
28.2 |
high |
|
COBLESKILL
2 ESE |
SCHOHARIE |
23.5 |
30.4 |
24.8 |
mod-high |
|
CONSTANTIA
6N |
OSWEGO |
23.3 |
29.4 |
24.3 |
mod-high |
|
COOPERSTOWN |
OTSEGO |
24.1 |
29.9 |
26.0 |
high |
|
COPAKE |
COLUMBIA |
23.8 |
31.4 |
27.7 |
mod-high |
|
CORNING |
STEUBEN |
23.8 |
30.8 |
27.1 |
mod-high |
|
DANSVILLE |
LIVINGSTON |
26.3 |
34.5 |
28.4 |
high |
|
DANSVILLE
MUNICIPAL AP |
LIVINGSTON |
27.4 |
35.6 |
29.8 |
high |
|
DELHI
2 SE |
DELAWARE |
23.0 |
30.0 |
25.0 |
mod-high |
|
DUNKIRK
CHAUTAUQUA CO AP |
CHAUTAUQUA |
31.1 |
36.7 |
30.3 |
high |
|
EAST
JEWETT |
GREENE |
21.5 |
28.6 |
23.7 |
low-mod |
|
EAST
SIDNEY |
DELAWARE |
22.8 |
29.8 |
24.8 |
mod-high |
|
ELLENBURG
DEPOT |
CLINTON |
21.7 |
24.0 |
20.2 |
low-mod |
|
ELMIRA |
CHEMUNG |
24.6 |
32.0 |
28.8 |
high |
|
ELMIRA
CORNING REGIONAL AP |
CHEMUNG |
24.2 |
31.9 |
27.1 |
high |
|
FARMINGDALE
REPUBLIC AP |
SUFFOLK |
34.9 |
39.2 |
34.3 |
high |
|
FRANKLINVILLE |
CATTARAUGUS |
22.7 |
31.3 |
23.5 |
low-mod |
|
FULTON
OSWEGO COUNTY AP |
OSWEGO |
25.4 |
31.7 |
24.9 |
high |
|
GENEVA
RESEARCH FARM |
ONTARIO |
26.2 |
33.0 |
27.6 |
high |
|
GLENS
FALLS MEMORIAL AP |
WARREN |
23.1 |
27.8 |
23.5 |
low-mod |
|
HIGHMARKET |
LEWIS |
18.1 |
23.1 |
16.2 |
negligible |
|
HONEOYE |
ONTARIO |
26.4 |
34.5 |
28.4 |
high |
|
HOOKER
12 NNW |
LEWIS |
21.6 |
27.4 |
20.0 |
low-mod |
|
HORNELL
ALMOND DAM |
STEUBEN |
22.8 |
30.2 |
24.8 |
mod-high |
|
ISLIP
LONG ISLAND |
SUFFOLK |
33.5 |
37.5 |
32.3 |
high |
|
ITHACA
CORNELL UNIV |
TOMPKINS |
25.0 |
31.9 |
28.1 |
high |
|
JAMESTOWN
4 ENE |
CHAUTAUQUA |
24.9 |
33.7 |
26.6 |
high |
|
LITTLE
FALLS CITY RE |
HERKIMER |
21.9 |
26.9 |
23.5 |
low-mod |
|
LOCKE
2 W |
CAUYGA |
23.0 |
28.9 |
24.8 |
mod-high |
|
LOWVILLE |
LEWIS |
21.1 |
27.0 |
20.1 |
low-mod |
|
MALONE |
FRANKLIN |
19.8 |
24.3 |
18.9 |
low-mod |
|
MASSENA
INTL AP |
OTSEGO |
20.9 |
22.2 |
20.0 |
negligible |
|
MECKLENBURG
4 SW |
SCHUYLER |
23.7 |
31.1 |
25.3 |
mod-high |
|
MONTGOMERY
|
ORANGE |
26.2 |
33.1 |
29.7 |
high |
|
MORRISVILLE
6 SW |
MADISON |
22.5 |
28.7 |
24.2 |
mod-high |
|
NEW
ALBION 2 |
CATTARAUGUS |
22.7 |
31.0 |
23.1 |
low-mod |
|
NEWCOMB |
ESSEX |
19.4 |
23.1 |
19.6 |
negligible |
|
NORWICH |
CHENANGO |
23.2 |
29.8 |
26.2 |
mod-high |
|
OCEANSIDE |
NASSAU |
36.0 |
39.3 |
35.5 |
high |
|
OLD
FORGE |
HERKIMER |
19.4 |
24.6 |
18.6 |
low-mod |
|
OLEAN |
CATTARAUGUS |
24.3 |
33.2 |
26.5 |
high |
|
ONEONTA |
OTSEGO |
27.2 |
32.6 |
28.7 |
high |
|
PAVILION |
GENESEE |
25.3 |
33.8 |
26.3 |
high |
|
PENN
YAN AIRPORT |
YATES |
27.1 |
34.0 |
27.9 |
high |
|
PISECO |
HAMILTON |
18.8 |
23.1 |
18.0 |
negligible |
|
PLATTSBURGH
|
CLINTON |
22.8 |
26.9 |
21.9 |
low-mod |
|
POUGHKEEPSIE
|
DUTCHESS |
27.3 |
33.8 |
30.1 |
high |
|
ROCHESTER
|
MONROE |
28.0 |
35.4 |
28.4 |
high |
|
ROCK
HILL 3 SW |
SULLIVAN |
24.1 |
30.7 |
27.5 |
high |
|
ROSENDALE
2 E |
ULSTER |
27.9 |
34.5 |
31.2 |
high |
|
SARANAC
LAKE |
FRANKLIN |
17.8 |
22.9 |
14.6 |
negligible |
|
SHERBURNE |
CHENANGO |
22.3 |
29.4 |
25.9 |
mod-high |
|
SHIRLEY
BROOKHAVEN AIRPORT |
CHENANGO |
33.4 |
37.3 |
32.4 |
high |
|
SILVER
CREEK 2 NE |
CHAUTAUQUA |
29.6 |
36.5 |
30.5 |
high |
|
SLIDE
MOUNTAIN |
ULSTER |
21.6 |
25.9 |
22.1 |
low-mod |
|
SPENCER
1 NE |
TIOGA |