Corn flea beetle and Stewart's wilt predictions for 2005
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. 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 |
2005 forecast:
The
winter of 2004-2005 was a moderate winter (64th coolest in 110
years). Last winter (2003-2004) cold
killed many of the overwintering corn flea beetles but we did observe an
increased number of beetles in August of 2004. We don’t know if that
represented a significant population heading into the 2004-2005 winter. Cold temperatures in January kept heat
summation relatively low and sufficient to somewhat lower risk. There is
low-moderate risk throughout much of NY.
Risk maps can be accessed at http://www.nrcc.cornell.edu/grass/stewart_maps.html.
Note that the information at this site provides predictions based on two
different models. For many years we
have been using the Steven-Boewe model in New York. The Iowa model is included
for your information. These predictions do not account for the
insulating effect of snow cover, but to date we have not been able to
demonstrate that heavy snow reduced beetle mortality. The predictions also do not account for the number of beetles
entering the winter, the number of surviving beetles that actually carry the
pathogen, or the effect of varietal susceptibility. Despite these knowledge gaps the predictive model has done
reasonably 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 many locations in NY.
|
Station |
Dec Avg Temp |
Jan Avg Temp |
Feb Avg Temp |
Winter Sum |
|
|
ADDISON |
28.7 |
21.5 |
25.8 |
76.0 |
Moderate |
|
ALBANY
COUNTY AP |
27.8 |
19.5 |
26.9 |
74.2 |
Absent |
|
ALBION
2 NE |
30.0 |
23.0 |
27.3 |
80.4 |
Moderate |
|
ALCOVE
DAM |
25.9 |
18.8 |
24.2 |
68.8 |
Absent |
|
ALFRED |
27.6 |
19.2 |
25.2 |
72.0 |
Absent |
|
ANGELICA |
28.8 |
19.4 |
22.6 |
70.7 |
Absent |
|
Appleton |
30.8 |
23.3 |
26.6 |
80.7 |
Moderate |
|
ARKVILLE
2 W |
26.5 |
19.2 |
24.6 |
70.3 |
Absent |
|
AUBURN |
29.0 |
20.5 |
24.9 |
74.4 |
Absent |
|
AURORA
RESEARCH FARM |
30.1 |
22.1 |
27.1 |
79.3 |
Moderate |
|
AVON |
29.6 |
21.9 |
24.8 |
76.3 |
Moderate |
|
BATAVIA |
28.0 |
23.1 |
27.1 |
78.2 |
Moderate |
|
BATH |
27.5 |
20.5 |
24.6 |
72.6 |
Absent |
|
BIG
MOOSE 3 SE |
22.1 |
15.2 |
21.0 |
58.4 |
Absent |
|
BINGHAMTON
EDWIN A LINK FIELD |
26.9 |
19.8 |
26.4 |
73.1 |
Absent |
|
BLOOMINGBURG
2 SW |
28.8 |
22.1 |
28.6 |
79.6 |
Moderate |
|
Branchport |
29.1 |
21.8 |
26.5 |
77.4 |
Moderate |
|
BRIDGEHAMPTON |
35.7 |
28.8 |
32.0 |
96.6 |
Moderate
to high |
|
BUFFALO
NIAGARA INTL AP |
29.7 |
23.8 |
25.3 |
78.8 |
Moderate |
|
CAIRO
4 NW |
28.3 |
18.8 |
27.5 |
74.6 |
Absent |
|
CAMDEN |
24.8 |
16.6 |
22.2 |
63.6 |
Absent |
|
CANANDAIGUA
3 S |
30.1 |
23.4 |
27.8 |
81.3 |
Moderate |
|
CARMEL
4 N |
29.1 |
21.9 |
29.3 |
80.3 |
Moderate |
|
CHEMUNG |
28.5 |
21.9 |
26.4 |
76.7 |
Moderate |
|
CHERRY
VALLEY 2 NNE |
27.0 |
18.3 |
25.2 |
70.6 |
Absent |
|
Clintondale |
27.3 |
20.8 |
25.3 |
73.4 |
Absent |
|
CONSTANTIA
6 N |
24.9 |
17.7 |
24.2 |
66.8 |
Absent |
|
COOPERSTOWN |
26.1 |
16.8 |
21.9 |
64.8 |
Absent |
|
COPAKE |
27.9 |
20.8 |
28.1 |
76.8 |
Moderate |
|
CORNING |
28.5 |
21.8 |
27.2 |
77.5 |
Moderate |
|
DANNEMORA |
20.7 |
14.3 |
21.8 |
56.9 |
Absent |
|
DANSVILLE |
29.9 |
22.9 |
25.8 |
78.6 |
Moderate |
|
DANSVILLE
MUNICIPAL AP |
32.6 |
23.1 |
27.4 |
83.1 |
Moderate |
|
DELHI
2 SE |
26.3 |
18.0 |
25.1 |
69.4 |
Absent |
|
DEPOSIT |
28.4 |
21.0 |
26.6 |
76.1 |
Moderate |
|
DOBBS
FERRY ARDSLEY |
36.0 |
28.5 |
33.7 |
98.2 |
Moderate
to high |
|
DUNKIRK
CHAUTAUQUA CO AP |
33.5 |
21.4 |
27.6 |
82.4 |
Moderate |
|
EAST
JEWETT |
24.4 |
18.7 |
23.8 |
66.8 |
Absent |
|
EAST
SIDNEY |
25.9 |
17.7 |
23.4 |
67.1 |
Absent |
|
Elba |
27.3 |
18.6 |
21.5 |
67.4 |
Absent |
|
ELLENBURG
DEPOT |
19.9 |
12.3 |
18.4 |
50.5 |
Absent |
|
ELMIRA |
29.0 |
22.0 |
26.1 |
77.1 |
Moderate |
|
ELMIRA
CORNING REGIONAL AP |
29.2 |
21.4 |
25.8 |
76.5 |
Moderate |
|
FARMINGDALE
REPUBLIC AP |
36.2 |
29.6 |
34.0 |
99.7 |
Moderate
to high |
|
FRANKLINVILLE |
26.4 |
20.1 |
22.5 |
69.0 |
Absent |
|
FREDONIA |
33.0 |
25.7 |
29.1 |
87.8 |
Moderate
to high |
|
FREEVILLE
1 NE |
27.3 |
18.9 |
24.2 |
70.4 |
Absent |
|
FULTON
OSWEGO COUNTY AP |
27.6 |
19.2 |
25.1 |
71.9 |
Absent |
|
Gainesville |
26.8 |
19.8 |
23.2 |
69.8 |
Absent |
|
Geneva |
29.2 |
21.3 |
25.7 |
76.2 |
Moderate |
|
GENEVA
RESEARCH FARM |
28.9 |
21.3 |
24.9 |
75.1 |
Moderate |
|
GLENS
FALLS MEMORIAL AP |
24.7 |
15.6 |
21.8 |
62.1 |
Absent |
|
GOUVERNEUR
3 NW |
21.4 |
13.9 |
18.4 |
53.7 |
Absent |
|
Groveland |
30.1 |
22.1 |
25.9 |
78.1 |
Moderate |
|
HEMLOCK |
29.6 |
22.4 |
25.6 |
77.5 |
Moderate |
|
HIGHMARKET |
18.0 |
11.3 |
17.7 |
47.0 |
Absent |
|
Himrod |
30.4 |
23 |
27.4 |
80.8 |
Moderate |
|
HONEOYE |
29.5 |
21.8 |
25.8 |
77.0 |
Moderate |
|
HOOKER
12 NNW |
22.9 |
14.9 |
19.6 |
57.4 |
Absent |
|
HORNELL
ALMOND DAM |
26.1 |
19.3 |
23.0 |
68.4 |
Absent |
|
HUDSON
CORRECTIONAL |
31.5 |
22.7 |
28.8 |
82.9 |
Moderate |
|
INDIAN
LAKE 2 SW |
19.7 |
13.6 |
18.4 |
51.7 |
Absent |
|
ISLIP
LONG ISLAND MACARTHUR AP |
35.2 |
28.6 |
31.9 |
95.7 |
Moderate
to high |
|
ITHACA
CORNELL UNIV |
28.9 |
20.1 |
25.1 |
74.0 |
Absent |
|
JAMESTOWN
4 ENE |
29.2 |
23.0 |
25.1 |
77.4 |
Moderate |
|
LAKE
PLACID 2 S |
20.9 |
13.9 |
20.5 |
55.3 |
Absent |
|
Lansing |
30.7 |
22.6 |
27.7 |
81 |
Moderate |
|
LANSING
MANOR |
27.5 |
18.9 |
26.2 |
72.6 |
Absent |
|
LAWRENCEVILLE
3 SW |
22.1 |
14.5 |
20.0 |
56.7 |
Absent |
|
LIBERTY
1 NE |
25.6 |
19.6 |
26.4 |
71.7 |
Absent |
|
LITTLE
VALLEY |
26.7 |
21.7 |
25.3 |
73.7 |
Absent |
|
LOCKE
2 W |
26.3 |
18.0 |
23.0 |
67.3 |
Absent |
|
LOWVILLE |
22.3 |
13.9 |
19.3 |
55.5 |
Absent |
|
LYNDONVILLE
4 ESE |
29.4 |
22.8 |