Refining Disease Prediction Systems for North Central Ohio Apple Orchards
Principal Investigator:
Ted W. Gastier, Huron County Agricultural Agent
ABSTRACT:
Twenty-four apple growers in ten Ohio counties, including five of the top ten apple
producing counties, plus eight Extension Agents received daily apple disease prediction products by
e-mail. These products were supplemented with weekly orchard visits to twenty-seven production
blocks. The objectives of this project were; 1). To monitor temperatures and leaf-wetness at ten
locations, 2). To compare two weather monitoring methods at eight locations, 3). To utilize
predictive computer software and weather products for managing apple scab and fire blight based
on weather observations, 4). To utilize weather products for managing sooty blotch and fly speck,
and 5). To deliver timely disease management information to County Agents, other Extension
personnel, and industry leaders including growers.
METHODS:
Disease products for apple scab, fire blight, and sooty blotch were purchased from
SkyBit, Inc. of Bellefonte, PA for six orchard locations which were representative of ten apple
producing counties. The six orchards were located in Lucas, Erie, Geauga, Wayne, Columbiana, and
Licking counties. The products were received through daily e-mail by the Huron County Extension
office and forwarded to growers and agents by 8:00 a.m. each morning during the growing season.
This information was presented in condensed form as a portion of the weekly (in-season) Ohio Fruit
ICM News and delivered to approximately 180 addresses by surface and e-mail. The format
allowed for a review of the month's infection periods and forecasts of expected infections during the
following seven days in five districts of the state designated as West, North-Central, Northeast,
Eastern Highlands, and Central.
Four temperature/leaf-wetness Spectrum Technologies monitors where positioned at eye-level within
the apple tree canopies at four locations. The apple scab computer Specware, based on the Modified
Mills Chart (available from Spectrum Technologies of Plainfield, IL) was utilized to indicate
expected apple scab infection periods. Although expected, SpecWare for fire blight and sooty blotch
were not yet available for the 1999 season. In addition, daily temperature and precipitation data
from eight Ohio weather stations were recorded to collaborate wetting periods . Fruit quality was
checked for disease-caused blemishes as apples were placed into storage at eighteen locations.
RESULTS & DISCUSSION:
After encountering severe apple scab infections during the 1998
growing season, growers experienced less disease pressures for 1999. Also growers, after suffering
heavy losses in some cases, were more diligent in their management of scab, fire blight, and sooty
blotch this year. Never-the-less, this project allowed some growers to reduce fungicide cover sprays
by one or two applications with fruit quality maintained at an adequately high level.
The following table compares SkyBit and SpecWare Apple Scab Prediction Products:
|
Days of Apple Scab Infection Indicated and Level of Pressure (where shown) |
| Source |
SkyBit |
SpecWare |
SkyBit |
SpecWare |
SkyBit |
SkyBit |
SkyBit |
| Month |
North Central |
North Central |
Eastern Highlands |
Eastern Highlands |
Western |
Central |
North East |
| April 1999 |
6 |
4 (light) |
NA |
NA |
NA |
NA |
NA |
| May
|
11 |
6 (medium) |
11 |
NA |
8 |
11 |
10 |
| June
|
7 |
10 (medium) |
9 |
NA |
12 |
5 |
9 |
| July
|
13 |
13 (medium) |
11 |
NA |
11 |
15 |
14 |
| August
|
18 |
17 (heavy) |
21 |
16 (heavy) |
16 |
18 |
17 |
| September |
NA |
NA |
NA |
12 (medium) |
NA |
NA |
NA |
| April 1998 |
14 |
7 (medium) |
NA |
NA |
15 |
NA |
NA |
| May |
13 |
21 (heavy) |
NA |
NA |
13 |
NA |
NA |
| June |
15 |
11 (heavy |
NA |
NA |
15 |
NA |
NA |
| July |
11 |
15 (heavy) |
NA |
NA |
NA |
NA |
NA |
| August |
15 |
15 (heavy) |
NA |
NA |
NA |
NA |
NA |
| September |
NA |
8 (medium) |
NA |
NA |
NA |
NA |
NA |
NA=not available (SpecWare - equipment failure, SkyBit - not purchased)
Differences between prediction methods appear to be related to duration of wetness periods
associated with actual rainfall as indicated by climatological data and wetness monitors rather than
SkyBit observations. However, the SkyBit delivery system is convenient and possesses an adequate
level of accuracy when actual rainfall is recorded. In no case was a possible infection period missed
by SkyBit. The SpecWare Scab Product is easy to use and adjust for sensitivity, and is based on
the widely accepted modified Mills Chart with options for the Cornell and Washington State
methodologies. However, the present reliability and user-friendliness of the monitoring devices has
created incomplete records as well as the need for timely downloading. The addition of a backup
unit in an orchard would increase the reliability of the leaf wetness/temperature monitors..
EXTENSION PROGRAM IMPLEMENTATION
These results will be shared through the Ohio Fruit ICM News as well as personal contacts with
apple producers. The Ohio Fruit and Vegetable Congress, to be held in February 2000, will provide
additional opportunities for sharing and improving grower awareness of these management tools
which can help maintain the judicious use of disease control materials.
For further information contact Ted Gastier , Ohio State University Extension, Huron County or the Ohio IPM Office.
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