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Looking for Volunteers to Participate in an Apple Scab Research Project
For a number of years a technique has been available to assess the number of scabbed leaves in autumn to determine if the orchard was a candidate for the "delayed-spray" strategy in the following spring. As outlined on page 13 of the 1998-1999 New England Apple Pest Management Guide, all the leaves on 600 shoots were to be examined and the number of leaves with one or more lesions would be recorded. If the number of scabbed leaves totaled 50 or less, then the first fungicide spray could be delayed until pink or until after three infection periods (but before the 4th infection period), whichever came first. [Note: This assumes that an SI fungicide was not used in the orchard during the growing season. SI applications may not kill the fungus, only suppress it, and thus, there may be more overwintering inoculum than what is indicated by an assessment of lesions in the autumn.] This technique has been successfully shown to work in a number of orchards but, wouldn't it be better if less shoots were required to determine if an orchard is a candidate for the "delayed-spray" strategy?
A new "scab sequential sampling technique" has been proposed 1. Potentially, as few as 100 shoots (10 shoots on 10 trees) is all that is needed to determine the level of scab risk. This new technique is based on the analysis of 66 previous autumn assessments of foliar scab in 15 predominantly McIntosh commercial apple orchards in New England over the past several years. The technique will provide an assessment of whether the orchard would be at low or high risk of unacceptable scab buildup next year if a "delayed-spray" strategy were to be implemented.
We are looking for orchards that would be interested in participating in a study to evaluate the new scab sequential sampling technique.
The following are criteria for participation:
SI fungicides, such as Nova, Rubigan or Procure, were not used in 1999.
A block of small to moderately tall trees on semi-dwarf rootstocks
No to very few scab lesions have been seen on the foliage this year in that block.
If the autumn foliar scab assessment indicated you were a candidate for the "delayed-spray" strategy, you would be willing to delay initial fungicide sprays in a part of the orchard block next spring. The other part would receive your normal fungicide schedule.
Between now and mid-October, we will assess the amount of scab in your orchard (i.e., block) using the new technique and determine if it is a candidate for the "delayed-spray" strategy. During the growing season, we will monitor infection periods and assess for any primary or secondary scab in both the "delayed-spray" part of your orchard and the part that received your normal fungicide schedule. The fruit from both areas would be assessed for any scab before harvest. Data will be evaluated and conclusions made as to the effectiveness of the sequential sampling technique for scab risk assessment.
We need volunteer orchards to evaluate this technique that potentially would reduce fungicide use and advance apple IPM.
If you are interested in being part of this study, please call Jessica Reardon at 802-656-2924 as soon as possible. We would like to have all scab assessments completed by October 15th. Jessica has been a member of the UVM Apple Team for over a year and is now a new graduate student.
Thank you !
Reference cited:
1 MacHardy, W.E., Berkett, L.P., Neefus, C.D., Gotlieb, A.R., and D.K. Sutton. 1999. An autumn foliar scab sequential sampling technique to predict the level of "scab-risk" next spring. Phytopathology 89: 47.
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