The situation is quite different for locations the did not get rain on June 6 - 9.  In Old Town, the final primary scab infection period of the season will arrive with the next warm (over 50F), soaking (over 0.1"), daytime (between 8am and 7pm) rain (possibly Tuesday June 15)..  Usually the season's final primary infection period is a whimper as the last bit of straggler ascospores are released.  Because of the lack of daytime since June 2, about 9% of the season's ascospore load remains to be released in the Old Town area.  As a result, the final primary infection period for locations that did not get daytime rain on June 6 - 9 could carry a greater than usual infection potential.

     Even after ascospore releases are finished, attention still needs to be given to scab management until you can verify success.  That requires looking for, and not finding, scab lesions. 

     A scab lesion is a colony of spore producing structures growing out of an infected leaf.  If fungicide protection was adequate during the April - early June infection periods, then there will be so few spore producing colonies that you can safely switch the focus of disease control away from scab and onto flyspeck. 

     There is a 9-17 day lag period between a primary scab infection period and when infections become visible as they start producing a new generation of spores.  Lesions from the season's final ascospore releases in Sanford will have had time to become visible by June 18.  The equivalent dates in Monmouth and Old Town are June 22 and June 26.

     But even then the risk of scab infection is still not completely known, at least in orchards with trees over 10 feet tall.  Fungicide protection is usually less, and thus scab infection potential is greater, in the tops of tall trees.  And just a few primary scab lesions, each producing about 40,000 spores over their 4 week lifetime, are enough to cause an economically significant degree of fruit infection.  So in taller trees, you can't really be sure that scab was adequately controlled until enough time has passed for 1st generation lesions to spread inoculum for 2nd generation lesions, and then enough time has passed for those infections to become visible.  Thus, with tall trees it isn't until almost a month after the final ascospore release that you can confirm successful primary (ascospore) scab control. 

     The dates for final 2nd generation lesion appearance can't be accurately predicted yet because doing so requires knowing the date of the first rain after all 1st generation lesions have appeared.  But we can make reasonable guesses.

     Here is a table to help keep the dates straight:

      What is the appropriate management strategy during this transition period after after the end of scab ascospore releases and before confirming successful scab control? 

     Should you maintain solid fungicide protection even though there may not be any 1st or 2nd generation lesions to produce spores?  Is is safe to let fungicide coverage lapse and just be ready to retreat quickly if scab lesions are found?  What's the middle ground between these two extremes? 

     The problem with the "keep spraying" approach is that it makes scab season last another 4 weeks after the end of ascospore releases.  You are getting paid to grow fruit, not spray fungicides.  The problem with the "relax and wait" approach is that unless you are checking the orchard daily and can treat as soon as any lesions appear before rain spreads infections to other leaves and fruit, you could be allowing a scab epidemic to build up momentum and fruit damage before you can react.    

     There is no single answer because the proper approach is situation dependent.  There are three objectives you want from a fungicide applied between the end of ascospore releases and the date when you can confirm that scab control was effective:
   1) reduce spore production on any scab lesions that develop
   2) protect leaves and fruit from potential secondary scab infections
   3) protect against other diseases - primarily flyspeck (more on summer diseases below).
 
     So if you have not fallen asleep already, keep reading for some thoughts intended to help you choose the appropriate degree of protection needed in this interim period.  Please note, what follows are suggestions to consider, not research validated guidelines!

PROCEDURE: 

        As a bare minimum, check 100 fruit clusters or vegetative shoots per block.  Select the cluster/shoots from tree at least 10 trees per block.  Your sample of fruit clusters and vegetative shoots should come from at least 10 trees per block (i.e. no more than 10 per tree).  Checking 5 clusters/shoots per tree on 20 trees is even better.  Randomly select clusters and shoots from all areas of the canopy.  Problems due to improper spray distribution can be limited to one section of the tree. 

Inspecting a block for scab requires looking at a lot of leaves.  In order to do that you don't have time to study each leaf, but instead do a quick "photographic flash" of about 15 leaves at a time.  You have to look at each cluster twice, once for the upper leaf surface and again for the underside.  By looking at about 15 leaves per cluster/shoot on 100 clusters/shoots, you will be checking about 1500 leaves.

Don't try to scout for other pests at the same time.  If you need to check for other pests, do it separately from the scab scouting, either as a separate visit or on the same visit but as a separate walk through the block.  To check 100 samples per block for scab takes about 30 minutes of walking and focused gazing.  It is not a stroll through the orchard, it is work.  But it is work worth doing.

A small hand clicker-counter held that leaves your hands free to grab shoots is useful to keep track of the number of shoots and clusters checked.  When you find a leaf with one or more scab lesions, put it in your pocket.  When the clicker reaches 100, stop and count the number of scabby leaves you have collected. 

INTERPRETATION:    

            It is impossible to devise a threshold number of infected leaves for two reasons.  Because of differences in tree size, orchard operation, marketing, cultivar, site characteristics etc., there is a unique context for evaluating the level of scab infection in each orchard.  And the relationship between scab lesions appearing shortly after petal fall and the consequences in terms of fruit infection at harvest is not understood well enough to provide a specific, reliable threshold.  With that caution in mind, a threshold of 0.5% of leaves infested (i.e. 8 infested leaves out of 1500 leaves checked) has been suggested by pathologists as a reasonable guess at a threshold for suppression treatments. 

The Fall Scab Indexing procedure which is part of the Delayed-First-Spray strategy (see page 13 of the 2003-2004 New England Apple Pest Management Guide) is also built around detecting scab infestation of 0.5% of the leaves.  Even though it is a tool built for a different purpose, we can use it as an interpretive guideline for June scab lesion scouting. 

If you find less than 5 scab-infested leaves per 100 fruit clusters & vegetative shoots, this suggests with a reasonable degree of confidence that protection during primary (ascospore) scab infection periods was adequate.

Conversely, if you find 18 or more scab-infested leaves per 100 clusters and shoots, that can be taken as evidence that lesion suppression is needed.  We used to call that ‘eradication’, but that terminology is misleading because you are not able to completely stop spore production on 100% of the lesions.

If the number of scab-infested leaves per 100 clusters/shoots is between 5 and 18, you can either increase the sample to see if a clear result comes out, or quit sampling and identify the degree of scab infestation as intermediate.  If do increase the sample size, the procedure calls for adding another 100 shoots/clusters from across the block and adding the number of scabbed leaves found in the second 100 shoots/clusters to the number found in the first 100.  For a combined 200 cluster/shoot sample, finding less than 12 scab infested leaves indicates adequate control.  Finding more than 24 infested leaves indicates need for eradication.

 Flyspeck and other 'Summer diseases'  

     If you control flyspeck, then you have done enough to control sooty blotch fungi.  The other two summer diseases of some consequence in Maine orchards are black rot and bitter rot. Unless there is either unusually hot, humid weather or an unusually high amount of inoculum (such as dead trees left in the orchard), a fungicide program designed for flyspeck will also keep black rot and bitter rot from becoming problems. 

     Black rot fruit infections are usually found on older trees where a branch canker is dropping spores onto underlying fruit.  While it manifests as leaf and fruit infections, black rot is probably more important for the branch cankers it can cause.  Black rot infection is facilitated by winter damage, which is in plentiful supply in Maine orchards this year.  Removing dead and dying wood will help keep black rot and opportunistic wood rot fungi from taking advantage of a free food supply in the orchard. 

     Bitter rot is rarely a problem in Maine, presumably because it likes hotter temperatures than Maine usually provides.  But it has been found causing fruit infections in Maine orchards in the past.

 Other stuff

The Farm Superintendent supervises and manages Highmoor Farm as a research facility for conducting field experiments planned and directed by scientists of the Maine Agricultural and Forest Experiment Station and the University of Maine Cooperative Extension. Housing for the Superintendent is provided at the farm as part of the compensation package and to provide after hour and weekend security at the farm.

B.S. degree in Agriculture or other related field or equivalent work experience is required. M.S. degree preferred. Experience in farm operations and management required and experience in apples, small fruits and vegetables preferred. Experience in supervising farm workers is required. A strong commitment to safety is also required. Ability to perform minor repairs of equipment and basic carpentry skills are preferred. Applicants must have an understanding of agricultural research and the needs of faculty doing the research. Applicant must have a Maine Class B driver's license or obtain one within 60 days of employment. Applicant must also have a Maine Research and Demonstration Pesticide Applicator's License or obtain one within 60 days of employment. Must be able to wear a respirator. Must have the ability to lift 50-60 lbs. loads several times daily. Excellent oral and written communication skills are also required.

The Superintendent works in numerous environments. While most work is performed at the Farm, some travel to the University of Maine campus is required as is some evening and weekend work. The job requires working out of doors in a variety of conditions, including heat, cold, dust, snow, and mud. The job also requires the operation of agricultural equipment. Pre-employment physical and appropriate background checks required.

Candidates should send a letter of application, a resume, copies of academic transcripts, and the names, addresses, and phone numbers of four professional references to Ryan Kuhl, Maine Agricultural and Forest Experiment Station, 5782 Winslow Hall, Orono, Maine 04469-5782. Review of applications will begin on June 25, 2004 and will continue until a suitable candidate is found. Salary Range $30,000 - $34,000.

The University of Maine is an Equal Opportunity/Affirmative Action Employer. Women and minorities are strongly urged to apply.

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