Berrien County Fruit Happenings

Volume 1, Issue 3, August, 1999

Dear Fruit Producer,

By the time you read this, harvest of early apples will be well underway. All signs point to a nice apple crop in 1999, and an improved ‘99–2000 marketing season.

In this Newsletter, I have included information on summer disease management; foliar analysis; and harvest date predictions. I’d like to bring special attention to two topics. First, if you do not already do it, I hope you consider starting a leaf analysis program. I’m a firm believer in the role of leaf analysis in orchard nutrition management. Second, the ‘Orchard Walk’, scheduled for August 16 at Vic and Bill Schenk’s orchard in Dowagiac, will be an excellent opportunity to tour their high-density apple blocks and discuss among fellow growers the issues/opportunities presented by intensive orcharding. The tour will start at 5:30 p.m., and we will meet at their orchard workshop, on the corner of Wilbur Hill and Peavine Roads, just south of Dowagiac. I hope you can make it.

As always, if you have any questions or concerns, please feel free to call me, and I hope you have a good harvest.

Sincerely,

Jon Clements

Extension ANR Agent,

Horticulture & Marketing

clementj@msue.msu.edu

www.msue.msu.edu/berrien/hort

August 17: Grape Berry Moth 3-M pheromone disruption demonstration; Kerlikowske's, corner of Scottdale and Lemon Creek, 3:00 p.m.

August 16: Orchard Walk, Bill and Vic Shank's, corner of Wilbur Hill and Peavine Rd., Dowagiac; 5:30 P.M.

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J. Clements

Summer pruning is one of your best tools to improve fruit quality and overall orchard productivity. Good reasons to summer prune include:

• improved fruit color: lots of research and observation has shown that summer pruning improves surface color and pack-out. This is particularly evident on more difficult to color varieties such as 'McIntosh.'
• improved fruit set and quality: summer pruning opens up the tree canopy for better sunlight penetration, resulting in stronger spurs and flower buds for next season. Better spurs equals larger fruit.
• improved vigor control: by its nature, summer pruning is less invigorating than dormant pruning. Overly vigorous orchard blocks are ideal candidates for a combination of dormant and summer pruning.
• improved pest control: summer pruning opens up the tree for better spray coverage and faster drying, preventing the summer diseases such as Sooty Blotch and Flyspeck from getting a foothold.
• improved labor use: summer pruning is an ideal activity for your labor crew to fill in slack time during the pre-harvest period.

Clearly summer pruning is an effective horticultural tool for achieving improved fruit quality and pack-out. Summer pruning ought to be in every growers toolbox.

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J. Clements

Sooty Blotch & Flyspeck (SB&FS) are summer diseases that occur sporadically, however, they can be costly in terms of reduced grade at pack-out in some years if not effectively controlled. Fortunately, understanding and controlling them is fairly straight-forward.

SB&FS are technically different diseases, however, they occur on the same fruit and thrive under similar conditions. Both originate from mostly outside the orchard, where they infect alternate hosts such as brambles. Both diseases like warmth and moisture -- night-time temperatures of 65-70 F, with high humidity, are perfect. Hence, their unwelcome appearance on fruit is much more likely during summers with abundant rainfall and high heat and humidity.

Although present during May and June, fungicide sprays for Scab usually keep SB&FS at bay. Late July and August, however, is when the diseases can reappear in the orchard. Sooty Blotch and Flyspeck need approximately 300 accumulated leaf wetness hours (from post-bloom) to start to infect fruit, so dry conditions do not favor their development. Still, even during dry summers, there are enough accumulated leaf wetness hours to give SB&FS a foothold.

The first step in preventing Sooty Blotch and Flyspeck relies on good cultural practices. Pruning -- both winter and summer -- opens up tree canopies, allowing them to dry out faster. Dwarf trees with 'lighter' canopies are less likely to develop summer disease problems on the fruit than standard and semi-dwarf trees with 'shady' canopies. Removal of dense hedge-rows that block air movement and prevents drying in orchards is a good practice. Plus, cutting-out those thickets will remove some of the alternate hosts for Sooty Blotch and Flyspeck. Finally, even close mowing of the groundcover and breaking up fruit clusters (adequate thinning) are small but important practices to reduce favorable SB&FS habitat.

Still, chemical control of summer diseases is a prerequisite in most years. At least two fungicide sprays, timed usually around the end of July and in mid-August are sufficient to control SB & FS in most years. Particularly rainy summers may need one or two more applications. Later maturing cultivars and 'hot-spots' may need an extra spray in late August.

Effective fungicides include Captan, Benlate, Topsin-M, and Ziram. For the July-August sprays, Benlate and Tospin-M provide some eradicant activity, while Captan and Benlate are protectants. Hence, a good strategy is tank-mixing Captan or Ziram with Benlate or Topsin-M. This will give you about three weeks of activity against SB&FS. Note that Benlate has been implicated in promoting lenticel 'spotting' when used during dry spells that are followed by rain and rapid fruit swelling.

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J. Clements

Mid-July through mid-August is the time to collect leaf samples for foliar nutrient analysis of tree fruit and grapes. I know many of you collect soil samples for analysis, however, I suspect leaf analysis is far less common. There are some very good reasons, however, for doing a foliar nutrient analysis, too. These include:

• Leaf nutrient concentration is the most accurate indication of current plant nutritional status. Although knowing the nutrient content of soil is useful, it does not always mirror the nutrient content in plants, particularly for immobile elements such as calcium.
• Leaf analysis is the only way to accurately find out the annual nitrogen status of your plants, particularly for tree fruit.
• Foliar tissue analysis gives you actual plant levels of the nutrients iron, copper, manganese, boron, etc. that are not available via the standard soil test. These micronutrients are essential plant growth elements, and deficiencies will limit productivity and fruit quality.
• Leaf analysis is particularly useful when troubleshooting the cause of poor growth and/or productivity.

The procedure for collecting samples for foliar analysis is fairly simple:

• For tree fruits, collect approximately 75 leaves with petioles attached from the middle of the current season’s terminal shoot growth. Do not select leaves from spurs. For each cultivar or orchard block, a different sample (i.e. 75 leaves) needs to be taken. Wash leaves immediately in a weak detergent solution, rinse and blot dry. Allow several days to fully dry before submitting to the lab.
• For grapes, only the petiole (stem) is used. Select the most recently matured leaves near the center of the current season’s growth. Do not select leaves close to fruit clusters. Snip the leaf off close to the shoot, then remove the leaf blade. About 100 petioles need to be collected for a sample. The best time to do this is just as the fruit begins to ripen, because potassium levels will be lowest in the vines at this point. (Assessing potassium status is one of the main reasons for doing a grape foliar nutrient analysis.)

Leaf samples can be submitted to the MSU Soil & Plant Nutrient Laboratory for analysis. The cost is $18 per sample. All samples should be dry and sent in boxed paper bags -- do not use plastic bags! I have enclosed a form to be submitted with the sample (one form per sample). There are also private labs which do plant tissue analysis and give recommendations.

If you have not done a leaf analysis in your orchard or vineyard blocks for several years, I would highly recommend it! A convenient way to do it is divide your orchard/vineyard into thirds, and sample one-third each year. I would also be happy to assist you in assessing your foliar nutrient analysis results and developing a fertilizer program -- just give me a call.

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By the time you read this, harvest of summer apple varieties will have begun. Every year, District Fruit Agent, Bill Shane, publishes apple harvest date predictions for the fall, early-, mid-, and late-season varieties: 'McIntosh,' 'Jonathan,' and 'Delicious.'

These predictions are based on the bloom date and the average daily temperature for the 30 days following bloom. This year, the predicted harvest dates are a few days ahead of average because bloom was early, and the temperatures for the month following bloom were nearly normal.

Of course you can't accept these dates as 'gospel' when it comes to harvest. You should always evaluate fruit maturity based on skin color (both foreground and background), taste, and sugar and starch content.

One of the best methods for determining maturity is the starch-iodine test, whereby sliced apples are dipped in a starch solution, and the resulting stained flesh pattern is compared to a standard chart. If you have not used the starch test before, let me know and I'd be happy to help you get started.

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The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by MSU Extension is implied.

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Michigan State University Extension programs and materials are available to all without regard to race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, marital status, or family status.

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