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Healthy Fruit 2011 Vol. 19:1

Apr 5, 2011

The way I see it

We are still distributing this Issue of Healthy Fruit to everyone who subscribed in 2010. NOTE, however, that this WILL BE your LAST ISSUE OF HEALTHY FRUIT for 2011 unless you renew your subscription by filling out and sending in the enclosed mail-in form with your information and $ remittance. ($50 for e-mailed Healthy Fruit, $70 for postal mail.) Any questions about the status of your subscription, let us know.

I want to remind you that the 2011 New England Tree Fruit Management Guide is available, and can be ordered using the same mail-in form with a personal check. Be sure to get yours before the season starts.

Everything is still dormant (or maybe silver tip) as far as I can tell, however, it looks like we might be finally breaking into a warmer (although still just seasonal) weather pattern. I don't expect to see green-tip for at least another week, but that may change if the forecast changes and the weather follows suit. Last year on this date McIntosh was at the 1/2-inch green (HIG) 'mouse-ears bud stage.

J. Clements

2011 New England Tree Fruit Management Guide available

The 2011 New England Tree Fruit Management Guide (NETFMG) is available NOW. For $50 you will receive the printed guide by postal mail. You can download and print a mail-in form to order the NETFPMG by personal check here.

Note that for 2011 the herbicide/weed control section has been completely revised, and all sections have been carefully reviewed for changes in 2011. Order yours today!

Also note that Commonwealth Quality produce certified growers should have the 2011 NETFMG in their possession to achieve the maximum score!

Local labor for local farms

"Local Labor for Local Farms" is a program intended to increase the availability of farm workers for farmers in New England. The program is collaboration between the New England Farm Workers' Council (NEFWC) that recruits the participants (future farm workers), the University of Massachusetts that provides the necessary training and certification to the participants and Nuestras Raices, Inc. that provides the farm land for the training and the necessary translation. Help stimulate the local economy by hiring the local farm labor force. For information or hiring, please contact: Touria Eaton, Program Director/Manager at UMass eaton@umext.umass.edu, 413-687-1044, or Jeannette Gordon, Program Manager at NEFWC jgordon@partnersforcommunity.org, 413-536-5403 X239.

Eye on copper -- spring copper sprays for fruit diseases

by Dave Rosenberger, Cornell University, Plant Pathology, Highland Lab. Reprinted from Scaffolds Fruit Journal, Vol. 20, No. 2, March 28, 2011.

Copper sprays can be applied in early spring to control several important diseases on tree fruits. On apples, pears, and quinces, copper applied at green tip may help to suppress fire blight in orchards where blight was present in either of the two previous years. A copper spray between bud swell and bud burst can be used to control peach leaf curl on peaches and nectarines. On sweet cherry, tart cherry, and apricot, a copper spray at bud burst may help to suppress bacterial canker, a disease caused by Pseudomonas syringae.

A recent search of the New York State pesticide registration database turned up more than 40 different labels for copper products registered for use on at least one tree fruit crop. Thirteen products were clearly designed for home gardens and/or organic famers, but tree fruit growers have many options when choosing a copper fungicide. The crops, diseases, and application timings listed vary greatly from one product to another. When using copper sprays, read the product label to ensure compliance with label restrictions.

For tree fruit applications, "fixed" coppers are more effective than copper sulfate applied alone. The term "fixed" copper refers to copper products that are formulated or tank-mixed in such a way as to create relatively insoluble or "fixed" deposits of copper on plants. Copper ions are gradually released from these deposits when plants are wet, and it is the copper ions that control diseases. Copper ions can also cause phytotoxicity to the treated crop if the concentration of copper ions is too high. Be- cause copper ions are released slowly from the spray deposits created by fixed copper sprays, the fixed coppers are usually less phytotoxic to plants and provide better residual activity against diseases than can be achieved with a non-fixed form of copper.

Copper hydroxide and copper oxychloride are both fixed coppers, whereas copper sulfate is not. If copper sulfate is mixed with spray lime to make a Bordeaux mixture, then the copper sulfate and cal- cium in the lime react together to form a fixed copper. Product labels for products containing copper sulfate can be confusing: The labels for Cuprofix Disperss indicate that the formulation contains ba- sic copper sulfate, so one might assume that this is not a fixed copper and that it will therefore lack the residual activity found in fixed coppers. However, Cuprofix Disperss is formulated with gypsum, a carrier that contributes the calcium ions needed to convert the copper sulfate into a fixed form of cop- per, and it therefore should work as well as any of the other fixed copper products.

What is the best product for any given application? Research in other cropping systems has shown that the major factor affecting efficacy of fixed copper sprays is the amount of elemental or metallic copper that is applied. The metallic copper equivalent is listed on all copper labels, usually in parentheses below the list of active ingredients. The metallic copper equivalent is always lower than the percent of the formulated copper molecule (e.g., copper hydroxide) listed on labels because the copper ion is only one part of the copper molecule.

Although the rate of metallic copper that is applied has the greatest effect on efficacy, the size of the copper particles in the product formulation can also play a role. There is evidence from both old (1940s and 1950s) and recent studies indicating that products that contain a finer grind of copper are often a bit more effective than products with larger particle sizes because the smaller particles are less subject to wash-off by rain or removal by wind. (Yes, one study has shown that wind alone can significantly reduce amounts of residual cop- per on plant surfaces!) Some manufacturers claim that their finely ground copper formulations are safer and/or can be used at lower rates of metallic copper per acre than older formulations. These claims may hold true for vegetable crops, where repeated applications are needed to cover new foliage as it develops and the improved retention with finely ground products can compensate for lower application rates so long as coverage is renewed at regular intervals. On tree fruits, where we depend on the long-term residual activity from a single copper spray, the best evidence suggests that the rate of metallic copper per acre is still the primary factor impacting efficacy.

Thus, for the most part, copper products used for dormant or delayed-dormant sprays on tree fruits can be selected based on the cost per pound of elemental copper. If costs per pound of metallic copper are similar for finely ground coppers and for older formulations, then go with the finely ground product. In addition to efficacy considerations, some of the liquid formulations or finely ground dry formulations may go into solution more easily in the sprayer tank than older and coarser for- mulations. Convenience for measuring and mixing should also be a consideration when deciding which product to purchase.

Copper sprays for pome fruits -- A copper spray applied at the green tip bud stage has been recommended for more than 40 years as part of a fire blight control strategy for apples and pears. Copper residues on the twigs and branches kill bacteria as they are released from overwintering cankers. Cankers usually begin releasing bacteria when trees are at the pink or bloom stages. However, copper must be applied at green tip to avoid the phytoxicity that can occur with later ap- plications.

Studies that I conducted in the early 1990s showed that when three inches of rain occurred between the copper application and bloom, virtually all of the copper residues were removed from the tree prior to bloom. In those cases, we would not expect any benefits from the copper spray on apples, because the copper residues were lost before fire blight bacteria become active. However, in years when there is less than three inches of rainfall between the copper application and bloom, the low levels of residual copper that persist on tree bark are apparently sufficient to reduce populations of the fire blight bacterium.

In years when no rain occurs between the green tip copper application and bloom, fruit may develop copper-induced russetting because too much copper residue will still be present at bloom. To avoid the potential for phytoxicity on apples, the copper rate should be reduced for any applications made after green tip, and no copper sprays should be applied to apples after half-inch green unless the block is intended for processing and fruit russetting is not a concern.

The old literature reports that copper residues can cause foliage injury if frosts occur soon after the copper application. This injury can be avoided by applying the copper spray before buds have pro- duced much green tissue. However, if the copper spray is applied near half-inch green, then applica- tions should be avoided ahead of predicted frosts.

Acids applied to trees that were recently treated with copper can cause a massive release of copper ions, thereby increasing chances that the copper spray will cause phytotoxicity. Therefore, trees treated with a copper fungicide should NOT be sprayed with Aliette or any of the phosphite fungicides for at least several weeks after the copper spray was applied. The phosphite products include ProPhyt, Phostrol, Agri-Fos, Nutriphyte, and many others.

A copper spray applied at silver tip or green tip will provide the same degree of protection against apple scab that one would expect from an application of a mancozeb fungicide. Thus, a copper spray will protect trees from scab for the next 7–10 days, and no other fungicide is needed during that time period.

Copper sprays for stone fruits -- Copper sprays applied either at leaf fall in autumn and/or as a dormant spray in spring have been very effective for controlling bacterial canker (Pseudomonas species) on sweet cherries and leaf curl (Taphrina deformans) on peaches and nectarines. An application of copper at bud burst on apricots may also help to prevent the severe bud blast that can occur if apricots are colonized by Pseudomonas during a cool wet spring when a light frost occurs during bloom. In some years and locations, the combination of Pseudomonas and light frost has caused nearly 100% kill of apricot flowers and foliage. Although no research has been conducted on the efficacy of copper sprays for preventing such damage, copper residues from a spray at bud burst should help to suppress bacterial populations that contribute to spur death following frost events.

Ecological impact of copper sprays -- Copper fungicides are receiving increasing scrutiny because copper is a heavy metal that can accumulate in soils. Copper has many adverse effects on soil ecology, especially in soils with a low pH. Adverse effects include toxicity to earthworms and other soil microorganisms. Most studies on copper accumulation in soils have been done in cropping systems where multiple copper sprays were applied every year for many years (e.g., grapes, bananas, avocados). Nevertheless, the spring copper spray recommended for pome fruit and stone fruit diseases may contribute to gradually increasing levels of copper in soils. Copper sprays should be used sparingly and only where we have no good alternatives for disease control.

Across the pond

During the week of March 20, Mo Tougas(Tougas Farm, Northboro, MA) and I traveled to Great Britain and Belgium with the objective to lay the groundwork for an upcoming International Fruit Tree Association(IFTA) Summer Study Tour to Great Britain, the Netherlands, and Belgium this upcoming July 24 - August 1 (www.ifruittree.org). Here is a very brief synopsis of what we saw.

Cherries under Haygrove Tunnels — Mark Woodhead, Haygrove Ltd. Regional Sales Manager (http://www.haygrove.com/), took us to a Haygrove cherry farm about 3 hours northwest of London, in the town of Kington. In this humid climate, cherries MUST be covered to be marketable. Cherry rows were typically 2-3 per tunnel, some had plastic mulch (organic cherries), pruned to a central leader with younger fruiting branches tied down with string to well below horizontal. All trees were on dwarfing Gisela rootstocks. Mark explained how significant acreage of strawberry, brambles, and cherry are grown under Haygrove tunnels in GB because the fruit quality is so far superior to what would be grown in the open. Tunnels are a modern technology, that despite the initial cost, make it possible to grow the high-quality fruit the market demands in what would otherwise be unsuitable locations. Tunnels are also a great boon to organic production and early ripening and harvesting of crops. Links to video (https://www.youtube.com/watch?v=W5i00Wuo-3M) and pictures (https://www.icloud.com/#100122).

IFTA Preview — The distance from London — where IFTA Study Tour participants will arrive — to visit the Haygrove facilities, however, is proving to be too great to fit into the study tour schedule. The drive from London up to Ledbury and Kington unfortunately totals some four hours at a minimum, and so viewing of high tunnels will take place in the East Malling area.

East Malling Research and Conference Center — Will host the IFTA Tour this summer. East Malling Research (EMR), located in (where else?) East Malling, about 1 hour southeast of London near the larger city of Maidstone. East Malling is of course famous for the development of clonal rootstocks that are the basis of modern apple orchards. The station was established 98 years ago as a grower initiative much the way the current UMass Cold Spring Orchard in Belchertown was. As is happening elsewhere, East Malling Research has to raise operating funds for resident scientists and research. They are using industry money now for cherry, pear, and soft fruit (strawberry, bramble) breeding and new variety introductions. Sustainable management (IPM) and reduced residues, post-harvest technology, and effect of climate change on food production are also foci of their work.

IFTA Preview — IFTA travelers will view and discuss the merits of a new 'Conference' Pear "Concept" orchard. (Pictures.) Results indicate that the training system will have the potential to deliver triple the yields of conventionally grown pear orchards. Irrigation management is also a focus of research at EMR. When combined with close root pruning, researchers are seeking methods which may reduce or eliminate the need for plant growth regulator applications. Christopher Atkinson, Head of Science at East Malling Research and Charlotte Box of the Conference Center were our hosts and after leaving East Malling, we were confident the IFTA Tour is in good hands and it will be top-notch.

In addition to visiting EMR, attendees will travel to several local farms where 'standard operating procedure' would be considered to be quite progressive here in Massachusetts. High tunnel cherry and soft fruit, tall spindle plantings and organic tree fruit production will be featured.

Cultural visits in this history-rich region will be traditional part of this summer tour. Leeds Castle, Canterbury, Thanet Earth (http://www.thanetearth.com/) and the Oyster Festival at Whitstable Harbor will be included. Topping off a couple of days of technical and cultural visits will be an Old English style dinner party at the Bradbourne House, complete with wine, live music offered by a local ensemble, dinner at the manor house, and visits to the espaliered apple orchard which features dozens of old style espaliered apple trees.

Carolus Trees and "Le Mur Fruitier" (The Fruiting Wall) — After a ferry crossing of the English Channel we drove to Belgium, and about an hour east of Brussels is the small city of Sint-Truiden which is the center of apple growing in Belgium. Here, we met with Koen Carolus, owner of Carolus Trees, a nursery and orchard. The nursery produces about 2 million trees per year and ships all over the EU and Canada and Asia. They produce mostly 2-year 'knip-boom' trees. But, the main point of this visit was to look how they are managing their 'fruiting wall' orchards. Originating in France, hence "Le Mur Fruitier," the fruiting wall orchard is planted app. 1 X 3 meters and pruned only once (well, twice at the start) during the growing season with a tractor-mounted sickle-bar hedger. Carolus claims yields have increased vs. more traditional hand-pruning, and of course labor cost is much lower. It was very interesting as we watched the mechanical hedger work a block of young trees that were being 'started' for the fruiting wall. Links to video and pictures.

One interesting aspect of this fruiting wall concept is that it is based upon the tall spindle apple plantings that we have been promoting here for several years. The conversion to mechanized pruning is not difficult, however, it does require a thorough understanding of the "Le Mur Fruitier" system. This is not simply a 'mechanized pruning,' but rather an entire system which utilizes keen observation of tree condition, specific 'interventions' made (or not made) at specific stages of tree growth thru the season. Trees are not simply hedged and forgotten, but rather balance is maintained within the canopy which results in surprisingly productive, tame trees. We observed trees going into their twelfth leaf, and were impressed with the lack of 'crows feet' that we expected. Various timings and combinations of intervention have been practiced over the years, and Carolus has maintained these combinations for viewers to study. Admittedly, the artistic satisfaction of our pruning practices will suffer. As the system does not view individual trees but rather a wall of fruit as it's goal, mechanical pruning does result in tree forms which perhaps appear to defy much of what we have been taught over the years. We'd say if we were to use one word to describe the appearance of individual tree, it might be 'hacked!' Bottom line though, this system offers an opportunity to spend more time chasing Mahi-Mahi in the Gulf vs. hand-pruning in 3 ft. of snow (after this winter)!

IFTA Preview — Other stops travelers will visit which time did not allow for us, will be Verbeek Nursery in The Netherlands (http://www.verbeek-boomkwekerijen.nl/English/index2.html),PCFruit research station in Sint-Truidan, Belgium, a pear grower using high density four leader system, and a cherry grower using Voen covers to protect his crop from rain cracking. (http://www.voen.eu)

Useful links

Scaffolds Fruit Journal

Network for Environment and Weather Applications (NEWA)

JMCEXTMAN Blog

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