What shall we do with a drunken sailor...

McIntosh 'visual' fruit thinning with numbers

Having reviewed A Growers Guide to Predicting the Response to a Chemical Thinner Application developed by Dr. Duane Greene, I decided that I did not have the time to complete the full measurement protocol, however, I was very interested in doing some fruit measurements and getting a 'visual' history of how a group (30) of 'Redmax' McIntosh apple trees trained to a super-spindle would behave during the fruit set and thinning period. (I also did not think I really needed to take all the measurements and use the accompanying predicting apple thinning spreadsheet in this small group of trees to get a handle on what was going on.)

So, I selected and tagged 5 spurs on 5 trees, and using digital calipers measured all the fruitlets on each spur (beginning 20-May) for a total of 125 spurs. I felt this was good representation of the fruit spurs on this group of trees. I made subsequent measurements on 24-May, 1-June, and 11-June for a total of 4 measurement dates.

I applied thinning sprays as follows: first, a petal-fall spray of Sevin XLR Plus (Bayer CropScience) on 17-May at 1.5 pt./acre, and then Maxcel (Valent BioSciences) on 25-May at 75 ppm. Note that the first thinning spray was applied 3 days before the first measurement date (20-May), and that Maxcel was applied between the 2nd (24-May) and 3rd (1-June) measurement dates. I should also mention that from June 7–11, temperatures exceeded 90 F. each day. (Temperature chart | Light chart)

Here are the visual results (click on a tree number below). They should be self-explanatory, but for each tree there are 5 spurs (rows), and 4 columns for each measurement date. The numbers under the picture(s) are the actual fruit measurements in mm.

Tree 1 | Tree 2 | Tree 3 | Tree 4 | Tree 5

So what? Well, by 24-June it was not clear to me if the petal fall spray of Sevin had done enough to thin the crop fully, although I was starting to see some pretty good size differentiation of (mostly) the king fruit. So I proceeded with the Maxcel spray at a moderate rate. By 1-June, however, it had become pretty clear that things were thinning down quite nicely and I decided that the two thinning applications were headed in the right direction. The heat wave described above cinched things for me.

Looking at the figures for final fruit set, it ranges from 8 to 20 %. I still have to make one final check to see how many fruit remain, and need to do an estimate of how many fruit I want per tree. My conclusion at this point, however, is that I have certainly thinned enough, and in fact, there may be less fruit per tree than I would like to reach my yield per acre goal of 600 to 700 boxes/acre.

Finally, my overall conclusion is that this process certainly helped me get a very good visual and numerical picture of what was going on. I do think I would have reached mostly the same conclusion without taking the measurements while using observation and experience to ascertain how my thinning sprays had worked and where final fruit set was ultimately headed.

It's here...

I found fire blight today in a block of 1st leaf Golden Delicious apples. (See more pictures.) Not unexpected, these trees had quite a profuse bloom. I suspect they were in bloom during the last week in May, which saw an increased -- in fact, threatening -- risk of fire blight. Of course existing apples were already mostly past bloom, with the exception of some cider varieties, so they were immune. But 1st leaf trees often get planted a little late, take a while to break bud and bloom, and can be in bloom when the weather conditions that favor fire blight are more likely. Thus, my recommendation is to plant as early as possible, apply copper after planting, de-bloom the trees, or make sure to apply streptomycin sprays as the trees bloom and weather indicates a high risk of fire blight infection. You do not want to get fire blight in a 1st leaf orchard on dwarf rootstocks! See F-133 An Annual Fire Blight Management Program for more information. But, in a nutshell for this grower, I would recommend first pruning out all the visible strikes (on a dry day), and maybe treating with a lower rate of copper once or twice. (Cuprofix MZ Disperss from Cerexagri-Nisso would be a good choice, it contains both copper and mancozeb.) Good luck.

MD for PTB, LPTB

Acronyms got you abuzz?

MD = Mating Disruption

PTB = Peach Tree Borer, found at the trunk-soil interface (most common)

LPTB = Lesser Peach Tree Borer (found on the scaffold limbs, including peaches and cherries)

Talking points from a recent Scaffolds Newsletter (http://www.nysaes.cornell.edu/ent/scaffolds/):

• In NY, there are two species of sesiid (clearwing) moths that attack peaches — the peachtree borer (PTB), Synanthedon exitiosa, and the lesser peachtree borer (LPTB), S. pictipes. The adult borers are striking clear-winged moths with yellow and steel-blue body markings.
• The PTB enters the tree near soil level and does not require the presence of wounds or breaks in the bark for entry, but the LPTB nearly always enters the tree at a pruning scar, canker, mechanical injury, or winter-injured area. The LPTB additionally attacks cherries, causing the same type of injury in the upper trunk and scaffold branches of these trees.
• Injury is caused by larval feeding on the cambium and inner bark of the trunk close to the soil level (PTB) or on the upper trunk and lower scaffold branches (LPTB).
• Control is difficult, owing to the concealed habit of the larvae, growers have traditionally relied on one or more coarse insecticide sprays (e.g., Asana, Lorsban, Proaxis, Thionex, Warrior) of the trunks and lower scaffold branches to deter egg laying and kill newly established larvae. Because this is a labor-intensive measure that often fails to completely control these pests, many growers choose not to elect treatment, or else do an incomplete job, with the intention of getting what they can out of a planting until infestations combine with other peach production factors to warrant tree removal. However, there is a good alternative in the form of pheromone mating disruption (MD) tools for the control of these perennial pests.
• At the end of May each year, Isomate-LPTB ties (CBC) were placed in the test blocks at a rate of approximately 200/acre (1/tree). It should be noted that this blend is formulated to be appropriate at this rate for disruption of both borers in situations where PTB is the predominant species or at least comparable in occurrence to LPTB. Although we assumed that LPTB was the main species at these sites, we chose to be conservative and not use the lower (100 ties/acre) rate recommended for such situations.
• The pheromone dispensers completely suppressed trap catches of both PTB and LPTB at both sites for both seasons, compared with relatively heavy flights noted in the non-disrupted comparison blocks, showing that this pheromone treatment was highly successful in disrupting the chemical communication of males and females of these two species.
• We concluded that these trials provided sufficient evidence that mating disruption alone is able to provide adequate protection from borer infestations in commercial orchards, giving growers an effective non-chemical alternative to trunk sprays for managing this pest complex in their stone fruit plantings.
  

For the complete article see: http://www.nysaes.cornell.edu/ent/scaffolds/2008/080602.html

Don't underestimate the importance of these pests!

JC

UMass 'Video' Fruit Advisor: Using BA (Promalin) to promote branching in young apple trees, May 25, 2008

UMass 'Video' Fruit Advisor: Apple full bloom at UMass Cold Spring Orchard, May 10, 2008

UMass Video Fruit Advisor, May 1, 2008 -- freeze injury to sweet cherry