Saturday, April 11, 2020

2015 Modi Organic NC-140 Apple Rootstock Trial and Drapenet Demonstration

Blogger note:waiting too long for this to appear in Fruit Notes/Horticultural News. Sorry Wes and Win...

Jon Clements, Elizabeth Garofalo, and Wesley Autio

This NC-140 ( rootstock planting in a commercial “Certified Naturally Grown” (CNG, orchard gets more disappointing every year. In 2019, now in its fifth-leaf, more trees are dying or failing, and fruit quality and yield in 2019 was pretty abysmal. It’s unclear if low fruit set and yields are a result of pollination issues or the “organic” management regimen? In 2018 there were virtually no apples, but the entire rest of the CNG orchard was light too. In 2019 the CNG orchard had a good crop, but these Modi trees had a light to moderate crop (at best) of apples. Another problem was the amount of insect damage, mostly plum curculio and internal lep worms (codling moth or Oriental fruit moth) which made the CNG apples quite deformed and small in size. Weed control and fertilization remain organic orchard issues. My take home to date is that G.890, because of its vigor, is a good choice for organic orchards. Although G.30, G.202, and G.41 are acceptable too. (Maybe throw G.969 and G.214 in the ring?) G.16 is not right in this planting, and M.9 has really under-performed. G.935 has some issues, wondering if it is the virus/rootstock/scion interaction? Liberty trees on G.935 planted between replications and as guard trees have all died. Marssonina leaf spot was confirmed in September, and has been causing early defoliation of these Modi trees.

In 2019 a Drapenet ( was installed over replications 1-6 (and not 7-12, there are two rows) the primary objective being to see if insect damage could be reduced. (Although there was a lot of hail around in 2019.) The Drapenet was installed on May 19, 2020 during late bloom, and was secured to the bottom wire with plastic wire ties. Inspection of the apples in late June showed that it was pretty much wholly ineffective at preventing plum curculio damage, however, a more formal harvest survey of 100 fruit per treatment (covered with Drapenet vs. uncovered) for damage showed that internal worms, mostly likely caused by codling moth or Oriental fruit moth, were greater in the uncovered (35% damage) vs. covered (12% damage) replications. But, as already mentioned, PC damage was greater in covered (80% damage) vs. uncovered (51% damage). Interestingly, the incidence of apple maggot fly injury was also greater in the covered (26%) vs. uncovered (5%) apples. Sooty blotch/flyspeck was also greater in the Drapenet apples (59% for sooty blotch, 21% for flyspeck) than the uncovered apples (19% and 12% respectively for sooty blotch and flyspeck). Note that at the UMass Orchard Modi performs just fine, and in fact, was one of the most beautiful apple crops I have ever seen. (Modi apple pictured above.)

These results are just investigatory, as the covered vs. uncovered was not randomized and replicated for statistical analysis. But a recent article in Fruit Quarterly ( also showed (research conducted at Michigan State University) that Drapenet is effective at reducing/minimizing flying moth damage (codling moth, Oriental fruit moth, oblique-banded leafroller).

Note that Modi is not available to apple growers outside of a California packing house ( It was bred in Italy, a cross of Gala X Liberty and is scab-resistant. It has been marketed in Europe as an enviro-friendly apple (

Installation of Drapenet on 15-May, 2019 over Modi apple trees in the
2015 NC-140 Organic Apple Roostock Trial in a CNG orchard.

Tree and yield characteristics in 2019 of Modi apple trees in the 2015 NC-140 Organic Apple Rootstock Trial in a CNG orchard.

Trunk cross-sectional area (sq. cm. trunk area) and cumulative yield efficiency (2017-19, kg. apple per sq. cm. trunk area) in 2019 of Modi apple trees in the 2015 NC-140 Orgamic Apple Rootstock trial.

Typical insect damage (and russet, Septmber 2019) on Modi grown in in a CNG orchard, includng plum curculio, Oriental fruit moth, and apple maggot fly.

Friday, March 20, 2020

Improvements to MaluSim (Cornell Apple Carbohydrate Thinning Model)

In the most recent Fruit Quarterly (Vol. 28, No. 1, Spring 2020) Dr. Terence Robinson and co-authors introduce some improvements to the Cornell Apple Carbohydrate Thinning Model, also known as MaluSim. If you remember, MaluSim is a decision support tool to help make effective chemical thinning applications based on predicted thinning efficacy. Inputs to the model require temperature and sunlight which are derived from a NEWA weather station. Outputs include a daily Thinning Index and recommendation to increase or decrease chemical thinner rates. Many apple growers have indicated the MaluSim (Apple Carbohydrate Thinning) is one of the most widely used decision support tools on NEWA: 
The rationale behind Robinson making these changes/improvements to MaluSim are based on their annual study from 2000 to 2011 where experimental thinning treatments (using carbaryl, NAA, and 6-BA) were applied to apple trees in Geneva, NY and annual data on flower bud density and then cropping (yield, fruit size) was recorded. Weather data was input into MaluSim where a daily carbohydrate balance during the chemical thinning period was calculated and compared to the crop load at harvest. It turns out:

  • The greatest effect on fruit set was timing of chemical thinning application, with the best thinning occurring at 200 to 250 degree days (Base 39 degrees F.) Note that king fruit diameter centered about 12 mm during this window. (I remember my MSU colleauge Phil Schwallier, who has done many chemical thinning trials over the years, saying he has consistently got the best results when chemical thinners were applied when fruitlet size was 10 to 12 mm.)
  • Initial flower counts (bloom intensity) have to be taken into the equation too. When there are more flowers, more aggressive thinning is needed vs. having fewer flowers.
  • Carbohydrate balance also had an effect on fruit set, but was much reduced (or non-existent) outside of this degree-day window of 200-250 DD’s.
  • And, the actual daily carbohydrate balance should be expanded to a longer period before and after the thinning application compared to the “old” MaluSim which used a 4 day running average to compute the daily carbohydrate balance.
So, based on this research the new Cornell Apple Carbohydrate Model on NEWA (Apple Carbohydrate Thinning v2019) was modified as follows:

  • Users must input % flowering spurs before running the model, with four choices: 76-100%, 51-75%,, 26-50%, or 0-25%. (Note the user must also input green tip and bloom dates. Don't accept the NEWA default green tip date, enter your own. Bloom date should be when 80% of the flowers are open on the north side of trees.)
  • Degree Days are automatically calculated, summed, and highlighted in the DD column when they are in the range of 200-250 DD’s (Base 39 degrees F.) from bloom.
  • Calculation of the “Thinning Index” (daily carbohydrate balance) is expanded to seven days (two days before the day of thinning to four days after)
  • And, thinning recommendation, taking into account % of spurs that are flowering, DD’s from bloom, and carbohydrate balance over seven days (all per above) will be color coded red=high risk of over-thinning, yellow=caution, possible over-thinning, green=expect good thinning, and blue=little or no thinning expected.
In 2019 the older Cornell Carbohydrate Thinning Model will be replaced by the new and improved Apple CHO Thinning v2019 MaluSim model and you are advised to use that. Note that CHO thinning is also available in the Malusim app available on both iOS and Android smartphones for mobile access to thinning recommendations.

Cornell Apple CHO v2019 NEWA interface

Cornell Apple CHO v2019 NEWA output