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 (http://nc140.org) rootstock planting in a commercial “Certified Naturally Grown” (CNG, https://www.cngfarming.org/) 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 (https://drapenetnorthamerica.com/) 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 (http://nyshs.org/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 (https://modiappleusa.com/). 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 (http://www.modiapple.com/about-us).

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.