CG30 APPLE ROOTSTOCK TRIAL
Established in 1997. CG30 is a new semi dwarf apple rootstock from the Cornell / Geneva breeding
program that is resistant to fireblight and between M 7A and M 26 in size. Five cultivars on CG30 are
being compared with the same five on M26 in a replicated randomized block experiment. Cultivars
include Myra Red Fuji, Braeburn, Imperial Gala, Gingergold, and JonaGoRed. Data and observation
indicates a variation of size and precocity between rootstocks and rootstock/ cultivar combinations. CG
30 has produced a larger, more vigorous tree at this point on all cultivars in every replicate. Breaburn
on both stocks displays moderate vigor, and retained the heaviest crop this season of all cultivars.
Imperial Gala, Myra Red Fuji and JonaGoRed were very lightly cropped on both stocks, and
Gingergold did not bear at all this season.
W. COWGILL, J. COMPTON, G. DONATO

CG16 APPLE ROOTSTOCK TRIAL
Established in 1998. Comparing CG 16 to the standard M9 EMLA, this trial is evaluating the advanced
selection from the Cornell / Geneva breeding program that is resistant to fireblight and wooly apple
aphids. CG16 is in the same size category as M9. There are 6 replicates to this trial with only the
cultivar of JonaGoRed as the scion. Neither rootstock produced a crop in 1999. A visual observation
of M9 shows a comparative trunk caliper and canopy volume to that of CG16 at this point, but a few
burrknots have developed on the shank of the M9 stocks.
W. COWGILL, J. COMPTON

APPLE PLANT GROWTH REGULATOR BLOCK
Plant Growth regulators are invaluable essential tools in the production of apples. This project will
allow for the development of recommendations for New Jersey apple producers via applied research
and demonstration with PGR compounds for chemical thinning, stop drop control, sucker control,
fruit finish, tree size control, fruit size enhancement and fruit quality improvement. New materials, as
well as new uses for existing materials will be examined. Two commercial apple cultivars,

representative of apple production in New Jersey, Fuji, cv. Sun Fuji^®, and Suncrisp^®(NJ55) will be
utilized to evaluate PGR's for efficacy and use in New Jersey. The planting will be established in a
randomized block design using three tree replications of the two cultivars. Replicated trials will be
established annually. Treatments will be applied with Rears Pullblast sprayer. The proper and
aggressive use of PGR's in apple production will enhance the economic return to NJ apple growers
and help ensure their assist in maintaining their viability. Plant Growth Regulator use in apples is the
least understood but most critical practice in modern fruit production. Information gleaned from trials
at the Snyder directly impacts apple growers statewide with publication in the NJ Tree Fruit Production
Guidelines.
W. COWGILL, J. COMPTON

AZOXYSTROBIN FUNGICIDE APPLE PHYTOTOXICITY STUDY
Quadris F and Abound SC are two new fungicides that are highly effective in controlling a broad
spectrum of plant diseases, but are highly phytotoxic to certain cultivars of apple. Complete defoliation
of apple cultivars such as McIntosh has been observed when minute amounts of this residue come into
contact with the variety's tissue. A 98 cultivar screening of apple varieties is being conducted at the
Snyder Farm and Cream Ridge in order to determine varietal sensitivity to these compounds has been
established. The screening at the Snyder Farm site is confirming McIntosh's hypersensitivity to
Azoxystrobin. All true Gala cultivars also are showing this same sensitivity, while other economically
crucial varieties such as Fuji and all true strains of Red Delicious are proving to be resistant.
W. COWGILL, J. COMPTON, N. LALANCETTE, G. DONATO

1999 North Jersey Tree Fruit Annual Report

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