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PRELIMINARY OBSERVATIONS ON THE EFFECTS OF HYDROGEN CYANAMIDE ON BREAKING DORMANCY AND HARVEST OF APPLES IN GUATEMALA
The result is 3 waves of flowering, paucity of lateral branches and buds, blind wood as a result of terminal bud dominance and a greatly reduced yield potential.
During 1988 we evaluated the effects of hydrogen cyanamide (Dormex-R) on breaking dormancy and yields of the varieties Winter Banana and Wealthy.
An average 15 year old orchard in the Quetzaltenango valley was chosen.
This area is characterized by excellent soils, an altitude of 2 300 m, average maximum temperature of 21.7°C, mean temperature of 13.3°C and an average minimal temperature of 5.96°C. Average annual rainfall is 809.7 mm with 106 days of rain during the growing season from May to October.
There are between 300 and 625 chilling hours but the coldest period during dormancy is also the hottest part of the year (Dec-Feb) which tends to defeat chilling effects.
The trees of each variety in the orchard were mapped and test trees were randomly selected.
All trees were equally managed by the orchardist, and the fruit was thinned to no more than 3 fruits per spur.
Three trees of each variety were chosen for each treatment.
Doses of 2% and 4% hydrogen cyanamide were applied to runoff on the 1st and 22nd of February before dormancy had broken.
Three branches per tree were selected at random.
Observations were made between the 14th and 17th of March during full bloom.
Counting of buds having or not having broken dormancy was accomplished starting at the longest ramet of each branch until 25 floral buds or 100 leaf buds accrued.
At harvest on the 15th of August, the first 10 fruits were harvested from each of the same branches without regarded to size or quality.
Harvest parameters included size, quality, hardness, degree brix, percent of fruit pigmentation and maladies.
Hydrogen cyanamide produced highly significantly greater breaking of floral and leaf bud dormancy compared to control trees, but there was no clear relationship between doses or application times.
Between 14 and 17 March the mean control percentage of open flowers and leaf buds for the 2 varieties was 33.9 and 16.8 respectively.
The combined varietal percentage of flowers and leaf bud break for the treatments was 79.4 and 87.3 respectively.
Winter Banana had the tendency to break dormancy earlier than Wealthy.
Within Winter Banana, no treatments were significantly different for percentage of open flowers, indicating a great latitude for time of application and the possibility of a reduced dosage to 2% lower.
Within Wealthy, results indicated that a dose of 2% applied six weeks before regular flowering (budbreak) would be advisable, but a 2% concentration could be applied up to 3 weeks before regular budbreak.
At harvest, it was discovered that some of the