ISHS Acta Horticulturae 591: III International Symposium on Pistachios and Almonds
EFFECT OF ROOTSTOCK AND TREATMENT DATE ON THE RESPONSE OF PISTACHIO TO DORMANT APPLIED HORTICULTURAL MINERAL OIL |
| Authors: | R.H. Beede, L. Ferguson |
| Keywords: | Pistachio, rootstock, oil, dormancy, rest-breaking. |
| DOI: | 10.17660/ActaHortic.2002.591.3 |
| Abstract:
A four-year study (1997-2000) on the rest-breaking effect of horticultural mineral oil applied at three different dormant timings was conducted on pistachio, 'Kerman' cultivar, grown on four rootstocks, P. atlantica, P. integerrima (Pioneer Gold), and the two interspecific hybrids Pioneer Gold II and UCB I (P. atlantica x P. integerrima). The treatments were applied to single-tree plots selected for uniform circumference. The rootstocks were grouped as four subplots per block in this split-plot experiment. Oil with a 50% distillation point of 2460 C. was applied at the equivalent rate of 6 gallons per acre in mid-January, February and March and compared to an untreated control. Each treatment was replicated five times on trees initially eight years old. Trees repeatedly sprayed with horticultural mineral oil during mid-January and February show significant increases in vegetative growth, bloom and kernel filling compared to untreated trees. The mid-February treatment provided the greatest advancement. The February timing also significantly increased average split nut yield by 2.7 kg per tree. A positive yield response was observed even when chills hours below 7.20 C. exceeded 1000. Increased fruit set appears responsible for this yield improvement rather than a reduction in blank nuts and edible closed nuts or larger nut size. In addition to increased production, crop maturity is enhanced by four to five days. This can be significant in scheduling harvest, improving processing efficiency and marketing. Trees treated with oil in mid-March did not show as much response as the two earlier treatments. Although flower development was enhanced, no improvement in vegetative growth was observed over the four years studied. Increased production of split nuts was also less consistent. Rootstock did not have a significant effect on oil response. Early split nuts, which enhance aflatoxin development, have not been consistently higher in the oil treatments. Rather, the data suggests that weather; crop load, rootstock and location may play a more significant role. Weather conditions during bloom are a major factor in determining the value of oil application. Advancing bud break and bloom by seven days into inclement, cold conditions should be avoided due to increased Botrytis infection, reduced fruit set and crop loss from frost. The probability of such events must be considered prior to dormant oil treatment. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
