Location: Crops Pathology and Genetics Research
2012 Annual Report
All of the fumigated plots have grown extremely vigorously, and give local walnut growers the impression that the Tulare English scion is four years old, rather than its actual three years. The non-fumigated plots, as mentioned previously, are noticeably smaller and less uniform in growth. During the 2011 season, the fumigated plots consistently produced 12-14 foot of growth. Because of the high vigor, the principle investigator directed the grower to delay pruning of the experiment until mid- April of 2012, when one to two inches of shoot growth had already developed. Delayed pruning of walnut is a horticultural technique used on highly vigorous trees to improve lateral bud break and reduce early season vigor somewhat. The principle investigator personally instructed and supervised the pruning by two of the grower’s employees. The trees were also minimally pruned in order to take advantage of the 2011 growth, which proved to be highly fruitful in 2012. The crop on the fumigated trees is estimated at 1000-1200 pounds per acre, which is definitely worth harvesting, since walnut prices are presently about $1.50 per dry, in-shell pound. This would also demonstrate that fumigation brings replant walnut trees into production at least two years ahead of non-fumigated trees.
The month of June experienced unseasonably severe winds for the San Joaquin Valley, gusting over 40 miles per hour during June 5-7. This unfortunately resulted in damage to the heavily cropped Methyl Bromide experiment. The trial was surveyed by the PI two days after the event, and damaged trees were rated for the percentage of canopy lost from limb breakage. A total of 60 trees suffered damaged. Nineteen trees lost suffered 2-10 % canopy loss. Twenty-four trees lost 15-30% of their canopy, eleven trees lost 40-60%, and six trees suffered 70-100% canopy loss. This unforeseen event proved very frustrating for both the researchers and the grower cooperator, who now questions the wisdom of the lighter pruning, since he is a traditionally severe pruner in his other blocks. However, the pattern of the damage suggests that a large whirlwind may have traversed the block, causing most of the loss. Hopefully, the high yield on the remaining undamaged trees will compensate for the wind loss. As mentioned previously in this report, the high vigor of the fumigated trees on VX211 and Vlach has made this project a real horticultural challenge.
Scientists from University of California Davis have agreed to perform another round of light bar readings this August. This is now very important, since it will help in adjusting the yield data to the percent shaded area existing per plot. The loss of trees early in the trial, along with the recent wind damage, may make such a correlation necessary for accurate yield comparisons between treatments. Nematode sampling of each plot and rootstock in one-foot increments to a depth of five feet is planned for this fall. Harvest data will also be taken mid-September, and the results will be presented at the 2012 MB Alternatives Conference in Florida in November.