IFAS Citrus Initiative Annual Research and Extension Progress Report 2008-09 Mechanical Harvesting and Abscission

Detailed Accomplishments in 2008-09: Processors are concerned about peel integrity of CMNP-treated fruit. We conducted 2 trials in March and April with Valencia oranges to determine the postharvest effect of CMNP applied to canopies for the purpose of loosening fruit on fruit crush force, peel puncture resistance, and peel puncture depth. Fruit were collected during our harvesting trial studies reported elsewhere. Briefly, 300 ppm CMNP was applied to canopies at 300 gal/acre, and canopy shaker machine harvesting commenced 4 days after application. The machine cpm settings were 180, 220 and 260 and the rate of travel was 1.0 mph. Trials were conducted on approximately 150 trees divided into 4-tree plots; 4 replicates were selected for each treatment. Machine harvested fruit were collected and transported to CREC, and stored overnight on the packinghouse floor under ambient conditions. The following day, fruit were prepared for peel integrity analysis or storage. Fruit crush force measures the force necessary to crush the fruit, whereas peel puncture resistance and peel puncture depth measures the force necessary to pierce the peel surface and the depth before piercing occurs, respectively. An instron instrument was used to measure these parameters. Postharvest storage studies were conducted simultaneously on a subset of fruit to determine if CMNP-treated fruit had higher decay than those not treated with CMNP. Storage studies were conducted at 27°C (80 OF) for one week, and decay evaluated 0, 1, 2 and 7 days during storage. Fruit crush force, peel puncture resistance or peel puncture depth was not statistically different between treatments. Fruit decay percentage, however, varied. No decay was measured after 1 day of storage in any treatment. After 2 days of storage, decay was numerically higher as compared with day 1 but not significant in any treatment. After 7 days of storage, decay was higher than the previous storage period. CMNP increased % decay, especially in fruit harvested at the higher cpm settings of the canopy shaker. Decay averaged 4% in untreated controls to 9.3% in 300 ppm CMNP fruit harvested at 260 cpm. Two additional trials are planned at the end of May and early June to complete the data set for this year.