1-MCP Applied Preharvest or Postharvest Improves the Quality of 'Bartlett' Pears

A sprayable formulation of 1-methylcyclopropene (1-MCP) was applied to mature 'Bartlett' pear trees 1 week prior to first harvest. Solutions were applied using a 3-gallon sprayer (CO2 pressure based) and spraying continued until the trees were dripping wet. 1-MCP concentrations were 65.9 or 132.2 mg/L (HarvistaTM, 3.8% a.i.) within 184.5 gallons of solution per acre, and the amount of 1-MCP applied per acre was calculated to be 46.0 or 92.3 g, respectively. Also included in the solutions were 1% oil and 0.5% surfactant. Fruit firmness at the time of spraying was 19.3 lb-force and soluble solids concentration was 10.8%.

Pears were harvested from three trees per treatment at 1 (optimum), 2, and 3 weeks after spray application. Fruit drop was substantially inhibited by preharvest 1-MCP application, as only sprayed pears remained on the trees after 2 weeks and consequently these increased in size. All harvested fruit were cooled overnight at 0-1oC. After 3 days at 0-1oC, some pears from the first harvest that received no spray were then treated postharvest with gaseous SmartFreshTM (1 MCP, 300 ppb, 3.3% a.i.) for 24 hours. Three boxes (one per tree) per treatment per harvest combination were held for 4 months in air at 0-1oC.

Ethylene production, firmness loss, and color change (green to yellow) were delayed by preharvest sprayable 1-MCP treatment. These effects were more notable in later harvested fruit and continued during 14 days at 22oC. Immediately after 4 months of storage in air at 0-1oC, pears treated with sprayable 1-MCP or postharvest SmartFresh remained greener and continued to exhibit less firmness loss than control fruit. However, these effects were no longer present after an additional 4 days at 22oC.

Both preharvest and postharvest 1-MCP treatments substantially reduced the incidence and severity of senescent scald, core breakdown, and storage rots. Nonetheless, pears from the later harvests (post-optimum) of all treatments developed high incidences of disorders and rots after 4 months at 0 1oC. There was also some notable color striping in 1-MCP-sprayed pears from the later harvests, as the fruit transitioned from green to yellow during air storage at 0-1oC. This phenomenon was not studied within the reported trials, but it needs to be investigated before any large commercial use of preharvest 1-MCP sprays.

Overall, sprayable 1-MCP applied preharvest (HarvistaTM) provided similar (or better) benefits to 'Bartlett' pear quality as postharvest treatment with gaseous 1-MCP (SmartFreshTM).

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