Mechanized Harvest of Southern Highbush Blueberries for the Fresh Market: An Introduction and Overview of the Workshop Proceedings

T he development of mechanical devices to assist in harvesting cultivated blueberries (Vaccinium species and hybrids) began in the late 1950s. In 1958, U.S. Department of Agriculture engineers located at Michigan State University developed handheld shakers that were used with fabric-lined catch frames as aids for harvesting processed blueberries (Hedden et al., 1959; Monroe and Levin, 1966). These devices substantially increased worker productivity and reduced harvest costs by 55% (Monroe and Levin, 1966). By 1963, 35% of the Michigan crop and 20% of the New Jersey crop were harvested in this fashion. Later Monroe and Levin (1966) described their early attempts to develop a continuous over-the-row blueberry harvester, which required a driver and two additional workers. Testing of over-the-row harvesters began in the late 1950s and by 1966 over-the-row harvesters were available commercially in the United States. Eck (1988) reported that over 100 such machines were in use in the United States by 1971. One of the earliest commercial models, the Harvey Harvester, was featured in an article entitled ‘‘Fantastic New Farm Machines’’ in Popular Mechanics in 1970 (Lamm, 1970). Over time, various harvesters were developed that used different methods to remove ripe berries from canes and they were generally classified as slappers, sway shakers, and rotary shakers (Brown et al., 1996; Mainland, 1993). In their review, Dale et al. (1994) provide a detailed account of blueberry harvester designs up through the early 1990s. Over-the-row harvesters were reported to increase worker productivity by almost 60 times and reduce the cost of harvesting by up to 85% (Brown et al., 1996). However, numerous problems were soon identified with harvesting blueberries mechanically. The primary ones were 1) ground loss of otherwise marketable fruit, 2) detachment of immature berries, 3) reduced berry firmness and quality, and 4) increased postharvest decay and reduced storage life. Machine harvest necessitates increased handling of fruit during grading and sorting, and on blueberries most postharvest decay occurs at the detachment point—the newly exposed stem scar (Ballinger et al., 1978). When both fungal spores and moisture are present on packing lines, this extra handling can greatly increase postharvest decay caused by fungi (Alternaria, Colletotrichum) due to the exposure (rolling) of berries over contaminated surfaces (Cline, 1996). In the first comprehensive report directly comparing the effects of machine and hand harvesting on highbush blueberry (V. corymbosum), Mainland et al. (1975) found that losses of marketable fruit of ‘Wolcott’, ‘Jersey’, ‘Morrow’, and ‘Murphy’ were from 19% to 44% greater for machine harvesting than for hand harvesting. Machine-harvested fruit were 10% to 38% softer than hand-harvested fruit, and soft berries were difficult to identify and remove during grading. Moreover, after 7 d of storage at 21 C, there was 11% to 41% more postharvest decay for the machine-harvested fruit. They concluded that the inability to remove bruised fruit during grading and sorting presented serious problems for maintaining quality during storage. Similar reductions in marketable yield from mechanical harvesting were reported in Michigan by Howell et al. (1976). In general, increased berry softening and decay during storage have been widely reported in association with mechanical blueberry harvesting (Ceponis and Cappellini, 1979; Dale et al., 1994; Howell et al., 1976; Mainland et al., 1971, 1975; Milholland and Jones, 1972). Ballinger et al. (1973) studied factors affecting blueberry firmness and emphasized the importance of careful harvesting and handling procedures, noting that blueberries are easily bruised, leading to softening and subsequent decay during storage. In a review of the literature, Morris (1983) stated that ‘‘decay of machineharvested blueberries during postharvest holding is perhaps the biggest problem of the industry.’’ Reductions in berry firmness and marketable yield were also found for machine-harvested rabbiteye blueberry (V. virgatum). Using the rabbiteye blueberry cultivar Tifblue, Austin and Williamson (1977) reported increased ground loss of marketable fruit, reduced fruit firmness, and more than twice the amount of unmarketable fruit from machine harvesting vs. hand harvesting. Increased berry softening following machine harvesting was also noted for ‘Climax’ and ‘Woodard’ (Miller and Smittle, 1987) and ‘Brightwell’ (NeSmith et al., 2002), although depending on cultivar, the softer machine-harvested fruit may still be considered marketable as fresh fruit. NeSmith et al. (2002) proportionally attributed the causes of ‘Brightwell’ rabbiteye berry softening to the following harvest activities: 20% to 30% loss of firmness due to