of total weight. From 3 to 14 percent came off with stems attached. The quality 

 of the mechanically harvested plums compared favorably with that of the hand- 

 picked being received at the same processing plant. The cooperating processor 

 stated that leaves, twigs, and stems could be removed during processing without 

 difficulty and that bruised plums were acceptable if processed promptly. 



AERD attempts to harvest Damson plums with the same equipment were 

 abandoned because about 5 percent of the plums came off with spurs attached. 

 AERD feared that losing so many fruit spurs might reduce the amount of plums 

 borne in succeeding years. 



Prunes 



Prune growers in the Sacramento Valley, Calif., have adopted mechanical har- 

 vesting methods. A three-man crew can harvest up to 70 trees per hour using 

 equipment and methods that AERD and the University of California developed. 

 The equipment consists of a conveyor belt 6 feet wide and 22 feet long, suitable 

 catching surfaces, and a shaker. As the fruit shakes from the tree, it falls or rolls 

 onto the conveyor and moves directly into bulk boxes. 



Labor costs with this equipment are about $2 per ton compared with $12 per 

 ton for hand harvesting. AERD estimates that a grower would have to harvest 

 3,200 trees (about 30 acres), four boxes to the tree, before he could afford such 

 mechanical harvesting equipment — the cost (including interest, taxes, and insur- 

 ance) amortized over 3 years. 



In the Santa Clara Valley, Calif., most of the prunes fall from the tree as 

 they mature. This phenomenon presents two problems: (1) Shakers and catching 

 frames could not be utilized efficiently every year because in any given year a large 

 percentage of the prunes might already be on the ground, and (2) handpicking 

 the fallen prunes is costly and slow. After studying these problems, AERD con- 

 cluded that a ground pickup device or a blower-catch operation to harvest many 

 trees quickly or both would be practical. 



The ground pickup device became a machine, self-propelled, 20 inches wide, 

 and operated by one man walking behind it. The man and this machine replaces 

 six or seven handpickers and can harvest about 1,000 pounds of prunes an hour. 

 The operation does not damage the fruit or pick up excessive amounts of soil or 

 trash. About 20 of these machines were in use last year. 



AERD engineers and their collaborators also produced a device to remove 

 prunes from trees by modifying a commercially available frost protector blower 

 (6-foot propeller; air velocity, over 100 miles per hour). They installed 9-inch 

 louvers that could be either rotated or oscillated in front of the air stream, and 

 harvested 4 plots of 60 trees every 4 or 7 days. Travel speeds of 2V2 and li/i miles 

 per hour and oscillation and rotation rates of 60 per minute were used. Results 

 showed that this method was selective in removing only ripe fruit, but the total 

 removed was lower than desirable especially on the last harvest. The results were 

 promising, however, and AERD will conduct more research using this device, per- 

 haps with supplemental shaking. 



Blueberries 



Cultivated blueberries are grown commercially in the Middle Atlantic States, 

 Great Lakes area, and the Pacific Northwest. About 35 percent of Michigan's 

 blueberries and 30 percent of New Jersey's are harvested mechanically by means 



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