In commercial practice, apples receive many bruises just before or after, passing through washing solutions,, which usually are contaminated with fungus spores from other apples, When there were two bruises per fruit on apples that were dipped in, contaminated water, the average number of infections per 100 fruits was 48, but there were only 5.9 infections per. 100 apples that were unbruised. Nearly three times the number of. infections were found at severe bruises as at slight ones and more than five times as many in bruises on large apples than in bruises on small apples. Large apples that had been picked at an advanced stage of maturity and severely bruised had the greatest number of infections; an average of 103 infections in each 100 bruises.

Experiments in 1948 showed that apples that had been bruised when withdrawn from cold storage at intervals during the winter became increasingly susceptible to blue mold infection as they ripened. Bruises made at the time of harvest, however, lost much of their earlier vulnerability to the blue mold organism when exposure to the spore-bearing bath was postponed until after various periods in storage. Experiments in 1949 showed that blue mold developed in 20 to 58 percent of the bruises in apples dipped in a spore bath immediately after they were bruised, as against only 2.5, 0, and 0 percent when apples were held in cold storage 3, 7, and 14 days, respectively, between the times of bruising and exposure to the spore-contaminated solutions.

Those findings; that blue mold infection may occur through the apparently unbroken skin at bruises, are important to the industry because of the' number of bruises caused during the washing and packing operations. In studies of apple bruising between harvest and distribution to retail stores it was found that many of the smaller bruises were caused during washing and packing either just before or immediately after immersion in washing solutions that may be heavily contaminated with blue mold spores. In certain instances all the apples were bruised; individual fruits showed 30 to 50 small bruises or dents.

Faulty operation and maintenance of packing-house machinery often are to blame for extensive bruising. Washing and packing equipment is often operated to handle from 400 to 450 bushels an hour instead of the rated capacity of 300 to 350 bushels an hour. Excessive bruising results. Often little is done to reduce the force of impact of fruit with machinery parts, particularly at the point where the apples are dumped onto the equipment and at points of transfer from one part of the machine to another.

Many rot-producing fungi can become established without a skin injury, but some cause decay in fruits and vegetables much earlier because of injuries from careless handling. Noteworthy among them are Botrytis cinerea and species of Rhizopus, which are responsible for enormous losses.

Rots caused by bacteria that enter through injuries are especially serious in some vegetables. Outstanding is bacterial soft rot, caused by Erwinia carotovora and other species. The organisms infect potato tubers chiefly through injuries and cause more extensive spoilage in the early and intermediate crops than any other factor. New potatoes exposed to excessive field temperatures during harvest often have surface temperatures of 109 to 122 and higher. Such surface temperatures are possible whenever air temperatures in the shade range from 90 to 95 . Potato tissues that have reached 109 to 113 are likely to develop soft rot.

In areas where hot weather prevails during harvest, it is advisable to dig and pick up the potatoes early in the morning or in the evening. Digging, sacking, and trucking should be so coordinated that freshly dug tubers are not allowed to lie exposed on the ground more than 15 minutes before being sacked, loaded, and moved to shelter. Ventilation and temperatures below 70 are essential during storage and transit to restrict growth of bacterial soft rot.

T. R. WRIGHT is a pathologist in the Bureau of Plant Industry, Soils, and Agricultural Engineering, United States Department of Agriculture, at Wenatchee, Wash. He is a graduate of Pennsylvania State College and did graduate study at the University of Minnesota.

EDWIN SMITH was head of the Wenatchee laboratory of the division of handling, transportation, and storage of horticultural crops from 1932 until his retirement in 1952. He has conducted research on the handling, transportation, and storage of apples and other fruits in Canada and England as well as in the United States.

Leaf blister on white oak.