of decay than low calcium fruit. Calcium chlo- 

 ride sprays during the growing season are ef- 

 fective in increasing fruit calcium. Fruit cal- 

 cium also may be enhanced by reduction of tree 

 vigor and promotion of dense and 

 heavycropping. 



For several tjrpes of postharvest decay, the 

 maturity of the fruit at the moment of harvest 

 has a critical effect on decay risk. Earlier har- 

 vest, within the range of acceptable maturity, 

 reduces decay risk. Earlier harvested fruit is 

 usually less prone to bruising during harvest, 

 and bruising may increase susceptibility to rot 

 during storage. 



Most postharvest rots begin with infection 

 by a fungus through a small puncture in the 

 skin of the fruit. Punctures can happen on the 

 tree, during harvest, in transport, or during 

 packing. In a study of frmt punctures in field 

 liins of Bosc pears in the Medford district in 

 1994, fruit harvested by workers paid by the 

 hour had significantly fewer punctures than 

 finiit harvested by workers paid piecework. 



In our research, several orchard and stor- 

 age factors have been combined into an inte- 

 grated program. Low fi-uit N, high ftmit cal- 

 ciiun, early harvest, and CA storage have all 

 reduced decay by several postharvest patho- 

 gens. When these treatments are combined, 

 their benefits add up to make a significant im- 

 pact on decay. Experiments have also shown 

 the value of integrating biological control and 

 thiabendazole (TBZ) fungicide treatments with 

 the orchard and storage factors described above. 

 This may be implemented when the biocontrol 

 agents we have tested experimentally become 

 products labeled for use. 



One of the expected benefits of an integrated 

 approach is stability. Since the factors in an 

 integrated program are independent of one an- 

 other, each is unaffected by the performance of 

 the other factors. As additional techniques are 

 developed or new fungicides or biocontrol agents 

 become available, they can be integrated as new 

 elements of this program. 



Growers also can work together with pack- 

 inghouse personnel in the area of bin sanita- 



tion. It is the responsibility of the packinghouse 

 to provide clean bins, but it is the responsibil- 

 ity of the grower to keep them clean before and 

 during harvest and to send full bins back to the 

 packinghouse as free as possible of dirt and de- 

 bris. In both AustraUa and South Africa, fruit 

 growers harvest into bins placed on trailers. The 

 South Africans often connect several trailers 

 into a train which is pulled between the rows 

 and "loaded" by pickers from both sides. The 

 main point is that bins should be kept as clean 

 as possible. Bins pushed through the dirt or 

 mud with a fork lift will carry tremendous niun- 

 bers of spores into the packinghouse, only to be 

 washed into the drench or dump water and de- 

 posited on all fruit passing through the system. 



In addition to the above decay reduction 

 measures, growers can reduce decay by appli- 

 cation of a preharvest fungicide. Several stud- 

 ies have been done on the effectiveness of 

 preharvest ziram and show an average reduc- 

 tion in decay of about 25-50% with a single ap- 

 plication. In some years, bull's-eye rot has been 

 reduced by over 80%. Preharvest ziram appli- 

 cation also has given over 90% control of an- 

 other decay, Coprinus rot {Coprinus 

 psychromorbidus), which appears similar to 

 bull's-eye rot and has been found on apples and 

 pears from Hood River to British Columbia. 

 Because ziram has good retention properties, 

 an application made two to four weeks before 

 harvest will still give a good residue at harvest. 

 Control of decay with aerial applications has 

 been better than when no fungicide is used but 

 is not as effective as a ground spray because of 

 poorer coverage. 



An integrated approach is essential for good 

 control of decay. Both the grower and the pack- 

 inghouse personnel must use all the tools dis- 

 cussed above to the best of their ability if 

 healthy, high quality fruit are to be shipped to 

 market. 



This article is reprinted with permission 

 from Washington State University Tree 

 Frxiit Postharvest Journal, Vol. 6, No. 2. 



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Fruit Notes, Summer, 1995 



15 



