- 9 



mended rate (12 lbs). The mulch decomposed rapidly and was less 

 effective in 1970 through 1972. In 1972, LMY appeared later and 

 was less severe than in 1971. Total rainfall from April through 

 June, 1972, was 148% of the 1967-71 average for these months and 

 the temperatures were lower than normal. These weather conditions 

 could have been responsible for the reduction of foliar injury 

 from dichlobenil in 1972 in comparison to previous years; the ef- 

 fect would most likely be due to temperature, since dichlobenil 

 does not leach readily. In 1973, foliar injury from dichlobenil 

 was again severe and mulch did not reduce severity. 



Weed 



control . The data 

 1968 was of 



in Table 2 show that the single application 

 little or no value for weed control and 



of mulch in 



this was mainly due to reinf estation by quackgrass. 



Table 2. Effects of soil management practices on weed control un- 

 - der Richhaven peach trees planted in 1968. 



Treatment 



Weed control in mid-August (I) 

 1969 1970 T§7J 1972 197T 



Cultivation 



Dichlobenil, 6 lbs 



Dichlobenil, 12 lbs 



Mulch 



Mulch + dichlobenil. 



6 lbs 



Mulch + dichlobenil, 12 lbs 



95a^ 



44c 



83b 



16d 



53c 



91ab 



56c 

 54c 

 81a 

 7d 

 68b 

 90a 



45d 

 50cd 

 77b 

 3e 

 61c 

 94a 



7c 



9c 



2 9b 



--y 



9c 

 60a 



2c 

 3c 

 8bc 



--y 



13b 

 44a 



^Mean separation, \\rithin columns, 

 at the 51 level. 



by Duncan's multiple range test 



y^Since the effectiveness of mulch for control of weeds had disap- 

 peared the data were not included in the statistical analysis. 



Several annual grassy weeds and quackgrass invaded the culti- 

 vated and herbicide treated areas particularly in 1972 and 1973. 

 During these 2 years, only 12 lbs dichlobenil applied on top of 

 the mulch residue resulted in an appreciable control of these an- 

 nual weeds. 



Tree performance . Due to the severity of leaf injury symptoms, one 

 would expect reductions in growth and productivity of the trees. 

 For the first 3 years of the experiment, there was no growth or 

 yield difference among treatments with the exception of the mulch 

 treatment. The mulched trees produced significantly less vegeta- 

 tive growth in 1970 and 1971 and had the least yield in 1971. 



Limb breakage and the presence of weak limbs invalidated the 

 growth and yield data after the 1971 growing season. This is in- 

 deed unfortunate, since leaves on the trees receiving either 6 or 

 12 lbs dichlobenil on bare soil had interveinal chlorosis and 

 brown, tattered leaf margins. Some of the more severely injured 

 leaves dropped in early September. Therefore, it is unfortunate 



