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<br />Thus, evidence indicates that a reduction of moisture stress <br />through snowpack augmentation will decrease the mortality asso- <br />ciated with canker fungi, F. annosUB, and bark beetle in sus- <br />ceptible species in the immediate downwind areas. <br /> <br />If weather modification during dry years can shorten the period <br />or reduce the severity of moisture stress on trees, then damage <br />from canker fungi and bark beetles would decrease. This effect <br />would be most likely to occur on the drier areas and southern <br />exposures that are marginal or poor sites for tree growth. <br /> <br />Monitoring of the effects of weather modification on the rela~ <br />tionship of moisture ,stress to bark beetle attack would be use- <br />less, since complicating variables and past cloud seeding <br />activities reduce the value of data on annual fluctuations in <br />bark beetle mortality. liowever, historic records could be <br />examined for possible correlations between amount of snowpack or <br />date of melt and episodes of unusual activity. <br /> <br />There are extensive plantations of young ponderosa and Jeffrey <br />pine on relatively dry sites northeast of the American River <br />watershed as well as within the study area. One of the more <br />serious pests of pine plantations is the pine reproduction <br />weevil, Cyti.ndztotoptuz-us eatoni.. Soil moisture is important in <br />regulating weevil populations, presumably through its effect on <br /> <br />1-10 <br />