Natural enemy promises control of Nantucket pine tip moth.
After severe damage to Pinus radiata (Monterey pine) at the Carlton Oaks golf course in San Diego County, California had in 1971, been traced to Rhyacionia frustrana (Comst.), a species not previously known in that state, studies on the mortality factors relating to this pest were undertaken in the locality. The results showed that P. radiata was the only pine species severely attacked, and that populations of R. frustrana were usually limited mainly by the availability of Monterey pine tips; although the natural enemies Erynnia tortricis (Coq.) and Scambus aplopappi (Ashm.) were frequently found with the pest, they did not cause more than 10% mortality. In 1974, 2 parasites controlling R. frustrana in its region of origin (the south-eastern and eastern states of USA) were introduced into California and released at Carlton Oaks; of these, the tachinid Lixophaga mediocris Aldr., was not recovered subsequently, but the ichneumonid Campoplex frustranae Cushm. was collected in small numbers from overwintering Rhyacionia pupae, increased rapidly in numbers in 1976-77 and gave 50% parasitism by the end of 1977. Monthly pine-tip samples showed that the number of uninfested tips increased each year after the release of C. frustranae, and that the onset of Rhyacionia attacks was not only less intense but slightly later each year than in the previous year. Further studies are required to determine whether biological control by C. frustranae is effective in other infested areas of San Diego County.