15 



about substantial control. 



Successful control of the twospotted spider mite has also been achieved 

 with a predator. Releases of the mite Phytoseiulus persimilis before spider 

 mite populations attained an average of one mite per leaf provided effective 

 control in California (8). This predatory mite has also been used successfully 

 in greenhouses and under row covers (5). Control is temporary as the mite 

 completely eradicates its prey and therefore its food source under these 

 conditions. Similar to the Typhlodromus species, P. persimilis would not 

 likely survive the climate extremes of the Northeast. This would necessitate 

 annual releases of the predator, and the cost required may be prohibitive. 



Despite inherent difficulties, biological control has some potential as a 

 component of an integrated pest management program for strawberries in the 

 northeastern United States. Research is needed to determine the effectiveness 

 of native natural enemies and the existence of exotic species. The strawberry 

 root weevil for example, is thought to have come originally from Europe, yet no 

 efforts have been reported to seek natural enemies there. Some strawberry 

 pests, including leaf rollers and aphids, are already known to be controlled 

 effectively by natural enemies (9). Only minor manipulation or alterations 

 may be required to bring about much greater biological control of other 

 species. 



The increased exploitation of biological control agents, combined with 

 proper cultural practices and improved application strategies for chemicals, 

 could greatly increase pest control efficiency in strawberries and hence, 

 profitability. In addition, such an integrated proeram likely would reduce the 

 amount of pesticides used, and thereby reduce the potential hazards of frequent 

 and repetitive pesticide use. 



References 



1. Barritt, B.H. and C.H. Shanks. 1980. Breeding strawberries for 

 resistance to the aphids Chaetosiphon fragaefolii and C. thomasi . 

 HortScience 15:823-825. 



2. Darrow, CM, 1962. The strawberry. Holt, Rhinehart and Winston. New 

 York. 447 pp. 



3. DeBach, P. 1974. Biological control by natural enemies. Cambridge 

 University Press. London. 323 pp. 



4. Downes, W. 1931. The strawberry root weevil. Can. Dept. Agric. Pamphlet 

 no. 5. 2nd ed. 



5. Gould, H.J. and J. Vernon. 1978. Biological control of Tetranychus 

 urt icae (Koch) on protected strawberries using Phytoseiulus persimilis 

 Athais-Henroit. Plant Path. 27: 136-139. 



6. Huffaker, C.B. and C.E. Kennett. 1956. Predation and cyclamen mite 

 populations on strawberries in California. Hilgardia 26(4): 191-222. 



7. Kishaba, A.N., V. Voth, A.F. Howland, R.S. Bringhurst, and H.H. Toba. 

 1972. Twospotted spider mite resistance in California strawberries. J. 



