Population growth of Brevipalpus lewisi McGregor (Acarina: Tenuipalpidae) on grapevines

In the Mildura district of Victoria, Brevipalpus lewisi McGregor is responsible for 'bunch mite' symptoms on grapevines. Age-specific life and fecundity tables, compiled in the laboratory, showed that B. lewisi is capable of positive population growth over a range of temperatures at relative humidity levels commonly encountered in the field. The maximum value of rm obtained in the laboratory was 0.04/day, at 28¦C and 35 % relative humidity. A field study of the seasonal abundance and intra-vine distribution of B. lewisi showed that populations increased about 60-fold during a season. The rate of population increase during summer was similar to laboratory estimates of population growth potential. Although the mites were present solely at the base of canes early in the season, later all green parts of the plant became infested. Predation and loss associated with leaf fall reduced the numbers of mites overwintering. Populations were further reduced by removal of mites during pruning.