Yellow-vein in Citrus

scales per 100 leaves varied from 3.3 to 8.7. Scales containing active forms of Aphytis numbered in excess of 18 per 100 healthy scales each month, and in one month were as high as 183 per 100 healthy scales. These figures demonstrate that Aphytis was active during each of the 15 months and present in sufficient numbers to hold purple scale at low level regardless of weather fluctuations. This finding is further confirmed by Figure 1 which shows that statewide pop ulations of purple scale maintained a relatively constant low level from June, 1959 through August, 1960. In view of the foregoing evi dence, it may be assumed that weather fluc tuations likely to be encountered in the Flo rida citrus belt will not greatly reduce the beneficial performance of Aphytis lepidosaphes. Summary Purple scale, a consistently important and widely distributed pest of Florida citrus for many years, has usually required one or two sprays each year for control. Prior to 1959, natural control factors were inadequate to hold populations below economic levels. This situation began to change markedly in 1958 when a new parasite, Aphytis lepidosaphes Compere, appeared in purple scale infesta tions. Establishment of the parasite through out the citrus belt decimated the purple scale population in 1959, and shows promise of holding purple scale at non-economic level in the future. During the year from August, 1959 to August, 1960, only 7 of 130 survey groves developed noteworthy scale infestations, most of which declined rapidly except where repeated or excessive sulfur applications were made. A study of 97 spray treatments in 22 groves disclosed that of commonly used pesti cides, only sulfur inhibited effective control of purple scale by Aphytis; hence, excessive sulfur applications should be avoided. Wea ther fluctuations appeared to have little ef fect on the ability of this outstanding new parasite to check purple scale.