Abstract
In the autumn of 1965 heavy infestations of California red scale on citrus fruits were observed in the suburbs of Nagasaki City. This was the first record of this species in Nagasaki Prefecture and was the northernmost of its distribution in Japan. Ecological observations of this scale were carried out in order to establish the control project.
Occurrence of this scale in this area were shown in Fig. 1. About 20 ha. of citrus orchards were infested. Infestation was observed to be heavier on hassaku orange than on the other citrus such as unshu or natsudaidai.
The scale has three generations a year, and seasonal abundance of the 1st instar larvae was shown in Fig. 3. Oviposition seemed to be made during May to December.
The controlling effect of winter spray of some kinds of oil emulsion and summer spray of three kinds of organic insecticides were examined. From the results of these experiments, it was observed that spray of Pestan at the end of June was most effective.
The control project in 1966 was successful and population density of the scale was decreased remarkably (see Fig.7 and Table 2).
