The Problem of Black Scale (Chrysomphalus Ficus, Ashm.) in Palestine

Abstract

The work which is described in this paper was undertaken owing to the conflicting results of standard fumigation practice in Palestine as it existed up to 1932, so that it became evident that the response of the Black Scale to Palestine conditions called for investigation.Owing to the difference in climate between the Northern Coastal Plain and the Jordan Valley a series of parallel investigations had to be initiated, with the interesting results which Dr. Schweig and Mr. Grunberg have set forth.There seems little doubt that the growers in the Jordan Valley will have to change from summer to winter fumigation and that in Acre Sub-District even if the double fumigation now under trial is not practicable (and there is no reason wh y it should not be) fumigation will have to be completed by the end of July—otherwise the fruit of the last fumigated groves will be infested before the gangs can reach them. With regard to biological control, this would be pf more value for keeping down the Black Scale population on alternative hosts, such as Eucalyptus groves and roadside trees. Negotiations for the importation of Comperiella bifasciata are in progress, and if this proves possible it will be given a trial in the Jordan Valley and the Coastal Plain.It is unfortunate that the pressure of other demands on the time of a small staff precluded the investigation of the behaviour of the Black Scale in Jaffa Sub-District, but general observations show that it tends to react more in the manner of the Jordan Valley race than of that of the Northern Coastal Plain.All the orange-groves between Jaffa and Haifa are heavily infested with Aonidiella aurantii, and it will be interesting to see, in view of the observations on mutual tolerance contained in this paper, whether Black Scale spreading from Jaffa will drive out the Red Scale or fail to make headway agaipst it.