The Possible Truer Status of the Red-Headed Scale-Fungus: A Preliminary Report

Abstract

For the past several years I extensive research into the biology and control of purple scale on citrus has been conducted. This is the most abundant of any of the scale insects preying upon citrus and doiubtless does more damage than any one other citrus pest. During the course of this work the abundances of friendly fungi have always been noted numerically. The which is the most conspicuous and which outnumbers all others in abundance is the red-headed scale-fungus. It is this organism on purple scale which is referred to in this paper. In tabulating its abundance two methods have been used. The first states the as a percentage of the total live and dead scale population. The second expresses it as the fungus ratio. This term, as used here, refers to an inverse ratio, i.e., the number of live purple scale to each fungus-infected scale. Thus, a high ratio would imply low populations, while a, low ratio implies high populations. In 1933 it was noticed that the ratio in randomly selected groves was rather uniform, except in such groves as had recent applications of Bordeaux, or other fungicidal sprays. As the period of time lapsed following the fungicidal spray the ratio gradually assumed lower proportions. The most interesting feature of this study was the total lack of any fluctuations in unsprayed trees which might express a hostparasite relationship between purple scale and the red-headed scale-fungus. At the same time it was found that the was attacking only a small percentage of the total dead scale. In many groves in Florida growers rely upon this for the control of purple scale. They use as an index of control the number of fungus-infected scale, omitting scalecidal sprays in many cases if the is very abundant. This theory of control by fungous is time-honored and has been backed by the scientific publications of various research departments.