The Influence of Fungicidal Sprays on Entomogenous Fungi and on the Purple Scale in Florida

Abstract

An investigation conducted in Orange County, Florida, during 1938 and 1939 using single-tree replicated plots to compare high and low residue treatments with and without Cu as a fungicide gave results which indicated that the inert residue contained in the sprays was the more important factor causing scale increase on Parson Brown orange trees. The Cu fungicides reduced infection of the scale by the entomogenous fungi, but the reduction caused no significant difference in the % of total scale mortality or in the total infestation. The % of total mortality was lower in both high residue treatments than in either low residue treatment but there was no difference due to the presence or absence of the Cu fungicide. After a yr. with no further treatment, there was no difference in total infestation which could be attributed to the use of Cu sprays. No increase in scale infection by entomogenous fungi was obtained by applying a spray which contained spores of Nectoria diploae and Sphaerostilbe aurantiicola.