2 BULLETIN" 1178, U. S. DEPARTMENT OF AGRICULTURE. 
It has long been known that spray materials containing copper 
salts are particularly destructive to entomogenous or "beneficial" 
fungi. The checking of the number of these fungi following the use 
of such spray materials develops conditions especially favorable for 
rapid increases in scale insects, white flies, rust mites, red spiders, 
and mealybugs. Often these insects become extremely numerous, 
depending largely upon the time of application of the spray. The 
closer the time of application is to the period of maximum activity 
of the entomogenous fungi, the greater is the likelihood of rapid 
insect increases. 
Sulphur spray materials, such as lime-sulphur solution, when 
applied at the usual dilutions for citrus, are at best only partially 
effective against citrus scab (usually, but erroneously, attributed to 
Cladosporium citri Massee) and melanose (caused by Phomopsis citri 
Fawcett) . They are not especially harmful to the crop of entomog- 
enous fungi, but possess marked insecticidal properties, killing rust 
mites, red spiders, and scale crawlers. 
The sulphur compounds oxidize rapidly under conditions of 
relatively high temperatures and in a short time lose their fungicidal 
potency. On the other hand, copper sprays as a class persist for a 
much longer time and are more or less fungicidal as long as traces 
of copper remain. 
Oil sprays are used principally for scale and white-fly control and 
have little or no fungicidal value. 
A very important problem in the control of diseases of citrus fruits 
in Florida is to develop a safe and cheap spraying material that will 
successfully control citrus scab and melanose without an excessive 
increase of insect pests following. 
In order to present the problem in graphic form Figure 1 has been 
drawn to show the approximate periods of activity of the prin- 
cipal fungi in a bearing grove in Florida and also the relative abun- 
dance of adult white flies, 1 scale insects, and rust mites. 2 The dates 
when insecticidal applications are usually made are also shown. 
It can be seen from Figure 1 that outbreaks of the principal para- 
sitic fungi are more or less continuous from early spring until late 
fall and that during that time the more important insect pests do 
most of their damage. It should be noted especially that while there 
are definite times when scale insects are hatching in large numbers, 
there is a more or less continuous hatch from early spring until late 
fall, and in certain parts of the State of Florida these insects are quite 
active throughout the year. It is thus apparent that any standard 
fungicide that will effectively control plant diseases will also prevent 
the diseases of insects and thus bring about an enormous increase in 
the number of insects, necessitating extra applications of insecticides. 
The logical solution of the problem would be to devise a combi- 
nation of fungicidal and insecticidal materials of high efficiency that 
will retain their respective properties when mixed. An important 
practical advantage would be the saving on labor and team expenses 
resulting from one application taking the place of two. A mixture 
of oil emulsion and copper compounds for use in citrus groves would 
seem to be a promising combination for this purpose. 
1 The white-fly curve represents the abundance of adults of Dialeurodes citri Ashmead throughout the 
year. (Adapted from Morrill and Back.) During the period from October 10 to December 1 a single 
spray application is required. 
» There are thousands of times more rust mites present in June than during any other month of the year, 
This is shown by the broken curve. 
