8 Farmers’ Bulletin 1261. 
it produces eggs, and the young which are hatched from these eggs 
give rise to another generation further to infest the tree. 
SEASONAL HISTORY. 
In Florida the seasonal history of this scale varies somewhat, 
depending upon the locality, its activities being influenced by changes 
of temperature. As a general rule, however, the young begin to 
appear about March 1 and infest the newer growth in great num- 
bers. At this time of year a generation requires approximately seven 
weeks to mature. As the weather becomes gradually warmer, the 
generations are a little shorter, and overlap considerably during the 
summer months. With the approach of cool weather in December 
and January a generation lengthens and requires over two and a 
half months in which to develop. In southern Florida, depending 
upon the locality, this scale may pass through from five to six gen- 
erations in a year. 
HOW THE SCALE MAY BE CONTROLLED. 
The best time to control the dictyospermum scale on the avocado 
is when the trees are dormant, from the middle of December until 
the Ist of February. Oil emulsions, such as are used against citrus 
insects, have been found to control the scale effectively. There are 
a number of oil emulsions on the market, some of which when com- 
bined with waters used in spraying in Florida work very satis- 
factorily. The waters used in southern Florida for spraying pur- 
poses are those which come from deep wells in limestone formation 
and are termed “hard,” and those which come from surface wells 
and are as a rule somewhat brackish. Certain oil emulsions, how- 
ever, when combined with these “hard” waters may prove at times 
unsatisfactory, because the lime and magnesium salts usually pres- 
ent in the water tend to break up the emulsion, causing the oil to 
be set free during spraying. If separation occurs in using an oil 
emulsion with ne water, the water should be first softened by means 
of caustic potash fish- a soap. Two to three pounds of caustic pot- 
ash fish-oil soap to a 125-gallon tank have been found sufficient to 
soften the ordinary hard water. After the water has been so softened 
the oil emulsion should be added. In using the oil emulsions on the 
avocado during the dormant season, the writer has found that a 
strength of 1 gallon to 70 gallons of water proved the most satis- 
factory. Two applications with a three-week interval during the 
dormant period will control this scale insect. In the nursery a 
strength of 1 gallon to 80 gallons of water should be used on account 
of the new growth generally present. 
