New York AcRicuiiTURAL Experiment Station. 19 



of the formaticn of the polar body in the parthenogenetic egg 

 have been worked out. 



San Jose scale. — These investigations may be divided under 

 two head's: (1) The development of the insect, and (2) the 

 methods of control. During development the insect passes 

 through three well-defined periods: (1) The period of activity; 

 (2) the period of growth, and (3) the period of reproduction. 

 The duration of all of the periods varied greatly with the tem- 

 perature. During the active period the larvse migrated readily 

 over smooth surfaces. Numerous insects, representing five 

 orders, were found from time to time with larvae clinging to 

 them. Ants, bees and wasps apparently do not carry them. 

 During the period of growth the scale is formed. The average 

 number of young produced per day by female of the fall broods 

 was a little over two. 



Experiments with kerosene oil, 100° fire test and 150° fire test, 

 showed the former to be dangerous to the trees at the lowest 

 percentage, when mixed with water, required to kill the scale. 

 The latter gave similar results with peach trees and injured plum 

 trees to a very slight degree when used strong enough to be 

 effective to the scales. Apples and pears were uninjured. Ex- 

 periments are also being made with crude petroleum and hydro- 

 cyanic acid gas. A fumigator for orchard trees has been devised 

 which was successfully used in the experiments. 



• 



department op horticulture. 



Fumi(pati(m of nursery stock. — The best known way of killing 

 San Jos^ scale on dormant nursery stock is by funnigation with 

 hydrocyanic acid gas. This treatment is valuable not only 

 against San Jos^ scale, but against all scale insects which do not 

 winter in the egg stage. It will doubtless also check the spread 

 of some other kinds of injurious insects which are liable to be 

 distributed on nursery stock: 



Plain directions for fumigating dormant nursery stock with 

 hydrocyanic acid gas are published in Bulletin 174 together with 



