20 Bulletin 328 



nicotine in such a fashion that all the lice and lice eggs are 

 coated, the cjuestion of the time of application becomes exceed- 

 ingly important. It seems clear from the laboratory and field 

 studies that the green-bud stage is the best, because at that time 

 the maximum number of lice will have hatched and are without 

 shelter, and the unhatched eggs are most susceptible. 



The term "green-bud stage" is rather elastic and somewhat 

 dil^cult to define. When the bud scales first separate at the tip 

 the parts exposed are silvery and only slightly green. The sil- 

 very look is due to the presence of a heavy pubescence on the 

 structures exposed. In the course of a very few days this silvery 

 look gives way to a decided green as the edges of the leaves be- 

 gin to project. Treatment should be completed by the time the 

 latter stage has been reached, for the next stage, which may fol- 

 low within a single warm day and night, and shows the young 

 leaves projecting from the buds like squirrel ears, is not only 

 liable to be injured by the treatment, but offers shelter to the 

 lice. 



Conclusions 



1. Three species of plant lice — green apple aphis, the rosy 

 apple aphis and the oat aphis, especially the first two — attack the 

 foliage and fruit of apple in New Jersey and are capable under 

 favorable conditions of destroying a larg'e percentage of the 

 crop. 



2. All species winter over on the water sprouts, twigs, and 

 smaller branches of the apple trees as small shining black oval 

 eggs just large enough to be seen with the naked eye. 



3. While it is not possible to forecast an outbreak with cer- 

 tainty, even when the eggs are on the trees, because of the effect 

 of weather and natural enemies, preparations should be made for 

 treatment as a matter of insurance if the eggs are present. 



14. Control by destruction of returning migrants and egg- 

 laying individuals in the fall is probably impracticable, l)ecause 

 of the number of sprayings that would l3e necessary. 



5. The probability of developing a method of control by 

 destroying the eggs during dormancy seems strong, but in the 

 present state of knowledge it should not be depended on. 



6. Control by destroying the aphis after the leaves are pretty 

 well unfolded is likely to prove impracticable because of the 

 shelter which the leaves afford the lice. 



7. The most practicable treatment for aphis control is the 

 application of winter-strength lime-sulfur to which 40 per cent 



