TIIK MONTHLY KI T U,KTIN. 



479 



Predators had been relied npon for tin- control of this pest previous to 1914. The 

 ones of greatest importance are Olln abdominal).? and I'sijUobora tuedata. CpcoineUa 

 cttlifornica, Hippodamia convergent, and Hippodamia ambigua are others of less 

 importance. For some unknown reason the number of ashy grey ladybird beetles in 

 i his section has been dwindling, and the importance of the common red and black 

 spotted ladybird beetle has been increasing. The status of the small ashy grey 

 beetle has remained stationary. I lining some seasons tbe predators are present in 

 sufficient numbers to completely check the aphid, and one possible explanation for. 

 the decrease in the number of ashy grey beetles is that they destroy so many aphids 

 that there are not enough left for them to feed on the next year, and they must 



migrate or perish. 



Early this season an entomogeuous fungus was 

 discovered destroying aphids in large numbers. A 

 grove adjacent to the one first sprayed with nico- 

 tine sulphate was badly infested, but the work had 

 been delayed on account of an inadequate supply 

 of water. A later inspection disclosed a fungus 

 belonging to the genus Entomophthora, which had 

 so cleaned up the grove that treatment was unnec- 

 essary. The high humidity no doubt accounts for 

 the rapid spread of this fungus. That conditions 

 were ideal for the development and spread of such 

 fungi is clearly shown by the fact that another 

 fungus, Entomophthora aphidis, belonging to the 

 same family, was found working on the destructive 

 pea aphis. Macrosiphum pisi. It destroyed the 

 ml ire infestation in a short time. 



An important fact brought out by our work on 

 this aphid is that trees sprayed with nicotine sul- 

 phate are much less damaged by the hot weather 

 than unsprayed trees. This can be accounted for 

 by the fact that the sprayed trees put out a new 

 growth which better protected the nuts. They 

 were also free from sooty mold fungus, which 

 remained on the leaves of trees where the pest 

 had been controlled by such natural agencies as 

 fungi, predators, and excessive heal. This is a great advantage of the liquid over 

 the dust spray. The liquid spray not only relieves the trees of the attacking aphis, 

 but also of the sticky excrement and sooty mold fungus resulting from their activi- 

 ties. Another great advantage of the summer spray over the dormant spray, aside 

 from the reduced cost and greater efficiency, is that it need not be applied until it 

 is evident that natural agencies will not control the pest; whereas the dormant 

 spray must be applied annually, without knowledge of what future conditions will be. 

 The eggs of predators taken from the leaves of sprayed trees hatched into 

 apparently healthy larva 3 , which would indicate that the summer spray does not 

 destroy the unhatched predators present. 



Our advice to growers is to watch their groves, and when the infestation becomes 

 severe enough to warrant treatment, spray with nicotine sulphate, unless there are 

 strong indications of natural enemies developing in sufficient numbers to control the 

 pest. 



I believe that the summer sprays will in the very near future be generally used 

 fur the control of the walnut aphis, and it the conclusions drawn from our work 

 here arc correct, it will prove to be a very efficient and economical means of control. 



Fig. 146. Spraying for wal- 

 nut aphis with M. A. C. 

 Nozzle. 



