February, '22] brittain: the apple sucker 97 



Character of Injury 



The injury is almost entirely the work of the nymphs, as the adults 

 do no appreciable damage. Both leaves and blossoms are affected, 

 the latter most seriously, since the insect prefers the blossom clusters 

 for food. Badly infested blossoms shrivel and die and remain hanging 

 to the injured trees for some time. The injury due to these creatures 

 seems, however, to result entirely from the amount of sap withdrawn 

 from the blossoms, there being an entire absence of that "poisoning" 

 effect, that seems to result from the punctures of certain Miridae. 



Injury to the foliage falls in four general categories:^ 



1. Brown withered leaves that may remain clinging to the trees 

 throughout the summer. 



2. Green leaves that are sometimes shed in showers about the end 

 of June in infested orchards, apparently due to the work of this pest. 



3. Yellow leaves which may begin to fall in mid- June and continue 

 for several weeks. 



4. Similar injury to No. 3, but greatly aggravated, which seems to 

 result from spraying injured trees with Bordeaux mixture or dusting 

 them with copper-lime-arsenate dust. The work of the insect seems 

 to render the foliage particularly susceptible to spray injury of this 

 kind and orchards so treated sometimes present a much worse appearance 

 than those left unsprayed. 



The insects may be present in large numbers without causing much 

 apparent damage and we are as yet unable to predict what place it will 

 eventually occupy as an apple pest. 



Life History 



The first emergence of nymphs from the eggs takes place when most 

 varieties of apple are in the so-called "mouse ear" stage, but on very- 

 late opening varieties such as Northern Spy, the buds may not have even 

 begun to burst. On the other hand the leaves of the Transcendent 

 Crab are well expanded. The insect hatches first on the earliest opening 

 varieties, there being a difference of as much as four or five days between 

 Gravenstein and Northern Spy, but the emergence does not correspond 

 perfectly, by any means, with the state of development of the buds. 

 The entire hatching period may extend over eleven days. In 1921 

 the first individuals emerged just one week later than those of Aphis 

 pomi De G. and just eleven days previous to those of Lygus communis 

 Knight. 



The nymphal stage lasts from thirty-one to thirty-six days, the emer- 

 gence of other adults reaching a maximum about six days after the first 

 individuals are seen and continuing for about eight days thereafter. 



