40 



THE EEPOET OF THE 



No. 36 



TABLE No. 7 — Showing Comparative Susceptibility of European Plums to 



Mite Injury. 



Severe 



Moderate 



Light 



Very Light 



Smith Orleans 



Arch Duke 



Duane 



Reine Claude 



German Prune 



Victoria 



Quackenboss 





Shipper's Pride 



Gueii 



Lombard 





Shropshire Damson 



Washington 



Grand Duke 





McLaughlin 



Hand 



Diamond 





Pond 



Monarch 



Tennant Prune 





King Damson 



Yellow Egg 



Warner's Late 





Moore's 



Imperial Gage 



Latchford 





French Damson 



Kingston 



Bleeker's Gage 





Ancaster 



Bradshaw 



Hulling's Superb 





Emerald 



Fellenburg 







Riley Damson 



John A. 







Belgium 



Field 







Wyedale 



Lawson 







Pearl 



Klondyke 

 Early Rivers 

 Moyer 

 Blue Prolific 

 Early Transparent 



Gage 

 Canada Orleans 

 Hudson 

 Large Golden 



Prolific. 

 Curlew 

 Sugar Plum 

 Pacific Prune 

 Improved Lombard 







Control. 



Natural Control. 



Depletion of Food Supply : The depletion of the food supply was undoubtedly 

 the most important natural check on the multiplication of the spider mite this 

 past season. The leaves of severely attacked trees became tough and dry in mid- 

 summer, and ceased to provide the mites with sufficient nourishment, consequently 

 most of them on such trees perished. Trees, which in July had been infested with 

 countless numbers of mites, became almost free towards the end of August. Thus 

 it happened that the smallest number of overwintering eggs were deposited on the 

 most severely infested trees. 



Weather: The mites, feeding as they do on the upper and lower surfaces of 

 the foliage, are not afforded very much shelter by the leaves during the storms. 

 Eains wash them off the upper surface, and heavy rains accompanied by strong 

 winds, wash them from the lower surface. Immediately after a heavy rain 

 storm last summer, infested trees were examined and it was found that approxima- 

 tely 90% of the mites had been washed off the upper surface, and approximately 

 70% from the lower. The eggs, of course, remained attached to the leaves. 



Predaceous Enemies: In view of the fact that the mite was so very abundant 

 this past season, it was very surprising to fin ! d that predaceous enemies were remark- 

 ably scarce. The minute, black ladybird beetle, Stethorus punctum Lee. was 

 found in small numbers feeding .on the mites. The well-known two-spotted lady- 

 bird beetle, Adalia bipunctata Linn, was also observed on infested foliage ap- 

 parently attacking the mites. But so far as we could judge, no predaceous enemies 

 had any appreciable effect in reducing the numbers of the spider mite. 



