1900 ] ENTOMOLOGICAL SOCIETY. 103 



APHELINUS FUSOIPENNIS AN IMPORTANT PARASITE UPON THE SAN 

 JOSE SCALE IN EASTERN UNITED STATES. 



By W. G. Johnson, Collkgb Park, Md. 



For the past eight years the writer has been paying particular atttention to the 

 parasites attacking scale insects. Daring this period many spccles have been bred, but 

 not many specimens from any particular scale. The instance cited below is, perhaps, 

 the most important from the economic standpoint yet discovered in these observations. 



Since we assumed charge of the State work in Maryland we have collected the 

 San Jose scale on various food plants, and inclosed infested twigs, about 4 inches iu 

 length, in glass cylinder tubes open at both ends. The ends were closed with cojton, 

 and if any parasites existed upon the scales they were easily detected and mounted for 

 study. Only upon rare occasions have we taken more than a half dozen specimens from 

 a single tube. This experience has been repeated year after year until the fall of 1899. 



Of the four species of true parasites known to feed upon the San Jose scale, three 

 of them have been bred in Maryland. So far as I know Anaphes gracilis How., bred by 

 Dr. L. 0. Howard from scales from Charles County, Md., has not been reared from this 

 scale from any other State. Aspidiophagus citrimcs Craw, has been reared only in Cal- 

 ifornia from this p? st. Aphefinus mytilaspidis Le B. and Aphelinus fuscipennis How. 

 have been reared from scales taken at the following places in this State : Riverside, 

 Annapolis Junctioa, Araby, aud Mitchell ville. L'ist fall, how^ever, I discovered a new 

 locality for A. fuscipennis nf ar Easton, Talbot County, in an infected orchard along the 

 Miles River. The orchard contained a miscellaneou? variety of fruits, and all the trees 

 were quite seriously infested with the San Jose scale. Instructions had been given the 

 owner to cut them down as soon as possible and burn them. A quantity of small 

 branches incrusted with scale were brought to the laboratory and inclosed in breeding 

 tubes. Much to my surprise these tubes were swarming with parasites a few days later 

 From one tube 1,114 specimens of Aphdi^ius fuscipennis were taken j while a second 

 tube gave 432, a third 1,478, and a fourth more than 1,000, but owing to an accident 

 the count in the case lasL mentioned was not exact. The writer was greatly elated orer 

 the discovery, and immediately sent out the following statement to the State press : 



I am advising my correspondents not to burn twigs and branches cut from trees 

 infected with the San Jose scale. If the tree is so seriously infested it can not be saved, 

 it should be dug up by the roots, trimmed, and tha brush and wood piled in the orchard, 

 where they should be left until about the 1st of June or longer. If the trees are to be 

 sprayed with either a 25 per cent solution of kerosene and water, whale-oil soap (2 

 pounds in a gallon of water), or crude petroleum, the pruning should be done first and the 

 cut branches gathered up and piled where the spray cannot reach them. 



This is done to preserve the little friends nature has supplied to help keep the scale 

 in check, If the twigs and branches are burned or sprayed the parasites would be des- 

 troyed, as they feed upon the scale insects and are now wintering under the shell-like 

 cover protecting them. These parasites are very small, being scarcely visible to the naked 

 eye, yet they play an important part in the economy of nature. They are wasp-like in 

 general appearance and quite active. It would be v^ry difiicnlt to estimate the actual 

 number of parasites present upon a 5 or 6 year old peach or plum tree, but it is safe to 

 say that they would run into the millions if the parasitism was at same rate as upon the 

 twigs in the tubes. 



If I had burned these twigs I should have destroyed all the parasites. On the other 

 hand, if I had left them on the ground in the orchard the little friends would have 

 escaped and concentrated their attacks upon other trees where the scale had been missed 

 by the sprays. It is clear, then, that by using a little jadgsnent in these matters we can 

 assist nature in restoring the balance she desires. Do nob sit down and fold your arms 

 thinking nature is going to restore this equilibrium at once ; you must do your part 

 faithfully and well. Prune your orchard as soon as possible and save every twig that 

 contains a scale ; then spray with a 25 per cent, solution of kerosene and water, using any 

 first-class spray pump, or with whale-oil soap (2 pounds to a gallon of water), before the 

 buds open. 



