110 PROTECTION OF PLANTS — 1923-24 



about on the bark in broad daylight may likely run considerable risk of attrac- 

 ting the attention of })irds or other enemies near at hand. 



METHODS OF CONTROL 

 Artificial. 



Carbon bisulphide was tried as a control measure with satisfactory results. 

 It was sprayed into the tunnels with an atomizer and the entrance holes stopped 

 with damp clay. The plugs were removed with a knife after three or four days, 

 and where no fresh borings appeared it was concluded that the fumes had 

 killed the larvae. Over 95% of the cases thus treated responded satisfactorily. 



While carbon bisulphide can be recommended for treatment of single 

 trees, and for use in small parks or along city boulevards, it, necessarily, would 

 be impracticable for control work in extensive forest groves and large areas. 

 Recently, Craighead (1), at Washington, D. C, has found that a lead arsenical. 



Some control experiments of this nature were conducted on P. jnacmurtrei, 

 and several materials of different strengths were tried out with various degrees 

 of success. Groups of trees, with their checks, were treated during the summer 

 with solutions of sodium arsenate and lead arsenate, with and without an oil 

 carrier. Carbolic acid, crude petroleum and pyrodene were also employed as 

 ingredients, but were found unsatisfactory for one reason or another. Sodium 

 arsenate proved severe on the foliage, even in small quantities, and was given 

 up for that reason. Lead arsenate in proportion of 3 lbs to 50 galls water without 

 a carrier appeared to have no effect upon the larvae. Even 4 lbs of lead arse- 

 nate with a carrier of 1 gal. kerosene emulsion gave only a partial control of 

 46%; whereas the same spray increased to 5 lbs. resulted in a further 35% of 

 the grubs remaining inactive, making a total of 81% for the last two experi- 

 ments. Where kerosene emulsion is not obtainable the use of any miscible oil 

 instead will be found ass atisfactory. 



Since trees situated in sheltered positions or with a southern exposure 

 appear to be special objects of attack, a careful watch should be kept on such, 

 and where evidences of the borer are noticed, steps taken to eradicate immedia- 

 tely. Very badly infested trees should be cut out and destroyed. This may be 

 done best in the fall or early spring. Such drastic measures, however, are not 

 advisable except as a last resource. 



A sharp knife can often be used to good advantage for removing very young 

 larvae from the outer bark. The cut is apt to leave an ugly scar on the trunk 

 if not carefully done; in any case where incisions are made of this kind the 

 wounds should be stopped with grafting wax or painted to prevent infection. 



Natural. 



Birds.' — It is very likely that birds play a most important part in natural 

 control of P. macmurtrei. Woodpeckers of different species are seen frequently 

 throughout the summer flying from tree to tree in search of food. It is safe to 

 say that these birds dispose of a large number of young larvae, particularly 

 those of the first year's growth, and since the borers then are not far from the 



(1) Protection from Locust Borer, Prof Paper Vi S , Dept Agric Bull 787 spray of the usual strengh of 8 lbs to 

 100 gallons of water has proved beneficia in the control of certain wood-boring species of Cylhne, Goes, etc The mate- 

 rial which is applied with a power-pump, soaks into the bark tissues and incidently about the tunnel entrances When 

 a larva visits the month of the burrow to remove debris, or enlarge the opening for further operations it will eat sufli- 

 cient of the poisoned bark at the time to kill it The method is a simple and direct one 



