230 INSECTS AFFECTING VEGETATION 



food plant and climatic conditions ; that is, the development will be 

 more rapid in softer cane and during the warm summer months than 

 during the low temperatures of winter. 



When ready to pupate that is, to transform to the inactive 

 stage preparatory to emerging from the stalk as an adult beetle 

 the larva forms about itself a cocoon from the fiber of the stalk within 

 the tunnels it has made in feeding. The adult beetle on issuing 

 from this cocoon bores its way through the side of the stalk to the 

 exterior, and this opening in the lower joints of the cane is the first 

 distinct symptom of the presence of the borer. The length of the 

 pupal period is as variable as that of the larval, the average time for 

 transformation and emergence being from two to three weeks. 



The beetles are night flying and hide during the day down with- 

 in the sheaths of the lower leaves. The softer varieties of cane are 

 more subject to attack than the hardier varieties, and the borer is 

 more abundant in the wet districts than in the dry. Cane which has 

 received an abundant supply of water by irrigation suffers more from 

 the work of the borer than unirrigated cane. The borers occur in 

 the largest numbers in young cane and the suckers are infested to a 

 much greater degree than the stalks. The borers always occur in 

 the largest numbers in the vicinity of the track used to haul cane 

 to the factory, issuing from infested stalks that have dropped from 

 the cars and have not been collected and destroyed afterwards. 



The borer is a strong flyer and spreads from field to field in this 

 manner. It is distributed in infested seed cane and also develops 

 from the stalks left in the field after harvest or dropped from the 

 wagons or cars in hauling to the factory. 



As has been mentioned, the softer varieties are more subject to 

 attack than the hardier ones. The Yellow Caledonia, a variety which 

 is replacing to a great extent the common Lahaina and Rose Bamboo 

 in Hawaii, is injured to a much less extent than other varieties. The 

 infestation is not necessarily less in Yellow Caledonia, but the borer 

 meets with greater resistance in its feeding and consequent develop- 

 ment because of the firmness of the fiber. 



Excessive irrigation favors the development of the pest, since 

 cane in a succulent condition is more easily infested by the borer and 

 its development within the stalk is more rapid. It is plain that in 

 fields heavily infested by the borer the minimum amount of water 

 should be used in irrigation. 



The burning of trash after harvesting the cane is the most ef- 

 fectual method of keeping the borer in check. In this practice not 

 only should the fields be burned over, but all the unburned stalks 

 left in the fields and all stalks dropped from carts and cars along the 

 roads and tracks used in hauling the cane to the factory should be 

 collected and burned. One plantation found it necessary to collect 

 such stalks in piles and use crude oil on them in order to destroy 

 them completely, and by a careful estimate of the labor and cost of 

 material found that the money had been well invested, as was shown 

 by the reduction in the numbers of borers in the fields the following 

 season, 



