225 



the larval tunnels. The moths emerge at the beginning d June, 

 and eggs are deposited generally on the lower surface of the foHage 

 of the host-pilant, in masses of from 5 to 50, the average number 

 being 350 for each female. When maize is attacked, the larvae feed 

 first upon the epidermis of the leaf-blades and then enter the stalk 

 jand tunnel through all parts of the plant except the fibrous roots. 

 This weakens the plant and retards development of the ear, while 

 in many cases proper fertilisation is prevented. The kernels and 

 cob are also frequently tunnelled, and as many as 15 larvae have 

 been found feeding in a single ear of maize. Badly infested fields 

 have averaged as many as 1,050,000 larvae per acre. The caterpillars 

 of this generation pupate within the host-plant about mid-July and 

 the resulting moths oviposit on late maize or other wild or cultivated 

 plants. The larvae of the second generation are particularly injurious 

 to the ears of maize, and they feed until hibernation occurs in November 

 or December. 



The chief danger of the dissemination of P. nubilaUs is through 

 the transportation of maize and its products. Dry stalks of maize, 

 for example, are frequently used as packing material, and as the 

 hibernating larvae remain dormant in the stalks from December to 

 May, and can survive almost any extremes of cold, heat or drought, 

 they may be in quite a healthy condition after being carried for 

 considerable distances. In order to obviate these dangers, a quaran- 

 tine order was issued, and became effective on 1st October 1918, 

 prohibiting inter-State movements of maize fodder or stalks, whether 

 for packing or otherwise, green sweet maize, roasting ears and 

 maize cobs from the towns within the area infested by the 

 European corn borer. As, however, there are many other food 

 materials that serve as hosts for P. nuhilalis, this quarantine 

 will not entirely restrict the spread of the insect, as the other plants 

 and vegetables on wliich it feeds may equally be included in consign- 

 ments to points outside the infested area. 



It is obvious that any measures aiming at the control of the pest 

 and its limitation to its present area must consist of the destruction 

 ■of the infested plants within that area, supplemented by quarantine 

 measures against the transportation of infested material. It is hoped 

 by these means that the pest may be prevented from reaching the great 

 maize belt that constitutes the most valuable crop of the country. 



In discussing the details of remedial measures, it is stated that 

 when a good fire is started over an area where the plants are dry, 

 all parts of the plants can be destroyed, but when the maize or weeds 

 are more or less green, sufficiently thorough burning to destroy the 

 larvae is very difficult to effect. Pulling up the plants and burning 

 them in a mass has been tried with much the same results. A 

 kerosene torch was useful in this connection if the plants were fairly 

 dry. Another method was to soak the mass of vegetation and the 

 •ground surface with kerosene combined with a cheap lubricating oil 

 known as black oil, and this ensured the thorough burning of the 

 vegetation. 



In the course of the discussion following this paper, the urgency 

 •of a prompt campaign against P. nubilalis was emphasised ; the 

 gipsy moth [Porthetria disjxir] and the boll weevil [Anthonomus 

 grandis] were quoted as instances where control measures had been 



