September, 1911.] 



241 



Plant Sanitation. 



uneatable. The maggots are of a creamy 

 white colour, tapering to a point in 

 front, and blunt at the hinder extremity, 

 When extracted from the fruit, they 

 are capable of leaping to a considerable 

 distance. 



' Cucumber Fly ' (Dacus cucurbifoe.) 

 Enlarged by 64 diameters. 

 Very little attention seems to be paid 

 to the ravages of these flies in Ceylon. 

 Though quantities of good fruit is 

 spoiled, year by year, no systematic 

 attempts have been undertaken to miti- 

 gate the pest. This apathy is due prin- 

 cipally to the fact that fruit growing is 

 not a commercial industry in the Island. 

 Private growers appear to accept the 

 damage as inevitable, or as part of the 

 • Curse of Adam.' The maggoty fruit is 

 allowed to rot on the ground, permitting 

 the full-fed grubs to emerge and pupate 

 in the soil, whence fresh swarms of the 

 destructive flies are produced. 



The systematic collection and des- 

 truction of the infested fruit is of the 

 greatest importance in combating the 

 pest. Wormy fruit usually falls pre- 

 maturely, and should be collected 

 regularly, day by day. With regard to 

 the disposal of the damaged fruit, Mr. 

 W. W. Frogatt — in a comprehensive 

 report on the fruit fly pest — says that 

 " it is preferable to destroy the fruit by 

 burning, but it may be disposed of by 

 burial, and when buried it should be 

 covered with at least 20 inches of soil." 

 Another method of disposal, which 

 may be convenient in some cases, is 

 to sink the fruit in water and leave 

 it there. This plan was adopted 

 in Bermuda, where the infested fruit 

 was enclosed in sacks, weighted 

 with stones and dumped in the sea. 

 Where fallen fruit has been permitted to 



31 



remain long enough for the maggots to 

 escape, the soil should be forked and 

 fowls allowed the run of the orchard. 



Infested cucumbers and marrows do 

 not fall off, but rot on the stem. The 

 presence of eggs or maggots may be 

 detected by a gummy excretion from the 

 punctures. All such wounded fruit 

 should be removed and destroyed at once. 



In a vegetable garden, cucumbers and 

 marrows may be preserved from attack 

 by enclosing them in muslin bags. It 

 should be remembered that the flies will 

 attack the fruit when still quite small, 

 so the bags should be applied immedi- 

 ately after the flower has withered, 

 taking care that they are of sufficient 

 size to permit of the full development of 

 the fruit. The bags should be tied round 

 the stalk of the fruit, but not so tightly 

 as to interfere with the circulation of 

 sap. This may be prevented by insert- 

 ing some cotton-wool in the mouth of 

 the bag. 



Besides the flies of the genus Dacus, 

 we have a species of Ceratitis which has 

 a different habit. For many years it 

 was observed that a large proportion of 

 the new shoots of the Giant Bamboos — 

 in the Peradeniya Gardens— failed to 

 develop, but rotted off when only from 

 two to three feet high; This has now 

 been proved to be the work of the fly 

 Ceratitis striata which breeds in enor- 

 mous numbers in the succulent shoots. 

 The only practical means of combating 

 this pest is to remove and destroy every 

 shoot as soon as it is found to be infested. 

 This is not difficult to determine; as such 

 shoots decay very rapidly and will break 

 off with a slight push. Where bamboos 

 are growing on river banks, the damaged 

 shoots could be merely thrown into the 

 water. They are heavier than water 

 and do not require any weighting to 

 sink them. 



Several methods have been employed 

 for the destruction of the adult flies. 

 Froggatt mentions that certain species 

 of fruit flies are strongly attracted by 

 the scent of citronella oil, and that 

 kerosene even has some attractions ; but 

 that the cucumber fly is unsusceptible 

 to this odour. By exposing shallow 

 trays of kerosene in the vicinity of fruit 

 trees large numbers of the insects have 

 been trapped. A mixture of kerosene 

 and citronella should be still more 

 effective. The flies fall into the mixture 

 and are drowned. 



It has also been obseived that all fruit 

 flies are fond of sweets and may be 

 killed by exposing poisoned baits. Mr. 

 C. W. Mally has perfected this treat- 

 ment in South Africa, and claims to 

 have completely protected orchards (at 



