170 



THE AGRICULTUKAL NEWS. 



Juke -2, 1917 



INSECT NOTES. 



CONTROL MEASURES AGAINST THE 



MEDITERRANEAN FRUIT FLY IN 



HAWAII. 



The Mediterranean fruit fly (Ceratitis capilata, Wieil.) 

 has for many years been known as a pest in the Mediterranean 

 countries, in differem parts of Africa, in Australia, and in 

 Bermuda. It is only within recent years that it has become 

 established in the Hawaiian Islands, and in 191-^ it was 

 reported from Madagascar for llie first time. This insect 

 is best known as a pest of citrus fruits, but it also attacks 

 a number of other fruits of economic importance, in addition 

 to many species of uncultivated plants. 



Ceratitis capilata gained entrance into Hawaii from 

 Australia probably about 1907, and at the time of its dis- 

 covery in 1910, was found to be pretty well established. It 

 spread rapidly, and at the present time it i-; known to be 

 prevalent throughout the more important islands of the 

 Hawaiian groupi^. Its host plants in those islands now 

 number upwards of seventy, and it has practically stopped 

 the growing of all fruit except pine-apples and bananas, and 

 a few mangoes and avocado pears. The Chinese banana is 

 immune in the green stage, since neither the eggs nor the 

 larvae of this fly can survive the tannin-'aden peel of green 

 though mature fruit. Even lipe bananas are not especially 

 attractive as hosts under Hawaiian conditions. It is now 

 considered by Back and Pemberton that with proper inspection 

 and removal of any prematurely ripe, cracked or partially 

 decayed fruits, there can be no danger in exporting banana.s, 

 provided that the bunches are packed in accordance with the 

 demands of the trade and the Federal regulations. 



The ability of this fruit fly to exist in many wild fruits 

 as well as cultivated varieties makes it a particularly diflicult 

 pest to control, and its eradication becomes a practical 

 impossibility when once it has become established in 

 a country where its wild host plants abound. 



So far it has been kept out of such citrus- growing coun- 

 tries as California and Florida bv the most rigid inspection 

 which has fpequently intercepted fruits from Hawaii infested 

 ■with ihe maggots of this fruit fly. The conditions both in 

 California and Florida would seem to be far from ideal for 

 the establishment of Ceratitis capitata in tho.se countries, 

 since the unsuitabiiity of the climate, the I'omparative 

 scarcity of its wild host plants, and the well organized 

 inspection service; would all militate against its spread, even 

 supposing that it gained an entrance. 



In Hawaii the fruit fly had everything in its favour for 

 the first few years until it was detected, but its discovery 

 led to the adoption of a systematic campaign against it, and 

 it may be of interest to give some of the main features of 

 the Wiir which still continues without ceasing. 



CONTROL MEASURES. 



As soon as it was discovered that the Mediterranean 

 fruit By was present in Hawaii, the local Board of Agric„|. 



ture recommended clean cultural methods, which included 

 the collection and burial of all fallen fruit, but these measures 

 gave little relief. 



A number of experiments were made by H. H. P. 

 Severin and H. C. Severin to discover the relative attractive- 

 ness of various animal and petroleum oils, but it was found 

 that practically only male flies were taken by traps baited 

 with many ditt'erent oils. Further trials with kerosene, the 

 most attractive of these oils, showed that out of every 

 thousand fruit flies caught by kerosene traps only three were 

 females. Kerosene traps, therefore, were a failure as far as 

 the control of this pest is concerned, since it is essential 

 to destroy the egg-producing females. 



VlJISOSEl) BAIT SPRAY. 



The Mally poisoned bait spray, which has been used 

 with good efl'ect in South Africa, was tried extensively by 

 the Severins. This spray consists of a mixture of 2!, lb. of 

 sugar, .1-5 oz. of arsenate of lead and 4 gals, of water, which 

 is sprayed on to the trees. The female flies feed greedily on 

 this mixture, especially during the two weeks or so which 

 elapse between their emergence and the beginning of egg- 

 laying. This spray has met with some success, but can make 

 but little headway against the enormous numbers of fruit 

 flies which are constantly being bred in the wild guava and 

 other fruits prevalent all over the mountains. 



I'AKASITIC ENEMIES. 



Meanwhile it had been decided to try and introduce some 

 of the parasites which are so eff'ective against Ceratitis capitata 

 in .\fric.i and Australia, since a thorough search failed to reveal 

 any parasitic enemies of this pest in Hawaii. 



The .success of Silvestri in introducing the parasites of 

 the sugar-cane leaf-hopper into the Hawaiian Islands led 

 Mr. Giflard, the President of the Hawaiian Board of Agricul- 

 ture and Forestry, to ask him to search for the parasucs of 

 the fruit fly and introduce them into Hawaii. 



Silvestri left in .July 19 12, and after visiting tlio.se parts of 

 Africa where the fruit fly was prevalent, returned to Honolulu 

 by way of Au.stralia in May 191.3. He brought with him 

 from West Africa -lno specimens of Galesu.s silvestiii and -500 

 specimens of Dirhinus gifardi, both pupa-parasites, and a very 

 few specimens of the larval parasites Opius perproximus, 

 0. humilis, and Diarhasma tri/oni. These parasites were 

 bred continuously during the journey, and on arrival in 

 Honolulu were turned over to Fullaway and BridwelL 

 The two pupa-parasit6fe, although received and subse 

 quently liberated in large numbers, have appearently ■■ot 

 yet become established, while two of the larval parasites 

 0. hv mills and U. iryoni have spread rapidly from a very 

 small beginning. O. perpri ximns failed. 



A subse. |uent expedition to West Africa by I'ullaway 

 and liridwell resulted in the discovery and introduction into 

 Hawaii of two nmre larval-parasites, Tetrastichus jifirdi 

 and Diachisina fullairayi. 



There are now four para.sites of the larval stages of 

 Ceratitis capitata established in Hawaii, and thousands of 

 these parasites are being bred and liberated on the islands 

 every month. The necessity of breeding such enormous 

 '.lumbers of parasites has led to the adoption of simple 

 methods of rearing fruit; fly larvae, .so that all stages of the 

 larvae may be available for parasitism 



It has been found by Back and Pemberton, who nre 

 conducting experiments connected with the biology and 

 control of this fruit fly in Hawaii, that while all four species 

 of parasites attack only the medium and well-grown larvae, 

 three of them, 0. humilis, D.trvomtLnd D.falhiwayi, are tnost 

 active in parasitizing the mature larvae while the host fruits 



