Biological Control of Insect Pests in Bermuda

Abstract

Projects undertaken on the biological control of insect pests in Bermuda since the first introduction of Bufo marinus in 1875 and including those still in progress are discussed. Work on 15 pests or groups of pests has been undertaken involving the introduction of over one hundred species of beneficial organisms.Icerya purchasi Mask. is considered to be under excellent control as a result of the introduction of the Coccinellid, Rodolia cardinalis (Muls.), and the fly, Cryptochetum iceryae (Will.). Pseudaulacaspis pentagona (Targ.), a serious pest of oleanders, was brought under control about 1922 by the introduction of Aphytis diaspidis (How.). However, in recent years heavy infestations have periodically developed. In addition to A. diaspidis, the Aphelinids, Aspidiotiphagus citrinus (Craw) and A. lounsburyi (Berl. & Paoli), the Coccinellids, Lindorus lophanthae (Blaisd.) and Chilocorus cacti (L.), and the Nitidulid, Cybocephalus sp., now attack it.Comstockiella sabalis (Comst.) at one time causing severe injury to the endemic palm, Sabal bermudiana, was brought under control by the introduction of Physcus sp. Bracon gelechiae Ashm. has been established on the potato tuber moth, Gnorimoschema operculella (Zell.), but satisfactory control has not resulted.Two cedar scales, Carulaspis minima (Targ.) and Lepidosaphes newsteadi (Sulc), have decimated the stands of Juniperus bermudiana despite an extensive programme of biological control. C. minima, which proved to be the more serious, is attacked by the Aphelinids, Prospaltella sp., Aspidiotiphagus lounsburyi, A. citrinus, probably introduced with the scale, and the Coccinellids, Lindorus lophanthae and Microweisia suturalis (Schwarz), which were liberated in large numbers. The predacious mite, Hemisarcoptes malus (Shimer), and the fungus, Myiophagus ucrainica, were established on Lepidosaphes newsteadi which for unknown causes became very scarce.Damage by Calpodes ethlius (Cram.), a pest of ornamental cannas, is less serious since the introduction of Ooencyrtus sp. and Trichogramma sp.Several parasites were liberated to control various species of mealybugs. Pseudococcus adonidum (L.), serious on a number of ornamentals, is under satisfactory control as the result of the establishment of the Encyrtids, Tetracnemus peregrinus Comp. and Anagyrus fusciventris (Gir.). Planococcus citri (Risso) is now attacked by the introduced Encyrtids, Leptomastidea abnormis (Gir.) and Pauridia peregrina Timb., as well as by Leptomastix dactylopii How., which was present at the start of the investigation. Acerophagus pallidus Timb. has been recovered from the mealybug, Phenacoccus gossypii Tns. & Ckll.The Encyrtid, Microterys kotinskyi (Full.), and the Coccinellids, Azya luteipes Muls. and Cryptolaemus montrouzieri Muls., have been effectively established on the soft scale, Pulvinaria psidii Mask. Tree lizards, Anolis spp., which feed readily on Azya and Cryptolaemus, are considered undesirable and accordingly the passerine bird, Pitangus sulphuratus, has recently been liberated in an attempt to reduce their numbers.Several species of parasites and predators were liberated against the soft scales, Saissetia oleae (Bern.), S. coffeae (Wlk.) and Coccus hesperidum L. Aphycus stanleyi (Comp.) is well established on Saissetia spp.Although the Braconid, Opius humilis Silv., was established on the Mediterranean fruit-fly, Ceratitis capitata (Wied.), for a number of years it has now disappeared.Parasites and predators introduced against Nipaecoccus nipae (Mask.), the onion thrips, Thrips tabaci Lind., and the red spider mite, Oligonychus ununguis (Jacobi), did not become established.Projects at present in progress to control tree lizards, Anolis spp., and snails cannot yet be evaluated.In the discussion a number of factors which may have contributed to the failure of establishment of some beneficial organisms are mentioned.