CARIBBEAN FOOD CROPS SOCIETY 37 Thirty Seventh Annual Meeting 2001
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^fOOD CROps CARIBBEAN FOOD CROPS SOCIETY 37 Thirty Seventh Annual Meeting 2001 Trinidad and Tobago Vol. xxxvn Proceedings of the Caribbean Food Crops Society. 37:104-109. 2001 PRELIMINARY INVESTIGATIONS INTO THE TAXONOMY OF THE GALL MIDGES (DIPTERA: CECIDOMYIIDAE) AFFECTING CAPSICUM SP IN JAMAICA Juliet Goldsmith, Ministry of Agriculture, Bodies Research Station, Old Harbour, St. Catherine, Jamaica ABSTRACT: Persistent interception of a Dipteran larva in shipments of hot pepper (Capsicum chinense) from Jamaica to the United States of America (USA) in recent years, has led to the imposition of mandatory fumigation of the commodity prior to export. The insect has been identified both as Contarinia lycopersici, a tomato pest of quarantine importance to the USA and Prodiplosis longifilia a citrus pest restricted in that country to Florida. The present study compares the pepper midges in Jamaica with C. lycopersici and P. longifilia based on morphological characteristics and host infestation. Preliminary results derived from comparative morphological examination of adult males, suggest that the pepper gall midges of Jamaica are distinguishable from C. lycopersici and P. longifilia. There is an urgent need to identify and or describe the species present in order to develop a management strategy for the pest. INTRODUCTION In February 1997, USD A-APHIS reported the interception of a Dipteran larva in shipments of hot pepper from Jamaica to the United States of America (USA). The insect was declared of Quarantine importance, as the USA has a zero tolerance for dipterans. Persistent interception of the pest led to a mandate, effective October 1998, that all hot peppers for export from Jamaica to the USA be fumigated with Methyl Bromide. The insect has been variously identified as Contarinia spp, Contarinia lycopersici and Prodiplosis longifilia. It was unclear to the Jamaican authorities whether one or both species were present. Thus the gall midge problem in Jamaica became known as the gall midge complex (Prodiplosis longifdia and Contarinia lycopersici). The Contarinia and Prodiplosis genera both belong to the tribe Cecidomyiini, a diverse group made up entirely of plant feeders (Gagne 1989). They are reportedly close relatives, being separable only by the males. The male terminalia of Prodiplosis is distinguishable from Contarinia by the long aedeagus relative to the length of the hypoproct and gonopods and the dorsoventral rather than mesoiateral articulation of the gonopods (Gagne 1986). Approximately 300 species have been assigned to the Contarinia genus, while there are 10 described Prodiplosis species. Member species of both genera attack flowers and buds of a wide range of hosts (Gagne 1994,1986). Contarinia lycopersici (Felt) has been reported from the West Indies (but not from Jamaica) from as early as 1932, where it was found to attack tomatoes. No alternate host was found. The larvae infested and caused injury to tomato flowers, which may wither and absciss or the ovary is damaged, resulting in malformation of fruits (Callan 1941). Prodiplosis longifilia (Gagne) is reported feeding on limes in Florida and from Columbia and Peru where it attacks tomatoes, potatoes, alfalfa and other crops (Pena and Mead 1988). The larvae completely destroy the ovaries of the flowers causing premature flower abscission. In Jamaica, gall midge larvae are found feeding within the pedicel of mature hot pepper fruits as well as in the flower buds of hot and bell peppers. A recent survey of infested farms across the island revealed that 66% of farms had larvae in both fruit pedicel and flower buds, 28% had only the fruit pedicel infested and 6% had larvae only in the flower buds (Goldsmith 2000,). Larval feeding within the fruit pedicel results in a brown to black scar that is often secondarily invaded by fungi (e.g. Altemaria sp.). The result is rotting of the fruit, which may fall from the plant or is otherwise unmarketable. Infested flower buds whither and may fall from the tree. 81 The present study compares the pepper midges in Jamaica with C. lycopersici and P. longifilia based on morphological characteristics and host infestation. MATERIALS AND METHODS Adult and larval mounts were prepared of gall midges found infesting hot pepper pedicel separate from those found within pepper flower buds. To obtain adults, larvae were placed in petri dishes or glass jars containing loose, damp soil. Emerged adults were collected from the top and sides of the container 10 to 12 days after incubation. Some larvae and reared adults were killed and placed in 70% ethyl alcohol. Specimens were mounted for microscopic study in Canada balsam, using the method outlined by Gagne (1989, 1994). All specimens were examined using a phase-contrast, compound microscope. Drawings were made of morphological characters including male genitalia, male and female antennae, ovipositor, legs and wings. The lengths of the female first and second antennae flagellomeres of 20 pepper 'bud' midges and 20 pepper 'stem' midges were measured. The ratio of the length of the first to the length of the second was calculated for both groups. Data were analyzed using the analysis of variance. Attempts were made to identify the genera and the species using taxonomic keys developed by Raymond Gagne (Gagne 1994). Tomato and citrus flowers from plants inter-cropped with or planted close to infested pepper fields were examined for gall midge infestation. Two pepper plots, each planted at Bodies Research Station and next to pepper plots infested with pepper 'bud' midge, were monitored for gall midge infestation. Each week, four flower buds were removed from each of ten plants and dissected using a dissecting microscope. A third plot, planted in Spring Village, St. Catherine (5 1cm east of previous site), where tomatoes were inter-cropped with "stem" midge infested hot peppers, was similarly monitored over a two- month period (March to May 2000). Two separate hot pepper plots planted at Bodies Research Station, March-August 2000 and October 2000 -June 2001, and infested with pepper 'bud' midge, were monitored for pepper 'stem' midge infestation. Three mature fruits were removed weekly from each of ten plants and dissected using a dissecting microscope. Tomato and citrus buds from plants isolated from infested fields were also examined. RESULTS AND DISCUSSION Gagne's taxonomic keys classify the Jamaican gall midges as: Subfamily: C'ecidomyiinae, Super tribe: Cecidomyiidi, Tribe: Cecidomyiini, Genus: Prodiplosis and Contarinia. The larval specimens examined were similar morphologically. They possessed a clove shaped spatula, one pair enlarged and asetose terminal papillae and three pairs of terminal papillae with short setae (Figure 1). The structure of the terminal papillae is characteristic of the Cecidomyiini tribe and is similar for both the Contarinia and Prodiplosis genera. According to Gagne (1995) larvae of the two genera are indistinguishable. All adult specimens examined during the study exhibited the following combinations of generic characters: palpus four segmented, antennae 2+12 segmented, male flagellomeres all bimodal and bifilar; female flagellomeres elongate with relatively short necks; tarsal claws simple, curved beyond mid-length, empodium as long as claws; ovipositor long and finely tapered; male terminalia with short simple tapered aedeagus, bilobed hypoproct; short, simple gonocoxite and tapered gonostylus. The species of gall midge found infesting pepper flower buds differ morphologically from those found in the pepper pedicel with regards to the relative size of the female first and second antennal flagellomere. Results revealed significant differences in the length of the first antennal flagellomere of the pepper 'stem' midge when compared with those of the pepper "bud" midge. The first flagellomere of the 82 'pedicel' midge averaged 17.0im in length and was 1.5 times that of the second, which averaged 11.lim. The mean length of the female first flagellomere of the 'bud' midge was 12.Olm in length, 1.3 times as long as the second which measured 9.2im in length (Figure 2). Differences in the lengths of the female first and second flagellomeres have been used by Gagne to distinguish between two similar Contarinia species: Contarinia lycopersici and Contarinia maculipennis. He reported that in C. maculipennis the female first flagellomere was 1.8 to 1.9 times that of the second while in C. lycopersici the difference was 1.4. The pepper 'bud' midge does not appear to infest the pepper pedicel. No midge was found affecting pepper stems at Bodies Research Station after five and eight months of monitoring plots infested with the 'bud' midge. The Jamaican gall midges differ from Prodiplosis longifilia with regards to the male terminalia, the male antennae and host preferences. The terminalia of male P. longifilia has a long aedeagus relative to the hypoproct while in the Jamaican midges the aedeagus is approximately the same length as the hypoproct (Figure 3). The long aedeagus is a character of the Prodiplosis genus and is used to separate it from Contarinia (Gagne 1986, 1989). In this regard the Jamaican gall midge is more like Contarinia. The flagellomeres of the male Jamaican gall midges are bifilar while those of P. longifilia are trifilar (Figure 4). Males in most of the Cecidomyiini genera, including the Contarinia genus, have two circumfila (bifilar) instead of three (trifilar) (Gagne 1989,1994). The male flagellomeres of Prodiplosis species, however, are variable and may have two or three circumfila (Gagne 1994). Examination of citrus flower buds removed from orange trees intercropped with infested pepper plants revealed no gall midge infestation. Morphologically, the Jamaican gall midges are quite similar to C. lycopersici. Preliminary investigations have revealed only one difference: the articulation of the male gonopods. All known species of Contarinia, including C. lycopersici, have mesolateral articulation of the gonopods (Gagnel986). The Jamaican gall midges, however, have dorsoventral articulation of the gonopods (Harris, Personal communications 2001). Importantly, the Jamaican midges have not been found to infest tomato flowers.