Ravindra C. Joshi

DNA Barcoding Applied to Invasive Leafminers (Diptera: Agromyzidae) in the Philippines

Abstract DNA barcoding involves the sequencing of a single gene region from all species to provide a means for identifying all of life. Although appealing to many scientists, this idea has caused considerable controversy among systematists. We applied a DNA barcoding approach to outbreak populations of invasive Liriomyza spp. leafminer pests in the Philippines to explore the use of barcoding in a relatively well studied, economically important group. We sequenced a 527-bp portion of mitochondrial cytochrome oxidase I (COI) from 258 leafminers from 26 plant host species in the Philippines. Neighbor-joining and parsimony analysis were used to compare COI sequences from the Philippines to an extensive database of COI sequences previously obtained from samples of the invasive leafminers Liriomyza huidobrensis (Blanchard), Liriomyza trifolii (Burgess), and Liriomyza sativae Blanchard from locations around the world. We conclude that although a DNA barcoding approach can provide rapid species identifications, in certain instances it is likely to either overestimate or underestimate the number of species present. Only when placed within the context of considerable other data can DNA barcoding be fully interpreted and used. For economically and medically important species, which can be well studied, DNA barcoding offers a powerful means for rapid identifications.

Molluscicidal activity of vulgarone B from Artemisia douglasiana (Besser) against the invasive, alien, mollusc pest, Pomacea canaliculata (Lamarck)

Abstract Golden apple snail (GAS), Pomacea canaliculata (Lamarck) is a pest in rice fields in Southeast Asia. Vulgarone B, a sesquiterpene from Artemisia douglasiana Besser, has been shown to have molluscicidal activity against rams horn snail (Planorbella trivolvis), and, in this study, it was tested against GAS. Laboratory bioassays indicated that vulgarone B had activity comparable to that of the commercial synthetic molluscicide metaldehyde, both with an LC50 at 24 h of about 30 μM. Sprayed vulgarone B is not toxic to rice seedlings at concentrations that caused 100% mortality of GAS. Vulgarone B, however, caused chlorosis when incorporated into agar on which rice seedlings were grown. At concentrations from 1 to 400 μM, there was no ovicidal activity on egg masses of various ages (1, 3, 5, 7, and 10 days). These data indicate that vulgarone B could be an effective molluscicide against GAS.

The rodent species of the Ifugao Rice Terraces, Philippines – target or non-target species for management?

Abstract We investigated the species diversity and habitat use of rodents in the Ifugao Rice Terraces (IRT), Luzon, Philippines, as a first step in their assessment either as pest species of rice or as potential non-target species of rodent control practice. Trapping was carried out in caneland and forest habitats adjacent to rice cropland using trap lines of 10 – 15 cage-traps. Four trapping rounds, each consisting of 5 nights trapping, were replicated at two sites during the months of May and June. A diverse rodent fauna was recorded, including the non-native pest species, Rattus tanezumi, and the native species, Rattus everetti and Chrotomys mindorensis. Results from trapping and spool-and-line tracking suggested that these native species do not contribute to rice damage and that several may actually be beneficial in the ricefield ecosystem as vermivores that feed on invertebrate pests. Control should therefore be directed at the pest species, R. tanezumi, minimising non-target effects on the non-pest rodent species.

The Invasive Liriomyza huidobrensis (Diptera: Agromyzidae): Understanding Its Pest Status and Management Globally

Liriomyza huidobrensis (Blanchard) is native to South America but has expanded its range and invaded many regions of the world, primarily on flowers and to a lesser extent on horticultural product shipments. As a result of initial invasion into an area, damage caused is usually significant but not necessarily sustained. Currently, it is an economic pest in selected native and invaded regions of the world. Adults cause damage by puncturing abaxial and adaxial leaf surfaces for feeding and egg laying sites. Larvae mine the leaf parenchyma tissues which can lead to leaves drying and wilting. We have recorded 365 host plant species from 49 families and more than 106 parasitoid species. In a subset of the Argentinian data, we found that parasitoid community composition attacking L. huidobrensis differs significantly in cultivated and uncultivated plants. No such effect was found at the world level, probably due to differences in collection methods in the different references. We review the existing knowledge as a means of setting the context for new and unpublished data. The main objective is to provide an update of widely dispersed and until now unpublished data, evaluate dispersion of the leafminer and management strategies in different regions of the world, and highlight the need to consider the possible effects of climate change on further regional invasions or expansions.