CARIBBEAN FOOD CROPS SOCIETY 42 Forty Second Annual Meeting 2006 Carolina, Puerto Rico Vol. XLII-Number 2 PROCEEDINGS OF THE 42th ANNUAL MEETING Caribbean Food Crops Society 42th Annual Meeting July 9-15, 2006 Intercontinental Hotel Carolina, Puerto Rico "Food Safety and Value Added Production and Marketing in Tropical Crops" Edited by Héctor L. Santiago and Wanda I. Lugo Published by the Caribbean Food Crops Society Use of a beneficial nematode against pest mole crickets in Puerto Rico Ν. E. Vicente1, J. H. Frank2, and N. C. Leppla2 ABSTRACT A beneficial nematode, Steinemema scapterisci (Rhabditida: Steinernematidae), has been researched at the University of Florida and is now marketed as a biopesticide. Its primary target is the mole cricket, Scapteriscus vicinus Scudder (Orthoptera: Gryllotalpidae), which has been a pest in Florida for about 100 years. The nematode survives so well in Florida's sandy, low-organic soils that it serves as a classical biological control agent to provide permanent suppression of pest mole cricket populations in places to which it has spread. In Puerto Rico and islands of the Lesser Antilles, where there is a much wider range of soils, the primary mole cricket pest is Scapteriscus didactylus (Latreille). Our research evaluates the use of the nematode to control Scapteriscus didactylus. Our earlier results in the field showed establishment and survival for up to seven months in a sandy loam with mole crickets, but no establishment in a highly organic sandy soil with mole crickets. A laboratory bioassay in sterilized sand showed 100% survival of controls, but up to 100% mortality of mole crickets within 168 h dependent upon number of nematodes applied (dose or 'rate'). Laboratory survival of nematodes was poorer in non-sterilized soils than in sterilized soils. Key words: Gryllotalpidae, Scapteriscus didactylus, Steinemema scapterisci, Biological control RESUMEN El nematodo beneficioso, Steinemema scapterisci (Rhabditida: Steinernematidae), ha sido evaluado en la Universidad de Florida, y es mercadeado en la actualidad como un bioplaguicida. Su foco principal es la changa ο grillotopo Scapteriscus vicinus Scudder (Orthoptera: Gryllotalpidae), la cual ha sido una plaga en la Florida por aproximadamente 100 anos. El nematodo sobrevive muy bien en los suelos arenosos y con bajo porcentaje de materia orgânica de la Florida, de forma tal, que sirve como un agente de control biolôgico clâsico para suprimir de manera permanente las poblaciones de la changa en los lugares en donde ésta se ha diseminado. En Puerto Rico y en las islas de las Antillas Menores, en donde la diversidad de suelos es mâs amplia, Scapteriscus didactylus (Latreille) es la especie mâs importante. Nuestra investigaciôn évalua el uso del nematodo para el control de Scapteriscus didactylus. Resultados previos a nivel de campo muestran el establecimiento y supervivencia del nematodo hasta por siete meses en un suelo franco arenoso infestado con changas, pero no se ha logrado lo mismo en un suelo arenoso altamente orgânico. Un bioensayo de laboratorio en arena esterilizada mostrô 100% de supervivencia de los contrôles, y 1 Crop Protection Department, University of Puerto Rico, Mayagüez, PR 00681-9030. 2 Entomology & Nematology Department, University of Florida, Gainesville, FL 32611-0630. 180 hasta 100% de mortalidad de las changas en un periodo de 168 h dependiendo del nûmero de nematodos aplicados (dosis). La supervivencia de los nematodos fue menor en suelos no esterilizados que en ios que fueron previamente esterilizados. INTRODUCTION The changa or West Indian mole cricket, Scapteriscus didactylus (Latreille) (Orthoptera: Gryllotalpidae), is the worst of a trio of invasive pest mole crickets of crop plants and turf in Puerto Rico, the Dominican Republic, and many of the Lesser Antilles, especially in irrigated, tilled, and sandy soils. It probably invaded Puerto Rico hundreds of years ago (JHF, unpublished). Introduction of biological control agents into Puerto Rico before 1940 may have partially solved the mole cricket pest problem (Cruz and Segarra, 1992), but not totally so. Those authors assumed that the specialist parasitoid wasp Larra bicolor (F.) (Hymenoptera: Sphecidae), introduced from South America in 1938 (Wolcott, 1938), caused a reduction in mole cricket populations. That may be so, but nobody seems to have evaluated absolute or even relative effects of L. bicolor. The tawny mole cricket, Scapteriscus vicinus (Scudder), is the worst of a trio of invasive pest mole crickets in Florida. It, too, was combated by introduction of L. bicolor from South America, but in 1988 (Frank et al., 1995). It also was combated by successful introduction of Ormia deplete (Wiedemann) (Diptera: Tachinidae) and Steinernema scapterisci Nguyen and Smart (Rhabditida: Steinernematidae) from South America in 1988 and 1985, respectively (Nguyen and Smart, 1990; Frank et al., 1996; Frank and Walker, 2006). Steinernema scapterisci was introduced into Florida as a classical biological control agent. However, it caught the attention of industry and is now marketed in the continental USA as a biopesticide under license from the University of Florida. Our objective was to evaluate how it might function in Puerto Rico as a classical biological control agent or as a biopesticide against Scapteriscus didactylus or the other two pest mole crickets that occur there. We have not attempted to introduce Ormia depleta into Puerto Rico. But in 2001-2004 we applied S. scapterisci at four field sites in western Puerto Rico. In November 2001 we applied S. scapterisci at (a) a sod farm near San German and (b) Punta Borinquen golf course (PB) in Aguadilla. Areas treated were in each case 0.2 ha. Applications were made in low evening light during light rain at the level of 2.47 billion infective-stage nemas per ha. Equipment was a hand-held sprayer nozzle attached to a truck-mounted pump and 95 L tank containing the nemas suspended in water. In May 2002, and again in August 2004, nemas were applied by sprinkling can, preceded and followed by copious irrigation, from a garden hose, to six (of thirteen) small plots of organically-grown vegetables in an organic sandy soil at Instituto Ann Wigmore in Aguada (AW). In February 2002, nemas were applied on two fairways of a golf course in south-central Puerto Rico in light rain in the early evening following irrigation and using a 568 L spray tank belonging to the golf course. In the final trial in August 2004 at PB, nemas were applied to five 0.2-ha plots (with five untreated plots) in an attempt to evaluate treatment effects; the manager/lessee insisted that all plots be in unirrigated areas (roughs); the golf course's spray equipment was used, but the manager/lessee would not allow application in the evening and insisted it be made 181 beginning at dawn to match his crew's normal work schedule. Although the employee who made the applications first applied 568 L of water from the tank (irrigation), and then applied the nematodes, the poor results in most plots suggest that inadequate irrigation and excessive exposure to ultraviolet radiation plus the hard-dried unirrigated soil caused rapid death of virtually all of the applied nematodes. Pitfall traps, modified from Lawrence (1982), were installed in all plots at all sites the day before application to collect mole crickets. Traps were emptied twice per week and all mole crickets were carried to the laboratory and held until death. All mole crickets that produced nematodes (or nematodes therefrom) were shipped in 5% formalin to Florida for nematode identification by Κ. B. Nguyen. Some of the applications were wasted effort. The sod farm near San German produced mole crickets parasitized by S. scapterisci for a few weeks until the entire area was flooded by a rising creek, after which no more nematode-parasitized mole crickets were obtained. The superintendent of the south-central golf course, who had been asked to check the pitfall traps twice weekly and send us mole crickets thus trapped, claimed that no mole crickets were ever trapped; we thought that was strange because we collected mole crickets on a pre-application visit to the site. The August 2004 application at PB was wasted effort when the manager/lessee insisted that we remove the pitfall traps after six months because they interfered with play - until then we had been collecting nematode-parasitized mole crickets. The most interesting applications were those of November 2001 at PB and in May 2002 and August 2004 at AW, but for disparate reasons. The soil at PB was a sandy loam of pH 6.87, which dried hard in the absence of rain or irrigation. The soil at AW was sand of pH 8.06 with a high organic content formed by addition of compost, and was kept moist by rain or irrigation. All mole crickets trapped at PB were S. didactylus; from November 2001 through June 2002 (7 mo) considerable numbers were trapped and a considerable proportion was parasitized by S. scapterisci. Then, the part-time student employee performing the field work left, another was hired in replacement, and the number of mole crickets recorded fell rapidly, with none recorded as parasitized. We may at least conclude that S. scapterisci became established for seven months after application in 2001. Mole crickets trapped at AW were a mixture of S. didactylus and S. abbreviatus (Scudder); none was ever recorded as parasitized despite the two applications of nematodes in seemingly ideal conditions. Because of this disparity and because we had read about nematode-suppressive soils (e.g., Kopppenhöfer et al., 1996; Gao and Becker, 2002) we resolved to test survival of S. scapterisci in soils of those two localities, as well as the dose of nematodes required to kill S. didactylus. MATERIALS AND METHODS Steinemema scapterisci bioassay against mole crickets. A bioassay was set up in plastic cups (120 ml, 7 cm depth) with perforated lids (to allow air circulation) to assess the effects of a range of closes of these beneficial nematodes on mortality of field-collected adult S.