R Agricultural and Forest Entomology (1999) 1, 209±217 Suppression of Colorado potato beetle infestation by pheromone- mediated augmentation of the predatory spined soldier bug, Podisus maculiventris (Say) (Heteroptera: Pentatomidae) J. R. Aldrich1 and W. W. Cantelo2 1USDA-ARS Insect Chemical Ecology Laboratory, Bldg. 007, Rm. 326, BARC-West, Beltsville, Maryland 20705, U.S.A. and 2USDA-ARS Vegetable Laboratory, Beltsville, Maryland 20705, U.S.A . Abstract 1 Hardware and protocols were tested to enable individual growers and insectary operators to mass-produce predatory spined soldier bugs (SSBs), Podisus maculi- ventris (Say) (Heteroptera: Pentatomidae: Asopinae), for augmentative biological control.Using pheromone-based technology, an average of 1775 female SSBs (potentially as many as 1.6 million offspring) were captured each year during 2± 3 weeks in early spring. 2 Data for the ®rst 2 years of a 3-year project to use SSB for biological suppression of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), veri®ed earlier research showing that augmentation of SSB (~5 nymphs/plant) can signi®cantly suppress CPB infestations.In the third year, wild SSBs were transferred directly from pheromone traps to mid-plot nursery cages having a mesh size chosen to retain the adult predators but allow their offspring to escape.Pheromone dispensers were placed peripherally to pro- mote dispersal of young predators and immigration of new wild spined soldier bug adults.Pheromone-mediated augmentation using porous nursery cages and pheromone dispensers was less labour-intensive than earlier methods, and resulted in signi®cantly improved potato yield. 3 Trapping SSB adults early in the spring protects them from parasitization by ta- chinid ¯ies and scelionid wasps that use the pheromone to facilitate host-®nding. The compatibility of pheromone-mediated predator augmentation/conservation with implementation of transgenic plants, imidacloprid insecticide, and other bio- control methods is discussed. Keywords Biological control, conservation, natural enemy, Harmonia, Lebia, ladybird beetles, kairomone, tachinid, scelionid. spectrum insecticide, and genetically engineered potato produ- Introduction cing Bacillus thuringiensis (Bt) proteins selectively toxic to The Colorado potato beetle (CPB), Leptinotarsa decemlineata beetles.However, cross-resistance to imidacloprid has already (Say) (Coleoptera: Chrysomelidae), quickly became the most been detected in some insects (Wen & Scott, 1997) and the destructive pest of potato in eastern North America after its host- ability of the CPB to evolve resistance to transgenic Bt-potato shift to cultivated potato some 150 years ago (Casagrande, has been demonstrated in the laboratory (Whalon & Wierenga, 1987).Since then, control of the beetle in eastern North America 1994). has relied almost totally on insecticides, but the beetle developed The likely evolution of resistant ®eld populations of the CPB resistance progressively faster to one insecticide after another (Olson et al., 1996) and the higher costs of new control measures, (Hare, 1990).Two new products have entered the marketplace to justi®es continued research to optimize deployment strategies of control CPB in potato: imidacloprid, a novel type of broad- new technologies, and to foster emerging non-insecticidal technologies.For transgenic potato, planting mixtures of Correspondence: Dr Jeffrey R.Aldrich.Tel: + 1 301 504 8531; susceptible and transformed potato should slow the appearance fax: + 1 301 504 6580; e-mail: [email protected] of resistant individuals (Gould, 1994), or Bt-transgenic potato ã 1999 Blackwell Science Ltd L 210 J. R. Aldrich and W. W. Cantelo could be planted peripherally prior to sowing a ®eld with forest at the Beltsville Agricultural Research Center-East untransformed potato to intercept colonizing CPB adults (BARC-E) at sites remote from potato plots.Each trap was (Whalon & Wierenga, 1994).Similarly, the best way to retard baited with ~350 mg of 20% pheromone in polyvinyl chloride evolution of resistance to imidacloprid by L. decemlineata, and (Aldrich et al., 1984) and rebaited every 2±4 days from mid- to reduce cost, may entail mixed-row or perimeter treatments to March to mid-May.In 1994 and 1995, 30 and 26 traps, intercept colonizing CPB adults.Nevertheless, `it is in the best respectively, were deployed at the same site; in 1996, 30 traps interest of potato growers to continue to use all available were deployed at a different BARC-E remote site.Traps were integrated pest management approaches, such as crop rotation, to ¯ushed with CO2 to remove spined soldier bugs, at which time minimize the use of imidacloprid' (Dively et al., 1998). the sex of the trapped adults was recorded. Biological control, of course, is an important component of In 1994 and 1995, wild SSB adults were brought to the integrated pest management that can positively or negatively laboratory, grouped in half-pint paper cartons (~15/carton) affect how rapidly insects come to tolerate transgenic crops provided with a water bottle, pupae of Tenebrio molitor L. (Gould et al., 1991; Arpaia et al., 1997). (Coleoptera: Tenebrionidae) (Rainbow Mealworms, Inc., We have been pursuing a novel approach to augment and Compton, CA, U.S.A.), a fresh green bean and a piece of conserve predators for biocontrol (Aldrich, 1998).Our goal has cheesecloth for oviposition.These cartons were kept in cool been to develop hardware and protocols to enable individual growth chambers (15°C; 65% relative humidity (RH); growers, insectary operators and gardeners to mass-produce LD 14 : 10 h photoperiod) to delay oviposition, and transferred nymphs of the predatory spined soldier bug (SSB), Podisus to a warm growth chamber (26°C, 65% RH, and LD 16 : 8 h) 2± maculiventris (Say) (Heteroptera: Pentatomidae: Asopinae), 3 weeks prior to augmentation to promote oviposition. from wild adults caught in pheromone-baited traps.We have Cheesecloth pieces were collected and replaced twice a week focused our efforts on the SSB because this predator is abundant and pieces with eggs were combined in a few large containers for throughout much of North America (McPherson, 1982), SSB emergence of nymphs.In 1996, spined soldier bugs were adults and nymphs prey on all stages of a wide variety of insects harvested and collected as before, but the wild adults were and SSB males produce a chemically simple, yet powerful transferred directly to nursery cages constructed in ®eld plots as aggregation pheromone that is commercially available (Aldrich described below. et al., 1984; Aldrich, 1995). In addition, SSB nymphs are attracted to the pheromone, suggesting that the synthetic 1994 and 1995 ®eld plots pheromone can be used to disperse nymphs from points of augmentation (Sant'Ana et al., 1997). Augmentation of SSBs Nine 500 m2 plots spaced > 25 m apart were planted with has shown promise for suppression of CPB infestations, as has potatoes on 24 April 1994, at BARC-E (Solanum tuberosum augmentation of the twospotted stink bug, Perillus bioculatus `Kennebec' variety; ~1040 plants/plot; 0.92 m row spacing; (F.) (Asopinae) (Boiteau, 1988; Biever & Chauvin, 1992; 46 cm between plants).The population of CPBs was very low at Hough-Goldstein & Whalen, 1993).However, the SSB is more this site because potato had not recently been grown in this fecund than P. bioculatus and can eat at least as many CPB eggs location; therefore, overwintered CPB adults were collected at and larvae as does the twospotted stink bug (Hough-Goldstein & other locations and released in the ®eld plots at the rate of one McPherson, 1996). beetle/plant in two releases (31 May and 10 June).Treatments (3 Here we describe results of a 3-year pilot test to mass-trap SSB replicates/treatment) consisted of: (1) plots augmented with adults in overwintering habitat for augmentation of their seven 2nd±4th-instar SSB nymphs per plant, (2) plots containing offspring in potato and to attract indigenous spined soldier bugs six evenly spaced SSB pheromone dispensers per plot (Soldier to infested potato ®elds.We sought to augment and conserve Bug Attractorsq, Sterling International, Inc., Liberty Lake, WA, SSB in potato ± with the least amount of labour possible ± at a U.S.A.) and (3) untreated check plots. SSB nymphs were placed larger scale than previously achieved and to employ techniques on potato plants by hand using camel-hair brushes in two compatible with the latest technologies to control the CPB. releases; 5 nymphs/plant (2±6 June) and 2 nymphs/plant (17 June).Pheromone dispensers were deployed on 2 June and replaced on 20 June. Materials and methods In 1995, ®eld plots were planted as is in 1994 but earlier (7 April) and the same treatments were applied to each plot as in the Spring harvest of Podisus maculiventris adults previous year with the following modi®cation.Pheromone- Live male and female SSBs were harvested annually in treatment plots included a walk-in cubicle screen cage (3.7 m per pheromone-baited traps as they emerged from overwintering. side) in which cold-hardy crucifers were transplanted from cold- Traps were made of transparent cylindrical containers frames on 17 April (18 plants/variety in two rows; 20 cm (20.2 3 19.7 cm; Tri-State Molded Plastics, Inc., Dixon, between plants, 30 cm between rows): Elisa cabbage, hybrid Kentucky, U.S.A.) by cutting two holes (9 cm diameter) in broccoli, snow crown cauli¯ower, leafy Chinese cabbage, opposite sides and covering each hole with