® Fruit, Vegetable and Cereal Science and Biotechnology ©2009 Global Science Books An Introduction to Microbial Control of Insect Pests of Potato Lawrence A. Lacey1* • Jürgen Kroschel2 • Stephen P. Wraight3 • Mark S. Goettel4 1 USDA-ARS-Yakima Agricultural Research Laboratory, Wapato, WA 98951 USA 2 Centro Internacional de la Papa, Lima, Peru 3 USDA-ARS Robert W. Holley Center for Agriculture and Health, Ithaca, NY 14853 USA 4 Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, T1J4B1 Canada Corresponding author : * [email protected] ABSTRACT A wide variety of insects are pests of potato plants and tubers. Several insect-specific pathogens have demonstrated efficacy for control of some of the more economically important insect pests of potato. Bacillus thuringiensis (Bt) and a granulovirus (PoGV) are effective in controlling potato tuber moth, Phthorimaea operculella, a serious pest of potato foliage and stored tubers in the tropics and subtropics. Naturally occurring PoGV has been reported in several countries where potato is grown. Colorado potato beetle (CPB), Leptinotarsa decemlineata, is a serious pest of potato in many countries worldwide. Bt var. tenebrionis effectively controls CPB when applied against first and second instar larvae. The fungus, Beauveria bassiana, has also been reported to control CPB under certain environmental conditions. Andean potato weevils, Premnotrypes spp., are pests of potatoes grown at high altitude in the Andes. An entomopathogenic nematode, Heterorhabditis sp., appears to be a potential candidate for microbial control of the weevil. A variety of other candidate entomopathogens are proposed for control of several additional insect pests including leaf miner fly, wireworms, lepidopterans, aphids, potato psyllid, leafhoppers, and other insects. The further development and use of microbial control agents will ultimately provide components for the integrated and sustainable control of insect pests of potato and in other agroecosystems. Although factors limiting the adoption and use of microbials include high cost and low efficacy, compared to most chemicals presently used, these costs could be offset by the premium price paid for safer food and a greener approach. _____________________________________________________________________________________________________________ Keywords: Andean potato weevil, Bacillus thuringiensis, Baculovirus, Beauveria bassiana, Colorado potato beetle, entomopathogenic fungus, entomopathogenic nematodes, Hemiptera, Heterorhabditis, leafminer fly, Lepidoptera, Leptinotarsa decemlineata, Liriomyza huidobrensis, Phthorimaea operculella, potato tuber moth, wireworms Abbreviations: APTM, Andean potato tuber moth; APW, Andean potato weevil; Bt, Bacillus thuringiensis; Btt, Bacillus thuringiensis var. tenebrionis; CPB, Colorado potato beetle; CIP, Centro Internacional de la Papa; GPTM, Guatemalan potato tuber moth; IPM, integrated pest management; LMF, leafminer fly; PTM, potato tuber moth CONTENTS THE POTATO AND ITS INSECT PESTS................................................................................................................................................... 20 POTATO TUBER MOTH COMPLEX ........................................................................................................................................................ 21 ANDEAN POTATO WEEVIL..................................................................................................................................................................... 21 LEAFMINER FLY....................................................................................................................................................................................... 21 COLORADO POTATO BEETLE ................................................................................................................................................................ 21 HEMIPTERAN PESTS................................................................................................................................................................................ 22 WIREWORMS ............................................................................................................................................................................................ 22 OTHER INSECT PESTS OF POTATO ....................................................................................................................................................... 22 CONCLUSIONS.......................................................................................................................................................................................... 23 ACKNOWLEDGEMENTS ......................................................................................................................................................................... 23 REFERENCES............................................................................................................................................................................................. 23 _____________________________________________________________________________________________________________ THE POTATO AND ITS INSECT PESTS numbers of economically important pest species occurring in potato agroecosystems of the neotropics in countries of The domestication of the potato, Solanum sp., started over potato origin (Kroschel et al. 2009). It is estimated that 8,000 years ago around Lake Titicaca in modern-day Peru mean potato losses due to insect pests are about 16% world- and Bolivia (CIP 2008). Today a multitude of potato vari- wide (Oerke et al. 1994). However, if not routinely con- eties are grown throughout the world. Despite alleloche- trolled, tuber yield and quality reductions are between 30- mical defenses, S. tuberosum L. is attacked by a multitude 70% for various insect pests (Raman and Radcliffe 1992). of invertebrate pests including insects, mites, slugs, and Predominant means of control are through the use of broad nematodes (Zehnder et al. 1994; Berry 1998; CIP 2008). spectrum chemical insecticides. According to the World Insects feed on every part of the plant (leaves, stems, and Health Organization 2002 classification, highly hazardous tubers) and several of these pests also serve as vectors of class 1a and 1b pesticides are still widely distributed and plant pathogens (Radcliffe and Ragsdale 2002; Munyaneza used by small-scale potato farmers in developing countries et al. 2006; Hansen et al. 2008). Insect pests and their rela- (Arica et al. 2006). Over-reliance on broad spectrum insec- tive importance vary from region to region with highest ticides in agroecosystems has often resulted in the develop- Received: 6 June, 2008. Accepted: 17 September, 2008. Invited Mini-Review Fruit, Vegetable and Cereal Science and Biotechnology 3 (Special Issue 1), 20-24 ©2009 Global Science Books ment of resistance in targeted pest populations, safety risks ANDEAN POTATO WEEVIL to farm workers and the food supply; outbreaks of secon- dary pests normally controlled by natural enemies; environ- The Andean potato weevil (APW), Premnotrypes spp., is mental contamination; and a decrease in biodiversity (Lacey another serious pest of potato in South America and is the et al. 2001). An integrated pest management (IPM) strategy, most damaging insect pest at altitudes between 2,800 and in which natural enemies of pest arthropods and other alter- 4,200 m in the Andean region of Bolivia, Peru, Ecuador, native measures play significant roles in crop protection, Colombia, and Venezuela (Alcázar and Cisneros 1998). should minimize these negative effects and provide a more Currently, 15-40% of high altitude tubers are commonly in- sustainable approach for the control of insect pests of potato fested with weevil larvae at harvest time despite the use of (Cisneros and Gregory 1994; Thurston 1994; Kroschel insecticides. Adult weevils add to the damage by feeding on 1995; Kroschel and Sporleder 2006). Due to their selec- potato foliage. The fungus, Beauveria bassiana (Balsamo) tivity and safety, microbial control agents (MCAs) appear Vuillmen, had been proposed as a potential microbial con- to be ready made components of IPM systems that do not trol agent for APW management in potato stores of Peru, pose a threat to applicators or the environment and allow Colombia, and Bolivia (Ewell et al. 1994; Raman 1994). other natural enemies to function (Lacey et al. 2001; Kaya However, it has not been widely made available and not and Lacey 2007). In this review, separate presentations on readily used by farmers. Since potato tubers become infes- the major potato insect pests and the potential for their ted by the APW during tuber development, they are there- microbial control are highlighted. fore already infested when stored after harvest. Here, the application of the fungus to tubers during storage was able POTATO TUBER MOTH COMPLEX to reduce the weevil population but not tuber damage which was unacceptable for farmers. The potato tuber moth complex consists of three species Entomopathogenic nematodes (EPNs) have demons- namely the common potato tuber moth Phthorimaea opercu- trated good activity against other weevil species with soil lella (Zeller) (PTM), the Andean potato tuber moth (APTM) dwelling larvae (Booth et al. 2007). In 2003, an EPN was Symmetrischema tangolias (Geyen), and the Guatemalan isolated from infected APW larvae and pupae of Premno- potato tuber