Pesticide Biochemistry and Physiology 65, 44–54 (1999) Article ID pest.1999.2426, available online at http://www.idealibrary.com on The Toxicity and Physiological Effects of Bacillus thuringiensis Toxins and Formulations on Thaumetopoea pityocampa, the Pine Processionary Caterpillar Carolina Rausell, Amparo Consuelo Martı ´nez-Ramı ´rez, Inmaculada Garcı ´a-Robles, and Marı ´a Dolores Real 1 Departamento de Gene ´tica, Facultad de Ciencias Biolo ´gicas, Doctor Moliner 50, 46100 Burjassot, Valencia, Spain Received January 19, 1999; accepted May 25, 1999 Toxicity of Bacillus thuringiensis Cry1B, Cry1C, and Cry1E toxins and B. thuringiensis-based bioinsectic- ides (Cordalene, Dipel, Foray 48B, and Foray 76B) was investigated in Thaumetopoea pityocampa (proces- sionary moth) larvae. Cry1B was toxic, while Cry1C and Cry1E were nontoxic. The toxicity of the bioinsecticides analyzed was of the same magnitude as that of the active purified toxins and determined mainly by one of the toxins present in the bioformulate. We also demonstrated that only the active toxins were able to produce cytotoxic effects on the midgut epithelial cells and specifically bound to T. pityocampa brush border membrane. Analysis of the receptor model of the active toxins showed that Cry1B did not compete for the Cry1A binding site. This finding provides useful information for optimizing the use of B. thuringiensis toxins against T. pityocampa. 1999 Academic Press INTRODUCTION B. thuringiensis is an infectious bacterium that produces insecticidal proteins that are proteolyti- cally activated by insect gut proteases and spe- Thaumetopoea pityocampa, the pine proces- cifically bind to receptors in the insect midgut. sionary caterpillar, is the most important Once the toxins are bound, pores are formed endemic pine pest in the Mediterranean area, that alter membrane permeability and eventually not only because of its high defoliating power, cause lysis of the epithelial cells, killing the but also due to the human health problems insect (6). Each B. thuringiensis strain exhibits caused by the urticating hairs of the larvae (1). different insecticidal activity spectra due primar- Although there is an increasing demand for envi- ily to the diversity of toxins that it can produce. ronmentally friendly alternative methods, efforts Several well-characterized B. thuringiensis iso- to control this lepidopteran insect involve mainly lates have been industrially formulated and are the use of chemical insecticides, particularly currently applied against Lepidoptera (the most insect growth inhibitors (2). destructive group of plant pests), Diptera (vec- Insect viruses (cytoplasmic polyhedrosis tors of human disease), and Coleoptera (7). virus, nuclear polyhedrosis virus, and granulosis Despite the important environmental damage virus), fungi (Beauveria bassiana), pheromones, and economic losses caused by T. pityocampa, parasites, and especially bacteria (mainly prepa- rations based on Bacillus thuringiensis Berliner basic laboratory research on this pest is unfortu- var. kurstaki) have been investigated for the bio- nately limited. Most of the research on proces- logical control of T. pityocampa (3). In some sionary moth has been done in the field and, cases, these insect pathogens have been evalu- regarding B. thuringiensis, it has focused mainly ated as biological control agents but only B. on determining the optimal timing of applica- thuringiensis is already in operational use (3–5). tion. This is a critical aspect in the control of T. pityocampa, because the duration of egg hatching is very long and only those larvae in 1 To whom correspondence should be addressed. Fax: 34 96 398 30 29. E-mail: realmd@uv.es. early instars die with the current doses used. 44 0048-3575/99 $30.00 Copyright  1999 by Academic Press All rights of reproduction in any form reserved.