Appl. Entomol. Zool. 45 (3): 489–496 (2010) http://odokon.org/ Behavioral responses of Steirastoma breve (Sulzer) (Coleoptera: Cerambycidae) to host plant Theobroma cacao L., brushwood piles, under field conditions Carmen V. LIENDO-BARANDIARAN,1,* Beatriz HERRERA-MALAVER,1 Franklin MORILLO,2 Pedro SÁNCHEZ2 and José V. HERNÁNDEZ1,* 1 Universidad Simón Bolívar, Biología de Organismos, Laboratorio de Ecología Química del Comportamiento; Caracas, 1080A- Venezuela 2 Instituto Nacional de Investigaciones Agrícolas, Estación Experimental Miranda, Calle El Placer; Caucagua, Estado Miranda- Venezuela (Received 10 September 2009; Accepted 27 May 2010) Abstract Steirastoma breve is one of the most important pests in cocoa plantations in the Neotropics. Preliminary studies sug- gest that the chemical communication system in S. breve may be modulated by kairomones produced by cocoa plants and pheromones released by males. We examined the role of Theobroma cacao brushwood in the communication sys- tem of S. breve under field conditions. Sixty kilograms of T. cacao and Bauhinia sp. branches were cut, grouped into separate piles, and placed in an experimental cocoa plantation as an odor source. The sex and number of S. breve adults landing on each pile were registered during 23 days from 9:00 to 15:00 h. Each individual arriving at a pile was marked with a coded color and then released onto the same pile. All behavioral activities undertaken by S. breve were evaluated and flight behavior towards the T. cacao piles was described. S. breve adults were attracted to T. cacao piles placed under both sunny and shaded conditions, but were not attracted to Bauhinia sp. S. breve males dispersed more in shaded piles than in those placed in the sun, and the proportion of encounters between sexes was higher in the piles at which they had first arrived. Analysis of the data confirmed the presence and importance of T. cacao kairomones in the chemical communication system of this important cocoa pest. Key words: Steirastoma breve; Theobroma cacao; kairomones; Cerambycidae; communication system laboratory conditions and few field behavioral INTRODUCTION studies have been performed using vegetal odors as Hines and Heikkenen (1977) first provided evi- Cerambycidae attractants. Field tests with dence of the capacity of Cerambycidae to locate kairomone-baited traps were conducted only to de- their hosts in the field by means of semiochemical termine the efficiency of attractants for the capture signals. Several chemical compounds of vegetal of adults (Nakamuta et al., 1997; Reddy et al., origin have been reported that attract the following 2005) Cerambycidae species: Monochanus alternatus Steirastoma breve (Cerambycidae: Lamiinae), (Ikeda et al., 1980; Sakai and Yamasaki, 1990, commonly known in Venezuela as the “Cocoa bee- 1991), Phoracantha semipunctata (Barata et al., tle”, is one of the main pests of Theobroma cacao 2000), Anaglyptus subfasciatus, Demonax transilis L. (Malvaceae) plantations in South America and (Ikeda et al., 1993; Nakashima et al., 1994), Ho- some Caribbean islands (Entwistle, 1972; Sánchez plocerambyx spinicornus (Varshney et al., 2005), and Capriles de Reyes, 1979). The larvae and Tetropium fuscum, T. castaneum and T. cin- adults of this pest species cause severe damage to namopterum (Sweeney et al., 2004, 2006). How- the branches and stems of cocoa plants; adult fe- ever, most of these studies were performed under males rip the bark with their mandibles and lay * To whom correspondence should be addressed at: E-mail: [email protected]; [email protected] DOI: 10.1303/aez.2010.489 489 490 C. V. LIENDO-BARANDIARAN et al. their eggs inside. When the larvae emerge, they respectively. feed on the vascular system, opening irregular gal- Olfactory behavior of S. breve towards T. leries that may cause stem or branch ringing, which cacao and Bauhinia sp. brushwood piles leads to plant or branch death. Adults also scrape Bioassay A (without removing S. breve adults). the bark of branches and stems to feed, thus facili- Sixty kilograms T. cacao branches from healthy tating infestation by pathogenic micro-organisms. adult plants were cut and placed in piles to be used Additionally, damage to floral clusters can occur, as an odor source for the bioassay. Two treatments thereby causing important economic losses. Olfac- were employed: some piles were exposed to the tometric and electroantennographic studies under sun whereas others where left in the shade. Like- laboratory conditions showed that the odors re- wise, 60 kg Bauhinia sp. (Fabaceae) (a common leased from S. breve males and pieces of T. cacao species in this region, but not reported as a S. breve branches attract adults (males and females) of this host) was used as a control for each treatment. All pest species. These results suggest that the chemi- piles were distributed in the experimental plots cal communication system in S. breve may be mod- along straight line transects, perpendicular to the ulated by kairomones produced by cocoa plants predominant wind direction, and separated by 20 and pheromones released by males (Liendo et al., m. Four T. cacao and two Bauhinia sp. branch 2005). piles were randomly placed in each of the two A simple method for controlling most cocoa treatments (shade and sun) and observations began pests and pathogens is to manage shade by pruning the day after setting up the bioassay. For each pile, cocoa trees and trees which are normally used for both the number and sex of all S. breve beetles permanent shade (Erythrina glauca: Fabaceae) in found were registered from 9:00 to 15:00 h over a cocoa plantations (Mendes and García, 1984). period of 23 d. Observers were randomly changed Cocoa plants are usually pruned as good agro- each day. nomic practice for the proper maintenance of plan- The data obtained from the application of both tations, and the cut branches are left on the ground treatments (shade and sun) were analyzed using a to decompose. In this study, we examined the role balanced nested ANOVA. Sex, day and time were of T. cacao cut branches (brushwood) in the com- preselected as fixed factors. Comparison between munication system of S. breve under field condi- factors was performed using the Bonferroni t-test. tions. Also, we attempted to investigate the behav- Bioassay B (removing S. breve adults). In ior of S. breve towards host plant brushwood piles order to verify if the odor from T. cacao brush- over time, in order to determine the following: 1) wood piles by itself was attractive to S. breve when the piles become most attractive to S. breve adults, we carried out the following experiment. adults; 2) other kinds of behavioral responses to This bioassay was conducted in the same way as the host; and 3) patterns of dispersion of S. breve bioassay A, except for three changes: 1) all piles adults with respect to other nearby T. cacao brush- were placed in the shade, 2) all S. breve adults wood piles. found on T. cacao brushwood piles were immedi- ately removed from the pile, and 3) for each pile, the number and sex of S. breve beetles found were MATERIALS AND METHODS registered between 11:00 and 15:00 h, every two Study sites. Bioassays were carried out in sev- days from day six to day 17 after the start of the eral T. cacao plots at the Padrón experimental field bioassay. The mean numbers of S. breve males and station 10°13Ј36ЉN, 66°18Ј30ЉW, 41 MSL, owned females per observation day were calculated by by the Instituto Nacional de Investigaciones main effects ANOVA. Agrícolas (INIA), Miranda State, Venezuela. Field S. breve behavior on T. cacao piles. During bioassay A was carried out between October 4 and bioassay A, the observer also made hourly observa- October 27, 2004, and field bioassay B was carried tions of the behavioral activities performed by S. out between October 30 and November 20, 2006. breve individuals under sunny and shady condi- During the study, the average temperature was tions, including the flight behavior of each beetle 27.4°C; relative humidity, 95%; and the evapora- when approaching the odor source (T. cacao brush- tion and precipitation rates were 6.3 and 4.3 mm, wood). Behavioral Responses of S. breve to Host Plant 491 Capture, mark and release of S. breve adults on T. cacao piles. S. breve adults found on the piles during bioassay A were captured and marked using nail polish. A different color code was as- signed to each pile. Males were marked on the right elytra and females on the left elytra. These marks permitted us to register the presence of these same individuals on the same or different brush- wood piles, without further manipulation. When an adult first arrived at a pile, it was marked with the respective color for that pile and then carefully re- leased on the same pile. Registers were made of all marked individuals found on each pile. Data ob- tained on days when the greatest average number of individuals arrived at the piles were analyzed using the Kruskal-Wallis test. RESULTS Olfactory behavior of S. breve towards T. cacao and Bauhinia sp. brushwood piles Bioassay A (without removing S. breve adults) The average number of adult males found on shaded T. cacao piles (0.92Ϯ0.07; meanϮSE) was higher than that found on piles placed in the sun (0.65Ϯ0.05) (Fig. 1A; nϭ161; Fϭ9.006; pϭ 0.003; ANOVA test). Similarly, the average number of adult females was higher on shady piles (0.49Ϯ 0.05) than on sunny piles (0.30Ϯ0.03) (nϭ161; Fϭ8.391; pϭ0.004; ANOVA test). The total average number of S. breve males ob- served on T. cacao brushwood piles was higher Fig. 1. (A) Bioassay A (without removing Steirastoma breve adults): Average number of Steirastoma breve males and than that of females, both under sunny (Fig.