Eur. J. Entomol. 106: 573–581, 2009 http://www.eje.cz/scripts/viewabstract.php?abstract=1490 ISSN 1210-5759 (print), 1802-8829 (online) Artificial diet for two flat-headed borers, Capnodis spp. (Coleoptera: Buprestidae) GALINA GINDIN1, TATIANA KUZNETSOVA1, ALEXEI PROTASOV1, SHAUL BEN YEHUDA2 and ZVI MENDEL1* 1Department of Entomology, ARO, The Volcani Center, Bet Dagan, Israel 2Ministry of Agriculture, Extension Service, Afula, Israel Key words. Coleoptera, Buprestidae, Capnodis spp., artificial diet, rearing, larval behaviour, stonefruits Abstract. The main objective was to develop an artificial diet for two flat-headed borers, Capnodis tenebrionis L. and C. carbonaria Klug. (Coleoptera: Buprestidae), which are severe pests of stonefruit plantations in the Mediterranean basin. The effect of proteins from various sources, percentage of cortex tissue in the diet and diet structure on larval growth and survival were investigated. The most successful diet contained 2.8% casein and 4.6% dry brewer’s yeast as the protein source. For complete larval development and successful pupation it is essential to include cortex tissue from the host plant in the diet. Mean larval development time was short- ened by 10–12 days when reared on a diet containing 20% cortex tissue compared with rearing on diet containing 10% cortex tissue. Two different diet structures were required, a viscous matrix for the first and second instar larvae and drier crumbly diet, which allows the larvae to move within the diet, for older larvae. At 28°C on the artificial diet C. tenebrionis and C. carbonaria completed their development in 2–2.5 months compared to the 6–11 months recorded in Israeli orchards. C. tenebrionis successfully completed two generations on the artificial diet. INTRODUCTION 1990; Sekkat et al., 1997; Ben-Yehuda et al., 2000; The flat-headed borers, Capnodis tenebrionis L. and C. Sanna-Passino & Delrio, 2001). Recently nematodes were carbonaria Klug. are severe pests of stone fruit (Prunus used to control C. tenebrionis (Marannino et al., 2003; spp., Rosaceae) plantations in the Mediterranean basin Martinez de Altube et al., 2008; Morton & García-del- and southern Europe (Garrido, 1984; Mahhou & Dennis, Pino, 2008) and the efficacy of entomopathogenic fungi 1992; Colasurdo et al., 1997; Mendel et al., 2003). The as biocontrol agents tested (Marannino et al., 2006, adult borers become active when temperatures exceed 2008). 28°C. One environmentally friendly way of replacing the Like many other species of Buprestidae, the young heavy dependence on insecticides for controlling Cap- adults feed on the cortex (live bark, including phloem, nodis spp. would be to breed a resistant rootstock (Salazar parenchyma, cambium and young xylem) of twigs and et al., 1991). Mendel et al. (2003) examined the relative young branches prior to mating and oviposition (Haak & resistance of the roots of nine major rootstock taxa of Slansky, 1987). The adults may live for more than 1 year stonefruits to colonization by larvae of these borers and (Rivnay, 1946) and one female may lay more than 1000 show that even the most resistant root stock is colonized. eggs (Rivnay, 1944). The eggs are placed in dry ground, Malagón & Garrido (1990) and Mulas (1994) suggest that imbedded in the soil, inserted in cracks or under stones, resistance to C. tenebrionis is directly related to the cya- usually near the base of stone fruit trees (Rivnay, 1944; nide content of the roots and hypothesize that prunasin is Garrido, 1984). The neonate larvae of these Capnodis probably involved in the resistance. Mendel et al. (2003) spp. penetrate and feed on the cortex of roots; they can present a different picture. These authors show that the locate a root from a distance of 60 cm (Rivnay, 1945). resistance is inversely proportional to the prunasin con- Depending on the ambient temperature and rootstock, tent, significantly correlated with the indices of suscepti- larval development takes 6–18 months in Israel (Rivnay, bility of the rootstocks to C. tenebrionis and C. carbon- 1945), whereas in cooler zones development may take 2 aria. years (Martin, 1951). The larvae excavate typical long Among the potential environmental benefits derived galleries, which are initially narrow but then widen, and from genetically modified trees is resistance to insect leave behind them compressed masticated frass (Rivnay, pests. It is suggested that enhancing resistance against 1945). Capnodis by using transgenic Prunus spp. offers great Naturally occurring arthropod enemies of these Cap- potential for developing rootstocks that are immune to nodis spp. are rare (Avidov & Harpaz, 1969; Marannino attack by neonates and even by advanced larval stages. & de Lillo, 2007a). These beetles are mainly controlled Such rootstocks might avoid the need for the frequent use by the application of synthetic insecticides (Garrido et al., of insecticides in stonefruit plantations. Therefore, the main objective of the present study was to develop an * Corresponding author; e-mail: [email protected] 573 artificial diet for C. tenebrionis and C. carbonaria, which immediately transferred to the test diets. Most of our tests were could be used to test the efficacy of toxins with a known done using C. tenebrionis. A diet suitable for rearing of C. car- genetic basis that might then be introduced into new bonaria was evaluated in the last part of the study after the stonefruit rootstocks. development of a suitable diet for the former species. Several semi-artificial diets developed for rearing cole- Scheme of diet development opteran pests contain the same array of ingredients, often The general approach was to modify existing diets for insects with the addition of dried and milled host plant material. with similar feeding habits (Cohen, 2004). Our first choice was This type of diet is reported for several pests: two weevils to rear the C. tenebrionis larvae on the diet proposed by (Coleoptera: Curculionidae), the West Indian sweet- Mourikis & Vasilaina-Alexopoulou (1975). None of the neo- potato weevil, Euscepes postfasciatus (Fairmaire) (Shi- nates survived for more than a week on that diet or several modifications of it. In light of the report that the larvae of the moji & Yanagishi, 2004) and the purple loosestrife root emerald ash borer (Gould et al., 2004) can survive for at least 4 weevil Hylobius transversovittatus Goeze (Blossey et al., weeks on a modified H. transversovittatus diet (Blossey et al., 2000); the Asian longhorned beetle, Anoplophora glab- 2000) we chose this diet as the starting model for our Capnodis ripennis (ALB) (Coleoptera: Cerambycidae) (Dubois et diet. In the first phase the survival of larvae on about 50 varia- al., 2002); the western corn rootworm, Diabrotica vir- tions of the diet was determined. These diets differed in the gifera LeConte (Coleoptera: Chrysomelidae) (Pleau et al., source of the protein and carbohydrates, the concentration of 2002); and two leaf beetles (Coleoptera: Chrysomelidae), antimicrobial compounds and presence of several specific com- Gastrophysa atrocyanea Motschulsky (Ojima et al., pounds such as choline chloride or cholesterol (data not pre- 2005) and the Colorado potato beetle, Leptinotarsa sented). Based on information accumulated in the first phase, decemlineata Say (Gelman et al., 2001). There is little the survival of C. tenebrionis on 10 representative diets were tested in the second phase. The composition of these 10 diets is information on artificial diets for rearing Buprestidae: presented in Table 1. All diets were prepared simultaneously. Gould et al. (2004) report some success in rearing the Each diet (about 50 g) was divided among 8 Petri dishes, (diam. larvae of the emerald ash borer, Agrilus planipennis Fair- 5.0 cm, with about 6 g diet per dish). Five neonates, 1–12 hours maire and Mourikis & Vasilaina-Alexopoulou (1975) old, were placed in each Petri dish (a total of 40 neonates per report an artificial diet that allowed some development of diet). The neonates were reared at 28°C for a week and their C. tenebrionis. However, the latter was tested in the pre- survival recorded. sent study and found to be useless for rearing Capnodis In the third phase diet no 10 (Table 1) was modified by incor- larvae (see below). porating cortex tissues from different sources and then tested: The present paper summarizes a series of trials that (1) plum (Prunus domestica) vs peach (Prunus persica), (2) cortex from peach roots vs stems, (3) fresh peach root cortex, vs formed part of an attempt to produce an artificial diet on dry, (4) dry peach root cortex added to the diet before vs after which C. tenebrionis and C. carbonaria could complete sterilization. The preparation details of these diets are presented their life cycle. The roles of different sources of proteins in section “Cortex preparation”. In a similar design of test to and host cortex were investigated. We also examined the that used previously, 40 neonates were reared on each of the effects of the concentration of cortex and matrix structure diets and their survival recorded after a week. of the diet on the growth and survival of these borers. In the fourth phase we tested the effect of incorporating dif- Rearing them in Petri dishes also allowed us to observe ferent percentages of cortex tissue (5, 10 and 20%) into the diet some previously unrecorded behavioural traits of Cap- on several developmental parameters of C. tenebrionis. In these nodis larvae. tests we used improved diet no 10, to which was added dry peach cortex (a blend of stem and root) prior to autoclaving the MATERIAL AND METHODS diet (Table 2). Diets were prepared in two formulations: as a dense paste-like substance or crumb-like substance, which was Capnodis Collection of adult and production of neonates prepared using a fine grater. Details of the diet preparation and Adults of C. tenebrionis were collected in apricot and plum the rearing of larvae are described below.