Capnodis tenebrionis L. and Capnodis carbonaria Klug
Taxonomic placing:
Common name: Flatheaded woodborers, Capnodis.
Geographical distribution: C. tenebrionis occurs widely in North Africa, in southern and central Europe, the Near East and around the Black and the Caspian Seas. The distribution of C. carbonaria overlaps much of the natural distribution of almond, ranging from Dalmatia to Asia Minor, the Near East, the Caucasus foothills and the area between the Black and the Caspian Seas, and southern Europe.
Host plants: Adults of both Capnodis spp. feed on the cortex and buds of twigs and young branches. Stone fruits (Prunus spp.) serve for reproduction. Adults feed also on other Rosaceae, and on subtropical fruit trees such as avocado and mango.
Morphology: Adults are flattened, compact, with a shiny black color. At low temperatures the thorax is black, whereas above 24ºC it is grayish with 6 black patches. In C. carbonaria, a typical black turnip-like shape occurs in the center of the thorax, close to the head. In C. tenebrionis six patches also occur but are fragmented. The antennae are 11-segmented and serrated]. Capnodis carbonaria is about 15-37 m long, whereas the length of C. tenebrionis 12-30 mm. The larvae are elongated, that of C. carbonaria is 100-13o mm in length, that of C. tenebrionis 90-120 mm.
Life cycle: The adults feed on the cortex of twigs and young branche, and mating takes place at these sites. Oviposition occurs above 26ºC and only in dry soil, a female laying >1000 eggs during her life, which lasts 3-4 months for C. tenebrionis, 4-6 months for C. carbonaria and sometimes even longer. Weak trees are preferred for feeding and oviposition. Eggs are usually laid in small clusters, either in the ground in light soils, or in cracks in heavy soils or under stones. The females usually lay their eggs close to the base of the tree stem, avoiding soils with more them 10% humidity or soils dusted with insecticidal powders. In such cases they will choose to deposit their eggs in dry soil free of insecticide, even at a distance of 120 cm or more from the tree base. The neonate larvae penetrate the roots and feed in the cortex, being able to locate the root at distances of 60 cm from the hatching site. Larval development lasts for 6-18 months. They eat their way through the stem forming long galleries, which are initially small but become larger as the larva grows, and leave behind them compressed frass. The favored pupation site is at the base of the stem. Pupal development lasts about 3-4 weeks.
Seasonal history: Mature and old adults of C. tenebrionis are seen in early May, with peak occurrence and highest percentage of young adults in July. The share of young adults decreases during the summer. Between early December and late March, adults are usually not seen in orchards. Adults of C. carbonaria occur in the groves all year round, and adults of different ages occur in about the same proportion, with young adults achieving prominence between June and August. Adult C. carbonaria remain in orchards wherea adults of C. tenebrionis tend to overwinter on or near evergreen tree groves.
Economic importance: Both C. tenebrioni and C. carbonaria are among the few buprestids that attack and kill apparently healthy trees. Both are severe pests throughout areas characterized by warm and dry summers of most cultivated stone-fruits: almond, apricot, cherry (Prunus vulgaris Linnaeus), nectarine and peach and plum. Tree mortality due to C. tenebrionis is known mainly from southern European and Mediterranean areas. Economic losses due to C. carbonaria have so far been reported only from Israel and Egypt. A single larva may suffice to kill a young tree, whereas a few may cause the death of an adult tree. Both species are seldom found on wild host plants outside stone-fruit orchards.
Management:
Horticultural methods: The method of watering the ground during the warm season to prevent egg laying had been abandoned because of water shortage and weeds. Placing polyethylene sheets at a distance of about 1m on both sides of trees prevented larvae from reaching the trees.
Plant resistance : Capnodis spp. populations are currently in part controlled by the use of resistant rootstocks. Good management enhances resistance, whereas under water stress all rootstocks are susceptible to Capnodis to some degree.
Chemical control: Good results can be obtained by foliar sprays of organophosphates, or dusting with carbamates. They are applied to the stem in late spring or prior to fruit harvest. Soil applications of imidacloprid protects young plantations and nurseries. Any applications of insecticides should be based on the monitoring of the adult beetles throughout the warm season.
Biological control: Naturally occurring arthropod enemies of Capnodis spp. are rare; ants may collect eggs and neonates, and jays and crows prey on adults. Entomopathogenic nematode, introduced into the soil with irrigation good pest control of the pest larvae.
References
Ben-Yehuda, S., Assael, F. and Mendel, Z. 2000. Improved chemical control of Capnodis tenebrionis L. and C. carbonaria Klug (Coleoptera: Buprestidae) in stone-fruit plantations in Israel. Phytoparasitica 28: 27-41.
Mendel, Z., Assael, F. and Ben-Yehuda, S. 2003. Host selection and root colonization of cyanogenic stonefruit species by Capnodis spp. (Coleoptera: Buprestidae). Annals of the Entomological Society of America 96:127-134.
Mulas, M. 1994. Almond genetic resources and resistance to Capnodis tenebrionis. Acta Horticulturae 373: 41-48.
Reuveny, H., Farkash, Z., Azulai, L. and Mendel, Z. 2013. Prevention of root colonization by Capnodis larvae using polyethylene sheets as ground cover. Alon Ha’notea 67 (10): 28-32 (in Hebrew with an English abstract).
Reuveny, H. (and 10 co-authors) 2015. Control of Capnodis tenebrionis (Coleoptera: Buprestidae) by entomopathogenic nematodes. Alon Ha’notea 70 (10): 28-33 (in Hebrew with an English abstract).
Rivnay, E., 1944. Physiological and ecological studies on the species of Capnodis in Palestine (Col., Buprestidae): I. Studies on the eggs. Bulletin of Entomological Research 35: 235-242.
Rivnay, E., 1945. Physiological and ecological studies on the species of Capnodis in Palestine (Col., Buprestidae): II. Studies on the larvae. Bulletin of Entomological Research 36: 103-119.
Rivnay, E., 1946. Ecological and physiological studies on Capnodis spp. (Col., Buprestidae) in Palestine: III. Studies on the adult. Bulletin of Entomological Research 37: 273-280.
Salazar, D.M., Miro, M. and Garcia, S. 1991. Rootstocks for dry region apricot tree faced with Capnodis tenebrionis L. Acta Horticulturae, 293: 401-404.
Zvi Mendel, Agricultural Research Organization, The Volcani Center, Department of Entomology, P.O. Box 6, Bet-Dagan, 50250 Israel. Tel: 972-3-9683636, Fax: 972-3-9683849.
E-mail: zmendel@netvision.net.il
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