Author
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WALSH, GUILLERMO - USDA/ARS/SABCL |
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CABRERA, NORA - UNIV DE LA PLATA Y MUSEO |
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Submitted to: Biology of Chrysomelidae
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/8/2003 Publication Date: 1/20/2004 Citation: New Developments in the Biology of Chrysomelidae (2004) pp. 333-350 Interpretive Summary: The reproductive biology, and larval and adult host range, and geographical distribution of the subtropical/temperate species of Diabroticites is described. These are highly variable traits that have important implications for the control of the pest species of these genera. Within the genus Diabrotica, there are two groups (virgifera and fucata groups) that are known to show very different life histories in North America. The virgifera group overwinters as an egg, the larvae are limited to feeding on annuals of the grass family, they have two generations a year, and are severe pests of maize. The other group (fucata) overwinter as adults, have several generations a year, and both larvae and adults feed, and are pests on, any number of crop plants. A similar pattern is known for the cucumber beetles of the genus Acalymma. However, this pattern was not known for the South American pest species, studied at the SABCL as hosts of parasites and diseases that may help control North American pest species. Adult feeding hosts were compared, among species, and within species in different seasons. Oviposition and larval development laboratory tests provided data on the suitable hosts for each species. Eggs of the pest species were exposed to low temperatures and dry conditions to detect the ability to overwinter in this stage. Multivoltinism and lack of egg diapause was demonstrated for all the laboratory reared species, and field data suggest other South American species present the same traits. D. speciosa (fucata group) larvae developed well on many hosts, and its oviposition preferences roughly paralleled larval suitability, but there was a clear preference for cucurbits as adult food, when available. D. viridula (virgifera group), preferred maize as adult and larval food, and for oviposition. Acalymma spp., were associated in every respect to cucurbits. While cucurbits were consistently visited by the adults of every species, the virgifera group species oviposited and developed exclusively on plants of the grass order (Monocotyledonae). However, D. speciosa, as expected for a fucata group species, oviposited and developed on a wide range of hosts. Current knowledge on North American Diabroticina did not apply in full to the South American fauna, mainly in respect to overwintering and the number of generations a year. Also the traditional views on the host biology of Diabroticites is discussed in the light of new evidence. Technical Abstract: The reproductive biology, and larval and adult host range of several subtropical/temperate South American Diabroticites is described. The adult feeding hosts were compared, among and within species in different seasons. Laboratory oviposition and larval development tests one on several host plants, provided the basis to construct a table of putative hosts, and general reproductive traits of the different suprageneric groups. Multivoltinism and the lack of egg diapause was demonstrated for several species and field data suggest other South American species present the same traits. Oviposition preferences roughly paralleled larval suitability. There was a clear preference for cucurbitaceans as adult food, when available; pigweed (Amaranthus quitensis Kunth), sunflower (Helianthus annuus L.), and alfalfa (Medicago sativa L.) were also preferred, but to a lesser extent. The virgifera group of Diabrotica preferred maize as adult and larval food, and for oviposition. Acalymma spp., were associated in every respect to cucurbits. Other species showed varying degrees of preference for oviposition and feeding, but in general, cucurbits were the preferred adult feeding hosts, followed by several wild plants, and maize as the preferred oviposition host. While cucurbits were consistently visited by the adults of every species, the species in the virgifera group of Diabrotica oviposited and developed exclusively on Monocotyledonae. This new knowledge of South American Diabroticites is discussed in the context of the current knowledge of North American species. The geographical distribution of the subtropical/temperate South American Diabroticites is also discussed in relation to their hosts and their association with human landscape management. Finally, the role of cucurbits, and particularly cucurbitacins, as the main host plants of the Diabroticites is discussed. We pose the hypothesis that the chemical association with this plant family may be only loosely related to their basic host plants. |
