Author
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WALSH, G. CABRERA - USDA/ARS/SABCL |
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Submitted to: The Coleopterists Bulletin
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/2/2002 Publication Date: 4/20/2003 Citation: Environ. Entomol. 32(2): 276-285 (2003) Interpretive Summary: The reproductive biology, and larval and adult host range of Diabrotica spp. (corn rootworms and cucumber beetles), and Acalymma spp. (cucumber beetles) 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 beetels 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. In this work we study the life history and host biology of Diabrotica speciosa, Diabrotica viridula and Acalymma spp. , and other Diabroticina. These Diabroticina are pests of several crops in South and Central America. The 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 the three 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. 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 chances of South American parasites adapting to North American pest Diabrotica are discussed. Technical Abstract: The reproductive biology, and larval and adult host range of Diabrotica speciosa (Germar), Diabrotica viridula (F.), Acalymma spp. (Coleoptera: Chrysomelidae: Galerucinae), and other Diabroticina are described. These Diabroticina are pests of several crops in South and Central America. The adult feeding hosts were compared, among species, and within species in different seasons. Laboratory oviposition and larval development tests on several hosts, provided the basis to construct a table of putative hosts, and general reproductive traits related to two species groups of Diabrotica (virgifera and fucata). Eggs of D. speciosa and D. viridula, were exposed to low temperatures to detect the ability to be dormant. Multivoltinism and lack of egg diapause was demonstrated for the three species, and field data suggest other South American species present the same traits. Diabrotica speciosa (fucata group) larvae developed well on maize (Zea mays L.), peanuts (Arachis hypogaea L.), and soybeans (Glycine max (L.) Merrill) roots, and not so well on pumpkin (Cucurbita maxima Duchesne and Cucurbita andreana Naudin), beans (Phaseolus spp.), and potato (Solanum tuberosum L.) roots. Oviposition preferences roughly paralleled larval suitability, but there was a clear preference for cucurbits as adult food, when available; pigweed (Amaranthus quitensis Kunth), sunflower (Helianthus annuus L.), and alfalfa (Medicago sativa L.) were in second place. Diabrotica viridula (virgifera group), 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 the preferred oviposition host. Whereas cucurbits were consistently visited by the adults of every species, the virgifera group species oviposited and developed exclusively on Monocotyledonae. However, D. speciosa, as expected for a fucata group species, oviposited and developed on a wide range of hosts. This new knowledge on South American Diabroticina is discussed in the context of the current knowledge on North American Diabroticina. Differences and similarities are discussed in connection with their pestiferous status, and their potential for adaptation to new hosts. |
