RESUMO
The genus Diabrotica has over 400 described species, the majority of them neotropical. However, only three species of neotropical Diabrotica are considered agricultural pests: D. speciosa, D. balteata, and D. viridula. D. speciosa and D. balteata are polyphagous both as adults and during the larval stage. D. viridula are stenophagous during the larval stage, feeding essentially on maize roots, and polyphagous as adults. The larvae of the three species are pests on maize, but D. speciosa larvae also feed on potatoes and peanuts, while D. balteata larvae feed on beans and peanuts. None of these species express a winter/dry season egg diapause, displaying instead several continuous, latitude-mediated generations per year. This hinders the use of crop rotation as a management tool, although early planting can help in the temperate regions of the distribution of D. speciosa. The parasitoids of adults, Celatoria bosqi and Centistes gasseni, do not exert much control on Diabrotica populations, or show potential for inundative biocontrol plans. Management options are limited to insecticide applications and Bt genetically modified (GM) maize. Other techniques that show promise are products using Beauveria bassiana and Heterorhabditis bacteriophora, semiochemical attractants for monitoring purposes or as toxic baits, and plant resistance.
RESUMO
The South American water primroses, Ludwigia grandiflora (Michx.) Greuter & Burdet, L. grandiflora subsp. hexapetala (Hook. & Arn.) G.L. Nesom & Kartesz, Ludwigia peploides (Kunth) P.H. Raven, and L. p. subsp. montevidensis (Spreng.) P.H. Raven (Onagraceae, Section Oligospermum), have become invasive in several watersheds of the United States and Europe. Surveys were carried out in center-east of Argentina to find insect species that might serve as biological control agents for L. g. subsp. hexapetala in California and elsewhere. Stems (0.5-0.6 m) of Ludwigia species, Sect. Oligospermum, were collected in 41 sites and analyzed in the laboratory; immature insects were reared to adults. The plant species found in the area were L. grandiflora (2 sites), L. g. subsp. hexapetala (33 sites), and L. p. subsp. montevidensis (4 sites). There was a variety of insect guilds feeding on L. g. subsp. hexapetala, including six species with stem-borer larvae, one species with fruit-feeding larvae, four species with defoliating larvae, two species with defoliating larvae on young leaves and axil meristems, one species of cell content feeder, and three species of sap feeders. Nine of these species also have defoliating adults. Biological information on most of them is provided. Of these insect herbivores, only two species were also found on L. grandiflora, and one on L. peploides. Several of the species found on L. g. hexapetala, such as the cell-content feeder Liothrips ludwigi (Thysanoptera), the stem-borers Merocnemus binotatus (Boheman) and Tyloderma spp. (Coleoptera), are promising candidates for biocontrol agents.