University of Minnesota, Duluth
AgEcon Search - Research in Agricultural & Applied EconomicsNot a member yet
211830 research outputs found
Sort by
A guide to the spider mites of cotton
No full textSpider mites are increasingly serious pests of cotton and forage crops. Because the acaricides now being developed are often highly selective among species, entomologists concerned with the control of these pests need to know the particular species they are dealing with. This report has been prepared to aid them. Both field guides and taxonomic keys are given. Suggestions are offered on how to sample, how to prepare slides, and what diagnostic characters to look for
The biology of the grape bud mite Eriophyes vitis (PGST.)
No full textField observation and laboratory studies, conducted on Carignane grape buds at Davis, have shown the grape bud mite to be capable of inflicting severe injury that may result in loss of crop and death of the infested vines. Typical symptoms of bud-mite injury are: deformation of the primordial clusters, distortion of the basal leaves, stunting of the main growing point of the buds, and death of the overwintered buds. Evaluation of mite damage in the field is often complicated by abnormal growth caused by diseases and other grape pests
Two new species and additional collection records for the genus Protodiaspis (Homoptera: Coccoidea: Diaspididae)
No full textStudies of two parasites of olive scale, Parlatoria oleae (Colvée): IV. Biological control of Parlatoria oleae (Colvée) through the compensatory action of two introduced parasites
No full textThe competitive population interactions between Aphytis maculicornis and Coccophagoides utilis were analyzed in order to determine their roles in controlling olive scale, Parlatoria oleae, in California olive groves. There is strong evidence that the two parasites working together give better control of olive scale than does A. maculicornis working alone. Conclusions are based on observations of parasite populations at selected groves over a period of five years
A note on competition
No full textThe experiments described in this paper are part of a continuing series on predator-prey interactions. The six-spotted mite, Eotetranychus sexmaculatus (Riley), was used for the study, which involved various ecosystems containing combinations of oranges and rubber balls, over which the mites moved in search of food. Effects of food dispersion on equilibrium level of a population, changes in its numbers, and its utilization of a limited resource were studied. Two main points are emphasized: First, food may be a limiting and regulating factor for a given population even if utilization of supply at equilibrium is low. Second, in some particular kinds of ecosystems, where competition for food is the regulating factor, superimposition of other mortality factors may alter the density level at which the competition is regulative, and thus result in levels of food utilization varying from low to high. Roles and importance of density-dependent and density-independent factors in the natural control of populations are also discussed
Photochemical oxidant injury and bark beetle (Coleoptera: Scolytidae) infestation of Ponderosa pine: I. Incidence of bark beetle infestation in injured trees
No full textCertain aspects of insect-disease relationships, especially those concerning transmission of pathogens, have been studied extensively and their significance has been well established. However, the role of diseases as factors predisposing coniferous trees to bark beetle infestation has received only minor attention. There has been little effort to determine the extent of the association between disease and bark beetle infestation, the significance of predisposing diseases in the ecology of the beetles, or the effects of disease upon the host that may increase susceptibility to beetle attack
A systematic study of the genus Acerophagus E. Smith with descriptions of new species (Hymenoptera: Encyrtidae)
No full textThis paper presents a revision of the genus Acerophagus E. Smith (Hymenoptera: Encyrtidae). Some morphological characters which may aid in distinguishing between species are discussed, and keys are given for both sexes. Several species are redescribed and illustrated, and the distinguishing characters of all species are presented
Seventh taxonomic study of North American mealybugs (Homoptera: Coccoidea: Pseudococcidae)
No full textIn this paper we redescribe 16 previously poorly known species of pseudococcids. Their taxonomic status, generic assignments, and relationships to other mealybugs are given. The species treated are: Cataenococcus formicarii (Ehrhorn); C. guatemalensis (Ferris); C. phoradendri (Cockerell); Cryptoripersia arizonensis (Ehrhorn); G. trichura (Cockerell); Dysmicoccus aurantius (Cockerell); D. lasii (Cockerell); D. morrisoni (Hollinger); D. roseotinctus (Cockerell and Cockerell); Puto lasiorum (Cockerell); P. sandini (Washburn); Spilococcus juniperi (Ehrhorn); Tridiscus sporoboli (Cockerell); Trionymus caricis McConnell; T. magnus (Cockerell and Cockerell); and T. violascens Cockerell