The rosy apple aphid, Dysaphis plantaginea, (Homoptera: Aphididae) is a serious pest of apples in British Columbia (BC), Canada and especially in organic orchards where conventional controls cannot be used. The goals of this study were to determine the environmental or management factors of an orchard that lead to high aphid populations, to conduct an economic assessment of the damage, to determine the timing of autumn migration, and to test several autumn and spring chemical control methods and two novel autumn mechanical control methods targeting the aphids while on their alternate host, Plantago major. To explain the variation among orchards, I evaluated several potential correlates of aphid density: abundance of the alternate host (plantain, Plantago major), foliar tree nitrogen, tree age, tree planting density, and the application of an oil treatment in spring. Stepwise regression indicated that foliar nitrogen and tree age explain 27% of the variation. Orchards receiving a spring oil application had a 53% lower average aphid infestation level. Plantain abundance was not related to aphid population on apple. However, experimental manipulation of leaf angle from the ground and size showed that significantly more alate and apterous aphids occurred on large, low angle leaves. Mowing prior to spring aphid migration was associated with 75% fewer alatae and apterae on the plantain. The loss in harvest resulting from aphid damage ranged from 3% to 76% of the crop. Effective autumn control depends on accurate timing of aphid flight. The peak of female flight occurred on the 27th of September, 2007 at 11:56 hours daylength (sunrise to sunset) and the peak of male flight occurred on the12th of October, 2007 at 11:02 hours daylength. Aphid densities in the spring of 2008 were very low, making comparisons between treatments and controls difficult. Autumn applications of Superior dormant oil and kaolin clay were not effective. The PureSpray Green treatments of two October applications and one April application showed a significant reduction in rosy apple aphid infested clusters compared with the untreated control. Mowing and rotavating did not result in a significant reduction in aphid infestation level.

The rosy apple aphid, Dysaphis plantaginea, (Homoptera: Aphididae) is a serious pest of apples in British Columbia (BC), Canada and especially in organic orchards where conventional controls cannot be used. The goals of this study were to determine the environmental or management factors of an orchard that lead to high aphid populations, to conduct an economic assessment of the damage, to determine the timing of autumn migration, and to test several autumn and spring chemical control methods and two novel autumn mechanical control methods targeting the aphids while on their alternate host, Plantago major. To explain the variation among orchards, I evaluated several potential correlates of aphid density: abundance of the alternate host (plantain, Plantago major), foliar tree nitrogen, tree age, tree planting density, and the application of an oil treatment in spring. Stepwise regression indicated that foliar nitrogen and tree age explain 27% of the variation. Orchards receiving a spring oil application had a 53% lower average aphid infestation level. Plantain abundance was not related to aphid population on apple. However, experimental manipulation of leaf angle from the ground and size showed that significantly more alate and apterous aphids occurred on large, low angle leaves. Mowing prior to spring aphid migration was associated with 75% fewer alatae and apterae on the plantain. The loss in harvest resulting from aphid damage ranged from 3% to 76% of the crop. Effective autumn control depends on accurate timing of aphid flight. The peak of female flight occurred on the 27th of September, 2007 at 11:56 hours daylength (sunrise to sunset) and the peak of male flight occurred on the12th of October, 2007 at 11:02 hours daylength. Aphid densities in the spring of 2008 were very low, making comparisons between treatments and controls difficult. Autumn applications of Superior dormant oil and kaolin clay were not effective. The PureSpray Green treatments of two October applications and one April application showed a significant reduction in rosy apple aphid infested clusters compared with the untreated control. Mowing and rotavating did not result in a significant reduction in aphid infestation level.

The rosy apple aphid, Dysaphis plantaginea, (Homoptera: Aphididae) is a serious pest of apples in British Columbia (BC), Canada and especially in organic orchards where conventional controls cannot be used. The goals of this study were to determine the environmental or management factors of an orchard that lead to high aphid populations, to conduct an economic assessment of the damage, to determine the timing of autumn migration, and to test several autumn and spring chemical control methods and two novel autumn mechanical control methods targeting the aphids while on their alternate host, Plantago major. To explain the variation among orchards, I evaluated several potential correlates of aphid density: abundance of the alternate host (plantain, Plantago major), foliar tree nitrogen, tree age, tree planting density, and the application of an oil treatment in spring. Stepwise regression indicated that foliar nitrogen and tree age explain 27% of the variation. Orchards receiving a spring oil application had a 53% lower average aphid infestation level. Plantain abundance was not related to aphid population on apple. However, experimental manipulation of leaf angle from the ground and size showed that significantly more alate and apterous aphids occurred on large, low angle leaves. Mowing prior to spring aphid migration was associated with 75% fewer alatae and apterae on the plantain. The loss in harvest resulting from aphid damage ranged from 3% to 76% of the crop. Effective autumn control depends on accurate timing of aphid flight. The peak of female flight occurred on the 27th of September, 2007 at 11:56 hours daylength (sunrise to sunset) and the peak of male flight occurred on the12th of October, 2007 at 11:02 hours daylength. Aphid densities in the spring of 2008 were very low, making comparisons between treatments and controls difficult. Autumn applications of Superior dormant oil and kaolin clay were not effective. The PureSpray Green treatments of two October applications and one April application showed a significant reduction in rosy apple aphid infested clusters compared with the untreated control. Mowing and rotavating did not result in a significant reduction in aphid infestation level. / Land and Food Systems, Faculty of / Graduate

The rosy apple aphid Dysaphis plantaginea (Passerini) (Homoptera: Aphididae) is the most serious pest apple aphid in view of the scale of damages inflicted to the fruits by a small number of individuals. Although numerous natural enemies have been associated with D. plantaginea, they are unable to halt infestations soon enough in most commercial apple orchards obliging fruit growers to control it chemically to prevent severe economic losses. In order to reinforce the contribution of indigenous aphidophaga in regulating rosy apple aphids, the use of insectary plants selected to support two groups of specialist aphid antagonists, notably aphid parasitoids and aphidophagous monovoltine syrphids, was investigated. 1. A first step consisted in selecting appropriate plant species. The rowan tree Sorbus aucuparia L. and the common elder Sambucus nigra L. were selected for their ability to support substitute aphids for the rosy apple aphid parasitoid E. persicae Froggatt (Hymenoptera: Braconidae, Aphidiinae) and monovotine syrphids (Diptera: Syrphidae) respectively. 2. Next, trials were conducted to induce substitute aphid infestations on their host plants by introducing eggs of Dysaphis sorbi Kaltenbach on rowan and small colonies of Aphis sambuci L. on elder. The resulting aphid populations which developed on their respective host plants in spring proved to be exploited by the natural enemies expected, i.e. E. persicae and monovoltine syrphids of the genus Epistrophe. Besides, diapause mummies of E. persicae and diapausing last-instar Epistrophe larvac were recorded on rowan and in the elder litter respectively, indicating the successful settlement of the antagonists in the orchard environment. A complementary investigation devoted to syrphid adults indicated that females of all species recorded ovipositing on the eider shrubs, including Epistrophe spp. had consumed a large majority of apple pollen grains as a protein source required for egg maturation. 3. To comfort our choice in the two groups of aphidophaga considered, a study dedicated to their respective phenology versus the one of D. plantaginea showed that they could both potentially halt rosy apple aphid infestations by attacking the aphids while the latter still occupied the primary, fundatrix-induced rosette leaf colonies, i.e. a critical moment in rosy apple aphid control. 4. Finally, marking methods were tested to label E. persicae internally and the egg load of gravid syrphids. These trials were intended to pave the way towards future mark-release-recapture experiments aimed to evaluate the antagonists’ activity range and thus strategically position the insectary plants for optimal aphid biological control in the whole orchard. The first step of new approach in the biological control of D. plantaginea has been set with this study. Its originality lies in the induction of economically indifferent aphid infestations on selected plants introduced in the orchard to encourage well-targeted groups of specialist aphid antagonists. Further trials are still needed to validate the field efficacy of the insectary plant systems developed and evaluate their possible integration within the whole array of pest management tools in both organic and integrated apple production. / Doctorat en sciences, Spécialisation biologie animale / info:eu-repo/semantics/nonPublished