UVM Theses and Dissertations
Format:
Print
Author:
Benedict, Christopher A.
Dept./Program:
Plant and Soil Science
Year:
2005
Degree:
MS
Abstract:
The enactment of the Food Quality Protection Act (1996) has stimulated the development of alternative pesticides. One insecticide alternative for apple produces is kaolin. Kaolin is a white, aluminosilicate powder that forms a barrier film which repels or confuses insects. However, with the development of any new pest management technique, potential non-target impacts must be studied. A two-year orchard experiment was conducted to determine the impact of kaolin on mite populations on the apple cultivars 'Liberty' and 'McIntosh' using a completely randomized design with treatments that compared early and late season kaolin applications with a standard integrated pest management (IPM) program which used phosmet. On eight evaluation dates in 2003 and 2004, 20 leaves per tree were collected from each of 5-6 single-tree replications of each treatment and brought to a laboratory where mite populations were assessed. The number of European red mites, Panonychus ulmi (Koch), and two-spotted spide mites, Tetranychus urticae (Koch), were counted; all other mites were preserved and counted following identification. A negative impact of kaolin on phytoseiid mites, primarily Typhlodromus pyri Scheuten, was clearly evident.
In both years, there were significantly fewer phytoseiid mites on kaolin-treated trees on both cultivars compared to trees sprayed with phosmet or no insecticide. On 'Liberty' trees, significantly higher populations of P. ulmi were observed in both years on kaolin-treated trees compared to trees receiving the IPM treatment or no insecticide. On 'McIntosh' trees, there were significantly higher populations of P. ulmi when kaolin applications began early in the season in 2003 and with all kaolin treatments in 2004, compared to the IPM treatment. When difference in T. urticae populations were detected on either cultivar, higher populations were found on kaolin-treated trees. This study documents that numerous applications of kaolin over multiple growing seasons have a negative, non-target impact on phytoseiid mites and can result in economically damaging population levels of phytophagous mites. To further understand the mechanism by which kaolin impacts phytoseiid mites, a laboratory experiment was initiated to evaluate the impact of kaolin on mortality and behavior of two predacious mites, Typhlodromus pyri Scheuten and Amblyseius fallacis (Garman). Assays were performed wherein bean leaf disks were placed singly in small dishes and treated with either kaolin or distilled water via a Potter spray tower.
Two experiments were conducted, one utilizing T. pyri and the other, A. fallacis. Each experiment consisted of a "No-Choice" assay in which the whole leaf disk was treated and a "Choice" assay where only half of the leaf disk was sprayed. Five T. pyri or A. fallacis were placed on each treated disk, and 10 Tetranychus urticae Koch mites were added as a food source. Data were collected every 24 hours for 7 days on mite mortality and, in the "Choice" assay where mites could migrate to the non-treated half of the leaf disk, the location of the live mites were noted. The experiment used a completely randomizeddesign, with 10 leaf disk replications for each of the assays in the T. pyri experiment and 24 leaf disk replications for each assay in the A. fallacis experiment. Each experiment was repeated twice. The study documents that kaolin, when applied to whole leaf disks, can cause predatory mite mortality. There was no strong evidence to support that kaolin has a repellency effect on predatory mites. Both the orchard and laboratory experiments document the impact that kaolin has on predacious phytoseiid mites.
In both years, there were significantly fewer phytoseiid mites on kaolin-treated trees on both cultivars compared to trees sprayed with phosmet or no insecticide. On 'Liberty' trees, significantly higher populations of P. ulmi were observed in both years on kaolin-treated trees compared to trees receiving the IPM treatment or no insecticide. On 'McIntosh' trees, there were significantly higher populations of P. ulmi when kaolin applications began early in the season in 2003 and with all kaolin treatments in 2004, compared to the IPM treatment. When difference in T. urticae populations were detected on either cultivar, higher populations were found on kaolin-treated trees. This study documents that numerous applications of kaolin over multiple growing seasons have a negative, non-target impact on phytoseiid mites and can result in economically damaging population levels of phytophagous mites. To further understand the mechanism by which kaolin impacts phytoseiid mites, a laboratory experiment was initiated to evaluate the impact of kaolin on mortality and behavior of two predacious mites, Typhlodromus pyri Scheuten and Amblyseius fallacis (Garman). Assays were performed wherein bean leaf disks were placed singly in small dishes and treated with either kaolin or distilled water via a Potter spray tower.
Two experiments were conducted, one utilizing T. pyri and the other, A. fallacis. Each experiment consisted of a "No-Choice" assay in which the whole leaf disk was treated and a "Choice" assay where only half of the leaf disk was sprayed. Five T. pyri or A. fallacis were placed on each treated disk, and 10 Tetranychus urticae Koch mites were added as a food source. Data were collected every 24 hours for 7 days on mite mortality and, in the "Choice" assay where mites could migrate to the non-treated half of the leaf disk, the location of the live mites were noted. The experiment used a completely randomizeddesign, with 10 leaf disk replications for each of the assays in the T. pyri experiment and 24 leaf disk replications for each assay in the A. fallacis experiment. Each experiment was repeated twice. The study documents that kaolin, when applied to whole leaf disks, can cause predatory mite mortality. There was no strong evidence to support that kaolin has a repellency effect on predatory mites. Both the orchard and laboratory experiments document the impact that kaolin has on predacious phytoseiid mites.