Entomologia Experimentalis Et Applicata, Feb 1, 2011
ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distri... more ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distribution among fruit and among trees largely due to the fact that most young settle on the same fruit as their mothers. The pattern of distribution and degree of dispersion of red scale within various sets of contiguous citrus trees in several orchards were recorded each autumn for 4 years. Changes in density and site occupancy within trees and within contiguous groups of trees were made to assess the strength of any link between populations and their dynamics on different trees. Aonidiella aurantii was found to have a very clumped distribution whereby trees with a level of scale infestation well above average for their block could be adjacent to trees with few or no detectable scale. However, patches of high density on a given tree usually did not recur for more than 2 years but were replaced with above average infestations on other trees. The stability of the red scale populations varied from block to block. Some blocks had few or no infested trees over the study period whereas others had widely fluctuating levels of infestation. Dispersion coefficients at ‘within tree’ and ‘within block’ levels were similar. Theoretical and statistical models of the relation of average scale levels to the percentage of fruit or trees infested were less precise than they are for other pests because of high variation of clumping intensity of scale within any block.
Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-... more Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-target motile foliage-dwelling arthropod communities that could be sampled by a portable suction system in a citrus orchard in the coastal region of New South Wales, Australia. Sprays of nC24 horticultural mineral oil (HMO) and an organophosphorous insecticide (methidathion) were applied at the level of whole blocks in the manner pertinent to successful control of (sessile) scale insects. The MDS model produced ordination figures for several sampling times before and after spray applications that showed that any effect of HMO was undetectable but methidathion was disruptive to the sampled motile foliage arthropod community for at least 18 weeks. This was confirmed with ANOVA of arthropod abundance. Thus if sprays were required several times per year it would be desirable to use HMOs to preserve biodiversity. Key words: biodiversity; conservation; pest control.
Outcrossing to wild or unrelated strains has been proposed as a counter to the negative effects o... more Outcrossing to wild or unrelated strains has been proposed as a counter to the negative effects of adaptation by domesticated animals to captive-breeding environments. However, for mass-reared insects intended for sterile insect technique release, outcrossing may reduce productivity in mass-rearing facilities. In this study, we characterized adaptation to mass-rearing in the Queensland fruit fly Bactrocera tryoni (Froggatt). The features of domesticated B. tryoni were similar to those of other domesticated tephritids: shortened preoviposition period, higher egg production and increased early survival. We also examined the practical use of outcrossing to improve mass-reared strains. The B. tryoni mass-reared strain was crossed with independent strains that had already been domesticated for a varying number of generations. Preoviposition period, egg production, survival and stress tolerance were measured in the resulting hybridized strains. The short preoviposition period of the mass-...
From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectivenes... more From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectiveness of the nC24 petroleum spray oil (PSO), D-C-Tron Plus, against two-spotted mite, Tetranychus urticae Koch (Acarina: Tetranychidae), and to determine how the oil could be most efficiently and effectively used in combination with the predatory mite Phytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae) in an integrated pest management program. The results showed that 0.5% PSO applied fortnightly to roses gave excellent protection from T urticae infestation when the mite population was not already established. However, PSO applied after roses were infested with T. urticae above the economic threshold only stabilised populations without reducing them below that threshold. Populations of P. persimilis in the upper and lower canopies were unchanged after two sprays of PSO at 7-day intervals, and application of PSO to the upper canopy was as effective in controlling T. urticae in the p...
Procedures are presented for declaring an area to be “pest free” following an area-wide eradicati... more Procedures are presented for declaring an area to be “pest free” following an area-wide eradication programme against a population of an insect pest. These involve two probability models to deal with null trapping results, and a growth model to help verify that pests were no longer present when control actions were stopped. The two probability models are presented for a
ABSTRACT This study investigated two factors potentially affecting the spatial distribution of Qu... more ABSTRACT This study investigated two factors potentially affecting the spatial distribution of Queensland fruit fly Bactrocera tryoni (Froggatt) after release from a single point. First, the effect of age at release was investigated using a single cohort of 205 000 males from a mass-rearing strain used for sterile insect releases. Approximately half were released as immature males and the remainder as sexually mature males (1 week later). Males were collected over 3 weeks from a grid of 135 traps, each containing a pheromone/insecticide bait, positioned between 4 and 500 m from the release point. Variation in the distribution of fly density around the release point was assessed by regressing trapped fly counts against distance. Unexpectedly, no significant differences were found in the spatial distribution of the flies. Second, the effect of inbreeding on spatial distribution was investigated using replicated simultaneous releases of two strains of B. tryoni. One strain was the existing (inbred) mass-rearing strain that has been selected for high productivity in a mass-rearing facility. The second strain was deliberately outbred but also selected for high productivity. Almost 100 000 males of each strain were released over the two experiments. Regression of trappings against distance differed significantly between strains in only one of five releases, but in all cases the outbred strain had a greater dispersal distance. As our trapping grid was not regular but contained gaps of up to 100 m, a small preliminary experiment investigated whether flies move faster along tree rows or across open fields. At distances up to 100 m, we found no detectable difference in fly distributions. These results are primarily relevant to the large-scale point releases carried out as part of an existing B. tryoni sterile insect programme and are discussed in that context.
ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distri... more ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distribution among fruit and among trees largely due to the fact that most young settle on the same fruit as their mothers. The pattern of distribution and degree of dispersion of red scale within various sets of contiguous citrus trees in several orchards were recorded each autumn for 4 years. Changes in density and site occupancy within trees and within contiguous groups of trees were made to assess the strength of any link between populations and their dynamics on different trees. Aonidiella aurantii was found to have a very clumped distribution whereby trees with a level of scale infestation well above average for their block could be adjacent to trees with few or no detectable scale. However, patches of high density on a given tree usually did not recur for more than 2 years but were replaced with above average infestations on other trees. The stability of the red scale populations varied from block to block. Some blocks had few or no infested trees over the study period whereas others had widely fluctuating levels of infestation. Dispersion coefficients at ‘within tree’ and ‘within block’ levels were similar. Theoretical and statistical models of the relation of average scale levels to the percentage of fruit or trees infested were less precise than they are for other pests because of high variation of clumping intensity of scale within any block.
Entomologia Experimentalis Et Applicata, Feb 1, 2011
ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distri... more ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distribution among fruit and among trees largely due to the fact that most young settle on the same fruit as their mothers. The pattern of distribution and degree of dispersion of red scale within various sets of contiguous citrus trees in several orchards were recorded each autumn for 4 years. Changes in density and site occupancy within trees and within contiguous groups of trees were made to assess the strength of any link between populations and their dynamics on different trees. Aonidiella aurantii was found to have a very clumped distribution whereby trees with a level of scale infestation well above average for their block could be adjacent to trees with few or no detectable scale. However, patches of high density on a given tree usually did not recur for more than 2 years but were replaced with above average infestations on other trees. The stability of the red scale populations varied from block to block. Some blocks had few or no infested trees over the study period whereas others had widely fluctuating levels of infestation. Dispersion coefficients at ‘within tree’ and ‘within block’ levels were similar. Theoretical and statistical models of the relation of average scale levels to the percentage of fruit or trees infested were less precise than they are for other pests because of high variation of clumping intensity of scale within any block.
Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-... more Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-target motile foliage-dwelling arthropod communities that could be sampled by a portable suction system in a citrus orchard in the coastal region of New South Wales, Australia. Sprays of nC24 horticultural mineral oil (HMO) and an organophosphorous insecticide (methidathion) were applied at the level of whole blocks in the manner pertinent to successful control of (sessile) scale insects. The MDS model produced ordination figures for several sampling times before and after spray applications that showed that any effect of HMO was undetectable but methidathion was disruptive to the sampled motile foliage arthropod community for at least 18 weeks. This was confirmed with ANOVA of arthropod abundance. Thus if sprays were required several times per year it would be desirable to use HMOs to preserve biodiversity. Key words: biodiversity; conservation; pest control.
Outcrossing to wild or unrelated strains has been proposed as a counter to the negative effects o... more Outcrossing to wild or unrelated strains has been proposed as a counter to the negative effects of adaptation by domesticated animals to captive-breeding environments. However, for mass-reared insects intended for sterile insect technique release, outcrossing may reduce productivity in mass-rearing facilities. In this study, we characterized adaptation to mass-rearing in the Queensland fruit fly Bactrocera tryoni (Froggatt). The features of domesticated B. tryoni were similar to those of other domesticated tephritids: shortened preoviposition period, higher egg production and increased early survival. We also examined the practical use of outcrossing to improve mass-reared strains. The B. tryoni mass-reared strain was crossed with independent strains that had already been domesticated for a varying number of generations. Preoviposition period, egg production, survival and stress tolerance were measured in the resulting hybridized strains. The short preoviposition period of the mass-...
From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectivenes... more From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectiveness of the nC24 petroleum spray oil (PSO), D-C-Tron Plus, against two-spotted mite, Tetranychus urticae Koch (Acarina: Tetranychidae), and to determine how the oil could be most efficiently and effectively used in combination with the predatory mite Phytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae) in an integrated pest management program. The results showed that 0.5% PSO applied fortnightly to roses gave excellent protection from T urticae infestation when the mite population was not already established. However, PSO applied after roses were infested with T. urticae above the economic threshold only stabilised populations without reducing them below that threshold. Populations of P. persimilis in the upper and lower canopies were unchanged after two sprays of PSO at 7-day intervals, and application of PSO to the upper canopy was as effective in controlling T. urticae in the p...
Procedures are presented for declaring an area to be “pest free” following an area-wide eradicati... more Procedures are presented for declaring an area to be “pest free” following an area-wide eradication programme against a population of an insect pest. These involve two probability models to deal with null trapping results, and a growth model to help verify that pests were no longer present when control actions were stopped. The two probability models are presented for a
ABSTRACT This study investigated two factors potentially affecting the spatial distribution of Qu... more ABSTRACT This study investigated two factors potentially affecting the spatial distribution of Queensland fruit fly Bactrocera tryoni (Froggatt) after release from a single point. First, the effect of age at release was investigated using a single cohort of 205 000 males from a mass-rearing strain used for sterile insect releases. Approximately half were released as immature males and the remainder as sexually mature males (1 week later). Males were collected over 3 weeks from a grid of 135 traps, each containing a pheromone/insecticide bait, positioned between 4 and 500 m from the release point. Variation in the distribution of fly density around the release point was assessed by regressing trapped fly counts against distance. Unexpectedly, no significant differences were found in the spatial distribution of the flies. Second, the effect of inbreeding on spatial distribution was investigated using replicated simultaneous releases of two strains of B. tryoni. One strain was the existing (inbred) mass-rearing strain that has been selected for high productivity in a mass-rearing facility. The second strain was deliberately outbred but also selected for high productivity. Almost 100 000 males of each strain were released over the two experiments. Regression of trappings against distance differed significantly between strains in only one of five releases, but in all cases the outbred strain had a greater dispersal distance. As our trapping grid was not regular but contained gaps of up to 100 m, a small preliminary experiment investigated whether flies move faster along tree rows or across open fields. At distances up to 100 m, we found no detectable difference in fly distributions. These results are primarily relevant to the large-scale point releases carried out as part of an existing B. tryoni sterile insect programme and are discussed in that context.
ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distri... more ABSTRACT Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distribution among fruit and among trees largely due to the fact that most young settle on the same fruit as their mothers. The pattern of distribution and degree of dispersion of red scale within various sets of contiguous citrus trees in several orchards were recorded each autumn for 4 years. Changes in density and site occupancy within trees and within contiguous groups of trees were made to assess the strength of any link between populations and their dynamics on different trees. Aonidiella aurantii was found to have a very clumped distribution whereby trees with a level of scale infestation well above average for their block could be adjacent to trees with few or no detectable scale. However, patches of high density on a given tree usually did not recur for more than 2 years but were replaced with above average infestations on other trees. The stability of the red scale populations varied from block to block. Some blocks had few or no infested trees over the study period whereas others had widely fluctuating levels of infestation. Dispersion coefficients at ‘within tree’ and ‘within block’ levels were similar. Theoretical and statistical models of the relation of average scale levels to the percentage of fruit or trees infested were less precise than they are for other pests because of high variation of clumping intensity of scale within any block.
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