Abstract
An organophosphate pyrethroid-resistant strain of Typhlodromus pyri Scheuten imported from New Zealand was reared on potted apple trees in an outdoor insectary. From 1988 to 1995, the population was selected one to three times per year with a dilute solution (1.7 ppm) of the pyrethroid cypermethrin. Petri dish bioassays with cypermethrin in 1995 indicated that the insectary-reared T. pyri had an LC50 of 81 ppm versus 0.006 ppm for native T. pyri taken from a research orchard. The bioassays suggested that recommended orchard rates of cypermethrin would cause heavy mortality in native populations of T. pyri but only moderate losses in the imported New Zealand strain. Bioassays in 1996 with the organophosphate insecticide dimethoate indicated both New Zealand and native T. pyri were susceptible and that recommended orchard rates of dimethoate likely would cause high mortality of T. pyri in apple orchards. These findings from bioassays were supported by data from orchard trials. In June and July 1993, insectary-reared New Zealand T. pyri were placed on five apple trees in each of eight 38-tree plots in the research orchard. In late August 1994, New Zealand T. pyri from orchard trees that had been sprayed twice by airblast sprayer with the full recommended rate of 50 g (AI)/ha (83 ppm) cypermethrin were placed on the other 33 trees in each of six plots. In the summers of 1994-1996, plots were treated with one of the following insecticide regimes: (1) conventional integrated pest management (IPM) (registered neurotoxic insecticides considered harmless or slightly toxic to T. pyri); (2) advanced IPM (use of newer, more selective insecticides); (3) pyrethroid (at least one full-rate application of cypermethrin); (4) dimethoate; and (5) dimethoate plus pyrethroid. Densities of European red mite, Panonychus ulmi (Koch), were highest in all plots treated with dimethoate and in pyrethroid plots not yet inoculated with New Zealand T. pyri. Densities of apple rust mite, Aculus schlechtendali (Nalepa), and of the stigmaeid predator Zetzellia mali (Ewing) were highest in plots treated with dimethoate and were nearly absent in the IPM plots. Densities of T. pyri were high enough for effective biocontrol in the IPM plots and in the pyrethroid plots 1-2 yr after release of the New Zealand strain, provided pyrethroid was applied just before the resistant strain was released in the orchard. A recurring theme of this study was the generally negative association between densities of phytophagous mites and those of T. pyri, suggesting the ability of this predator to suppress their prey. In contrast, the positive association between phytophagous mites and Z. mali suggests the inability of this predator to regulate their prey at least under the conditions of this study.
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Claims 10
Claim · model-written summary
The imported Typhlodromus pyri strain had much higher cypermethrin LC50 than native mites.
Verbatim
e0“the insectary-reared T. pyri had an LC50 of 81 ppm versus 0.006 ppm for native T. pyri”
Claim · model-written summary
Recommended cypermethrin rates were predicted to cause heavy native T. pyri mortality but moderate losses in the imported strain.
Verbatim
e0“recommended orchard rates of cypermethrin would cause heavy mortality in native populations of T. pyri but only moderate losses in the imported New Zealand strain”
Claim · model-written summary
Both New Zealand and native T. pyri were susceptible to dimethoate.
- Taxon
- T. pyriTyphlodromus pyrie0
- Material
- New Zealand and native T. pyrie0
- Outcome
- susceptiblee0
Verbatim
e0“both New Zealand and native T. pyri were susceptible”
Claim · model-written summary
Recommended dimethoate rates were expected to cause high T. pyri mortality in apple orchards.
Verbatim
e0“recommended orchard rates of dimethoate likely would cause high mortality of T. pyri in apple orchards”
Claim · model-written summary
European red mite densities were highest in dimethoate plots and uninoculated pyrethroid plots.
- Taxon
- Panonychus ulmi
Panonychus ulmie0 - Treatment
- dimethoatee0
- Interactor
- T. pyriTyphlodromus pyrie0biocontrol_agent
- Outcome
- Densities of European red mitee0
- Direction
- higheste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Densities of European red mite, Panonychus ulmi (Koch), were highest in all plots treated with dimethoate and in pyrethroid plots not yet inoculated with New Zealand T. pyri”
Claim · model-written summary
Apple rust mite densities were highest with dimethoate and nearly absent in IPM plots.
Verbatim
e0“Densities of apple rust mite, Aculus schlechtendali (Nalepa), and of the stigmaeid predator Zetzellia mali (Ewing) were highest in plots treated with dimethoate and were nearly absent in the IPM plots”
Claim · model-written summary
Zetzellia mali densities were highest with dimethoate and nearly absent in IPM plots.
Verbatim
e0“Densities of apple rust mite, Aculus schlechtendali (Nalepa), and of the stigmaeid predator Zetzellia mali (Ewing) were highest in plots treated with dimethoate and were nearly absent in the IPM plots”
Claim · model-written summary
T. pyri densities supported biocontrol in IPM plots and pyrethroid plots one to two years after resistant strain release.
Verbatim
e0“Densities of T. pyri were high enough for effective biocontrol in the IPM plots and in the pyrethroid plots 1-2 yr after release of the New Zealand strain, provided pyrethroid was applied just before the resistant strain was released in the orchard”
Claim · model-written summary
Phytophagous mite density was negatively associated with T. pyri density.
- Taxon
- phytophagous mitese0
- Interactor
- T. pyriTyphlodromus pyrie0biocontrol_agent
- Outcome
- densities of phytophagous mitese0
- Direction
- negativee0
Verbatim
e0“negative association between densities of phytophagous mites and those of T. pyri”
Claim · model-written summary
Phytophagous mite density was positively associated with Z. mali density.
- Taxon
- phytophagous mitese0
- Interactor
- Z. maliZetzellia malie0biocontrol_agent
- Outcome
- phytophagous mitese0
- Direction
- positivee0
Verbatim
e0“positive association between phytophagous mites and Z. mali”