Relative Tolerance of Six Bactrocera (Diptera: Tephritidae) Species to Phytosanitary Cold Treatment.

To compare relative cold treatment tolerance across the economically important tephritid fruit flies (Diptera: Tephritidae), Bactrocera carambolae Drew & Hancock, Bactrocera correcta (Bezzi), Bactrocera cucurbitae (Coquillett), four populations of Bactrocera dorsalis (Hendel), Bactrocera zonata (Saunders), and Bactrocera tryoni (Froggatt), eggs (in vitro), and larvae (in infested fruit or on carrot diet) were cold treated at 2.0 ± 0.2 °C for selected durations. The study was performed to assess whether a single (i.e., generic) cold treatment could be developed that would control the entire group of fruit flies that were tested. Probit regression models showed that the hierarchy of cold resistance was third-instar larvae reared on carrot diet > third-instar larvae reared on orange > eggs test in vitro. Differences in mortality responses of third-instar larvae reared in oranges across populations of B. dorsalis were observed only at subefficacious levels of control. The majority of Bactrocera species responded the same at the high levels of control demanded of phytosanitary treatments, which indicated that cold treatments would be similarly effective across the species and populations tested. B. cucurbitae was found to be the most cold tolerant of all the species tested.

Economic feasibility of methoprene applied as a surface treatment and as an aerosol alone and in combination with two other insecticides.

Economic evaluations of integrated pest management strategies are becoming increasingly important as restrictions on conventional insecticides continue to become more stringent and chemical control costs rise. Aerosol treatments with insect growth regulators alone and in combination with conventional contact insecticides may be a feasible alternative to expensive and highly toxic fumigants such as methyl bromide for control of the Indianmeal moth (Plodia interpunctella (Hübner)). Average calculated mortality of Indianmeal moth eggs exposed to surface applied methoprene, aerosol methoprene alone and in combination with esfenvalerate and synergized pyrethrins is 55.0, 69.0, and 94.6%, respectively. Temperature effects on development time makes frequency and timing of insecticide applications very important as evidenced by simulations of population levels in response to a variety of treatment dates by diet, and become critical in situations where survival of Indianmeal moth is high. Using a measurement of risk that is equal to deviations below a target mortality goal (99%), we are able to optimize cost and frequency of application using simulated mortality data for each of the treatment strategies. Optimal timing of each insecticide treatment depends heavily on the rate of development by diet. This type of analysis helps pest control operators and managers by showing consequences of treatment scenarios in time and cost.

Phytosanitary cold treatment for oranges infested with Bactrocera zonata (Diptera: Tephritidae).

The peach fruit fly, Bactrocera zonata (Saunders), attacks a wide range of tree fruits in countries from Egypt to Vietnam and is occasionally trapped in the United States. Phytosanitary treatments may be required to export fruit hosts of this insect from countries where it is endemic to countries where it is absent but could become established. This research describes comparative studies to determine if B. zonata could be phytosanitarily controlled by cold treatment schedules existing for Ceratitis capitata (Wiedemann) and Anastrepha ludens (Loew), and the development of a cold treatment of 18 d at 1.7 degrees C for B. zonata infesting oranges. Fruit were infested by puncturing holes in oranges and allowing tephritids to oviposit in the holes. The treatments were initiated when the larvae reached late third instar because previous research had shown that stage to be the most cold-tolerant. B. zonata was not found to be confidently as or less cold tolerant than C. capitata; therefore, treatment schedules for the latter are not supported by this research for the former. B. zonata was found to be more susceptible to 1.7 degrees C than A. ludens; therefore, the use of treatment schedules for A. ludens is supported by this research for B. zonata. However, the treatment for A. ludens requires 22 d. A shorter treatment was verified for B. zonata when 36,820 third instars reared from the eggs in oranges were stored at 1.7 degrees C for 18 d with no larvae moving on examination 24 h after removal from the cold treatment chamber.

Residual activity of methoprene and novaluron as surface treatments to manage the flour beetles, Tribolium castaneum and Tribolium confusum.

The juvenile hormone analog methoprene, and the chitin synthesis inhibitor novaluron, were evaluated by exposing late-stage larvae of Tribolium castaneum (Herbst) or Tribolium confusum (Jacqueline DuVal) (Coleoptera: Tenebrionidae) to it. The larvae were exposed to it in food material, on concrete, on plywood, and on floor tile. Larvae of T. castaneum were more susceptible than T. confusum larvae to both methoprene and novaluron on all surfaces. A further evaluation was done by exposing adult T. confusum to methoprene and novaluron through food placed on concrete treated with methoprene and novaluron, and then assessing resulting progeny production. The emergence of adults with normal morphology was reduced for both chemicals, with more malformed adults appearing in the methoprene treatment, and fewer adults of any form emerging in the novaluron treatment. The results show direct exposures to larvae, or determining progeny production from exposed adults, are valid methods for assessing the susceptibility of flour beetles to insecticides.

Evaluation of catmint oil and hydrogenated catmint oil as repellents for the flour beetles, Tribolium castaneum and Tribolium confusum.

Catmint oil and hydrogenated catmint oil were evaluated as repellents for adult Tribolium casteneum (Herbst) (Coleoptera: Tenebrionidae), the red flour beetle, and T. confusum (DuVal), the confused flour beetle, using both a traditional method of visual assessment of distribution and a video recording method to determine movement patterns of individual insects. Visual assessments of distribution using groups of adults showed that the hydrogenated catmint oil was more effective than the pure catmint oil, but there was no significant difference between species. However, when repellency was measured using single insects and the visual recording system, both oils were significantly more repellent to T. castaneum than T. confusum at the concentrations evaluated in the study. Avoidance movement and change in direction when T. castaneum encountered the repellent were observed. Results indicate that repellents may be more accurately assessed using single insects rather than groups of individuals, and simple visual observations of distribution may be less sensitive in measuring repellent efficacy. Procedures for utilizing a video system are described as models for future evaluations of repellents for stored-product beetles.