ANDRE RICARDO MACHI
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Artigo IPEN-doc 23556 Milbemectin and etoxazol acaricide resistant and susceptible strains of Tetranychus urticae (Trombidiformes: Tetranychidae) are equally radiosusceptible and unable to reproduce when irradiated with 400 Gy2016 - ARTHUR, VALTER; NICASTRO, ROBERTO L.; SATO, MARIO E.; MACHI, ANDRE R.The twospotted spider mite, Tetranychus urticae Koch (Trombidiformes: Tetranychidae), is considered one of the most important phytophagous mites causing considerable damage in several agricultural crops. The aim of this study was to evaluate the susceptibility to gamma irradiation of strains of T. urticae resistant (R) and susceptible (S) to the acaricides, milbemectin and etoxazol. The R and S strains for milbemectin and etoxazol were irradiated with 200 and 400 Gy of gamma radiation in a Gammacell 220 source to evaluate the effects of gamma radiation on the growth rate of the mites. A dose of 400 Gy totally eliminated populations of both R and S strains of T. urticae within 10 d. A dose of 200 Gy was not sufficient to totally eliminate both T. urticae strains, but it significantly reduced egg viability of both strains. In the most likely measure of efficacy for phytosanitary irradiation of mites—i.e., prevention of F1 egg hatch when parent adults are irradiated—no differences were found in response to irradiation among the 4 strains.Artigo IPEN-doc 23543 Oxygen atmosphere potentiates radiation effects on Brevipalpus yothersi (Trombidiformes: Tenuipalpidae)2016 - MACHI, ANDRE R.; ARTHUR, VALTERThe objective of the study was to compare the effect of pure oxygen to that of ambient air on gamma irradiation of Brevipalpus yothersi (Baker) (Trombidiformes: Tenuipalpidae). Flasks containing the mites were irradiated in a Gammacell-220 irradiator with Cobalt-60 emitting gamma radiation at a rate of 381 Gy/h. Seventy mites per flask replicated 4 times were irradiated in either pure oxygen or air with 0 (control), 200, 230, 270, or 300 Gy as the intended doses. All eggs, deutonymphs and adults were counted each day and the parameters of egg production, egg hatch, development and mortality were recorded. Data were analyzed with ANOVA and means were separated with Tukey’s Honestly Significant Difference (HSD) test at 5% probability. Generally, irradiation of females with progressively larger doses—whether in oxygen or in air—resulted in progressively greater negative biological effects, and these effects were greater when females were irradiated in oxygen than in air. Non-irradiated gravid females exposed to pure oxygen deposited 79.3 ± 0.3 eggs per female compared to 73.0 ± 0.3 per female in ambient air. The numbers of eggs oviposited by females irradiated with the largest dose (300 Gy) were 29.1 ± 0.2 in air and 18.1 ± 0.3 in oxygen. In the ambient air + 270 Gy treatment egg hatch was 3.8 ± 0.1%, but in the oxygen + 270 Gy treatment it was 0%. When females were irradiated in air with 300 Gy, egg hatch was totally prevented. The number of F1 deutonymphs per P generation female irradiated with 270 Gy in ambient air was 4.0 ± 0.1, but the corresponding number that descended from females irradiated in pure oxygen was significantly reduced to zero. Percentage survival of females at 22 d post treatment was 13.0 ± 0.1 d when females were irradiated in oxygen with 270 Gy compared to 16 ± 0.2 d when irradiated in air with 300 Gy. Therefore, 300 Gy is recommended as an appropriate candidate for phytosanitary irradiation of B. yothersi in air, and 270 Gy is recommended as an appropriate candidate for phytosanitary irradiation of B. yothersi in oxygen.Artigo IPEN-doc 23951 Pupation, adult emergence, and F1 egg hatch after irradiation of Spodoptera frugiperda (Lepidoptera: Noctuidae) last instars2016 - ARTHUR, VALTER; ARTHUR, PAULA B.; MACHI, ANDRÉ R.The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a quarantine pest that may be found as eggs or larvae on a number of fresh vegetable and fruit commodities. The objective of the research was to evaluate the effects of gamma radiation as a phytosanitary treatment applied to the 5th (last) instar larvae. Larvae were reared on an artificial diet. Each treatment of twenty 15–20 d-old larvae had 5 repetitions. The larvae were irradiated with doses of gamma radiation of 0 (non-irradiated control), 50, 100, 200 and 300 Gy in a Cobalt-60 source (Gammacell-220) at a dose rate of 508 Gy/h. Pupation, adult emergence and hatching of F1 eggs were monitored. When the last instars were irradiated with100 Gy the rates of pupation, adult emergence and F1 egg hatch were 85, 39 and 50 percent, respectively, and the corresponding values in the non-irradiated control were 95, 85 and 90 percent, respectively. However, when the last instars were irradiated with 200 Gy, the pupation rate was reduced to 30 percent and adult emergence was reduced to 10 percent, and all of the adults that emerged were deformed, unable to fly, and died after about 2 h. Therefore, irradiation with 200 Gy is recommended as the appropriate dose for phytosanitary irradiation of S. frugiperda eggs and larvae. In addition this study supports the previously proposed generic dose of 250 Gy for eggs and larvae of lepidopteran pest species generally.