			Home About us Contact

Control Failure (control + failure)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Resistance to carbosulfan in Anopheles gambiae from Ivory Coast, based on reduced sensitivity of acetylcholinesterase

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2003
R. N'Guessan
Abstract. Resistance to carbosulfan, a carbamate insecticide, was detected in field populations of the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) from two ecologically contrasted localities near Bouaké, Ivory Coast: rural M'bé with predominantly M form of An. gambiae susceptible to pyrethroids; suburban Yaokoffikro with predominantly S form of An. gambiae highly resistant to pyrethroids (96% kdr). The discriminating concentration of 0.4% carbosulfan (i.e. double the LC100) was determined from bioassays with the susceptible An. gambiae Kisumu strain. Following exposure to the diagnostic dosage (0.4% carbosulfan for 1 h), mortality rates of female An. gambiae adults (reared from larvae collected from ricefields) were 62% and 29% of those from M'bé and Yaokoffikro, respectively, 24 h post-exposure. Exposure for 3 min to netting impregnated with the operational dosage of carbosulfan 200 mg/m2 gave mortality rates of 88% of those from M'bé and only 12.2% for Yaokoffikro. In each case the control untreated mortality rate was insignificant. Biochemical assays to detect possible resistance mechanism(s) revealed the presence of insensitive AChE in populations of An. gambiae at both localities, more prevalent in the S form at Yaokoffikro than in M form at M'bé, as expected from bioassays results. Our study demonstrates the need to monitor carbamate resistance among populations of the An. gambiae complex in Africa, to determine its spread and anticipate vector control failure if these insecticides are employed. [source]

Radiosurgical treatment of vestibular schwannomas in patients with neurofibromatosis type 2

CANCER, Issue 2 2009
Tumor control, hearing preservation
Abstract BACKGROUND: The radiosurgical treatment of vestibular schwannomas in patients with neurofibromatosis type 2 (NF2) is controversial. The authors investigated the radiologically proven tumor control rate after gamma knife radiosurgery. The factors that affect tumor control and serviceable hearing preservation were analyzed. METHODS: Thirty-six lesions in 30 patients were included. The median lengths of the clinical and radiologic follow-ups were 48.5 months and 36.5 months, respectively. The median tumor volume was 3.2 cm3. The mean marginal dose was 12.1 grays (Gy) (range, 8,14 Gy) at an isodose line of 50%±0.6%. The Kaplan-Meier method and Cox proportional hazards model were used for the statistical analyses. RESULTS: The actuarial tumor control rate was 81%, 74%, and 66%, respectively, in the first, second, and fifth years. Five tumors required a salvage surgery because of tumor control failure. A low marginal dose and a young age at radiosurgery were associated with poor tumor control. Of the 16 tumors with which ipsilateral hearing was serviceable, the actuarial serviceable hearing preservation rates were 50%, 45%, and 33%, respectively, in the first, second, and fifth years. Better ipsilateral hearing (Gardner-Robertson grade 1, compared with grade 2) at the time of radiosurgery was associated with significantly greater serviceable hearing preservation. CONCLUSIONS: Gamma knife radiosurgery for vestibular schwannomas in NF2 patients provided 5-year tumor control in approximately two-thirds of patients and preserved serviceable hearing in approximately one-third. The rates of other cranial nerve deficits were low, and no secondary malignancy was observed. Radiosurgery should be included in treatment options for NF2 patients. Cancer 2009. © 2009 American Cancer Society. [source]

Responses of Corcyra cephalonica (Stainton) to pirimiphos-methyl, spinosad, and combinations of pirimiphos-methyl and synergized pyrethrins,

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2004
Fangneng Huang
Abstract Field control failures with pirimiphos-methyl against the rice moth, Corcyra cephalonica (Stainton), in Weslaco, Texas, USA, led us to investigate the susceptibility of this particular strain to pirimiphos-methyl, spinosad, pyrethrins synergized with piperonyl butoxide, and pirimiphos-methyl combined with synergized pyrethrins. In laboratory bioassays, 50 eggs of C cephalonica were exposed to untreated and insecticide-treated corn and sunflower seeds to determine larval survival after 21 days, egg-to-adult emergence after 49 days, and larval damage to seeds at both exposure periods. Pirimiphos-methyl at both 4 and 8 mg kg,1 did not prevent larval survival or egg-to-adult emergence of C cephalonica on either corn or sunflower seeds, and seed damage was evident at both rates. The C cephalonica strain was highly susceptible to spinosad at 0.5 and 1 mg kg,1. At both spinosad rates, reduction in larval survival, egg-to-adult emergence, and seed damage relative to the control treatment was ,93% on both corn and sunflower seeds. Pirimiphos-methyl and spinosad were generally more effective against C cephalonica on corn than sunflower seeds. The C cephalonica strain was completely controlled on corn treated with 1.5 mg kg,1 of pyrethrins synergized with 15 mg kg,1 of piperonyl butoxide. Many larvae survived and became adults on corn treated with synergized pyrethrins at ,0.75 mg kg,1. Corn treated with pirimiphos-methyl at 4, 6 or 8 mg kg,1 in combination with 0.38 to 1.5 mg kg,1 of synergized pyrethrins reduced larval survival by ,95%, egg-to-adult emergence by ,97%, and seed damage by ,94%. Our results suggest that the C cephalonica strain can be controlled on corn by combining pirimiphos-methyl with synergized pyrethrins or with synergized pyrethrins at the labeled rate. Although spinosad is not currently labeled for use on stored corn and sunflower seeds, it appears to be effective against C cephalonica on both commodities at very low rates. Copyright © 2004 Society of Chemical Industry [source]

Australian populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), are resistant to some insecticides used for their control

AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008
Grant A Herron
Abstract Onion thrips, Thrips tabaci Lindeman, is a major pest of Australian field onion Allium cepa Linnaeus with their control heavily reliant on a few insecticides. An earlier study after grower complaints of control failures did not detect resistance in three populations. After testing an additional nine populations via a Potter spray tower laboratory bioassay unequally against ,-cypermethrin, diazinon, dimethoate, ,-cyhalothrin, malathion and methidathion, we document resistance in T. tabaci for the first time in Australia. The maximum difference in response (resistance) for each insecticide was detected by dividing the most resistant LC50 response by the least resistant LC50 response. Comparison of the most susceptible to the least susceptible population tested produced ,-cypermethrin and ,-cyhalothrin resistance at 164- and 606-fold, respectively. Diazinon and dimethoate resistance was also detected at 27-fold and 5.2-fold respectively although omethoate, malathion and methidathion resistance were not detected. [source]