Field evaluations of granular fly bait, Quick Bayt® and the paint-on fly bait, Agita® against synanthropic flies

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Field evaluations of granular fly bait, Quick Bayt® and the paint-on fly bait, Agita® against synanthropic flies
  126 Tropical Biomedicine 25(2): 126–133 (2008) Field evaluations of the granular fly bait, Quick Bayt ®  andthe paint-on fly bait, Agita ®  against synanthropic flies Nurita, A.T., Abu Hassan, A., Nur Aida, H. & Norasmah Basari Medical Entomology Laboratory, School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia.Corresponding author E-mail: aahassan@usm.myReceived 5 January 2007; received in revised form 25 June 2008; accepted 28 June 2008  Abstract. The efficacy and residual efficacy of commercial baits, Quick Bayt ® (0.5% w/wimidacloprid) and Agita  ® (10.0% w/w thiamethoxam) against synanthropic flies were evaluatedunder field conditions. Efficacy was evaluated based on knockdown percentage (KD %). The baitefficacy and residual efficacy evaluation were conducted for a period of 3 weeks and 6 weeksrespectively. Baits were applied onto bait targets and placed on fly-count targets to facilitate thecounting of flies. All baits were applied according to the manufacturer’s recommended applicationrate. Three replicate treatments for each type of bait were placed at the study site each week. Thenumber of flies feeding on baits and the knocked down flies were counted and collected. Theefficacy of Agita  ®  and Quick Bayt ®  did not differ significantly (t-test, P>0.05) over the 3-week period, even though Quick Bayt ®  had a slightly higher KD% than Agita  ® . In the residual efficacyevaluation, the (knockdown) KD% of Quick Bayt ® was consistent at around 36% for the first fiveweeks but dropped to 33.8 ± 0.4% on the sixth week. The KD% for Agita  ®  on the first week was33.6 ± 12.2% and remained relatively consistent for the first 4 weeks at around 31%. KD% droppedto 16.7 ± 3.3% on week 5 and to 15.7 ± 1.2% on week 6. The difference in residual efficacy of thetwo baits was significant (t-test, p<0.05). INTRODUCTIONThe propensity of the adults of manysynanthropic fly species to feed on humanfood, as well as garbage and excrement,gives them the potential for mechanicaltransmission of pathogenic organisms(Crosskey & Lane, 1993). They are knownto carry many pathogens internally in their  vomit and faeces and externally on their body. They are known to transmit dysentery,diarrhea, cholera and typhoid (WHO, 1991).Some also cause myiasis in humans andlivestock (Hall & Smith, 1993). This is not tosuggest that every fly brings disease, but theannoyance and public health risks associatedwith large populations of flies could beconsiderable and requires prompt attention.Considerable use has been made of chemical bait formulations in fly control programmes due to the problems of resistance and lack of effectiveness of somecontact insecticides. When contactinsecticides are formulated in fly baits, oraluptake appears to slow down the rate of increase of resistance (Barson, 1987).Chemical baits can also be easily replacedand are therefore not left to decay for long periods with a consequent reduction in toxiceffect (Webb, 1986).Neonicotinoids or chloronicotinyls,which resemble the natural product nicotineare a new class of synthetic insecticidesand is as a viable alternative toorganophosphates, carbamates and pyrethroids for use in bait formulations(Ware, 2000; Cox, 2001). Chemicals in thisclass include the widely used imidaclopridand newer chemicals such as thiamethoxam(Antunes-Kenyon & Kennedy, 2001).Imidacloprid is a systemic and contactinsecticide used against piercing-suckinginsects, flies and termites (Pedigo, 2002). A  variety of imidacloprid products including 126 - 133 Nurita AT.pmd8/15/2008, 11:32 AM126  127the granular fly bait Quick Bayt ®  are beingmarketed (Cox, 2001; Pospischil et al. , 2005).Similar to imidacloprid, thiamethoxam actsby interfering with acetylcholine receptors,however the specific binding sites are stillbeing investigated (Antunes-Kenyon &Kennedy, 2001).The present study was designed tocompare the efficacy of the granular fly bait,Quick Bayt ® (Bayer Environmental ScienceMalaysia) with that of the paint-on fly baitformulation, Agita  ®  10WG (Distributed bySyngenta) against synanthropic flies. Theresidual efficacy of both these baits after initial exposure in the field was alsoevaluated.MATERIAL & METHODS Field sites The field evaluations were conducted in anurban location in Pulau Pinang. The urbanlocation chosen for this study was the MedanSuri food court. A small chicken slaughteringfacility and a municipal garbage collection point which are in the vicinity of the foodcourt and located adjacent to each other. Baits and fly-count targets Quick Bayt ®  fly bait consists of red granulescontaining 0.5% w/w of imidacloprid and 1.0g/kg   of the fly sex pheromone Z-(9)-Tricosene. Agita  ®  10 WG is a water-solublegranule containing 10.0% w/w of thiamethoxam and 0.5g/kg of Z-(9)-Tricosene. Agita  ® and Quick Bayt ® containthe fly sex pheromone Z-(9)-Tricosene. Whendissolved in water Agita  ®  becomes a milkybeige suspension broth.Fly-count targets, made out of whiteexpanded polystyrene boards, were used tofacilitate knockdown counts of flies. Paper  plates (20 cm in diameter) and transparent plastic sheets measuring (30 x 21 cm) wereused as bait targets and placed onto the fly-count targets. Bait evaluation 1: Comparison baitefficacy  This experiment was conducted once a weekfor 3 weeks. Quick Bayt ®  granules weredistributed evenly into two paper plates(2g/m 2 , equivalent to manufacturer’srecommended practical application rate). Agita  ®  10WG was prepared according to themanufacturer’s recommendation (1.3 kg/ 1liter water) and painted onto twotransparent plastic sheets. The transparent plastic sheets did not repel the flies. Therewere three replicate treatments per day for each of the baits. Fresh baits were used eachweek. The replicate treatments wererandomly placed at the study site throughoutthe duration of the study. Bait evaluation 2: Comparison of residual efficacy  This experiment was conducted once a weekfor 6 weeks. Application methods for bothbaits in this evaluation are similar to the firstevaluation (refer to bait evaluation 1). Ten percent sugar solution was used as thecontrol target and was applied onto cotton pads, which were placed onto paper plates.Three replicate treatments for each of thebait and control targets were randomly placed within the study location every week.The treatments including the control targetwere placed at the study location 3 metersapart.The baits and the bait receptacles usedin the first week were not discarded andwere used again in the following weeks, rightuntil the sixth week. However, the baitscould not be left in the field because thestudy site is a public place. Human activitiesat the location could disrupt the experiment.Therefore, the baits had to be brought backand kept at the laboratory.To ensure that the volume of the reusedbaits was not reduced due to spillage, theywere placed with their respective receptaclein clear plastic bags. The clear plastic bagscontaining the reused baits were storedunder room temperature. Feeding and knocked down fly counts In both bait evaluations, feeding andknocked down fly count methods weresimilar. Once the baits were applied ontotargets, flies were allowed to feed on thebaits from 12 noon to 4pm which is a timewhen fly density is highest (Habibah, 1997). 126 - 133 Nurita AT.pmd8/15/2008, 11:32 AM127  128The number of flies feeding on the baitswere recorded. Dead flies or those that wereknocked down within bait targets and fly-count targets were placed in ventilatedcontainers and brought back to thelaboratory for identification. Flies wereconsidered knocked down if they wereunable to co-ordinate their locomotorymovements. Fly species were identifiedusing keys given by McAlpine et al . (1981-1989). The knocked down flies wereobserved after 24 and 48 hours for signs of recovery. The number of flies that recoveredfrom their knocked down state wasrecorded.The efficacy and residual efficacy of thebaits were evaluated based on knockdown percentage. Knockdown percentage wascalculated as the percentage of flies thatwere knocked down out of the total number of flies that fed on baits. Data analysis Knockdown percentages were transformedby Arcsine and tested for normality by usingthe Kolmogorov-Smirnov statistic. Whendata was confirmed for normality it wasfurther analyzed using the t-test analysis. Theanalysis was conducted by a PC version of Statistical Packages for the Social Sciences(SPSS).RESULTS Bait evaluation 1: Comparison of baitefficacy  Table 1 shows the mean number of fliescounted around the bait targets and the mean percentage of knocked down flies. Overall,the mean number of flies feeding on Agita  ® (265.2 ± 15.3) was higher compared to QuickBayt ® (196.1 ± 20.5) per replicate.Mean knockdown percentage per replicate for Agita   ® was 24.3 ± 2.0 comparedto 25.2 ± 6.3 for Quick Bayt ® . A t-test analysisshowed that the difference in meanknockdown percentage between the twobaits was not significant (t = -0.695, df =10, p>0.05). Therefore, the efficacy in terms of knock down effect of the two baits was notsignificantly different.Observations made after 24 hours and48 hours showed that Agita  ®  had a low percentage of fly recovery. Only one out of the total number of flies knocked down by Agita  ® recovered from the condition.However, Quick Bayt ®  showed a higher mean recovery percentage, at 3.3 percent.Most of the flies that recovered fromknockdown lost their ability to fly (hoppers)but subsequently survived the treatments.Figure 1 shows the percentages of different species of flies knocked down bythe two different baits.  Musca domestica was the predominant species   knocked downby the two baits. Overall, Agita  ®  and QuickBayt ® knocked down was as follows: 78.3% and 75.3%  M. domestica , 7.0% and 8.5%   Musca sorbens , 7.7% and 2.8% Chrysomya megacephala  and 7.0% and 12.9%  Luciliacuprina  respectively. Table 1. Mean number of flies feeding on baits and mean percentage of knocked down flies per replicate as wellas percentage recovery of knocked down flies over a  period of 3 weeks (mean ± SD)Mean no.MeanFlyBaitsnfeedingknockdownrecoveryflies ± SD% ± SD% ± SD Agita9265.2 ± 15.324.3 ± 2.00.2Quick Bayt9196.1 ± 20.525.2 ± 6.33.3 n = number of replicates Bait evaluation 2:   Comparison of residual efficacy  The mean number of flies feeding on the baittargets recorded weekly is shown in Figure2. A mean number of 229.8 ± 14.8 and 204.8± 11.8 flies fed on Agita  ®  and Quick Bayt ® respectively per week during the 6 week period. Only 83.3 ± 8.9 flies fed on the sugar (control) baits per week.Figure 3 shows that Quick Bayt ®  has a higher weekly mean knockdown percentagecompared to Agita  ® . In the first week, themean knockdown percentage was at 41.5 ±4.9%, after which a slight decrease in mean percentage occurred but stayed consistentat around 36% for the next 4 weeks. On thesixth week, the mean percentage dropped 126 - 133 Nurita AT.pmd8/15/2008, 11:32 AM128  129 Figure 1. Overall percentages of different species of flies knocked down by Agita  ®  and Quick Bayt ® .Figure 2. The weekly mean number of flies feeding on baits and control targets. Values aremean ± SD. 126 - 133 Nurita AT.pmd8/15/2008, 11:32 AM129  130only to 33.8 ± 0.4%. This shows that QuickBayt ®  residual efficacy remained high evenafter six weeks.The knockdown percentage of Agita  ® was found to be slightly lower than that of Quick Bayt ®  (Figure 3). The meanknockdown percentage for Agita  ®  for thefirst week was 33.6 ± 12.2% and remainedrelatively consistent for the first 4 weeks at31%. On week 5, however, there was a sharpdecrease in efficacy of this bait, as can beseen from the lower knockdown percentage.The knockdown percentage for Agita  ® at week 5 and week 6 was 16.7 ± 3.3% and15.7 ± 1.2% respectively. A t-test determinedthat the difference in residual efficacy of thetwo baits was significant (t 0.05 ,  10  = -2.919, p<0.05). From this result, it can be seen that Agita  ®  has a shorter residual efficacycompared to Quick Bayt ® .DISCUSSION Bait Evaluation 1: Comparison of BaitEfficacy  The results show that, the mean number of flies landing on targets baited with Agita  ® was higher compared to targets baited withQuick Bayt ® . The reason for the differencein attractiveness of the two baits is unclear.Both baits have sugar based formulationsand both have the fly pheromone Z-(9)-Tricosene added into the formulation. QuickBayt ® has a Z-(9)-Tricosene content of 1.0 g/ kg whereas Agita  ® only has 0.5 g/kg. Thediscrepancy in the mean number of fliesfeeding on the baits could be due to thedifference in the application methods of baits.Results of the present study show thatthere was no significant difference in theefficacy of Quick Bayt ®  and Agita  ® . Thiscontradicts results of the study by Novartis Animal Health Inc. (2002) in two pig-breeding units in Poland where Agita  ® demonstrated clear superiority compared toimidacloprid against houseflies. There weresignificant differences in the accumulatednumber of dead flies after 24 hours as wellas the reduction of live flies on animalsbetween the two products. When usedagainst fruit flies (Tephritidae) however,thiamethoxam (2-4% AI) was significantlyless effective than imidacloprid (2% AI)(Ayyappath et al.,  2000). Unlike the previous Figure 3. The efficacy of Quick Bayt ®  and Agita  ®  in the field showing the weekly mean percentageof flies knocked down by the baits. Values are mean ± SD. 126 - 133 Nurita AT.pmd8/15/2008, 11:32 AM130
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