Residual Bioassay to Assess the Toxicity of Acaricides Against Aceria guerreronis (Acari: Eriophyidae) Under Laboratory Conditions

Transcription

1 Residual Bioassay to Assess the Toxicity of Acaricides Against Aceria guerreronis (Acari: Eriophyidae) Under Laboratory Conditions Author(s): Vaneska B. Monteiro, Debora B. Lima, Manoel G. C. Gondim, Jr., and Herbert A. A. Siqueira Source: Journal of Economic Entomology, 105(4): Published By: Entomological Society of America DOI: URL: BioOne ( is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne s Terms of Use, available at Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.

2 INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT Residual Bioassay to Assess the Toxicity of Acaricides Against Aceria guerreronis (Acari: Eriophyidae) Under Laboratory Conditions VANESKA B. MONTEIRO, DEBORA B. LIMA, 1 MANOEL G. C. GONDIM, JR., AND HERBERT A. A. SIQUEIRA Departamento de Agronomia-(Entomologia), Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros s/n, Dois Irmãos, , Recife, PE, Brazil J. Econ. Entomol. 105(4): 1419Ð1425 (2012); DOI: ABSTRACT Aceria guerreronis Keifer (Acari: Eriophyidae) is considered a major pest of the coconut (Cocos nucifera L.), and the use of pesticides is the current method to control it. However, no standard toxicological tests exist to select and assess the efþciency of molecules against the coconut mite. The aim of this study was to develop a methodology that allows for the evaluation of the relative toxicity of acaricides to A. guerreronis through rapid laboratory procedures. We conþned A. guerreronis on arenas made out of coconut leaßets and tested two application methods: immersing the leaf fragments in acaricides and spraying acaricides on the leaf fragments under a Potter spray tower. In the latter application method, we sprayed leaf fragments both populated with and devoid of mites. We evaluated the comparative toxicity of two populations (Itamaracá and Petrolina, Pernambuco, Brazil) by spraying on leaßets without mites and submitted the mortality data to probit analysis after 24 h of exposure. No difference was observed in the LC 50, regardless of whether the leaßets were immersed or sprayed with acaricide (abamectin, chlorfenapyr or fenpyroximate). The toxicity of chlorfenapyr and fenpyroximate did not differ, irrespective of whether it was applied directly to the leaßet or to the mite; however, the toxicity of abamectin was higher when applied directly to the mite. Chlorpyrifos and abamectin toxicities were lower for the Petrolina population than for the Itamaracá population. Immersing and spraying coconut leaßets can be used to assess the mortality of A. guerreronis under laboratory conditions. KEY WORDS Cocos nucifera, method, standardization, pesticide The mite Aceria guerreronis Keifer (Acari: Eriophyidae) is considered a major pest of the coconut (Cocos nucifera L.) (Moore and Howard 1996, Fernando et al. 2002, Seguni 2002, Lawson-Balagbo et al. 2008). These eriophyid mites build their colonies beneath the fruitõs perianth (the area of the fruit covered by bracts) and create a triangular white patch on the fruitõs skin. This patch becomes necrotic and spreads over most of the fruitõs surface as it develops (Haq et al. 2002, Fernando et al. 2003, Lawson-Balagbo et al. 2007b). Often, this process will cause the fruit to abort (Moore and Howard 1996, Nair 2002). A. guerreronis causes signiþcant losses in all coconut growing regions of the world, severely reducing the number of fruits per bunch. The fruits that do not abort are usually smaller and weigh less and thus are worth less (Moore 2000, Ferreira et al. 2002, Haq et al. 2002). The losses that this mite causes in Africa and Latin America range from 10 to 80% per harvest (Mariau and Julia 1970, Olvera-Fonseca 1986, Moore et al. 1989). Recently, A. guerreronis was introduced in to Asia, greatly affecting major coconut producer 1 Corresponding author, deboralima_85@yahoo.com.br. countries such as India and Sri Lanka (Fernando et al. 2002, Nair 2002). A. guerreronis predators have been under evaluation both in the laboratory and in the Þeld (Lawson- Balagbo et al. 2007a,b; Domingos et al. 2010, Fernando et al. 2010). Currently, producers usually control the mite with synthetic or biorational acaricides (Moore and Alexander 1987, Moreira and Nascimento 2002, Ramaraju et al. 2002, Lokesh 2008). However, because the mites inhabit the fruit perianth, acaricide efþciency is hampered (Ferreira et al. 2002, Haq et al. 2002). Moreover, the coconut dossal size and low production hinder the adoption of the regular application of acaricides (Ferreira et al. 2002, Moreira and Nascimento 2002), and there are no suitable sprayers on the market to apply acaricides over developing coconut clusters. Some studies have investigated the efþcacy of synthetic and botanical acaricides in controlling A. guerreronis (Moore and Alexander 1987, Cabrera 1991, Muthiah et al. 2001, Moreira and Nascimento 2002, Lokesh 2008). However, these tests have been performed exclusively in the Þeld, which hinders the rapid assessment and comparative toxicity of these /12/1419Ð1425$04.00/ Entomological Society of America

3 1420 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 4 molecules to the mite. These studies typically correlate the population density of A. guerreronis with injury intensity scales (Mariau 1977, Moore et al. 1989) or with estimates of the number of mites beneath the fruit perianth (Fernando et al. 2003, Siriwardena et al. 2005, Galvão et al. 2008, Pushpa and Nandihalli 2010). The procedure is time consuming and prone to errors in both cases (Galvão et al. 2008). The performance of toxicological tests in the laboratory is essential in selecting and evaluating molecules for the control of arthropods. These tests are also useful for diagnosing resistance and evaluating selectivity to natural enemies (IRAC 2009). The advantages and drawbacks of many of these procedures have been discussed previously (Hassan 1977, Havron et al. 1987); the testing of molecules against the coconut mite has not been standardized perhaps because of its tiny size ( 100Ð150 m in length), delicate exoskeleton, negative phototropism, and high host-speciþcity behavior (Moore and Howard 1996). These characteristics make it difþcult to conþne and maintain the mite in arenas for long periods or on speciþc parts of plants under laboratory conditions (de Silva and Fernando 2008). Therefore, this work aimed to develop a standard and practical toxicological method for measuring acaricide toxicities on A. guerreronis. Materials and Methods A. guerreronis Colony. Coconut fruit infested with A. guerreronis were collected in Itamaracá-PE ( S, W) and Petrolina-PE ( S, W) municipalities from July 2009 until December The Itamaracá population was collected on a small island off the coast of Pernambuco where no pesticides have been used. The Petrolina population came from a commercial Þeld of coconuts that was controlled with regular applications of abamectin (9 g/ha) during Before this time, grower was monthly alternating sprays of abamectin and carbosulfan. Fruit were collected, transported to the laboratory, and stored (27 2 C, 70 10% RH, and a photoperiod of 12:12 [L:D] h). Mites from coconuts stored up to 5 d after collection were harvested as needed, because at those conditions, health alterations of mites are not observed. Experimental Unit. The leaßets used for constructing the experimental units were removed from leaf no. 14, starting from the Þrst open leaf (Sobral 1994) of ÔGreen DwarfÕ coconut. A rectangular piece of leaßet (3.5 by 2.5 cm), with the lower surface side up, was placed on a Þlter paper disc (9 cm in diameter), and its margins were covered with pieces of paper towels. The Þlter paper disc was placed inside a petri dish containing same-diameter polyethylene foam (1 cm in thickness) (Fig. 1A). The foam was moistened with distilled water to keep the leaßets turgid. The petri dish was sealed with a clear acrylic lid, containing a 4-cm-diameter screen vent to prevent condensation within the unit (Fig. 1B). Acaricide Bioassays. Five commercial acaricides or insecticides in four groups were used in the bioassays (Table 1). Method 1. Potter Tower Spray of Coconut Leaflets. Seven to eight concentrations of each acaricide molecule were used in the bioassays. They were chosen after a range of 10 factor concentrations was tested in a preliminary bioassay to establish an all or none response. The acaricide formulations were dissolved in distilled water, and the control consisted of only water. The experimental unit was sprayed with 1.5 ml of each concentration of acaricide or water in the Potter tower (Standard model, Burkard ScientiÞc, Rickmansworth, Herts, United Kingdom) and calibrated at 10 psi according to IOBC/WPRS Methodology (Hassan et al. 1985) that corresponded to an average deposition of 2.5 mg/cm 2 water droplets. After applying the solution, the arena was left to dry under room temperature for 15 min, after which 30 A. guerreronis females were transferred to each experimental unit (Fig. 1C) by using a brush with a single bristle. Each treatment was repeated three times. Finally, all units were transferred to an incubator at 27 C, 70 10% RH, and 24 h of scotophase. The evaluations were performed after 24 h of exposure, when total and dead mites were counted. Mites were considered dead if no movement was observed after being prodded by a brush. The whole bioassay was repeated more two times on different days. Method 2. Potter Tower Spray of A. guerreronis. This procedure was similar to method 1, except that mites were Þrst transferred to a petri dish and sprayed with the treatments. After spraying, 30 mites were transferred to each experimental unit. An all or none response was also established, and bioassays were repeated three times on different days. Method 3. Coconut Leaflet Immersion. Rectangular coconut leaßets (3.5 by 2.5 cm) were immersed (method 4 in the series of susceptibility test methods of the Insecticide Resistance Action Committee) in each treatment for 5 s and left to dry for 15 min at room temperature. After drying, the leaßets were used to mount the experimental unit, as in methods 1 and 2. Subsequent procedures were similar to the procedures used in those methods as well. Statistical Analysis. Bioassays that showed mortality rates 10% in the control were discarded, and the entire bioassay was repeated. Mortality data were subjected to probit analysis (Finney 1971) at P 0.05 by using the POLO-Plus 2.0 (LeOra Software 2005) after correcting for natural mortality observed in the controls (Abbott 1925). To test for differences between methods, the null hypothesis that slopes and intercepts of the regression lines were the same was tested with the likelihood ratio test for equality within the POLO-Plus 2.0. This procedure was also performed to test for equality among bioassay replications, and pooled population bioassay data for each acaricide were again analyzed by probit analysis using POLO- Plus 2.0. The toxicity ratios were calculated by the lethal ratio test and were considered signiþcant when

4 August 2012 MONTEIRO ET AL.: ACARICIDE TOXICITY TO A. guerreronis 1421 Fig. 1. Excised coconut leaßet method. (A) Plate has no cover. (B) Window is covered with a 40- m mesh Pecap polyester screen. (C) A. guerreronis on the experimental unit. the 95% conþdence interval (CI) did not include the value 1.0 (Robertson and Preisler 1992). Results All methods tested were effective for evaluating the toxicity of acaricides on A. guerreronis. The probit model Þtted the bioassay data ( 2 value not signiþcant, P 0.05), making it possible to estimate any lethal concentrations (LCs). The LC 50 s ranged from 0.51 to mg/liter and LC 95 s ranged from 3.52 to mg/liter for the acaricides applied through the Potter spray tower and from 0.52 to and 2.93 to mg/liter for the acaricides applied by immersion (Table 2). The curves were similar for each product in both methods after an equality test (abamectin: , P 0.05; fenpyroximate: , P 0.05; and chlorfenapyr: , P 0.05). Based on the overlapping CIs, there was no signiþcant difference between the LCs and the toxicity ratios for each Table 1. Acaricides used in the A. guerreronis bioassays Acaricide or insecticide Formulation Class (IRAC group a ) Manufacturer Abamectin Kraft 36 CE Chloride channel activator (group 6) Cheminova Brasil Ltda Chlorfenapyr Pirate Uncoupler of oxidative phosphorylation via disruption Basf Brasil of proton gradient (group 13) Fenpyroximate Ortus 50 SC Mitochondrial complex I electron transport inhibitors Arysta LifeScience (group 21) Chlorpyrifos Klorpan 480 CE Acetylcholine esterase inhibitor (group 1B) Nufarm Brasil Methamidophos Tamaron BR Acetylcholine esterase inhibitor (group 1B) Bayer CropScience Brasil a Mode of action group, as given by IRAC.

5 1422 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 4 Table 2. Toxicity of acaricides to A. guerreronis (Itamaracá-PE pop) applied on coconut leaflets by Potter tower and immersion Acaricide N a Slope SE LC 50 (CI 95%), mg/liter water LC 95 (CI 95%) 2 (P) df TR 50 (95% FL) b Potter spray tower Abamectin (9.24Ð37.89) (54.88Ð110.76) 3.71 (0.59) (16.6Ð28.1) c Chlorfenapyr (0.96Ð1.56) 3.82 (2.65Ð8.41) 5.19 (0.27) (1.9Ð3.1) c Fenpyroximate (0.36Ð0.69) 3.52 (2.29Ð7.04) 6.37 (0.27) 5 Ñ d Immersion Abamectin (9.96Ð14.79) (63.84Ð136.48) 2.33 (0.80) (17.4Ð31.3) c Chlorfenapyr (0.92Ð1.29) 4.62 (3.46Ð7.01) 3.22 (0.52) (1.6Ð2.8) c Fenpyroximate (0.38Ð0.68) 2.93 (1.99Ð5.30) 5.31 (0.38) 5 Ñ a Total number of mites. b Toxicity ratio, Þducial limits at 95%. c Toxicity ratio signiþcant (Þducial limits does not include the value 1.0). d Ñ, calculated between the estimated LC 50 for the acaricides and fenpyroximate through Robertson and Preisler (1992). product either by Potter spray tower or immersion approach. Comparisons of the Potter spray tower method in the presence and absence of A. guerreronis showed differences for fenpyroximate, abamectin, and methamidophos. LC 50 s ranged from 2.82 to mg/liter and LC 95 s ranged from to 1, mg/liter for the products tested when applied through the Potter spray tower in the presence of A. guerreronis and from 0.86 to 3, and 5.05 to 12, mg/liter when applied in the absence of the mite (Table 3). The curves did not differ by the equality test between the approaches for fenpyroximate ( , P 0.05) and chlorfenapyr ( , P 0.05), regardless of whether the products were applied to the leaßet or to the mites. Fenpyroximate was the most toxic acaricide to A. guerreronis, followed by chlorfenapyr and abamectin, irrespective of the method used. Where products were applied to leaßet, it is fenpyroximate, chlorfenapyr, and abamectin. However, where products were applied to mites, it is fenpyroximate, abamectin, and chlorfenapyr. Both chlorpyrifos and methamidophos were not very toxic to A. guerreronis although the former was much more toxic than the latter. Table 4 lists comparisons of product toxicity between two populations of A. guerreronis. Both populations exhibited a similar spectrum of susceptibility to the acaricides or insecticides, with fenpyroximate being the most toxic to both populations, followed by chlorfenapyr, abamectin, chlorpyrifos, and methamidophos. SigniÞcant differences in the toxicity ratio were observed in both populations for all products except for fenpyroximate. However, increased tolerance to abamectin and chlorpyrifos (3.5 and 3.2, respectively) was observed in the Petrolina population. Discussion Coconut cropping is becoming very important in the São Francisco Valley of Brazil. Increasing coconut yield requires many inputs by producers, particularly those producers in Petrolina municipality. The coconut mite has become a recurrent pest requiring more attention from growers. A few products, including fenpyroximate, hexythiazox, and spirodiclofen, are registered in Brazil to control A. guerreronis; however, producers in the Petrolina area typically use abamectin to control this mite. Table 3. Toxicity of acaricides to A. guerreronis (Itamaracá-PE pop) applied by Potter spray tower Acaricide N a Slope SE LC 50 (CI 95%), mg/liter water LC 95 (CI 95%) 2 (P) df TR 50 (95% FL) b Potter spray tower of A. guerreronis Fenpyroximate (2.31Ð3.33) (13.27Ð22.97) 3.77 (0.52) 5 Ñ c Abamectin (6.75Ð9.13) (37.08Ð64.13) 4.61 (0.46) (2.2Ð3.6) d Chlorfenapyr (6.48Ð11.31) (32.65Ð85.88) 7.62 (0.18) (2.5Ð4.0) d Chlorpyrifos (124.58Ð247.18) 1, (764.70Ð1.4E3) 8.46 (0.54) (50.2Ð86.1) d Methamidophos (369.03Ð980.23) 12, (7.1E3Ð28.0E3) 4.82 (0.43) (143.2Ð389.6) d Potter spray tower of coconut leaßets Fenpyroximate (0.65Ð1.15) 5.05 (3.26Ð10.11) 7.04 (0.22) 5 Ñ Chlorfenapyr (4.68Ð10.47) 46.6 (27.17Ð129.88) 8.66 (0.12) (6.3Ð11.1) d Abamectin (11.05Ð15.94) (62.23Ð114.77) 3.09 (0.69) (12.3Ð20.0) d Chlorpyrifos (38.46Ð135.99) (811.94Ð3.7E3) 6.29 (0.13) (68.5Ð143.9) d Methamidophos , (3.0E3Ð4.1E3) 12, (9.6E3Ð16.8E3) 6.07 (0.27) 4 4,189.9 (3.3E3Ð5.0E3) d a Total number of mites. b Toxicity ratio, Þducial limits at 95%. c Ñ, calculated between the estimated LC 50 for the acaricides and fenpyroximate through Robertson and Preisler (1992). d Toxicity ratio signiþcant (Þducial limits does not include the value 1.0).

6 August 2012 MONTEIRO ET AL.: ACARICIDE TOXICITY TO A. guerreronis 1423 Table 4. Comparative toxicity of acaricides for two A. guerreronis populations by Potter spray tower of coconut leaflets Acaricide Mite strain N a Slope SE LC 50 (CI 95%), mg/liter water LC 95 (CI 95%) 2 (P) df TR 50 (95% FL) b Abamectin Itamaracá (10.79Ð14.41) (61.03Ð106.68) 2.51 (0.77) 5 Ñ c Petrolina (39.03Ð50.22) (347.31Ð558.67) 4.74 (0.58) (2.2Ð5.6) d Chlorfenapyr Itamaracá (6.46Ð11.51) (28.69Ð88.95) 8.46 (0.13) 5 Ñ Petrolina (4.34Ð6.05) (28.67Ð48.67) 3.24 (0.66) (0.4Ð0.8) d Fenpyroximate Itamaracá (0.52Ð0.80) 3.53 (2.63Ð5.29) 5.79 (0.33) 5 Ñ Petrolina (0.39Ð0.85) 3.86 (2.64Ð7.61) (0.05) (0.8Ð1.2) Chlorpyrifos Itamaracá (38.46Ð135.99) (811.94Ð3.7E3) 6.29 (0.13) 4 Ñ Petrolina (236Ð310.93) (1.3E3Ð2.1E3) 3.72 (0.35) (1.1Ð9.0) d Methamidophos Itamaracá (3.0E3Ð4.1E3) (9.6E3 16.8E3) 6.07 (0.29) 4 Ñ Petrolina ( E3) (14.3E3Ð44.8E3) 7.84 (0.84) (0.3Ð0.4) d a Total number of mites. b Toxicity ratio, Þducial limits at 95%. c Ñ, calculated between the estimated LC 50 for Itamaracá and Petrolina populations through Robertson and Preisler (1992). d Toxicity ratio signiþcant (Þducial limits does not include the value 1). A major problem in chemically controlling A. guerreronis in coconut crops is the lack of methods available for evaluating the toxicity of acaricides toward these mites, in particular the evolution of resistance. The lack of data is largely a result of the difþculty of raising mites in the laboratory and in the Þeld. There are no mite diets available, they do not stand on harvested coconuts for a signiþcant period of time, and they are too small to be handled. This study is the Þrst attempt to establish reproducible, repeatable, practicable, and low-cost bioassays to evaluate the toxicity of acaricides against coconut mites. After unsuccessfully attempting to treat the coconut perianth with acaricides, the use of leaflets from coconut trees emerged as the best way to perform bioassays. As far as we know, this is the Þrst time that pesticide bioassays have successfully evaluated toxicity toward A. guerreronis. Methods for assessing the efþciency of acaricides against this pest were developed previously (Moreira and Nascimento 2002, Lokesh 2008, Pushpa and Nandihalli 2010). However, researchers based the evaluation criterion on either the population dynamics in the perianth or on the injury scale over the fruit epidermis, both of which can cause errors (mainly because of mite habits). Conversely, criteria based on mite mortality would be more appropriate for evaluating acaricide efþcacies. Acaricides cannot reach coconut mites easily (Ferreira et al. 2002, Haq et al. 2002) because the mites develop in the perianth, part of the drupe protected by bracts (Moore and Alexander 1987). Acaricides particularly act when mites disperse in search of new feeding sites. Dispersion usually intensiþes in drupes that are 4 mo of age because of intra- and interspeciþc competition and because of factors related to food quality (Fernando et al. 2003, Galvão et al. 2011). The evaluation criterion based on the mitesõ population density in the perianth ignores the fact that mites may disperse after drupe detachment from plants. Moreover, the number of living and dead mites in the perianth cannot usually be determined when using this criterion. Therefore, population density methods may under- or overestimate the efþcacy of acaricides. Because A. guerreronis is associated with several predators from the Ascidae and Phytoseiidae families (Moraes et al. 2004, Lawson-Balagbo et al. 2008), one also may fail to consider the possible side effects of acaricides on natural enemies in experiments using the injury scale criterion, as the toxicity of acaricides may reduce the population of beneþcial organisms and indirectly inßuence the mitesõ population density. We suggest rectifying these drawbacks by sampling mites from the perianth (thereby providing a known number of tests) and using mortality as a criterion to assess acaricide toxicities. Both Potter spray tower and immersion methods showed similar results. We tested acaricides or insecticides with Potter spray tower because it is a standard method for evaluating mite toxicity. However, those who lack a Potter spray tower also may use the immersion method without reducing the quality of the results. The LC 50 s and LC 95 s were comparable in both cases. To increase the convenience of the Potter spray tower method as well as to simulate its effect on mites when they are sprayed with acaricides in the Þeld during dispersal, we tested the response to acaricides by either spraying the arenas before transferring the A. guerreronis or directly spraying the A. guerreronis and then transferring them to the arenas. Although these approaches produced similar results only for chlorfenapyr, for abamectin and fenpyroximate they were more toxic when applied directly to the mite and sprayed in the arena devoid of mites, respectively. Possible explanations for these outcomes may be related to the time of penetration for the acaricide and the behavioral responses of the mites (such as to stimulation or inhibition of locomotion). A more rapid penetration of the product can overwhelm detoxiþcation mechanisms and lead to faster organism death (Cochran 1995). A. guerreronis has only two pairs of legs on the front of its body; by moving its body, it contacts the acaricide-treated surface (Lindquist 1996). Thus, stimulating locomotion can lead to greater molecules uptake (Cochran 1995). The spray method most accurately simulates what occurs in the Þeld. In general, chemical control is performed proactively. However, this method requires handling the mites twice, which can kill them

7 1424 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 4 because of their fragile bodies. Therefore, we sprayed the arena without mites to compare the Itamaracá and Petrolina populations. The Petrolina population was collected in a Þeld under a regular regimen of abamectin sprays; therefore, the difference in the toxicity ratio may suggest an onset of resistance to abamectin. This result indicates that the continued use of abamectin may select mite populations for resistance to this product. Because Itamaracá population was never sprayed with pesticides, differences observed for both chlorfenapyr and methamidophos might be associated with a negative cross-resistance to abamectin. However, further studies with synergist, for example, could clarify this hypothesis. Also, these outcomes could be a mere natural response of both populations, particularly because of the inconsistence of chlorpyrifos toxicity ratio, for which would be also expected a negative cross-resistance to abamectin like with methamidophos, both proinsecticides activated by mixed function oxidases. Unless another resistance mechanism is developing in the Petrolina population to chlorpyrifos, probable cross-resistance exists between abamectin and chlorpyrifos or data reßect a natural variation in this species to both. The spray method is also suitable for assessing topical products. Fenpyroximate and chlorfenapyr toxicity was the same regardless of whether the product was applied directly to the mite or to the leaßet (residual effect). This is particularly important to the mite management because mites mortality inßicted by products in the Þeld resumes only while mites are dispersing, by walking over sprayed fruit. At spray moment most of the mitesõ population is concealed in the perianth, thus protected from direct contact with the products. Therefore, development of these approaches was necessary to validate studies based on toxicological evaluation of acaricides either in the Þeld or in the laboratory. This study provides a tentative standardization of bioassays to evaluate pesticide toxicity to A. guerreronis. Potter tower spraying and leaflet immersion are cheap, practical, and efþcient methods for assessing mite toxicity. Acknowledgments We thank the National Council of ScientiÞc and Technological Development-CNPq for the assistantship to the Þrst author through the ScientiÞc Starter Program and for the Þnancial support for this project. References Cited Abbott, W. S A method of computing the effectiveness of an insecticide. J. Econ. Entomol. 18: 265Ð267. Cabrera, R El ácaro Eriophyes guerreronis, su importancia econômica y métodos de lucha. Estación Nacional de Sanidad de los Citricos y otros Frutales, Habana, Cuba. Cochran, D. G Insecticide resistance, pp. 171Ð192. In M. K. Rust, J. M. Owens, and D. A. Reierson (eds.), Understanding and controlling the German cockroach. Press, Cambridge, Oxford University, England. de Silva, P.H.P.R., and L.C.P. Fernando Rearing of coconut mite Aceria guerreronis and the predatory mite Neoseiulus baraki in the laboratory. Exp. Appl. Acarol. 44: 37Ð42. Domingos, C. A., J.W.S. Melo, M.G.C. Gondim, Jr., G. J. de Moraes, R. Hanna, L. M. Lawson-Balagbo, and P. Schausberger Diet-dependent life history, feeding preference and thermal requirements of the predatory mite Neoseiulus baraki (Acari: Phytoseiidae). Exp. Appl. Acarol. 50: 201Ð215. Fernando, L.C.P., I. R. Wickramananda, and N. S. Aratchige Status of coconut mite, Aceria guerreronis in Sri Lanka, pp. 1Ð8. In L.C.P. Fernando, G. J. de Moraes, and I. R. 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