Printer Friendly

Effect of contact and systemic insecticides on the sharpshooter Bucephalogonia xanthophis (Hemiptera: cicadellidae), a vector of xylella fastidiosa in citrus.

Brazilian citriculture has been affected by diseases associated with insect vectors, such as Citrus variegated chlorosis (CVC), whose causal agent is a vector-borne bacterium, Xylella fastidiosa Welles et al., 1987; Xanthomonadales: Xanthomonadaceae. The vectors are leafhoppers from the subfamily Cicadellinae (Hemiptera: Cicadellidael, also called sharpshooters. Around 40 species of sharpshooters are registered as vectors of X. fastidiosa, but less than 1/3 of them are associated with plant disease epidemics (Redak et al. 2004). In the case of CVC, 12 sharpshooter species have been identified as vectors (Redak et al. 2004; Yamamoto et al. 2007), but only Acrogonia citrina Marucci & Caviehioli, Bucephalagonia xanthophis (Berg), Dilobopterus costalimai Young and Oncometopia facialis (Signoret) are commonly found on citrus trees (Paiva et al. 1996). Among them, B. xanthophis is the predominant species in open nurseries and young citrus orchards up to 2 yr old (Roberto et al. 2000; Yamamoto et al. 2001), the period when citrus plants are most vulnerable to X. fastidiosa infection. Disease management during this critical period involves rogueing of diseased plants (reduction of inoculum sources) and vector control (Lopes, 1999).

In the absence of other effective vector control methods, insecticide applications in citrus orchards are important to suppress sharpshooter populations and reduce CVC spread. The application of systemic insecticides in the soil or on the plant trunk is a strategy recommended to control the sharpshooter O. facialis on young citrus trees (Yamamoto et al. 2000, 2001, 2002a, 2002b, 2003). Older citrus orchards need aerial sprays for vector control because the uptake and distribution in the tree canopy of soil-applied systemic insecticides is inefficient (Yamamoto et al. 2002a).

There are no insecticides registered for control of B. xanthophis on citrus in Brazil and the effects of insecticides on this sharpshooter species are undocumented to date. Ideally any contact or systemic insecticide should act rapidly on the insect vector, if possible preventing stylet penetration or feeding on the plant, in order to avoid pathogen transmission. Therefore, the knockdown and toxic effects of different chemical groups and modes of action of insecticides registered for citrus were investigated for the control of B. xanthophis.

MATERIAL AND METHODS

Insects and Plants

A healthy colony of B. xanthophis was established on plants of Vernonia condensata Baker (Asteraceae), as described by Marucci et al. (2003), with adults collected on young branches of the ornamental shrub, Duranta repens L., in Piracicaba, SP, Brazil. The colony was maintained in a greenhouse without exposure to insecticides, and oviposition cages were set up every 2 wk in order to obtain adults of known age (1-2 wk old) for the experiments.

The citrus plants used in the experiment were healthy sweet orange [Citrus sinensis (L.) Osbeck, cv. PeraJ nursery trees, grafted on rangpur lime {Citrus x limonia Osbeckl, kept in a vector-proof greenhouse. The nursery trees were about 1 m high, grown in 5-L plastic bags containing potting soil mix (Tropstrato V8[R]), and fertilized weekly with macronutrients (ammonium nitrate and calcium nitrate) and micronutrients (magnesium sulfate, potassium nitrate, monoammonium phosphate, zinc, copper and iron) diluted in the irrigation water and applied on the plants. The plants were pruned 3-4 wk before the experiment, and treated with insecticides when the young shoots showed totally expanded leaves. The experiments were carried out in a greenhouse with temperatures in the range of 20-32 [degrees]C.

Insecticides

The commercial formulations of 4 insecticides, from different chemical groups and modes of action, were evaluated (Table 1). All the insecticides are registered for citrus pest management in Brazil. Provado[R] (imidacloprid) and Actara[C] (thiamethoxam) are registered for control of the sharpshooter, O. facialis. Karate[R] (lambda-cyhalothrin) is registered to control the sharpshooter, D. costalimai. Finally, Perfekthion[R] (dimethoate) is not registered for sharpshooters, but is registered for the control of other piercing-sucking insects, e.g. mealybugs and aphids (Agrofit 2012).

Contact Effect

The active ingredients, dimethoate (1 mL/L), imidacloprid (0.2 mL/L), lambda-cyhalothrin (0.2 mL/L) and a control (water), were sprayed onto citrus nursery trees using a compression sprayer (Guarany[R]), covering the whole plant until product runoff, as in field applications. After the spraying and drying of the insecticides, groups of 10 adult sharpshooters per replicate were confined to a single branch of the treated plants using sleeve cages. Insect mortality was evaluated at 2 h (knockdown), 24 h and 48 h after confinement. The experimental design was completely randomized with 4 treatments (insecticides) and 5 repetitions.

Residual Contact Effect

The active ingredients, dimethoate (1 mL/L), imidacloprid (0.2 mL/L|, lambda-cyhalothrin (0.2 mL/L) and a control (water), were sprayed onto new nursery trees using a compression sprayer (Guarany[R]), as described in the previous experiment. At intervals of 1, 2, 3, 6 and 8 wk after insecticide spraying, groups of 10 adult sharpshooters were confined on a single branch of the treated plants with sleeve cages. Insect mortality was evaluated at 2 h (knockdown), 24 h and 48 h after confinement. Different groups of plants were used for assessing insect mortality at each weekly interval after insecticide application. The experimental design was completely randomized with 4 treatments and 5 repetitions per weekly interval.

Systemic Effect

The insecticides thiamethoxam (Actara 250 WG) and imidacloprid (Provado 200 SO were diluted into 5 concentrations and 50 mL of each dilution were applied per plant in the soil (via "drench"). Ten days after application, groups of 10 sharpshooters were confined to a single branch of the treated plants with sleeve cages. Insect mortality was evaluated at 2 (knockdown), 24 and 48 h after sharpshooter confinement. The experimental design was entirely randomized with 11 treatments (2 insecticides x 5 dilutions and a control) and 5 repetitions.

Data Analysis

The mortality data of the contact effect experiment were submitted to a factorial (4 x 3) analysis of variance using the F and Tukey's test, with factors represented by the 'insecticide treatments' (dimethoate, imidacloprid, lambda-cyhalothrin or water) and the 'contact time' (2 h, 24 h or 48 h). For the residual contact experiment, the mortality data of each time interval after insecticide application (1, 2, 3, 6 and 8 wk) were submitted to a factorial (4 x 3) analysis of variance using the F and the Tukey tests, with 'insecticide treatments' (dimethoate, imidacloprid, lambda-cyhalothrin or water) and the 'contact time' (2 h, 24 h or 48 h) as factors. In the systemic effect experiment, the mortality data were submitted to an analysis of variance using the F test and the Tukey tests, with a 11 x 3 factorial design, in which the 'insecticide treatments' and the 'exposure time' (2 h, 24 h or 48 h) were considered as factors. The tests of Bartlett (Bartlett 1937) and Shapiro-Wilk (Shapiro & Wilk 1965) were applied to evaluate the assumptions of homoscedasticity for treatment variances and residual normality, respectively. The analyses in this study were done using the SAS statistical software (SAS Institute, 2003).

RESULTS

Contact Effect

The active ingredients imidacloprid and lambda-cyhalothrin caused a knockdown effect on the sharpshooter (Table 2), with more than 80% mortality to confined insects immediately after spraying and evaluated after 2 hr of confinement (F = 21.69; P < 0.0001). After 24 hr, the 3 insecticides (imidacloprid; lambda-cyhalothrin and dimethoate) caused a high mortality to B. xanthophis (F = 379.72; P < 0.0001), and after 48 hr, practically 100% of the adults were killed by the insecticides (F = 200.81; P < 0.0001). There was an interaction between the insecticides and the contact time (F = 11.40; P < 0.0001).

Residual Contact Effect

There was an interaction between the treatments and the contact time for wk 1 (F - 4.27; P = 0.0016) and wk 2 (F = 2.74; P = 0.0226) for the residual analysis of the first 2 wk. However, this interaction was not found after the third wk (Table 3). Considering only the first 2 hr of contact, it was observed that the insecticide lambda- cyhalothrin caused 78% and 48% mortality in the first and second wk after spraying, respectively, differing from the control [wk 1 (F = 7.14; P = 0.0029); wk 2 (F = 4.41; P = 0.0193 )] (Table 3).

After 24 hr of contact, it was found that the 3 insecticides caused significant mortality to confined insects for up to 3 wk after spraying [wk 1 (F = 35.58; P < 0.0001); wk 2 (F - 19.80; P < 0.0001); wk3 (F= 6.96; P - 0.0033 )]. The residual activity of the 3 insecticides after 48 hr of contact was consistent until 21 d after spraying (wk 3). During these 3 wk, the active ingredients differed significantly from the control [wk 1 (F - 111.49; P < 0.0001); wk 2 (F = 24.78; P < 0.0001); wk 3 (F = 11.55; P = 0.0003)]. Insecticide efficiency for this period was a 70% (Table 3). The sixth week showed no significance between treatments [wk 6 <F = 2.98; P = 0.0626)J. Finally, in the eighth week, treatments were significantly different [wk 8 (F = 5.98; P = 0.0062)], but insecticide efficacy was < 70% (Table 3).

Systemic Effect

A significant interaction was found between the each of the 2 insecticide treatments (thiamethoxam and imidacloprid) and insect exposure time on treated plants (F= 8.33; P < 0.0001) (Table 4). There were no mortality differences between treatments when the exposure time was a 24 h, with the exception of imidacloprid at 1.40 ppm. On the other hand, the mortality rates caused by both insecticides during the first 2 h were lower than those observed at 24 and 48 h of exposure to treated plants.

The knockdown effect on the insect vector by ingestion was observed when the insecticides were applied systemically at the highest concentrations (F = 8.92;P < 0.0001) (Table 4). Thiamethoxam caused a knockdown effect on B. xanthophis at a concentration of 20 ppm, and mortality was higher than that caused by the other treatments, with the exception of thiamethoxam at 2 ppm and imidacloprid at 35 ppm. After 24 h of exposure, mortality rates a 80% were observed even for the smallest concentration of the imidacloprid and thiamethoxam (Table 4); the mortality rates caused by all the concentrations differed numerically from the control, although there was no significant statistical difference between them (F = 8.92; P < 0.0001). After 48 h, nearly 100% of the insects were killed by the insecticides (Table 4), and the mortality caused by different insecticide concentrations were similar, only differing from the control (F = 415.31; P < 0.0001). Ninety-six percent of sharpshooters in the control were still alive after 48 h (Table 4).

The insecticides Provado[R] (imidacloprid) and Actara[R] (thiamethoxam) were highly toxic to B. xanthophis after 48 h of exposure (Table 4). Thiamethoxam caused s. 96% mortality in the first 24 h and all concentrations of this insecticide reached 100% efficacy after 48 h (Table 4). For imidacloprid, most concentrations reached 100% efficacy after 48 h; the only exception was 1.74 ppm, with an efficacy of 93.75%.

DISCUSSION

Chemical control has been commonly used to manage diseases caused by X. fastidiosa in various crops, aiming to reduce vector population numbers and their frequency of visits to susceptible crops and inoculum sources. Insecticides may also affect vector behavior and competence for acquisition and inoculation of X. fastidiosa. In the case of oleander leaf scorch, for example, Bethke et al. (2001) observed that insecticides inhibit feeding of the sharpshooter vector, Homalodisca coagulata (Say), resulting in a substantial decrease in transmission efficiency of X. fastidiosa to oleander (Nerium oleander L.; Gentianales: Apocynaceae).

X. fastidiosa has a wide host plant range, which includes species from more than 30 families of mono and dicotyledons (Hopkins 1989; Purcell & Hopkins 1996), and some of them may serve as inoculum sources for infection of susceptible crops (Hopkins 1989; Leite et al. 1997). In Brazilian citrus groves, however, infected trees appear to be the most important (if not the only) sources of inoculums for CVC spread by sharpshooter vectors (Laranjeira, 1997; Lopes 1999). In this case, a knockdown effect of insecticides on sharpshooters could drastically reduce vector efficiency in acquiring and/or inoculating bacterial cells when feeding on treated citrus trees. Based on this hypothesis, we conducted a series of experiments to verify the contact and systemic toxicity as well as possible knockdown effects of some insecticides commonly used in Brazilian citriculture.

We showed that imidacloprid and lambdacyhalothrin cause a contact knockdown effect on the sharpshooter, B, xanthophis, which is an important vector of X fastidiosa in young citrus groves (Yamamoto et al., 2001). These 2 insecticides are registered for citrus in Brazil to control the sharpshooters, O. facialis and D. costalimai, respectively (Agrofit 2012). Both cause mortality by provoking hyperexcitability, but with distinct modes of action. Imidacloprid is a neonicotinoid and acts as an acetylcholine agonist on the postsynaptic nicotinic receptors (Nauen et al. 2001). As a pyrethorid, lambda-cyhalothrin is a sodium channel modulator, causing a potential repetitive action and consequent mortality (Soderlund & Knipple 2003). The knockdown effect of pyrethroids on insects are well known. Imidacloprid is widely used as a systemic insecticide to control piercing-sucking insects (Nauen et at. 1998; 1999), including sharpshooters in citrus orchards and vineyards (Yamamoto et al, 2000; Castle et al. 2005; Byrne & Toscano 2006; Byrne & Toscano 2007). The contact effect of imidacloprid, causing high sharpshooter mortality within a short period of time, is described here for the first time.

It is also important to determine the duration of the crop protection period by using these insecticides. Our data shows that effective knockdown activity by lambda-cyhalothrin is maintained for about 1 wk after spraying, decreasing thereafter. Only 48% and 30% insect mortalities within 2 h of exposure to treated plants were recorded in the second and third weeks after application, respectively. In the case of imidacloprid, no residual knockdown effect was detected.

The contact knockdown effect of insecticides to control sharpshooter vectors of X. fastidiosa has been little studied. However, this effect is very desirable to avoid disease spread. Up to now, only acetamiprid (6 g of active ingredient/100 L) had been described as having a knockdown effect against O. facialis on citrus (Yamamoto et al. 2003), as well as fenpropathrin, fenpropathrin + acephate and carbaryl on H. coagulata on oleander (Bethke et al. 2001).

With longer exposure periods on sprayed plants, B. xanthophis is effectively controlled by imidacloprid, lambda-cyhalothrin and dimethoate through their contact effects. When the insects were confined immediately after the spraying of the active ingredients, about 100% mortality was observed for the 3 insecticides during the first 24 h. The residual contact activity of these compounds lasted for 3 wk after spraying. Other insecticides are also considered effective for controlling sharpshooters by contact action. Pyrethroids such as bifenthrin, esfenvalerate and fenpropathrin were highly toxic to adults and nymphs of H. coagulata under laboratory conditions (Prabhaker et al. 2006a; Prabhaker et al. 2006b). The neonicotinoids imidacloprid and acetamiprid caused mortality to O. facialis adults in a greenhouse study (Yamamoto et al. 2003).

In Brazil, the control of sharpshooter and other vectors of plant pathogens in young citrus groves (up to 3 yr old) is done mainly with systemic insecticides applied in the soil or on the plant trunk. Thus, we already expected an efficient control of B. xanthophis by adopting this strategy. The toxic effect of the 2 systemic insecticides, thiamethoxam and imidacloprid, at all concentrations tested, was indeed very clear after 24 h of sharpshooter exposure to treated plants. Interestingly, we also noted a strong knockdown effect (94% mortality in only 2 h of exposure) caused by thiamethoxam at the highest concentration (20 ppm). This knockdown effect is often less evident for a systemic insecticide applied in the soil than for a contact insecticide sprayed directly on the leaves. In adult citrus trees under field conditions, thiamethoxam needs less time for translocation in the plant compared to imidacloprid (Castle et al. 2005), and this characteristic may explain the greater knockdown effect of thiamethoxam observed on B. xanthophis when applied via soil in citrus nursery trees in the present study. On the other hand, imidacloprid has a greater residual effect on citrus in the field (Castle et al. 2005).

Systemic insecticides are used for sharpshooter control due to their longer residual action compared to contact insecticides. Therefore, they provide a longer protection period to the plant, with a lower number of applications and, consequently, with lower production cost. Apart from this, systemic applications have the advantage of being selective to natural enemies, whose preservation can contribute to an increase in the biological control of citrus pests (Gravena et al. 1997).

Because lambda-cyhalothrin and thiamethoxam have a knockdown effect on B. xanthophix for at least one wk after application, both insecticides might be effective to avoid X. fastidiosa transmission by this sharpshooter. For up to 3 wk, imidacloprid, lambda-cyhalothrin and dimethoate showed an effective contact action that can be helpful to manage CVC by suppressing vector populations and perhaps affecting vector feeding behavior and competence to transmit the pathogen in citrus groves. More detailed studies are needed to confirm the efficacy of these insecticides in preventing bacterial acquisition and/or inoculation by sharpshooters.

ACKNOWLEDGMENTS

We thank the Programa Nacional de Pos-Doutorado --PNPD/CAPES, for awarding a post-doctoral scholarship to the first author and financial support for this research (Process no. 23038.039426/2008-97).

REFERENCES CITED

Agrofit. 2012. Ministerio de Agricultura. Disponivel em; <http://extranet.agricultura.gov.br/agrofit_cons/ principal_agrofit_cons >. Acesso em: 02 Jan. 2012.

Bartlett, M. S. 1937. Properties of sufficiency and statistical tests. Proc. R. Soc. London Series A. 160: 268-282.

Bethke, J. A., Blua, M. J., and Redak, R. A. 2001. Effect of selected insecticides on Homalodisca coagulata (Homoptera: Cicadellidae) and transmission of oleander leaf scorch in a greenhouse study, J, Econ. Entomol. 94: 1031-1036.

Byrne F. J., and Toscano, N. C. 2006. Uptake and persistence of imidacloprid in grapevines treated by chemigation. Crop Prot. 25: 831-834.

Byrne F. J., and Toscano, N. C. 2007. Lethal toxicity of systemic residues of imidacloprid against Homalodisca vitripennis (Homoptera: Cicadellidae) eggs and its parasitoid Gonatocerus ashmmdi (Hymenoptera: Mymaridae). Biol. Control. 43: 130-135.

Castle S. J., Byrne, F. J., Bi, J. L., and Toscano, N. C. 2005. Spatial and temporal distribution of imidacloprid and thiamethoxam in citrus and impact on Homalodisca coagulate populations. Pest Manag. Sci. 61: 75-84.

Gravena S., Lopes, J. R. S., Paiva, P. E. B., Yamamoto, P. T., and Roberto, S. R. 1997. Os vetores da Xylella fastidiosa, pp. 37-53 In L. C. Donadio and C. S. Moreira [eds.], Clorose variegada dos citros. Bebedouro: Estacao Experimental de Citricultura,

Hopkins, D. L. 1989. Xylella fastidiosa: Xylem-limited bacterial pathogen of plants. Aunu. Rev. Phytophatol. 27: 271-290.

Laranjeira, F. F. 1997. Dez anos de clorose variegada dos citros: O que sabemos? Laranja 18:123-141.

Leite, R, M. V. B. C., Leite Jr, R, P., and Cerezine, P. C. 1997. Flutuacao populacional de Xylella fastidiosa em ameixeiras suscetfveis e resistentes a escaldadura da folha. Fitopatol. Brasileira 22: 58-63.

Lopes, J. R. S. 1999. Estudo com vetores de Xylella fastidiosa e implicacoes no manejo da clorose variegada dos citros. Laranja 20: 329-344.

Marucci, R. C, Giustulin, T. A., Miranda, M. P., Miquelote, M" At.mf.ida, R, P. P., and Lopes, J, R, S. 2003. Identification of a non-host plant of Xylella fastidiosa to rear healthy sharpshooter vectors. Sci. Agric. 60: 669-675.

Nauen, R., Hungenberg, H., Tollo, B., Tietjen, K., and Elbert, A. 1998. Antifeedant effect, biological efficacy and high affinity binding of imidacloprid to acetylcholine receptors in Myzus persicae and Myzits nicotianae. Pestic. Sci, 53: 133-140.

Nauen, R., Koob, B., and Elbert, A. 1999. Antifeedant effects of sublethal dosages of imidacloprid on Bemisia tabaci. Entomol. Exp. Appl, 88: 287-293.

Nauen, R., Ebbinghaus-Kintscher, U., Elbert, A., Jeschke, P., and Tietjen, K. 2001. Acetylcoline receptors as sites for developing neonicotinoid insecticides, pp. 77-105 In I. Ishaaya Ted.l, Biochemical sites in insecticide action and resistance. Springer. New York.

Paiva, P. E. B., Silva, J. L., Gravena, S., and Yamamoto, P. T. 1996. Cigarrinhas de xilema em pomares de laranja no Estado de Sao Paulo. Laranja 17: 41-54,

Prabhaker, N., Castle, S. J., and Toscano, N. C. 2006a. Susceptibility of immature stages of Homalodisca coagulate {Hemiptera: Cicadellidae) to selected insecticides, J. Econ. Entomol. 99: 1805-1812.

Prabhaker, N., Castle, S., Byrne, F., Henneberry, T. J., and Toscano, N. C. 2006b. Establishment of baseline susceptibility data to various insecticides for Homalodisca coagulata (Homoptera: Cicadellidae) by comparative bioassay techniques. J. Econ. Entomol. 99: 141-154.

Purcell, A., and Hopkins, D. L. 1996. Fastidious xylemlimited bacterial plant pathogens, Annu. Rev. Phytopathol. 34: 131-151.

Redak, R. A., Purcell, A. H., Lopes, J. R. S., Blua, M. J., Mizell III, R. F., and Andersen, P, C, 2004. The biology of xylem fluid - feeding insect vectors of Xylella fastidiosa and their relation to disease epidemiology Annu. Rev. Entomol. 49: 243-270.

Roberto, S. R., Dalla Pria Junior, W., Yamamoto, P. T., Fet.i.ipe, M. R., and Frettas, E. P. 2000. Especies e flutuacao populacional de cigarrinhas em viveiros de citros, em Gaviao Peixoto (SP). Laranja 21: 65-79. SAS, Institute. 2003. SAS User guide: versao 9.1. Cary, NC.

Shapiro, S. S., and Wilk, M. B. 1965. An analysis of variance test for normality. Biometrika 52: 591-611.

Soderlund, D. M., and Knipple, D. C. 2003, The molecular biology of knockdown resistance to pyrethroid insecticides. Insect Biochem. Mol. Biol. 33: 563-577.

Yamamoto, P. T., Roberto, S. R., and Dalla Pria Junior, W. 2000. Inseticidas sistemicos aplicados via tronco para controle de Oncometopia facialis, Phyilocnistis citrella e Toxaptera citricida em citros. Sci. Agric. 57: 415-420.

Yamamoto, P. T., Roberto, S. R., Dalla Pria Junior, W., Fei.ippe, M, R., Freitas, E, P., Caetano, A. C, and Sanches, A. L. 2001. Inseticidas sistemicos aplicados via tronco no controle da cigarrinha Oncometopia em citros. Laranja 22: 49-63.

Yamamoto, P. T., Felippe, M, R., Caetano, A, C, Sanches, A. L., Almeida, E. J., and Nociti, L. A. S. 2002a. Eficiencia de inseticidas neonicotinoides aplicados via tronco no controle de Oncometopia Facialis (Signoret) (Hemiptera, Cicadellidae) em mudas de laranja 'pera'. Laranja 23: 101-114.

Yamamoto P. T., Dalla Pria Junior, W., Roberto, S. R., Felippe, M. R., Almeida, E. J., and Freitas, E. P. 2002b. Controle quimico da cigarrinha em citros. Laranja 23: 141-154.

Yamamoto, P. T., Felippe, M. R., Nociti, L. A. S., Montesino, L. H., and Coeliio, J. H. C, 2003. Uso deAcetamiprid no controle da cigarrinha em citros. Laranja 24: 337-351.

Yamamoto, P. T., Feldppe, M. R., Caetano, A C, Sanches, A L., and Lopes, J, R. S. 2007, First report oTFingeriana dubia Cavichioli transmitting Xylella fastidiosa to citrus. Fitopatol. Brasileira 32: 266-267.

GERANE CELLY DIAS BEZERRA-SILVA (1), MARCIO ALVES SILVA (1), MARCELO PEDREIRA DE MIRANDA (2) AND JOAO ROBERTO SPOTTI LOPES (1)

(1) Department of Entomology and Acarology, ESALQ/University of Sao Paulo, CP. 9, 13418-900, Piracicaba, SP, Brazil

(2) Fundecitrus, CP 391,14807-070, Araraquara, SP, Brazil

* Corresponding author; E-mail: gcdbezerra@gmail.com
TABLE 1. INSECTICIDES TESTED AGAINST BUCEPHALOGONIA
XANTHOPHIS IN THE ASSAYS.

Active ingredient     Trade name          Class

Dimethoate            Perfekthion         Organoph osph ate
Imidacloprid          Provado 200 SC      Neonicotinoid
Lambda-cyhal othrin   Karate Zeon 50 CS   Synthetic Pyrethroid
Thiamethoxam          Actara 250 WG       Neonicotinoid

Active ingredient     Mode of action                   Manufacturer

Dimethoate            Acetylcholinesterase inhibitor   BASF
Imidacloprid          Nicotinic acetylcholine          BAYER S. A.
                      receptor agonist/antagonist
Lambda-cyhal othrin   Sodium channel modulator         SYNGENTA
Thiamethoxam          Nicotinic acetylcholine          SYNGENTA
                      receptor agonist/antagonist

Active ingredient       (1) Dosage on citrus
                        (cicadellid species)

Dimethoate            -- (2)
Imidacloprid          15 to 20 mL/lOOL
                      (Oncometopia facialis)
Lambda-cyhal othrin   200 to 400 mL/ha
                      (Dilobopterus costalimai)
Thiamethoxam          3g/plant or 600g/ha
                      (Oncometopia facialis)

(1) Dose of commercial product registered for sharpshooter control
(Hemiptera: Cicadellidae} in citrus (Agrofit, 2012).

(2) Insecticide without registration for sharpshooter control in
citrus (Agrofit, 2012).

TABLE 2. CONTACT INSECTICIDE KNOCKDOWN AND TOXIC EFFECTS
ON BUCEPHALOGONIA XANTHOPHIS.

Treatments                Knockdown (1)

                          Mortality (2)      E (3)

Water                   0 [+ or -] 0.0 bA     --
Dimethoate             20 [+ or -] 15.5 bB    20
Imidacloprid           84 [+ or -] 5.1 aA     84
Lambda-cyhalothrin     82 [+ or -] 8.6 aA     82

Factor                         DF

Treatments (T)                  3
Time of contact (Tc)            2
T x Tc                          6

Treatments                    24 h

                          Mortality (2)      E (3)

Water                   2 [+ or -] 2.0bA
Dimethoate             98 [+ or -] 2,0 aA     98
Imidacloprid           94 [+ or -] 4.0 aA    93.9
Lambda-cyhalothrin     100 [+ or -] 0.0 aA    100

Factor                          F

Treatments (T)                157.2
Time of contact (Tc)          33.95
T x Tc                        11.4

Treatments                     48h

                          Mortality (2)      E (3)

Water                  12 [+ or -] 2.4 bA
Dimethoate             100 [+ or -] 0.0 aA    100
Imidacloprid           98 [+ or -] 2.0 aA    97.7
Lambda-cyhalothrin     100 [+ or -] 0.0 aA    100

Factor                          P

Treatments (T)              < 0.0001
Time of contact (Tc)        < 0.0001
T x Tc                      < 0.0001

(1) Evaluation made 2 hr after confinement.

(2) Means in a column followed by different small letter,
or in a row by different capital letter are significantly
different by Tukey's test (P < 0.05).

(3) E: Efficacy calculated from Abbott's formula, 1925.

TABLE 3. INSECTICIDE RESIDUAL EFFECTS BY CONTACT ON
BUCEPHALOGONIA XANTHOPHIS.

Sampling        Treatment            Mortality (2)
interval

                                     Knockdown (1)

Weekl      Water                   0 [+ or -] 0.0 bA
           Dimethoate             32 [+ or -] 19.9 abB
           Imidacloprid            16 [+ or -] 8.1bC
           Lambda-cyhalothrin     78 [+ or -] 13.2 aA

           Factor                          DF

           Treatments (T)                  3
           Time of contact (Tc)            2
           T x Tc                          6
Week 2     Water                   0 [+ or -] 0.0 bA
           Dimethoate             20 [+ or -] 11.4 abB
           Imidacloprid           28 [+ or -] 8.6 abB
           Lambda-cyhalothrin     48 [+ or -] 12.4 aB

           Factor                          DF

           Treatments (T)                  3
           Time of contact (Tc)            2
           T x Tc                          6
Week 3     Water                   0 [+ or -] 0.0 aB
           Dimethoate              28 [+ or -] 12.0aB
           Imidacloprid            10 [+ or -] 4,5 aB
           Lambda-cyhalothrin     30 [+ or -] 18.4 aA

           Factor                          DF

           Treatments (T)                  3
           Time of contact (Tc)            2
           T x Tc                          6
Week 6     Water                  14 [+ or -] 14.0 aB
           Dimethoate             14 [+ or -] 14,0 aB
           Imidacloprid            6 [+ or -] 4,0 aB
           Lambda-cyhalothrin      22 [+ or -] 9.7 aA

           Factor                          DF

           Treatments (T)                  3
           Time of contact (Tc)            2
           T x Tc                          6
WeekS      Water                   0 [+ or -] 0.0 aA
           Dimethoate              0 [+ or -] 0.0 aA
           Imidacloprid           10 [+ or -] 10,0 aA
           Lambda-cyhalothrin       O [+ or -] 0.0aA

           Factor                          DF

           Treatments (T)                  3
           Time of contact (Tc)            2
           T x Tc                          6

Sampling        Treatment            Mortality (2)
interval

                                          24 h

Weekl      Water                    2 [+ or -] 2.0cA
           Dimethoate             72 [+ or -] 8.6 abAB
           Imidacloprid            50 [+ or -] 8.9 bB
           Lambda-cyhalothrin      94 [+ or -] 4.0 aA

           Factor                          F

           Treatments (T)                 56.6
           Time of contact (Tc)          20.87
           T x Tc                         4.27
Week 2     Water                   10 [+ or -] 5.5 bA
           Dimethoate              82 [+ or -] 5.4 aA
           Imidacloprid           78 [+ or -] 10.2 aA
           Lambda-cyhalothrin      B6 [+ or -] 9.8 aA

           Factor                          F

           Treatments (T)                 38.4
           Time of contact (Tc)          44.45
           T x Tc                         2.74
Week 3     Water                  12 [+ or -] 5.4 bAB
           Dimethoate             74 [+ or -] 12.5 aA
           Imidacloprid           68 [+ or -] 11.1 aA
           Lambda-cyhalothrin     68 [+ or -] 13,2 aA

           Factor                          F

           Treatments (T)                14.76
           Time of contact (Tc)          31.17
           T x Tc                         1.37
Week 6     Water                  34 [+ or -] 19.1 aA
           Dimethoate             68 [+ or -] 10.7 aA
           Imidacloprid           74 [+ or -] 19.4 aA
           Lambda-cyhalothrin      90 [+ or -] 5,5aA

           Factor                          F

           Treatments (T)                 4,28
           Time of contact (Tc)          29.5B
           T x Tc                         1.02
WeekS      Water                   0 [+ or -] 0.0 aA
           Dimethoate              2 [+ or -] 2,0 aA
           Imidacloprid           32 [+ or -] 17.4 aAB
           Lambda-cyhalothrin      16 [+ or -] 6.8 aA

           Factor                          F

           Treatments (T)                 9.13
           Time of contact (Tc)           9.46
           T x Tc                         1.86

Sampling        Treatment                        Mortality (2)
interval

                                          48 h           Efficacy (3)

Weekl      Water                   2 [+ or -] 2.0 bA          --
           Dimethoate              100 [+ or -] 0.0aA        100
           Imidacloprid            86 [+ or -] 7.5 aA        85.7
           Lambda-cyhalothrin         94 + 4,0 aA            93,9

           Factor                          P

           Treatments (T)               < 0.0001
           Time of contact (Tc)         < 0.0001
           T x Tc                        0.0016
Week 2     Water                  22 [+ or -] 13.2 bA         --
           Dimethoate              96 [+ or -] 4.0 aA        94.9
           Imidacloprid           100 [+ or -] 0.0 aA        100
           Lambda-cyhalothrin      94 [+ or -] 6.0 aA        92.3

           Factor                          P

           Treatments (T)               < 0.0001
           Time of contact (Tc)         < 0.0001
           T x Tc                        0.0226
Week 3     Water                   32 [+ or -] 8.6 bA         --
           Dimethoate              90 [+ or -] 6.3 aA        85.3
           Imidacloprid            92 [+ or -] 8.0 aA        88.2
           Lambda-cyhalothrin      78 [+ or -] 9.7 aA        67.6

           Factor                          P

           Treatments (T)               < 0.0001
           Time of contact (Tc)         < 0.0001
           T x Tc                        0.2458
Week 6     Water                  50 [+ or -] 18.2 aA
           Dimethoate              94 [+ or -] 4.0 aA         88
           Imidacloprid           82 [+ or -] 15,6 aA        64,0
           Lambda-cyhalothrin      96 [+ or -] 4,0 aA        92,0

           Factor                          P

           Treatments (T)               < 0.0001
           Time of contact (Tc)          0.0093
           T x Tc                        0.4248
WeekS      Water                    2 [+ or -] 2.0bA
           Dimethoate              14 [+ or -] 9.3 bA        12.2
           Imidacloprid           68 [+ or -] 11.6 aB        67,3
           Lambda-cyhalothrin     38 [+ or -] 18,6 abA       36.7

           Factor                          P

           Treatments (T)               < 0.0001
           Time of contact (Tc)          0.0003
           T x Tc                        0.1077

(1) Evaluation made 2 hr after confinement.

(2) Means in a column followed by different small letter, or in a
row by different capital letter are significantly different by
Tukey's test (P < 0.05).

(3) E: Efficacy at 48 h after exposure calculated from Abbott's
formula, 1925.

TABLE 4. SYSTEMIC INSECTICIDE KNOCKDOWN AND TOXIC EFFECTS
ON BUCEPHALOGONIA XANTHOPHIS.

Treatment (ppm)                        Mortality (2)

                             Knockdown (1)         Mortality-24 h

Water                0     0 [+ or -] 0.0 dA        2 [+ or -] 2.0 bA
Thiamethoxam      0.08    22 [+ or -] 8.0 bcdB     98 [+ or -] 2.0 aA
                     1    24 [+ or -] 12.1 bcdB   100 [+ or -] 0.0 aA
                  1.34    40 [+ or -] 15.2 bcdB    96 [+ or -] 2.4 aA
                     2    60 [+ or -] 16.4 abB     98 [+ or -] 2.0 aA
                    20    94 [+ or -] 2.4 aB      100 [+ or -] 0.0 aA
Imidacloprid       1.4    12 [+ or -] 5.8 cdC      80 [+ or -] 7.1 aB
                  1.74     2 [+ or -] 2.0 dB       82 [+ or -] 9.2 aA
                  2.34    10 [+ or -] 3.2 cdB      92 [+ or -] 5.8 aA
                   3.5    20 [+ or -] 5.5 bcdB     92 [+ or -] 4.9 aA
                    35    54 [+ or -] 15.0 abcB    98 [+ or -] 2.0 aA

Factor                            DF                      F

Treatments (T)                    10                    48.18
Time (Ti)                          2                   318.15
T x Ti                            20                    8.33

Treatment (ppm)                    Mortality (2)

                                48 h           Efficacy (3)

Water                0     4 [+ or -] 2.4 bA        --
Thiamethoxam      0.08   100 [+ or -] 0.0 aA        100
                     1   100 [+ or -] 0.0 aA        100
                  1.34   100 [+ or -] 0.0 aA        100
                     2   100 [+ or -] 0.0 aA        100
                    20   100 [+ or -] 0.0 aA        100
Imidacloprid       1.4   100 [+ or -] 0.0 aA        100
                  1.74    94 [+ or -] 4.0 aA       93.7
                  2.34   100 [+ or -] 0.0 aA        100
                   3.5   100 [+ or -] 0.0 aA        100
                    35   100 [+ or -] 0.0 aA        100

Factor                            P

Treatments (T)                < 0.0001
Time (Ti)                     < 0.0001
T x Ti                        < 0.0001

(1) Evaluation made 2 hr after confinement.

(2) Means in a column followed by different small letters, or
in a line by different capital letters are significantly
different by Tukey's test (P < 0.05).

(3) E: Efficacy at 48 h after exposure calculated from
Abbott's formula, 1925.
COPYRIGHT 2012 Florida Entomological Society
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2012 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Bezerra-Silva, Gerane Celly Dias; Silva, Marcio Alves; De Miranda, Marcelo Pedreira; Lopes, Joao Rob
Publication:Florida Entomologist
Article Type:Report
Geographic Code:3BRAZ
Date:Dec 1, 2012
Words:5207
Previous Article:Report of Homoeocerus variabilis (Hemiptera: Coreidae) on khejri (Prosopis cineraria) in Rajasthan, India: incidence and morphometric analysis.
Next Article:Seasonal abundance of hemipterans on Caryocar brasiliense (Malpighiales: Caryocaraceae) trees in the cerrado.
Topics:

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters