BIOFERTILIZER AS INDUCING RESISTANCE AGAINST COLONIZATION OF WHITE FLY ON BEAN

SUMMARY

The potential for populations of Bemisia tabaci (Gennadius) become resistant to insecticides has stimulated the study of alternative tactics for Integrated Pest Management, for example, the induction of resistance in the host plant. Therefore, the objective of this study was to evaluate the effect of this fertilizer in reducing the oviposition (laying or depositing of eggs) preference of whitefly on plants.Tests were conducted with and without possibility of choice for oviposition on the bean cultivar Carioca. The design was completely randomized design with four treatments and ten repetitions. We performed a general application in the soil, except for control. After the appearance of the first pair of leaves final applications were foliar, getting treatment as follows: 1) control 2) only one application on the ground, 3) an application in the soil a foliar application, 4) an application in ground plus two foliar applications. The biofertilizer caused negative effect on the population of whitefly by reducing oviposition. Thus, this product can be effective in the management of whitefly in crops of beans.

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ABSTRACT

The potential for resistant Bemisia tabaci populations to develop as a consequence of intensive use of chemical insecticides has stimulated studies on integrated pest management tactics, for example, the induction of host-plant resistance. The objective of this work was to evaluate the effect of the biofertilizer in the induction in bean resistance to the whitefly. Tests were accomplished with free-choice and no-choice tests of oviposition preference of the insect in cultivating of carioca bean. The design was completely randomized, with four treatments, being accomplished a general application in the soil, except for control. After the pair’s first definitive appearance of leaves the applications were road leaf, being the treatments in the following way: 1, Control, 2) just an application in the soil, 3) an application in the soil one more application to foliate, 4) an application in the soil two more applications foliate. The biofertilizer caused negative effect in the population of the whitefly is the reduction of the oviposition. In that way, that product can be efficient in the handling of the whitefly in bean plantings.

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INTRODUCTION

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a pest of most cultivated plants of the world (Buntin et al., 1993). One of the most important problems caused by the attack of this pest is the transmission of viral diseases of the Geminivirus group (Villas Boas et al., 2002). In bean, these insects have toxigenic action, with the greatest losses are due to transmission of viruses such as bean golden mosaic – BGMV dwarf mosaic (Gallo et al., 2002). In Brazil, B. tabaci has gained more prominence in the middle of 1990/91, when the B biotype, also known as Bemisia argentifolii, was found attacking various crops (Villas Boas et al., 1997). Although showing the same morphology, biotype B has shown a greater resistance to insecticides, better adaptation to different regions and different climates, virus transmission in several different plants and different hosts (Bellows & Perring, 1994).

Traditionally the control of Bemisia spp. is accomplished through the use of chemicals. However, intensive use of insecticides can cause resurgence of target pest, and the appearance of new pests, as most of these products has a high level of biological action and persistence in the environment, thus impairing the health of consumers and professionals involved in production processes (Pratissoli, 2002). In the search for alternatives to chemical control, research related to plant resistance has been one of the most effective practices in the integrated pest management (Torres & Garcia, 1996). Induced resistance, which is an increased level of plant resistance through the use of external agents (inducers), no change in the genome of the plant is an alternative control for easy handling and low cost (Stadnyk, 2000).Silicon has been cited as an example of a resistance inducer. According to Epstein (1999), the supply of silicon has benefited from many plant species, encouraging the growth and yield, as well as providing protection against abiotic stresses and reduce the incidence of insect pests and diseases. The silicon skin prevents the penetration and chewing by insects due to the hardening of the walls of plant cells (Datnoff et al., 1991). As Basagli et al. (2003) the application of silicon reduced preference and reproduction of Schizaphis graminum on sorghumplants and wheat.

The sources of silicon, calcium silicate (CaSiO 3) is the most used in most commercial products (Barbosa Filho et al., 2000). Among the products sold have been the biofertilizer, whose commercial name is Ergofito ®, which works by providing a rapid assimilation of nutrients available, increasing the production of plant material, which may make the plant resistant to pathogens (Tecnobiol, 2005). Thus, the objective of this study was to evaluate the use of this fertilizer, reducing the preference for oviposition was in bean plants.

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METHODS

The experiment was conducted at the Entomology Laboratory at the Center for Scientific and Technological Development in Management of Plant Pests and Diseases (NUDEMAFI) located Center of Agrarian Sciences, Federal University of Espírito Santo (CCA-UFES) in Alegre-ES, Brazil. The creation of whitefly was conducted in greenhouse gases of anti-aphid, using plants of beans, tomatoes and peppers planted directly in soil with manure and NPK (04-14-08). After obtaining high infestations of whitefly host plants in the greenhouse, began tests with biofertilizer (Ergofito ®). Whitefly adults were subjected to two different tests. In the first test no-choice, unlike the second, where the insects were submitted to free choice.For the two tests was carried out the planting of beans (Phaseolus vulgaris L.) var. Rio, planted in plastic bottles cut in half with 1 liter of soil in place free of whitefly. 4 treatments were performed with 10 repetitions; each received different numbers of applications of this fertilizer to 0.5% concentration in water. We performed a general application in the soil, except for control.

After the appearance of the first pair of leaves was made final a second application on 2 and 3 treatments and 15 days was performed a third application in the 3rd treatment. Upon reaching the desired number of applications for each treatment was performed the tests. In free-choice test, the bean plants treated with this fertilizer plants clean and were placed in a cage (1.0 x 0.8 x 1.0 m) of anti-greenhouse aphids. Adults of B. tabaci, were collected with a vacuum cleaner manual, plants in the greenhouse of NUDEMAFI and released into the cage of anti-greenhouse aphid, the proportion of 10 adults per plant. Being performed ten replicates per treatment. Seven days after the release of insects, the leaves were removed and taken to the entomology laboratory to assess the rate of egg laying insect. In a no-choice (confinement), we used individual cages for each repetition. The cages were made of transparent PET bottles, which had part of his side replaced by tissue type tulle, allowing photosynthesis. Adults of B. tabaci, were collected with a manual vacuum cleaner plant in the greenhouse of NUDEMAFI and placed in cages (plastic bottles), which contained the treatments mentioned above. Were placed 10 adult whiteflies per plant in each treatment, each replication consisted of a cage with a bean plant. Seven days after inoculation of the insects, the leaves were removed and taken to the entomology laboratory to assess the rate of egg laying insect. The design was completely randomized design with four treatments and ten repetitions, and means were compared by Tukey test at 5% probability by the Software SAEG 9.0.

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RESULTS AND DISCUSSION

The biofertilizer affects the preference for oviposition of B. tabaci on bean leaves (Table 1). However, plants that received only one application of this fertilizer in the soil did not differ significantly from the control. The most notable effect of the reduction of oviposition was observed in treatment with two and three applications (Table 1). Similar to these results Correa et al. (2005), concluded that the calcium silicate and acibenzolrmethyl (BTH), applied to cucumber plants, induce the non-preference for oviposition of B. tabaci (biotype B) in conditions of free choice. Paschoalati & Leite (1995) also reported that the induced protection is dependent on the time interval that occurs between the treatment with the inducer and the subsequent inoculation of the plant is not enough just one application to achieve the desired level of resistance, because this process involves synthesis and accumulation of substances that confer resistance to the plant. Thus, it is observed that when there is a chance to choose, the whitefly preferred oviposition substrates are favorable to the development of nymphs. Similar results were presented by Villas Boas et al. (2002).