Effectiveness of BPMC Application Against Bemisia Tabaci (Gennadius) Population and CMMV Disease Incidence on Soybean

Control of whitefly (Bemisia tabaci (Gennadius)) is the starting point in suppressing the CMMV disease (cowpea mild mottle virus). This study aims to determine the influence of applications BPMC (500 g a.i./l) against B. tabaci populations and disease incidence of CMMV on soybean plants. Research was conducted in the field with randomized complete block design consisting of 5 treatments i.e. five concentration levels: 0.75, 1.50,2.25, and 3.00 ml/l including control (untreated) with 5 replications. The results showed that BPMC is effective in suppressing the adult population of B. tabaci and disease incidence of CMMV.


INTRODUCTION
Soybean is one of the staple foods of Indonesian people. This is because soybean is a raw material for the manufacture of tempeh and tofu that has become a daily menu of Indonesian society in general. The national needs for soybean reached 2.2 million tons per year. However, only 20 to 30 percent of those needs can be met by domestic production; while, 70 to 80 percent of the lack, depending on imports.
In an effort to increase soybean production, pest and disease are still to be the problem. Several potential pests that may cause significant damage to crops of soybean include seed flies, caterpillars, pod sucking and pod borer pest (Harnoto et al. 1985;Harnoto et al. 1993). Some of insect pest of soybean also play an important role as a vectors of disease.
In addition to aphids, insect vectors often found on soybean is whitefly Bemisa tabaci Gennadius (Hemiptera: Aleyrodidae). The sweetpotato whitefly is a major pest of economically important crops worldwide (Gerling et al. 1980;Nomikou et al. 2000). Damage can be caused directly by feeding on phloem sap or indirectly by the large amounts of honeydew produced lowering photosynthesis. Bemisia tabaci is also a vector of many plant viruses (Alegbejo 2000: Simón et al. 2003). There are more than 110 species of virus in various host plants transmitted by this vector. One of the viruses that are transmitted by B. tabaci on soybean is cowpea mild mottle virus (CMMV). CMMV is very easily transmitted by B. tabaci in a non-persistent manner (Muniyappa & Reddy 1982;Iwaki et al. 1983). CMMV was known to be widely spread in soybean production centers in Indonesia, in line with the increasing of viral vector population (B. tabaci) in the field. In Java, CMMV was a prevalent disease (Nasir et al. 1989). CMMV disease can cause yield loss until 80% (Saleh et al. 2004;Saleh et al. 2005), depending on variety and age at the time of infected soybean plants.
Control of B. tabaci can be done by using chemical synthetic insecticide. The use of insecticide is preferable due to its easy application and its fast effects in suppressing the target pest. However, its use must be done carefully, so as to reduce negative impacts on the environment and the occurrence of resistance. Selection of the active ingredient is also needed to know the mode of action of the active ingredient with the target pest to be controlled.
BPMC or fenobucarb is a contact insecticide that is effective in controlling caterpillar pests, trips, and aphids. All the time, this insecticide is often used to control pests on paddy. BPMC testing on other crops need to be done, in order to know its effectiveness against other pests.
This study was conducted to determine the effect BPMC application on population of B. tabaci and disease incidence of CMMV on soybean plants.

MATERIALS AND METHODS
The research was conducted at the experimental plantation of Citayam, Indonesian Center for Agricultural Biotechnology and Genetic Resources Research and Development (ICABIO-GRAD), Bogor, West Java during growing season in 2010. Randomized block design was used consisting of 5 treatments with 5 replications. Tested insecticide was BPMC (500 g a.i./l) consisting of five levels of concentration, namely: 0.75, 1.50, 2.25, and 3.00 ml/l including control (untreated).
Experimental plots size was 8 m x 5 m with a spacing of 20 cm x 40 cm. Distance between plots were 40 cm. Variety of soybean planted was Grobogan with two seeds per planting hole. Fertilization was done at the time of planting with 200 kg of Urea, SP-36 150 kg and 150 kg KCl/ha sown around the planting hole.
Soybean plants are maintained well, watering and weeding were carried out as needed. Observation was made on 10 plants of which are determined systematically. Observations of population of B. tabaci were done by counting the imago population that was caught by the sweeping cloth. Five swings were performed using a dark colored cloth with a diameter of 20 cm and length of 50 cm. CMMV disease was observed by looking at the symptoms. To define the symptom, ELISA test was conducted in the laboratory with NCM-ELISA (nitro cellulose membrane -enzyme linked immunosorbent assay) (Lazarovits et al. 1989). Antiserum CMMV was obtained from the collections of Biochemistry Research Group of ICABIO-GRAD. The visual symptom of CMMV infection then was used to calculate the percentage of disease incidence based on the equation: a DI = x 100 a + b DI = disease incidence a = numbers of plant with CMMV symptoms b = numbers of plant looked healthy Insecticide application was done a day after the appearance of the target pest. Applications were made at intervals of one week to two weeks prior to harvest. Application is done by spraying using high-pressure sprayer with a sprayed volume 500-600 ml/l or as the result of calibration.
Data on population of B. tabaci and the disease incidence of CMMV were used to calculate the efficacy of the tested insecticides. If the first observation of target pest population or disease incidence was not significantly different between treatments, the efficacy of the tested insecticides was calculated with the formula Abbot (1925): of control plot after insecticides application Ta = populations or disease incidence of treatment plot after insecticides application If the first observation of the population or the disease incidence was significantly different between treatments, the efficacy was calculated with the formula Henderson and Tilton

RESULTS AND DISCUSSION
Observation in the field indicated that the level of B. tabaci population fluctuated over time (Table 1.) This fluctuation may be not only affected by treatment applications, but also influenced by environmental factors. Fluctuations in population were thought to relate to the intensity of rainfall that varies during the experiment. B. tabaci population could decrease when high rainfall, whereas population increased when rainfall is low (Horowitz 1986). In addition, temperature also affects the ability of B. tabaci to survive, with an optimum temperature between 17-35 °C (Bonato et al. 2006).
In general, the population of B. tabaci on BPMC (500 g a.i./l) treatment were significantly lower than control. On 21 DAP, the suppression of population B. tabaci that reached 50.0% was occurred in plots applied with BPMC (500 g a.i./l) at concentration of 2.25 and 3.00 ml/l. Consistency of BPMC (500 g a.i./l) at concentration of 2.25 and 3.00 ml/l in reducing population of up to 50% also occurred at 28 and 35 DAP ( Table 1).
The experiment results also showed that the suppression rate of population B. tabaci is correlated with the concentration of application. Increasing concentrations of BPMC caused the disease of insect population (500 g a.i./l) is followed by the decrease of the level of insect population lower. This pattern was rou-tinely discussed in observations. Table  1 showed that at concentration of 3.00 ml/l, population was lowest, then gradually increased with decreasing concentration, i.e. from 2.25, 1.5, and 0.75 ml/l. The Effect of BPMC (500 g a.i./l) application of in controlling B. tabaci seems to be associated with the occurrence of cowpea mild mottle virus (CMMV). Based on field observations, it appeared that symptoms of the CMMV disease clearly visible on the   Figure  1). Symptoms of disease vary depending on CMMV infected soybean cultivars (Mitsuro 2001). CMMV symptom was proven positive by NCM-ELISA test results as shown in Figure  2. NCM-ELISA test results showed that the leaf samples taken from the field randomly showed a positive reaction infected by CMMV.
Disease incidence of CMMV observed at 5 and 8 weeks after planting (WAP) showed varying value. Table 2 showed that the disease incidence in plots treated with BPMC (500 g a.i./l) was significantly smaller than control.
Disease incidence of plants applied with BPMC (500 g a.i./l) at concentration of 0.75 to 3.0 ml / l was no more than 3.2%. While in control, until the eighth weeks of observation, the disease incidence reached 98.2%. This result indicated that suppression of B. tabaci influenced to disease incidence of CMMV.
Based on the results of this study, the treatment of BPMC (500 g a.i./l) concentration was inversely proportional to the population and disease incidence of CMMV. Figure 3 showed that population of B. tabaci and disease incidence of CMMV was lower when the application concentration was increased.
Column 1 to 8 were the leaf samples from each treatment Row 1 to 5 were the treatment Control (-) was the negative reaction of healthy leaf Control (+) was the positive reaction of the CMMV infected leaf   CMMV is part of non-persistent viruses. In controlling non-persistent viruses, chemical is widely used. This is intended to suppress the population of B. tabaci which act as vectors or transmitters of the virus. Reduction on vector population will reduce the spread of viruses by insects. BPMC effectiveness in suppressing populations of B. tabaci is one way that proved effective in suppressing the disease incidence of CMMV. Several studies also showed that the spraying of insecticides such as cypermethrin, deltamethrin, permethrin, fanfalerate, disulfoton and acephate can reduce vector population and reduce or slow the spread of the virus (Asjes 1985Atiri et al. 1987Piron et al. 1988).
The effectiveness of insecticide BPMC in controlling the population of B. tabaci is caused by the disruption the nervous system and muscle of the insect. BPMC is an active ingredient of carbamates group that inhibit the production of insect acetylcholinesterase (IRAC 2010). The effectiveness of BPMC was proven reportedly effective in controlling some types of pests from other food commodities, for examples it was used to control Nilaparvata lugens, Leptocorisa oratorius, Hydrella philippina, Spodoptera litura, Empoasca sp., Helicoverpa armigera, Aphis sp., Valanga nigricornis, and Helopheltis sp. (Supriyatin 2000;Surachman and Suryanto 2007;BBPadi 2009;Baehaki 2011).

CONCLUSION
The application of BPMC (500 g a.i./l) reduced B. tabaci population. The suppression rate of B. tabaci population correlated with the concentration of BPMC application. Effect of BPMC application in controlling B. tabaci seems to be associated with the occurrence CMMV.