Field Evaluation Of Carbosulfan 25 Ec (ns) Against Rice Green Leafhoppers (nephotettix Virescens Distant. And Nephotettix Nigropictus Stal.)

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A. RAJESH*, T. MANOHARAN AND G. RANJITHA

Department of Agricultural Entomology, TNAU, Coimbatore – 641 003, T.N.

ABSTRACT

Supervised field experiments were conducted in rice for two seasons to evaluate the bioefficacy of carbosulfan 25 EC (New Source) as foliar spray against green leafhoppers (GLH) (Nephotettix virescens Distant. and Nephotettix nigropictus Stal.) in rice ecosystem. Application of carbosulfan 25 EC (NS) at 300, 250, 200 and 150 g a.i. ha-1 recorded 83.90, 79.49, 62.94, 55.43 and 80.95, 76.49, 54.44, 41.97 per cent reduction of GLH population during first and second season, whereas carbosulfan 25 EC (Existing Source) 250 g a.i. ha-1 recorded 77.60 and 75.37 per cent reduction of GLH population during first and second season, respectively. The standard check chlorpyrifos 20 EC at 375 g a.i. ha-1 and at 250 g a.i. ha-1 recorded 61.29, 53,54 and 51.69, 40.38 per cent reduction of GLH population during first and second season, respectively. Carbosulfan 25 EC (NS) recorded a significant reduction in the GLH population and the effect was remarkable in both the seasons. Carbosulfan 25 EC (NS) at 300 g a.i. ha-1 was more effective in reducing GLH population than the lower doses 150, 200 and 250 g a.i. ha-1. Based on the per cent reduction in mean GLH population over untreated check after two sprays in both seasons, the order of efficacy of different treatments is as follows: carbosulfan 25 EC (NS) 300 g a.i. ha-1, carbosulfan 25 EC (NS) 250 g a.i. ha-1, carbosulfan 25 EC (ES) 250 g a.i. ha-1, carbosulfan 25 EC (NS) 200 g a.i. ha-1, chlorpyrifos 20 EC 375 g a.i. ha-1, carbosulfan 25 EC (NS) 150 g a.i. ha-1 and chlorpyrifos 20 EC 250 g a.i. ha-1.

KEYWORDS:

Carbosulfan 25 EC (NS), Chlorpyrifos, Nephotettix nigropictus, Nephotettix virescens.

INTRODUCTION

Rice is the staple food for more than 65 per cent Indian population, with largest area of 44.6 m ha under rice cultivation. Rice production in India is limited by severe outbreak of insect pests and diseases. More than 70 insect species are infesting rice in India and among them 20 are of regular occurrence (Pathak, 1975). On an average, farmers lose 37 per cent of their rice yield due to pests and diseases, these losses range between 24 and 41 per cent depending on the production situation (Sparks et al., 2012). Among the biotic stresses, insect pests cause about 10-15 per cent yield losses. Yellow stem borer, brown planthopper and gall midge were the key pests in rice causing 25-30, 10-70 and 15-60 per cent yield losses, respectively. At national level, stem borers accounted for 30 per cent of the loss, while that of planthoppers, gall midge, leaf folder and other pests was 10-25 per cent (Herdt, 1991). Two species of green leafhoppers, viz., Nephotettix virescens (Distant.) and Nephotettix nigropictus (Stal.) are the most common and act as a

vector for Tungro/ yellow dwarf/ Transitory yellowing diseases (Bapreddy, 1968). Rice Tungro Virus (RTV) confined to eastern states till 1981, caused extensive damage in coastal Tamil Nadu and Andhra Pradesh during 1983 and 1984, respectively (Krishnaiah and Varma, 2010).

In order to combat the threat posed by the wide range of insect pest complex and to sustain the production, farmers are using insecticides as first line of defense among the various strategies adopted due to their higher efficacy. In India, about one fifth (17-18%) of the pesticides used in agriculture is on rice (Kapadia and Mohla, 1980).

Carbosulfan 25 EC (Marshal®), carbamate insecticide both contact and systemic in action developed by Farm Machinery and Chemicals (FMC) is recommended for the management of insect pests in agriculture. Carbosulfan both 25 EC and 25 DS formulations have proved effective as foliar spray and seed dresser against many insect pests of okra, chillies, rice, beans, maize, apple, cotton, brinjal, citrus and

cauliflower as well as found to be a safer molecule (Ali and Chinniah., 1999; Karthikeyan and Purushothaman., 2000; Singh et al., 2000; Sontakke and Dash., 2000; Srinivasan and Rabindra., 2001).

Krishnaiah and Kalode (1986) reported that root dip treatment of carbosulfan showed the best control against green leafhopper, Nephotettix virescens (Distant). Studies with neem oil, monocrotophos at 0.3l g a.i. ha-1 and carbosulfan 0.3l g a.i. ha-1 on rice green leafhopper indicated that plots treated with monocrotophos and carbosulfan showed higher yield than control plots. At 32 DAT, monocrotophos treated plots had significantly less green leafhopper population than control and at 36 DAT carbosulfan treated plots had significantly less GLH than control plots. (Jahn, 1992). Efficacy of carbosulfan granules against rice pest complex was observed as similar to carbofuran granules through multilocation trials (DRR, 2001). Carbosulfan (Marshal) was found to be the least toxic to predators in cotton ecosystem. Isofenphos 5 G (2 kg a.i. ha-1), carbosulfan 10 G (4 kg a.i. ha-1), isofenphos

5 G (5 kg a.i. ha-1) and phorate 10 G (4 kg a.i. ha-1) were found to be safer to natural enemies in groundnut (Rajagopal and Gowda, 1992).

In the event of change in source material of carbosulfan 25EC, it is mandatory to generate data on the bioefficacy, phytotoxicity, residues and safety to the natural enemies as per the guidelines of Central Insecticides Board (CIB). To elucidate more information on the impact of carbosulfan 25 EC New Source (NS) in rice ecosystem, the present investigation was under taken.

MATERIALS AND METHODS

Field experiments were conducted at Paddy Breeding Station (PBS), Tamil Nadu Agricultural University, Coimbatore to assess the bioefficacy of carbosulfan 25 EC against rice green leafhoppers, viz., Nephotettix virescens (Distant.) and Nephotettix nigropictus (Stal.). Two field experiments were laid out using Randomized Block Design (RBD) with the varietal line CB 06 535, one during August – November 2012 and another during December 2012 to March 2013, with three replications, with each plot having size of 40 m2. Bioefficacy of carbosulfan 25 EC (New Source- NS) and carbosulfan 25 EC (Existing Source- ES) was evaluated against green leafhopper, along with chlorpyrifos 20 EC as standard check. The treatments evaluated were as follows:

Two rounds of sprayings were given, one at 21 days after transplanting (DAT) and other at 45 DAT with battery operated knapsack sprayer by using 500 litres of spray fluid per hectare.

Assessment of Pest Population

The populations of green leafhoppers (GLH) were recorded on five randomly selected hills from each plot. The observations were recorded one day before spraying and 7, 14 and 21 days after each spraying. Both adults and nymphs were counted on five randomly selected hills from each plot and expressed as number of adults and nymphs per hill. The observations recorded were later averaged to per replication basis.

The data on population number was transformed into

0.5 before statistical analysis. The data obtained

from field experiments were analysed using factorial randomised block design (Gomez and Gomez, 1984) and the mean values were separated using Duncan’s Multiple Range Test (DMRT) (Duncan, 1951).

RESULTS AND DISCUSSION

The results of the field experiment during first season showed that the population was uniform in the pre treatment count ranging between 5.73 and 6.23 per hill among different experimental plots and was found to be non significant (Table 1). The population observed after first spraying on 7 DAA was the least (1.74 hill-1) in carbosulfan 25 EC (NS) 300 g a.i. ha-1 treated plots

followed by 2.08, 2.17, 3.26, 3.48, 3.97, 4.25 and 8.74 per hill in carbosulfan 25 EC (NS) 250 g a.i. ha-1, carbosulfan 25 EC (ES) 250 g a.i. ha-1, carbosulfan 25 EC (ES) 200 g a.i. ha-1, chlorpyrifos 20 EC 375 g a.i. ha-1, carbosulfan 25 EC (NS) 150 g a.i. ha-1, chlorpyrifos 20 EC 250 g a.i. ha-1 and untreated check plots, respectively. At 14 and 21 DAA, the green leafhopper population was found significantly minimum in carbosulfan 25 EC (NS) at 300 g a.i. ha-1 treated plots with a population of 2.34 and 2.54 per hill respectively compared to all other treatments.

After second application also, the population was observed to be the lowest in plots treated with carbosulfan 25 EC (NS) 300 g a.i. ha-1 with pest population of 1.17, 1.56 and 1.60 per hills on 7, 14 and 21 DAA, respectively which were on par with carbosulfan 25 EC (NS) 250 g a.i. ha-1, (1.64, 1.70 and 1.84 hill-1, respectively) and carbosulfan 25 EC (ES) 250 g a.i. ha-1 (1.78,1.81 and 2.17 hill-1, respectively) (Table 1).

In second season, at 7 DAA, the population per hill observed after first spray was found to be the least (2.82) in carbosulfan 25 EC (NS) 300 g a.i. ha-1 treated plots followed by 3.67, 3.79, 4.16, 4.74, 5.63, 5.97 and 9.26 in carbosulfan 25 EC (NS) 250 g a.i. ha-1, carbosulfan 25 EC (ES) 250 g a.i. ha-1, carbosulfan 25 EC (ES) 200 g a.i. ha-1, chlorpyrifos 20 EC 375 g a.i. ha-1, carbosulfan 25 EC (NS) 150 g a.i. ha-1, chlorpyrifos 20 EC 250 g a.i. ha-1 and untreated check, respectively. On 14 DAA, carbosulfan 25 EC (NS) 300 g a.i. ha-1 treated plots recorded significantly the lowest (2.90 hill-1). On 21 DAA, the population was on par in carbosulfan 25 EC (NS)

300 g a.i. ha-1(3.74 hill-1), carbosulfan 25 EC (NS) 250 g a.i. ha-1 (4.16 per hill) and carbosulfan 25 EC (ES) 250 g a.i. ha-1(4.30 hill-1) (Table 2). After second application, carbosulfan 25 EC (NS) at 300 g a.i. ha-1 treated plot recorded the least population count of 0.97, 1.62 and 1.73 hill-1 on 7, 14 and 21 DAA, respectively compared to all other treatments. The order of pest population found in different treatments were similar to that observed in first season. At 21 DAA, carbosulfan 25 EC (NS) 300 g a.i. ha-1 (1.73 hill-1), carbosulfan 25 EC (NS) 250 g a.i. ha-1 (1.98 hill-1) and carbosulfan 25 EC (ES) 250 g a.i. ha-1

(2.10 hill-1) were on par with one another (Table 2).

Based on the per cent reduction in mean GLH population over untreated check after two sprays in both seasons, the order of efficacy of different treatments is as follows: carbosulfan 25 EC (NS) 300 g a.i. ha-1,

carbosulfan 25 EC (NS) 250 g a.i. ha-1, carbosulfan 25 EC (ES) 250 g a.i. ha-1, carbosulfan 25 EC (NS) 200 g a.i. ha-1, chlorpyrifos 20 EC 375 g a.i.ha-1, carbosulfan 25 EC (NS) 150 g a.i. ha-1 and chlorpyrifos 20 EC 250 g a.i. ha-1. Carbosulfan 25 EC (NS) recorded a significant reduction in the GLH population and the effect was remarkable in both the seasons. Carbosulfan 25 EC (NS) at the test doses viz., 150, 200, 250 and 300 g a.i. ha-1 registered 55.43 to 83.90 and 41.97 to 80.95 per cent mean reduction in GLH population in season I and season II, respectively. Carbosulfan 25 EC (NS) at 300 g a.i. ha-1 was more effective in reducing GLH population than the lower doses 150, 200 and 250 g a.i. ha-1 (Fig. 5).

Several workers confirmed the effectiveness of carbosulfan against rice leafhoppers. Reissig et al. (1986) reported that monocrotophos and carbosulfan treatments significantly reduced the density of Green leafhopper than the untreated check. Jahn (1992) also reported that even at 36 DAT, carbosulfan treated plots had significantly less GLH population than control plots. Krishnaiah and Kalode (1986) reported that root dip treatment of carbosulfan showed the best control against green leafhopper, N. virescens. Superiority of higher doses of carbosulfan 25 EC in these studies were in consonance with the findings of Jasmine (2002) who reported that the highest dose of carbosulfan 25 EC at 300 g a.i. ha-1 was superior to the lower dose of 200 g a.i. ha-1 in controlling the thrips on cotton.

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