LR-3600 [1-7]

Legume Research, AGRICULTURAL RESEARCH COMMUNICATION CENTRE Print ISSN:0250-5371 / Online ISSN:0976-0571 www.arccjournals.com/www.legumeresearch.in

Seasonal abundance of predatory bugs, Eocanthecona furcellata (Wolff.) and Rhynocoris fuscipes (F.) and its olfactory responses towards plant and pest mediated semiochemical cues in Pigeonpea ecosystem

Snehel Chakravarty*, Meena Agnihotri and Jaba Jagdish Department of Entomology, G. B. Pant University of Agriculture and Technology, Pantnagar-263 145, . Received: 31-08-2015 Accepted: 19-03-2016 ABSTRACT Studies on seasonal abundance of the predatory bugs, Eocanthecona furcellata (Wolff.) and Rhynocoris fuscipes (F.) on short duration pigeonpea variety Manak during 2012-14 revealed that the incidence of both the heteropteran bugs commenced from the 36th meteorological standard week and persisted up to 47th meteorological standard week of both the years. These bugs were found predating on larvae of spotted pod borer, Maruca vitrata (Geyer), one of the major pests of pigeonpea. Correlation studies with different weather variables indicated that the populations build up of these bugs exhibited a significant positive correlation with maximum temperature, minimum relative humidity and rainfall. In order to identify the semiochemical cues mediating the host seeking behavior of these predatory bugs towards M. vitrata, a laboratory experiment was conducted using four-arm olfactometer. The predatory bugs displayed a much higher preference for volatiles produced by M. vitrata infested pigeonpea flowers and early instar larvae of M. vitrata. Key words: Eocanthecona furcellata (Wolff.), Maruca vitrata (Geyer), Rhynocoris fuscipes (F.), Semiochemicals, Pigeonpea. INTRODUCTION have remained stagnant for the past 3 to 4 decades, largely Pulses, the food legumes, have been grown by due to damage inflicted by insect pests (Basandrai et al., farmers since millennia providing nutritionally balanced food 2011). Nearly 300 species of insect pests are known to infest to the people of India (Nene, 2006) and many other countries pigeonpea crop at various growth stages in India but the in the world. It has been described that India is the largest maximum yield loss is caused by pod borer complex. producer and consumer of pulses in the world accounting Amongst many insect pests, the pod borers, Maruca vitrata for 33 per cent of world’s area and 22 per cent of world’s (Geyer), atomosa (Wals.), Lampides boeticus (L.), production of pulses. The area covered by pulses in the Helicoverpa armigera (Hubner) and Melanagromyza obtusa country is 14.35 per cent of the total cropped area. In India, (Malloch), on the pigeonpea are of major importance (Lal the total pulse production for the year 2013-14 was 18.43 and Singh, 1998). Considerable loss in grain yield is inflicted million tons on an area of 26 million ha, with an average on account of their association with fruiting bodies. -1 productivity of 758 kg ha (Anonymous, 2014). During recent years due to introduction of short Pigeonpea (Cajanus cajan L. Millsp.) is an duration pigeonpea cultivars, the incidence of M. vitrata has important grain legume that occupies second largest area been aggravated as flowering of these varieties occur during among the various pulse crops grown in India. It acts as a periods of high humidity and moderate temperature which principal source of dietary protein among vegetarians and is is congenial for the development of this pest (Sharma, 1998). an integrate part of daily diet in several forms worldwide The grain yield loss by this pest is estimated to be 9-84% (Tabo et al., 1995). In addition to being a source of dietary (Vishakantaiah and Jagadeesh Babu, 1980). Maruca is proteins and income to poor farmers, it plays an important basically a hidden pest and completes its larval development role in sustainable agriculture because of its efficient nitrogen inside the web formed by rolling and tying together leaves, fixing ability, tolerance to drought and contribution to soil flowers, buds and pods. It is therefore essential to kill the organic matter. Pigeonpea is grown on relatively marginal first instar larvae during the period when they hatch and till soils and has the potential to provide up to three crops per they enter the flowers and buds. year (Rao and Shanower, 1999). Numerous chemical insecticides have been tested Though, India is largest producer of pigeonpea, and few were found effective against pod borer complex in contributing more than 90 per cent of the world’s production, pigeonpea (Mohapatra and Srivastava, 2002; Bhoyar et al., the productivity has always been a concern. Pigeonpea yields 2004; Srinivasan, 2008; Dodia et al., 2009; Sonune et al.,

*Corresponding author’s e-mail: [email protected]. 2 LEGUME RESEARCH An International Journal 2010; Singh et al., 2013). However, increasing concern for of Agriculture and Technology, Pantnagar, during kharif the degradation of environment, and the development of season of 2012-13 and 2013-14 on early maturing pigeonpea resistance in insect pests to insecticides (Armes et al., 1996) variety, Manak. The crop was raised in a plot measuring have prompted the search for more effective and ecofriendly 150 m2 uniformly following all recommended agronomic alternatives for pest control. Thus, attempts are now being practices except plant protection measures. The bug activities pinned on the use of bio-intensive pest management to reduce were watched from their appearance to till they disappeared. the resistance risk and the harmful effects of chemical The population trend of the bugs was determined by insecticides. following the methodology as adopted by Pillai and Agnihotri (2011). Weekly meteorological data were obtained from Some investigators have suggested that insect meteorological observatory of the university. The data were predators could be applied to pest management against statistically analyzed to find out correlation and regression various pest . Among the entomophagous group of coefficients of these predatory bugs with existing weather insects, heteropteran predators are important bio-control variables with the help of SPSS 16 software following agents. In recent years, Eocanthecona furcellata (Wolff.), standard procedure. (Hemiptera: Pentatomidae), has received much attention as biological control agent due to its potential to control In order to find the olfactory response of the outbreaks of lepidopteran, coleopteran and heteropteran predatory bugs, E. furcellata and R. fuscipes to different insects (De Clercq, 2000). This bug has also been reported stages of M. vitrata and infested plant parts of pigeonpea, a to be a potential predator of M. vitrata on pigeonpea laboratory experiment was conducted at Pulse Entomology (Nebapure and Agnihotri, 2011) and the maximum per cent laboratory, Pantnagar using a four arm olfactometer. predation of M. vitrata by this bug was recorded up to 56.40 Insect predator collection and maintenance: The nymphs per cent under laboratory conditions (Pillai and Agnihotri, and the adult bugs of E. furcellata were collected from 2013). Similarly Rhynocoris fuscipes (Fabricus) is a unsprayed field of pigeonpea in NEB-CRC, Pantnagar. These polyphagous predator inhabiting diverse agro ecosystems bugs were brought to the laboratory and five pairs were (Nagarajan and Ambrose, 2013). Reduviids are common in placed in plastic jars (1 L capacity) covered inside by blotting pigeonpea fields and many of its members are found to be paper and provided with disease free larvae of M. vitrata as potential predators of a number of lepidopteran insect pests regular food along with flower buds and tender pods of (Ambrose and Claver, 2001; Kumar and Ambrose, 2014). pigeonpea. Jars were covered with muslin cloth for proper Information on its prey record, bioecology, ecophysiology aeration. Eggs deposited by female bugs on the leaves and and behavior indicate that it could be harnessed as an on blotting paper were kept separately in the plastic vials effective biocontrol agent in the Integrated Pest Management with sieve cap for hatching. Newly hatched first instar Programme (Ambrose, 1999). nymphs were provided with fresh and clean leaves of castor. A few studies have revealed that herbivore induced Second instar nymphs were used for the stock culture and infochemicals are important cues for foraging predators. the adult bugs were used for semiochemical cue experiment. Ninkovic et al. (2001) reported that the seven spotted-lady bird The same methodology was adopted for rearing of R. Coccinella septempunctata responded positively towards fuscipes. volatiles emitted from the aphid Rhopalosiphum padi Fitch, Insect pest collection and maintenance: The larvae of M. and aphid infested plants of Hordeum vulgare. Hislop and vitrata were also collected from unsprayed pigeonpea fields Prokopy (1981) confounded that acarine predators, in NEB-CRC, Pantnagar. The stock culture of M. vitrata Amblyseius fallacies and Phytoseiulus macropilis, respond was maintained in the laboratory in 5 L capacity glass jars. to silk and feces of a prey mite, Tetranychus urticae. However First and second instar larvae were fed with flower buds and no tangible studies have been carried out to identify the flowers and later instars with flowers and tender pods. Food semiochemical cues mediating the host seeking behavior of was changed daily in the morning till the larvae pupated. any of these heteropteran predators towards the spotted pod Faecal matter was also removed daily from rearing container borer, M. vitrata, one of the major insect pests of pigeonpea. to prevent fungal contamination. Hence, an attempt has been made to study the seasonal Dynamic olfactometer set up: After placing the treatments abundance of these predatory bugs on pigeonpea and to (different M. vitrata infested plant parts of pigeonpea or assess the role of volatiles produced by M. vitrata and its different stages of M. vitrata or different larval instars of M. host plant, pigeonpea, in the host selection process by the vitrata) into the odour arms of the olfactometer, their outer predatory bugs, E. furcellata and R. fuscipes. openings were firmly closed with a lid. During the set up, MATERIALS AND METHODS vaseline was smeared at the connecting inlets of each arm to To study the seasonal abundance of the predatory prevent air entry from outside. A small axial flow fan (DC bugs on pigeonpea, a field survey was conducted at Norman 10 V, 3.5 cm diameter) was installed at each of the four distal E. Borlaug Crop Research Centre of G. B. Pant University openings of the arms to provide uniform airflow. The axial Vol. Issue , () fan was screwed on to an acrylic sheet and housed on a were studied in separate olfactometer experiments in similar wooden base in such a way to direct the airflow towards the manner as mentioned above. inside of olfactometer. The wind speed in the olfactometer RESULTS AND DISCUSSION was controlled at 4 L/min. The odour source was kept at the Seasonal abundance of the predatory bug, E. furcellata: distal end of each arm. This set up allowed the insects to The results on the seasonal abundance of predatory bug, E. receive airflow bathing the olfactory cues from the odour furcellata in relation to the abiotic factors prevailing from source and travel upwind in response to the volatiles. the month of September to November, 2013-14 and 2014- After five minutes of saturation of odour from 15 are depicted in Table 1. During both the years, the predator different treatments, twelve hours starved ten adults of E. marked its first appearance during 36th meteorological furcellata were released in to the olfactometer chamber standard week at flowering and pod initiation stage of the through the central hole. Finally the olfactometer was covered crop, with scanty population of 1.2 bugs/sq. m and 1.6 bugs/ with a black colored muslin cloth to avoid visual cues. The sq. m, respectively, followed by a gradual increase and number of adult bugs settled on each arm was recorded at attained peak population of 5.8 bugs/sq. m and 6.4 bugs/ one hour interval. The whole experiment was carried out for sq.m, respectively during 39th standard week and it was three hours and replicated five times by interchanging the observed predating on Spodoptera litura (F.), Grapholita treatments among the arms to eliminate any photo tactic or critica (Meyr.) and M. vitrata, after which the population rd th directional influence. The percentage orientation of predatory declined markedly in the following weeks (43 to 47 bugs in different treatments was calculated and then subjected standard week) and attained lowest population (0.6 bugs/ th to statistical analysis. The experiment was conducted in the sq. m. and 0.4 bugs/sq. m., respectively) during 47 meteorological standard week of both the years. The results same manner for the other predatory bug, R. fuscipes. are in close conformity with Nebapure and Agnihotri (2011) Olfactory response predatory bugs towards different who reported that at Pantnagar, the maximum population of herbivore induced plant parts of pigeonpea: The influence predatory stink bug, E. furcellata was observed in Red gram, of volatiles produced by different infested plant parts of Cajanus cajan during 40th standard week and it was continued pigeonpea on the host selection behavior of the predators up to 46th standard week. Similar types of results were also was investigated by testing the following odour reported by Ahmad et al. (1996); Bhat et al. (2009) and combinations: four grams each of healthy undamaged Ahirwar et al. (2015). pigeonpea flowers, M. vitrata infested flowers and pods of Influence of weather parameters on the predatory bug, pigeonpea from which larvae were removed 15 minutes prior E. furcellata: Simple correlation worked out between to experiment vs. clean air (control). Response of E. predatory bug population and weather parameters is furcellata and R. fuscipes were studied in separate presented in Table 2. During the year 2012-13, population olfactometer experiments in similar manner as mentioned build up of E. furcellata in pigeonpea crop showed significant above. positive correlation with maximum temperature (r = 0.750**) Olfactory response of the predatory bugs towards and rainfall (r = 0.725*) whereas with other meteorological different stages of legume pod borer, M. vitrata: The parameters, the correlation was found to be non significant. influence of volatiles produced by different stages of M. But during the year 2013-14, E. furcellata population showed vitrata on the host selection behaviour of the predators was a significant positive association with maximum temperature investigated by testing the following odour combinations: (r = 0.715**), minimum temperature (r = 0.790**), evening a) healthy M. vitrata larvae (four in number), b) pupa of M. relative humidity (r = 0.706*) and rainfall (r = 0.603*). The vitrata (four in number) and c) faecal matter of M. vitrata present finding is partly confirmed with those of Pillai and larvae (four grams) versus clean air (control). Response of Agnihotri (2011) who reported that the predatory sting bug E. furcellata and R. fuscipes were studied in separate population density was positively correlated with maximum olfactometer experiments in similar manner as mentioned and minimum temperature and evening relative humidity in above. case of green gram. Olfactory response of the predatory bugs towards The multiple linear regressions revealed that the different larval instars of legume pod borer, M. vitrata: various abiotic factors were found to be most influencing The influence of volatiles produced by different larval instars factor, which contributed 81.9 and 76.7 per cent variation of M. vitrata on the host selection behaviour of the predators respectively, in E. furcellata population during both the years was investigated by testing the following odour (Table 3). The regression equation was fitted to study the combinations: a) early instar larvae of M. vitrata (four in effectiveness of weather parameters indicated that for every number), b) late instar larvae of M. vitrata (four in number) 1oC increase in maximum and minimum temperature, for and c) pre pupal stage of M. vitrata (four in number) vs. every one per cent increase in morning relative humidity clean air (control). Response of E. furcellata and R. fuscipes and for every one mm increase in rainfall, there would be an 4 LEGUME RESEARCH An International Journal increase of 1.271 and 0.147, 2.84 and 0.522, 0.176 and 0.102, 0.016 and 0.020 numbers of nymph and adult population of E. furcellata respectively, while, for every one per cent increase in evening relative humidity and for every one hour increase in sunshine hour there would be a decrease of 0.001 and 0.152, and 0.232 numbers of E. furcellata nymph and adult population respectively, for both the years 2012-13 and 2013-14. Agnihotri et al. (2012) also reported that among the various abiotic factors mean temperature (R2 = 0.001 and 0.001) and bright sunshine hours (R2 = 0.339 & 0.129) were found to be most influencing factor, in which mean temperature contributed 0.1% variation whereas bright sunshine hrs contributed 33 % and 12 % variations in predatory bug population on pigeonpea. Seasonal abundance of the predatory bug, R. fuscipes: The results on the seasonal abundance of predatory bug, R. fuscipes in relation to the abiotic factors prevailing from the month of September to November, 2013-14 and 2014-15 are depicted in Table 1. During both the years, R. fuscipes marked its first appearance during 36th meteorological standard week at flowering and pod initiation stage of the crop, with scanty population of 0.4 bugs/sq. m and 0.6 bugs/ sq. m, respectively, followed by a gradual increase and attained peak population of 4.2 bugs/sq. m and 3.4 bugs/ sq.m, respectively during 39th standard week and it was found to prey upon the larvae of M. vitrata, Helicoverpa armigera (Hubner) and nymphs and adults of Spinola, after which the population declined markedly in the following weeks (43rd to 47th standard week) and attained lowest population (0.4 bugs/sq. m. and 0.2 bugs/sq. m., on pigeonpea during 2012-14 respectively) during 47th meteorological standard week of both the years. As the temperature started declining from 45th SW, the bug population also started declining. R. fuscipes Influence of weather parameters on the predatory bug, and R. fuscipes: Simple correlation worked out between the population of R. fuscipes and weather parameters is presented in Table 2. During the year 2012-13, population build up of R. fuscipes on pigeonpea crop showed a significant positive E. furcellata correlation with maximum temperature (r = 0.605*) whereas with other meteorological parameters, the correlation was found to be non significant. But during the year 2013-14, R. fuscipes population showed a significant positive association with maximum temperature (r = 0.653**), minimum temperature (r = 0.695*), evening relative humidity (r = 0.589*) and rainfall (r = 0.669*). The multiple linear regressions revealed that the various abiotic factors were found to be most influencing factor, which contributed 69.6 and 81.2 per cent variation respectively, in R. fuscipes population during both the years (Table 3). The regression equation was fitted to study the Seasonal Seasonal abundance of predatory bugs, effectiveness of weather parameters indicated that for every 1 oC increase in maximum temperature, for every one per

Table Table 1: cent increase in evening relative humidity and for every 1 Vol. Issue , () Table 2: Correlation coefficients of E. furcellata and R. fuscipes population with abiotic factors ABIOTIC FACTORS E. furcellata R. fuscipes 2012-13 2013-14 2012-13 2013-14 Maximum temperature (ºC) 0.750** 0.715** 0.605* 0.653* Minimum temperature (ºC) 0.472 0.790** 0.260 0.695* Maximum relative humidity (%) -0.224 -0.556 -0.221 -0.422 Minimum relative humidity (%) 0.359 0.706* 0.195 0.589* Rainfall (mm) 0.640* 0.603* 0.449 0.669* Sunshine hours 0.262 0.043 0.372 0.073 *Correlation is significant at the 0.05 level (Two-tailed), ** Correlation is significant at 0.01 level (Two-tailed)

Table 3: Multiple linear regression analysis between weather parameters and population of predatory bugs on pigeonpea PREDATOR Regression Equation R2 value

E. furcellata (2012-13) Y = – 45.469 + 1.271 (X1) + 2.84 (X2) + 0.176 (X3) – 0.001 (X4) + 0.016 (X5) – 0.232 (X6) 0.819 E. furcellata (2013-14) Y = 17.357 + 0.147 (X1) + 0.522 (X2) + 0.102 (X3) – 0.152 (X4) + 0.020 (X5) – 0.232 (X6) 0.767 R. fuscipes (2012-13) Y = – 34.501 + 0.987 (X1) – 0.338 (X2) – 0.118 (X3) + 0.041 (X4) + 0.007 (X5) – 0.099 (X6) 0.696 R. fuscipes (2013-14) Y = 0.863 + 0.567 (X1) – 0.081 (X2) – 0.098 (X3) + 0.043 (X4) + 0.023 (X5) – 0.618 (X6) 0.812

X1= Maximum temperature (ºC), X2 = Minimum temperature (ºC), X3 = Maximum relative humidity (%), X4 = Minimum relative humidity (%), X5 = Rainfall (mm), X6 = Sunshine (hours) mm increase in rainfall, there would be an increase of 0.987 Therefore, it can be concluded that both these and 0.567, 0.041 and 0.043, 0.007 and 0.023 numbers of predatory bugs were most attracted to the floral volatiles nymph and adult population of R. fuscipes respectively, while produced by pigeonpea flowers that had been infested with for every 1 oC increase in minimum temperature, for every M. vitrata larvae and from which larvae had been removed. one per cent increase in morning relative humidity and for A more or less similar result was obtained by Dannon et al. every one hour increase in sunshine hour, there would be a (2010) for the parasitoid Apanteles taragamae. They also decrease of 0.338 and 0.081, 0.118 and 0.098, 0.099 and reported that the A. taragamae female wasps were 0.618 numbers of R. fuscipes nymph and adult population significantly attracted to M. vitrata-infested flowers of respectively, for both the years 2012-13 and 2013-14. cowpea from which larvae had been removed. A similar Olfactory response of the predatory bugs, E. furcellata mechanism has been shown to enhance the prey search of and R. fuscipes to different stages of M. vitrata and the parasitic wasp Cotesia marginiventris Cresson attacking infested plant parts of pigeonpea beet armyworm larvae Spodoptera exigua (Huebner) on corn The results of the experiment conducted in the plants. Infestation by larvae caused the plants to emit a blend laboratory using a four arm olfactometer is presented below:- of volatiles that attract the parasitoid (Turlings et al., 1991). Response of predatory bugs towards herbivore induced Response of predatory bugs towards different stages of volatiles of different plant parts of pigeonpea: The M. vitrata: The predatory stink bug, E. furcellata responded predatory bugs, E. furcellata and R. fuscipes responded positively and differentially to the different stages of M. positively and differentially to the different infested plant vitrata (Table 4). Among the different life stages and faecal parts of pigeonpea as presented in Table 4. Among the matter of M. vitrata, a significant higher response was noticed different treatments used, a significant higher response was towards the healthy M. vitrata larvae (treatment 2) with mean shown towards treatment 2 (M. vitrata infested pigeonpea percent orientation of 37.33 per cent. This was followed by flowers from which larvae were removed prior to experiment) 6 per cent mean per cent orientation towards treatment 1 with mean percent orientation of 36 and 38.67 per cent, (faecal matter of M. vitrata larvae), 2.66 per cent towards respectively. This was followed by 32 and 30.67 per cent treatment 3 (M. vitrata pupa) and 1.99 per cent towards orientation respectively, on treatment 3 (M. vitrata infested control arm. The predatory reduviid bug, R. fuscipes also pigeonpea pods from which larvae were removed prior to responded positively and differentially to the different experiment) and 6.67 and 8.88 per cent orientation treatments (Table 4). In this case also, a significant higher respectively, on treatment 1 (undamaged healthy pigeonpea response was observed towards the healthy M. vitrata larvae flowers). Mean per cent orientation towards control arm was (treatment 2) with mean percent orientation of 38.67 per only 1.99 per cent in case of E. furcellata and 1.33 per cent cent. This was followed by 6.67 per cent mean per cent in case of R. fuscipes. This clearly indicated that the odour orientation towards treatment 1 (faecal matter of M. vitrata experiences from pigeonpea were preferred by these larvae), 2.00 per cent towards treatment 3 (M. vitrata pupa) predatory bugs over clean air. and 1.33 per cent towards control arm. 6 LEGUME RESEARCH An International Journal Table 4: Olfactory responses of E. furcellata and R. fuscipes to plant and pest mediated semiochemicals Per cent orientation of predatory bugs, E. furcellata and R. fuscipes

SET 1 SET 2 SET 3 TREATMENTS Orientation towards different Orientation towards different Orientation towards different infested plant parts of pigeonpea stages of M. vitrata larval instars of M. vitrata E. furcellata R. fuscipes E. furcellata R. fuscipes E. furcellata R. fuscipes

b b a a c e Treatment 1 (T1) 6.67 (14.77)* 8.88 (16.06) 6.00 (13.88) 6.67 (14.77) 36.67 (37.26) 38.00 (38.05) d e b b b d Treatment 2 (T2) 36.00 (36.87) 38.67 (38.43) 37.33 (37.62) 38.67 (38.42) 31.33 (34.03) 32.67 (34.84) d d a a a b Treatment 3 (T3) 32.00 (34.41) 30.67 (33.55) 2.66 (8.41) 2.00 (6.31) 4.00 (10.19) 5.33 (13.18) Control 1.99a (6.31) 1.33a (4.21) 1.99a (6.31) 1.33a (4.21) 1.33a (4.21) 1.33a (4.21) Unsettled 26.67c (28.31) 21.33c (27.44) 51.99c (46.15) 52.66c (46.15) 27.33b (31.43) 24.00c (29.30) S.Em. ± 1.56 1.81 1.85 1.73 1.41 1.01 CD at 5% 4.61 5.35 5.46 5.09 4.17 2.98 CV (%) 17.59 20.27 20.69 19.16 15.70 11.16 *Data presented in parentheses are angular transformed value In a column, means followed by the common letter (s) are not significant in DMRT @ 5% level of significance

Treatment details of SET 1: T1 – Undamaged healthy flowers of pigeonpea, T2 – M. vitrata infested pigeonpea flowers from which larvae were removed prior to experiment, T3 – M. vitrata infested pigeonpea pods from which larvae were removed prior to experiment Treatment details of SET 2: T1 – Faecal matter of M. vitrata larvae, T2 – Healthy M. vitrata larvae, T3 – Pupa of M. vitrata Treatment details of SET 3: T1 – Early instar larvae of M. vitrata, T2 – Late instar larvae of M. vitrata, T3 – Pre pupal stage of M. vitrata

Thus it can be concluded that both the predatory bugs case of both the predators. This clearly indicated that the displayed a much higher preference for volatiles produced odour experiences from different larval instars of M. vitrata by healthy M. vitrata larvae as compared to other life stages, were preferred by E. furcellata over clean air (control). larval faecal matter or clean air. Though the bugs did Thus both the predatory bugs displayed a higher discriminate volatiles from M. vitrata pupa and its larval preference for volatiles produced by early instar M. vitrata faecal matter against clean air but they did not show much larvae as compared to late instar larvae or pre pupal stage of preference for these volatiles over clean air (control). Dannon M. vitrata. Pillai and Agnihotri (2013) also observed et al. (2010) also reported that olfactory cues from M. vitrata maximum predation by Eocanthecona furcellata on second larvae were used by the wasp, Apanteles taragamae in its instar larvae of M. vitrata. host selection process. Response of predatory bugs towards different larval Hence on the basis of above results and discussion, instars of M. vitrata: Among the different larval instars of it is concluded that the two heteropteran bugs, E. furcellata M. vitrata, a significant higher response was shown by the and R. fuscipes were found abundant during flowering and predatory bugs, E. furcellata and R. fuscipes towards pod initiation stage of pigeonpea crop. These two bugs were treatment 1 (early instar larvae of M. vitrata) with mean observed as important predators of M. vitrata, a major insect percent orientation of 36.67 and 38.00 per cent, respectively. pest of pigeonpea. Higher temperatures and cloudy This was followed by 31.33 and 32.67 per cent orientation conditions favoured the population build up of both these respectively towards treatment 2 (late instar larvae of M. predators. The results from this study also depicted the vitrata) and 4.00 and 5.33 per cent, respectively towards importance of M. vitrata induced floral volatiles produced treatment 1 (pre pupal stage of M. vitrata). Mean per cent by pigeonpea in the host selection process of these two orientation towards control arm was only 1.33 per cent in predatory bugs.

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