Vol.4 No.1, 46-51 (2015) Received: April.2015; Accepted: May, 2015 Effect of Weather Factors on Seasonal Incidence of Insect-Pests of Soybean Pragya Yadav 1, S. Banerjee 2, M. P. Gupta 3 and V. K. Yadav 4 Department of Zoology, M. L. B. Govt. PG. College, Bhopal 1,2 JNKVV,College of Agriculture, Ganjbasoda, M.P.,4 Email: pragya_zoology@yahoo.com Abstract During kharif season of 2010, some major, minor insects, natural enemies and one entomopathogenic fungus were recorded on soybean at Tikamgarh (M.P.). Among these insects, population of blue beetle increased with the increase in minimum temperature, RH and rainfall. But population of semilooper, tobacco caterpillar, jassid decreased with increase in rainfall and RH. Similarly the population of white fly, stem fly and girdle beetle also decreased with the increase in rainfall. Population of some natural enemies i.e. coccinelids, predatory bug and Beauveria bassiana decreases with the increase in maximum temperature but population of predatory bug increases with increase in minimum temperature and RH. High RH and low temperature favours the incidence of Beauveria bassiana. Population of coccinelids and spiders increased with increase in rainfall. Key words: Abiotic factors, Glycine max, insect pests, natural enemies Introduction Soybean [Glycine max (L.) Merrill] is a unique crop with high nutritional value, providing 40 per cent protein and 20 per cent edible oil besides minerals and vitamins. It also supports many industries, soybean oil is used as raw material in manufacturing antibiotics, paints, varnishes, adhesives, lubricants etc. Soybean meal is used as protein supplement in human diet, cattle and poultry feed [1]. Soybean is a major oil seed crop of world grown in an area of 113.01 million ha with production of 283.79 million tons and productivity of 2.51 t/ha, India ranks fourth in world in respect of area and [2] production. In Madhya Pradesh, soybean occupies an area of 5.12 million ha with production of 5.85 mt and productivity of 1142 kg per ha during 2008-09. In Indian scenario, Madhya 46 Pradesh contributes about 53.88% and 59.06% in total area and production of soybean, respectively in the country and is known as soya state. The luxuriant crop growth, soft and succulent foliage attracts many insects and provides unlimited source of food, space and shelter. Soybean crop is reported to be attacked by about 350 species of insects in many parts of the world [8]. More than 150 insect pests cause damage to soybean in various parts of Madhya Pradesh [17], and damage due to these insect-pests is one of major constrains for soybean production. The incidence of these pests is very much variable perhaps due to fluctuation in the weather parameters. Keeping this in view, the seasonal incidence of these pests was studied at Tikamgarh (M.P.) during kharif season of 2010 in relation to abiotic factors i.e. temperature, relative humidity and rainfall.
Materials and Methods Studies on seasonal incidence of insect-pests of soybean was carried out during kharif season of 2010 at Farmers Field near College of Agriculture, Kundeshwar Road, Tikamgarh (M.P.). Soybean variety JS 93-05 was sown in first week of July, 2010 @ 80kg/ha in row, in an area of 200 square meters. Crop was grown following the recommended doses of fertilizer 20kg N: 60kg P 2 O 5 : 20kg K 2 O/ha as basal dose. Distance between rows and plants were maintained at 40 and 10 cm, respectively. All the recommended agronomic practices were followed to grow the crop except the measures for insect pest control. The observations on the appearance of major insect pests were recorded from germination to harvest of the crop at weekly intervals as per procedure approved in All India Coordinated Research Project on soybean. Observations on different insect pests and their natural enemies were recorded at 10 sites of 1 meter row length/site once in standard week and coefficient of correlation was worked out between the pest population and weather parameters. Results and discussion A) Seasonal incidence of important insect pests of soybean During Kharif season of 2010, seven major insect pests and four natural enemy including one micro-organism were observed on the soybean crop at Tikamgarh Table1. Among seven insect pests, one seed and seedling feeders (Cneoranae sp.) two Stem borers (Obereopsis brevis, Melanogromyza sojae), two Foliage feeders: Chrysodeixis acuta, Spodoptera litura and two Sap feeders: Bemisia tabaci, Amrasca bigutula were recorded. The incidence and injuriousness of about 20 insect-pests of soybean in Orissa, Bihar and M.P.have been reported earlier [3, 5, 10 and 18]. Blue beetle The blue beetle (adult) infestation was observed on the crop just after the emergence of cotyledon with the average population of 0.2 adults/mrl and found in increasing trend and reached at peak (1.1 beetle/mrl) during first week of August. The population of pest decreased in 2 nd week of August and disappeared from the field in last week of August. During the period of pest infestation average weekly maximum and minimum temperature ranged between 31.7 to 35.3 0 C and 24.8 to 26.0 0 C respectively. The crop received 362.8 mm rainfall during the activity period of the pest. Similarly its appearance just after the emergence of the cotyledons in the last week of July with maximum population in the second week of August [3] and severe infestation of blue beetle in Bhopal, Raisen and Sehore districts of Madhya Pradesh [12] have been reported in the past. The average population of 3.7 beetles/mrl caused severe damage to cotyledons and trifoliate leaves. Earlier, was recorded estimated its economic threshold level less than 4.0 adults/mrl of soybean crop at Sehore. The results support the findings of these workers as climate conditions were almost similar to Tikamgarh [14]. Semilooper The infestation of semilooper started at 21 DAG, in the last week of July 2010, with an average population of 0.40 larvae/mrl then it reached at peak (5.10 larvae/mrl) at 56 DAG (Table -1). Thereafter a gradual reduction in the larval population of the pest was observed and finally disappeared from the field in the last week of September. Similarly relative humidity (72 to 83%) during month of 47
September also favored the multiplication of parasitic fungus, Beauveria bassiana, which might have reduced the larval population. During the period of activity, the pest devoured leaves, flowers and young pods, which corroborates with the [3, 10, 11 and findings of many investigators 13]. Tobacco caterpillar Infestation of tobacco caterpillar started in the third week of August, 2010 at 42 DAG, recording 0.2 larva/mrl. The larval population slightly increased and reached maximum in second week of September at 70 DAG with an average of 2.80 larvae/mrl (Table 1). Earlier, weakers found the maximum population densities around the second half of October [7]. This slight variation in appearance of tobacco caterpillar may be due to agro-climatic variation or crop age. Jassid The population of adults was observed from July 20 (Table -1) to September 28, 2010. During the infestation period the peak population (2.7/plant) was recorded on September 14, 2010 when crop was 70 days old. During this period weekly average maximum, minimum temperature and relative humidity were 32 0 C, 24.8 0 C and 72 per cent respectively. Thereafter a gradual reduction in the population of the pest was observed and finally disappeared from the field. The lowest population was recorded on July 20, 2010, when the crop age was 14 days and the weekly average maximum, minimum temperature and relative humidity were 33.5 0 C, 25.9 0 C and 77 per cent respectively (Table -1). Any increase in rainfall and maximum temperature caused decline in population [4,12]. Whitefly The whitefly infestation was observed on the crop on 13 th July, 2010 at 7 DAG, recording 1.2 nymphs and adult/plant. The population of whitefly increased gradually in third week of July and second week of August, 2010 at 21 and 35 DAG. The maximum temperature of 32.5 to 32.0 C and RH of 78 to 79% seem to be favourable for the pest. Thereafter, there was slight decrease in population of the pest, however, whitefly remained active up to third week of September at 77 DAG, and disappeared in the fourth week of the September. Earlier also determined the population of Bemisia tabaci in six different places in M. P. and found the similar levels of pest in all areas [10, 12]. Stem fly The infestation of stem fly started in first week of August, 2010 at 28 DAG with 10 per cent plant infestation and 0.30 per cent stem tunneling. Plant infestation gradually increased and reached up to 73 per cent with 48.50 per cent stem tunneling in the third week of September, 2010 (Table -1). Any Increase in rainfall, minimum temperature and Relative humidity caused decline in population. Earlier, investigators also reported that the fly infested 100 per cent plants and tunneled up to 70 per cent of stem length [15, 16]. Girdle beetle The infestation of girdle beetle started in first week of August, 2010 at 28 DAG with 0.60 per cent plant infestation. Infestation caused by grub of girdle beetle gradually increased and reaches 13.0 per cent with 38.5 per cent stem tunneling (Table 1). Any Increase in rainfall, and Relative humidity caused decline in population. The plant infestation by girdle beetle has been reported to the tune 48
of 43.10% [11], 80.8% [11] 9.8% [6] in different parts of Madhya Pradesh. Some investigators reported increased activity in the last week of August recording 3.2 damaged plants per meter row with seasonal mean of 1.73 damaged plants. The date of abundance and activity was in close observations with these workers [6]. Natural enemies Coccinelids The predatory beetle was recorded 0.3/mrl in 2nd week of August, 2010 at 35 DAG. Its population slightly increased and reached at peak (2.4 /mrl) at 63 DAG. Predatory beetles and host (pest) both were disappeared after 77 DAG (Table -2). Bug The activity of predatory bug was recorded in the 1st week of September 2010 i.e. 63 DAG, and remained active up to last week of September (84 DAG). The maximum population of predatory bug was observed in 2nd week of September at 70 DAG. Afterwards its population declined and completely disappeared after 84 DAG. Spiders The spiders appeared at 35 DAG, in the second week of August 2010, with an average population of 0.60/mrl. Spiders population slightly increased up to 49 DAG, thereafter a gradual reduction in the population was observed and finally disappeared after 77 DAG from the field. Entomopathogenic fungus, Beauveria bassiana The entomopathogenic fungus, Beauveria bassiana appeared and infect the larvae of lepidopterous pest in the last week of the August 2010, at 56 DAG. At that time maximum and minimum temperature was 33.2 o C and 25.7 o C respectively and relative humidity was 74%. The fungus remained up to third week of September i.e. 77 DAG. Due to constant rainfall and increased relative humidity, the entomophagous fungus Beauveria bassiana appeared and infect the larvae of green semilooper in the second week of September. In the present findings, it was found that the infection of Beauveria bassiana was positive correlation with RH and negative correlation with rainfall. The present findings are similar to that of earlier workers, who also observed the entomopathogenic fungus, Nomuraea rileyi in populations of the soybean green semilooper in the humid south eastern plain zone of Rajasthan. However no work has been done by other workers to find out the correlation of temperature, rainfall, RH etc. with the incidence/ appearance of entomopathogenic fungi [6]. References 1. Alexander, M.W. (1974). Soybean production in Virginia experimentation division. Virginia polytech inst. State Univ., pp. 44. 2. Anonymous. (2014). Annual report, 2013-14, Directors Report, All India Co-ordinated Research Project on soybean, Indore M. P., pp. 341. 3. Chaturvedi, S., Singh. K. J., Singh, O. P. and Dubey, M. P. (1998). Seasonal incidence and damage of major insect pest of soybean in Madhya Pradesh. Crop Reserch. 15 (2-3):260-264. 49
Table-1: Seasonal incidence of major insect pests of soybean during kharif 2010 Date of observation 13.7.10 7 DAG 20.7.10 14 DAG 27.7.10 21 DAG 3.8.10 28 DAG 10.8.10 35 DAG 17.8.10 42 DAG 24.8.10 49 DAG 31.8.10 56 DAG 7.9.10 63 DAG 14.9.10 70 DAG 21.9.10 77 DAG 28.9.10 84 DAG 4.10.10 90 DAG Blue beetle Larvae/mrl Jassids/ plant White fly Stem fly incidence (%) Girdle beetle incidence (%) adult/mrl Semilooper Tobacco caterpillar /plant Plant infestation Stem tunneling Plant infestation Stem tunneling 0.2-1.2 0.6-0.3 2.3 0.7 0.4-0.5 6.7 1.1 1.1-0.3 6.5 10 0.30 0.6 3.5 0.5 3.6-0.6 8.4 25 3.20 1 5.8 0.6 2.9 0.2 0.3 6.4 27 4.50 5.6 10.4 0.1 3.1 1.5 1.6 6.2 39 11.40 6 13.5 0.0 5.1 1.7 2.1 5.0 42 18.70 6.9 17.4 0.0 3.2 1.6 2.3 4.3 45 37.05 7 20.2 0.0 2.6 2.8 2.7 4.2 70 42.20 12.7 26.8 0.0 0.5 0.3 2.2 2.1 73 48.50 13 38.5 0.0-2.4 0.0 - Table-2: Seasonal incidence of natural enemies of soybean during kharif 2010 Date of observation 6.7.10 (germination) 13.7.10 7 DAG 20.7.10 14 DAG 27.7.10 21 DAG 3.8.10 28 DAG 10.8.10 35 DAG 17.8.10 42 DAG 24.8.10 49 DAG 31.8.10 56 DAG 7.9.10 63 DAG 14.9.10 70 DAG 21.9.10 77 DAG 28.9.10 84 DAG 4.10.10 90 DAG Coccinelids (beetles/mrl) Bugs (nymph and adults /mrl) Spiders (Spiders/mrl) Beauveria bassiana 0.3-0.6-0.4-0.8-0.5-1.2-0.1-0.9 0.4 2.4 0.3 0.8 2.5 0.2 0.9 0.5 1.3 0.2 0.5 0.3 0.6-0.2 - - 50
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