Studies on Population Dynamics of Major Insect Pests Of Soybean (Glycine max (L.) Merrill and their Management Through Promising Botanicals and Newer Insecticides
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Date
2013
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JNKVV
Abstract
ABSTRACT
Present research work on “Studies on population dynamics of major insect pests of soybean (Glycine max ( L.) Merril) and their management through promising botanicals and newer insecticides” was conducted in kharif 2012-13 at J.N.K.V.V., Research Farm, College of Agriculture, Tikamgarh (M.P.).The experiment was conducted with the following objectives.
1. To find out the peak period of incidence of major insect pests of soybean in relation to weather factors.
2. To find out the efficacy of some botanicals and chemical pesticides against the major insect pests of soybean.
3. To workout the economics of the management of major insect pests of soybean.
Studies on population dynamics of major insect pests of soybean (Glycine max ( L.) Merril) and their management through promising botanicals and newer insecticides revealed that white fly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), jassid, Amrasca devastans (Hemiptera: Cicadellidae), green semilooper, Thysanoplusia orchalcea Walker (Lepidoptera: Noctuidae), tobacco caterpillar, Spodoptera litura Fabricius (Lepidoptera: Noctuidae), Stem fly, Melanagromyza sojae Zehntner (Diptera: Agromyzidae), girdle beetle Obereopsis bravis (coleoptera: Cerambycidae) were the main pests which damaged the crop.
The green semilooper, Thysanoplusia orchalcea infested the crop from the 33rd SW (13August to 19August) to 40th SW (01Octomber to 07Octomber). During the pest activity, the maximum population (2.30 larvae/mrl) was recorded in the 35th SW (27August to 02September).
. During the peak larval population the maximum and minimum temperature were 32.40 C and 25.00 C, respectively, and maximum and minimum relative humidity were 92.7% and 71.7% respectively, whereas rainfall was 37.4mm.
Correlation studies revealed that maximum temperature and evaporation exhibited significantly positive correlation (r= 0.51, 0.56 respectively) with green semilooper larval population.
Whereas minimum temperature, morning relative humidity and evening relative humidity observed significantly negative correlation(r = -0.76, -0.53, -0.71 respectively) with green semilooper larval population while rainfall was found to be negatively correlated(r = -0.33) with green semilooper larval population but to the non-significant level.
The first appearance of tobacco caterpillar was recorded during 33rd standard week (13 august to 19 august). The larval population of tobacco caterpillar was 0.6 larvae/mrl during 33rd SW, which reached at its first peak (1.6 larvae/mrl) during 34th SW (20 August to 26 August). During this week the maximum and minimum temperature were 30.80 C and 24.10 C, respectively, and morning and evening relative humidity were 95.0% and 83.0% respectively. Whereas rainfall was 30.7mm.
Thereafter, the tobacco caterpillar population attained its second peak (2.3 larvae/plant) during 37th SW (10 September to 16 September). During this period the maximum and minimum temperature were 30.70 C and 24.30 C, respectively, and morning and evening relative humidity were 98.0% and 80.0% respectively. Whereas rainfall was 82.8 mm.
Correlation studies revealed that maximum temperature and morning relative humidity exhibited significant positive correlation (r= 0.53, 0.57) with larval population of this pest.
Correlation studies further revealed that minimum temperature, evening relative humidity, rainfall and evaporation were found to be negatively correlated (r = -0.08, -0.19, -0.37,-0.06 respectively) to non significant level.
The first appearance of white fly was recorded during 33rd standard week (13 august to 19 august) with the population of whitefly 1.6 per 3 leaves/plant, which reached at its first peak (6.1per 3 leaves/plant) during 39th SW (24 September to 30 September). During the peak period of white fly population the maximum and minimum temperature were 33.70 C and 21.80 C, respectively, and morning and evening relative humidity were 93.4% and 51.9% respectively and rainfall was nil.
Correlation studies revealed that maximum temperature and evaporation exhibited significant positive correlation (r= +0.70, +0.58 respectively) with white fly population.
While evening relative humidity, and rainfall were found to be negatively correlated (r = -0.63, -0.71 respectively) with white fly population to the level of significance.
However, morning relative humidity and minimum temperature observed non-significant correlation.
In the present study, first appearance of Jassid was recorded during 33rd standard week (13 august to 19 august) with 1.4 Jassid per 3leaves/plant and was at its first peak (2.5 Jassid per 3leaves/plant) during next week (20 august to 26 august). During this peak period of Jassid population, maximum and minimum temperature were 30.80 C and 24.10 C, respectively, and morning and evening relative humidity were 95.0% and 83.0% respectively whereas rainfall was 30.7mm.
Thereafter attained its second peak (2.5 Jassid per 3leves/plant) during 38th SW (17 September to 23 September). During this period, maximum and minimum temperatures were 31.60 C and 23.40 C, respectively, and morning and evening relative humidity were 92.7% and 63.4% respectively. Whereas rainfall was only 0.3mm.
Correlation studies revealed that incidence of Jassid did not exhibit any significant correlation with any weather factor.
Infestation of stem fly started in 34st SW (20 august to 26 august) with 1.4% stem tunneling.
After 34th SW there was a sudden increase in the per cent infestation by stem fly to (7.6%) tunnel of stem in the 35th SW (27 august to 02 September). During this period maximum and minimum temperatures were 32.40C and 25.00C respectively, and maximum and minimum relative humidity were 92.7% and 71.7% respectively. Whereas rainfall was 37.4mm.
After 35th SW there was a gradual increase in the infestation by stem fly at being 11.0 % tunneling of stem in 40th SW (before harvest of the crop).
Correlation studies revealed that maximum temperature exhibited significant positive correlation (r= 0.79), with stem fly infestation .However, morning relative humidity, minimum temperature and evaporation exhibit not significant correlation.
Whereas, Evening relative humidity, and rainfall were found to be negatively correlated (r = -0.67, -0.65 respectively) with stem fly infestation to the level of significance.
Infestation of girdle beetle was observed in 33rd standard week (13 august to 19 august) with 1.8 girdled plant /mrl which reached to its peak (0.56 girdle/mrl) during 36th SW (03 September to 09 September). During this week, maximum and minimum temperature were 31.10 C and 24.20 C, respectively, and morning and evening relative humidity were 96.7% and 78.1% respectively. Whereas rainfall was 36.4mm.
Correlation studies revealed that maximum temperature, exhibited significant positive correlation (r= 0.68) with the infestation of girdle beetle.
Whereas minimum temperature, evening relative humidity, and rainfall were found to be negatively correlated (r = -0.58, -0.68, -0.57 respectively) with the incidence of this pest to the level of significance.
Other a biotic factors did not have significant impact on the incidence of girdle beetle.
On the basis of effectiveness of different chemicals and botanicals treatments against defoliators and grain yield obtained, it can be said that Indoxacarb 14.5 SC 500ml/ha followed by Cypermethrin 10 EC 600ml/ha were the most effective treatments when applied as foliar sprays at 45 and 60 days old crop. However, among the three botanicals insecticides, NSKE was found best treatment for reducing the defoliator’s larval population.
These treatments were effective not only in reducing the defoliator’s larval population but also recorded higher grain yields.
On the basis of effectiveness of different chemicals and botanicals treatments against stem borers(Girdle beetle) and grain yield obtained, it can be said that Triazophos 40 EC 1200ml/ha followed by Lambda-cyhalothrin 5 EC 300ml/ha were the most effective treatments when applied as foliar sprays at 45 and 60 days old crop. However, among the botanicals insecticides, NSKE was proved to be most effective treatment for reducing the stem borer population. While tobacco leaf extract was least effective.
These treatments were effective not only in reducing the stem borer but also recorded higher grain yield.
In case of stem tunneling caused by stem fly, Imidaclopride 17.8 SL @ 300ml/ha was found most effective in reducing the stem tunneling followed by Cypermethrin10 EC and Chlorpyriphos 20 EC. Whereas the Lambda-cyhalothrin 5 EC was observed least effective in reducing stem tunneling. Among the three botanicals insecticides, NSKE was found most effective in reducing the stem tunneling.
Treatment Cypermethrin 10 EC gave maximum net profit among all the treatments followed by Triazophos 40 EC and Indoxacarb 14.5 SC, whereas Incremental cost benefit ratio was maximum with the treatment of Lambda-cyhalothrin 5 EC. The minimum net profit and Incremental cost benefit ratio was recorded in the treatment of Tobacco leaf extract and NSKE respectively.