Field experiment was conducted during
rabi, 2016-17 to evaluate the efficacy of nine insecticides/botanicals against pea stemfly, in the field were assessed at different intervals.
Plant mortality after 7 days of insecticidal/ botanical application
After seven days of insecticides/botanicals application, it was observed that all the treatments were found significantly superior in reducing the plant mortality over control. However, non significance difference was observed within different treatments. The minimum plant mortality of 2.78 per cent was observed in the treatment of cartap-hydrochloride whereas; the maximum plant mortality was recorded in NSKE which was at par with the treatments of azadirachtin and neem. The order of effectiveness of insec--ticides/botanicals after seven days of application was found to be cartaphydrochloride) >phorate>acephate>oxydemetonmethyl >quinalphos > dimethoate>azadirachtin > neem oil > NSKE.
Plant mortality after 14 days of insecticidal/ botanical application
It is evident from the Table 1, that all the treatments were found significantly superior over control after fourteen days of application of insecticides/botanicals in reducing the plant mortality. The minimum plant mortality was recorded in the treatment of cartap-hydrochloride, which was statistically non- significant with phorate, acephate, oxydemeton-methyl, dimethoate and quinalphos resulted in plant mortality. The maximum plant mortality of 6.13 per cent was recorded in the treatment of NSKE.
Plant mortality after 21 days of insecticidal/ botanical application
It was observed that no significant difference was found among the insecticidal/botanical treatments and all these treatments were significantly superior in reducing the plant mortality over control. The plant mortality in different insecticides/ botanicals treatments ranged from 2.05 to 5.87 per cent. The minimum and maximum plant mortality of 2.05 per cent and 5.87 per cent were recorded in the treatment of cartap-hydrochloride and neem oil, respectively whereas, in control the plant mortality was 6.00 per cent.
Plant mortality after 28 days of insecticidal/ botanical application
All the treatments were found significantly superior in decreasing the plant mortality over control. The minimum plant mortality of 1.92 per cent was recorded in the treatment of cartap-hydrochloride followed by phorate, acephate, oxydemeton-methyl, quinalphos and dimethoate, respectively. The maximum plant mortality of 5.00 per cent was observed in the treatments of neem oil and NSKE which was non- significant with control (5.24%).
Plant mortality after 35 days of insecticidal/ botanical application
Thirty five days after the application of insecticides/botanicals, it was observed that all the treatments were significantly better in reducing the infestation of pea stemfly over control. The minimum plant mortality 0.56 per cent was observed in the treatment of cartap-hydrochloride.
Plant mortality after 42 days of insecticidal/ botanical application
After forty two days of application of different insecticides/botanicals, it was observed that no plant mortality was observed in insecticidal treatments except NSKE (0.78%), while in control it was 1.67 per cent.
The present findings were also in confirmation with the findings of
Singh et al., (1988) where they found minimum and maximum plant mortality in plots which were treated with phorate (basal dressing) and dimethoate, respectively whereas, in present findings the minimum infestation was found in cartap-hydrochloride.
Brar et al., (1993) further confirms the present finding that phorate 1 kg a.i. ha
-1 was found most effective insecticide against stemfly in pea.
Srivastava and Sehgal (2000) evaluated bio-efficacy of various insecticide against stemfly and found that acephate has given good control of stemfly population, they have also tested nimbecidine for the control of stemfly and found that a comparative good control of pea stemfly. The present result corroborated with findings of
Kumar and Sharma (2003) they found dimethoate and nimbecidine as significantly superior treatment against stemfly on pea.
However, the present findings were partially supported by findings of
Purwar and Yadav (2004) where they reported NSKE 4% have considerably reduced the stemfly infestation. They further found that in chemical control acephate 0.1% have recorded less stemfly infestation followed by quinalphos 0.05%.
Krishankant (2005) worked on synthetic pyrethroids with plant product like neem oil, which also reduce the incidence of stemfly where in present findings neem oil have also reduced the infestation compare to control. Likewise, Mittal and Ujjagir (2005) found NSKE 5 per cent as a minimum effective botanical against stemfly, as in the present findings NSKE also showed minimum effect on infestation of stemfly.
In present findings cartap-hydrochloride proved best in minimizing the stemfly infestation. Similar observations were also taken by
Singh et al., (2010) where they also recorded the same trend of effectiveness. However in both the findings NSKE has resulted the least effect against stemfly.
Effect of insecticidal/botanicals application on the seed yield of pea
All the insecticidal/botanical treatments increased seed yield of pea over untreated control (Table 1). The maximum seed yield of pea 21.55 q ha
-1 was obtained from the treatment of cartap-hydrochloride followed by phorate 10, acephate, oxydemeton-methyl, quinalphos and dimethoate resulted in 21.00, 20.80, 20.60, 20.45 and 19.95 q ha-while, the minimum seed yield of pea was recorded in the untreated control (16.05 q ha
-1). In the treatments of botanicals the seed yield of pea 17.40, 17.16 and 17.10 q ha
-1 was obtained from the treatments of azadirachtin neem oil and NSKE, respectively. Similarly,
Singh et al., (2010) also obtained the highest seed yield of field pea in the treatment of cartap-hydrochloride.
Assessment of losses and economics of insecticidal / botanicals treatments
Assessment of losses and increase in seed yield
In plots treated with cartap-hydrochloride the avoidable loss and total avoidable loss was zero (Table 2) followed by phorate, acephate (0.075 %), oxydemeton-methyl, quinalphos and dimethoate. The maximum per cent avoidable losses of 25.51 q ha
-1 and total avoidable loss 5.50 q ha
-1 was recorded in control followed by the treated plots with NSKE, neem oil and azadirachtin. The maximum increase in yield over control was recorded in the plots treated with cartap-hydrochloride in which the per cent increase in yield over control was 34.24 and total increase in yield over control was 5.50 q ha
-1. The minimum increase in yield over control was recorded in NSKE in which the per cent increase in yield over control was 6.54, whereas, total increase in yield over control was 1.05 q ha
-1 followed by neem oil and azadirachtin.
Economics of insecticidal/botanical treatments:
While judging the utility of any insecticide/botanical in the pest management programme, the effectiveness of the chemicals is as curtained not only by its relative potency against target pest and period for which its application provides protection, but economics of the treatments also remain a major consideration. The maximum incremental benefit-cost ratio was recorded in the treatment of acephate 0.075 per cent which gave a incremental benefit-cost ratio of 33.22 (Table 2) followed by dimethoate, oxydemeton-methyl, quinalphos, cartap-hydrochloride and phorate. The minimum incremental benefit-cost ratio of 2.77 was recorded in the treatment of NSKE followed by neem oil and azadirachtin, respectively. However, the net return of RS. 25846 ha
-1 was obtained from the treatment of cartap-hydrochloride 4G followed by acephate 0.075 per cent which resulted net profit of Rs. 23056 ha
-1 whereas, the least net return of Rs. 3856 ha
-1 was obtained from the treatment of NSKE. These results support from the findings of
Singh et al., (2010) Since they have also found the maximum net return of Rs. 13830 ha
-1 from field pea with the treatment of cartap-hydrochloride + endosulfan against pea stemfly on field pea.
