Bio-Efficacy of Spinetoram 6% W/V (5.66% W/W) + Methoxyfenozide 30% W/V (28.3% W/W) SC against Pod Borers Infesting Greengram [Vigna radiata (L.) Wilczek]

Mung gram or greengram (Vigna radiata L.) is a significant legume in South Asia. It is indigenous to India and Central Asia and has been grown in these regions since prehistoric times. Moreover, their role in improving the fertility of the soil, by microbial fixation of atmospheric nitrogen, further enhances their importance and utility. The total area covered by pulses in India was around 30.37 million hectares (Anonymous, 2022) and India is the largest producer of greengram. Pulses occupy a unique position in the Indian economy and being the major source of proteins in diet. It consists of easily digestible high-quality protein (24%), phosphorus (0.32%), iron (0.0073%), carotene (0.00039%), niacin (0.0021%) and energy 334 cal/100 g of greengram (Singh et al., 2009). A number of factors are responsible for less yield, however, losses caused by insect pests are one of the major factors, therefore, appropriate and efficient pest control techniques should be undertaken to reduce these losses. The blue butterfly (Lampides boeticus L.) and spotted pod borer (Maruca vitrata F.) are the two major pests infesting greengram. Thus, the unique insecticide combination was evaluated to curb insect pests of greengram.

Effect of spinetoram 6% w/v + methoxyfenozide 30% w/v SC on borers
 
Number of L. boeticus and M. vitrata larvae varied from 6.0 to 7.3 and 3.3 to 4.6 per ten plants, respectively, before imposing treatments. Spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 144 g a.i./ha was significantly superior and registered the lowest larval population of L. boeticus (1.42 per ten plants) (85.75% reduction over control) and M. vitrata (0.97 per ten plants) (86.97% reduction over control) (Table 1).
 
Spinetoram 6% w/v + methoxyfenozide 30% w/v SC against pod damage due to pod borers
 
Flubendiamide 34.35 SC @ 48 g a.i./ha was superior in minimizing the pod damage (5.7%) which was statistically on par with spinetoram 6% w/v + methoxyfenozide 30% w/v @ 144 and 126 g a.i./ha (5.9%) (Table 2).

 

The present findings are in agreement with Singh and Singh (2019) who found minimum pod and grain damage in green gram by M. vitrata due to spinosad 60 g a.i. ha^-1 (7.17, 2.84%) followed by emamectin benzoate 8 g a.i. ha^-1 (9.50, 4.88%) and fipronil 100 g a.i. ha^-1 (11.33, 7.44%). Similar reports were given by Yadav and Singh (2014) and Sonune et al. (2010). Similarly, spinosad 45 SC was proved to be effective against Helicoverpa armigera Hubner and M. testulalis infesting greengram (Meena et al., 2022). Selvam et al. (2020) stated that flubendiamide 480 SC recorded the lowest larval population of gram blue butterfly, Euchrysops cnejus Fab. (1.83 larvae/ plant).
 
Effect of spinetoram 6% w/v + methoxyfenozide 30% w/v SC on grain yield of greengram
 
The highest grain yield was recorded for spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 144  g a.i./ha (578.96 kg/ha), which was followed by flubendiamide 34.35 SC @ 48g a.i./ha (555 kg/ha). compared to untreated plot which recorded 287.96 kg/ha grain yield (Table 2).

Similarly, an  increase in grain yield (8.86 q/ ha) was obtained in spinosad treated green gram field by Singh and Singh (2019). The present findings are in agreement in Umbarkar and Parsana (2014), Yadav and Singh (2014), Kaushik et al. (2016) and Meena et al. (2022) who reported the maximum grain yield from spinosad treatment. Singh et al. (2020) recorded the highest marketable yield in flubendiamide 20 WG @ 1.0 g/l (9.14 q/ ha) and spinosad 45 SC @ 0.3 ml/l (9.13 q/ ha).
 
Effect of spinetoram 6% w/v + methoxyfenozide 30% w/v SC on spiders
 
Data on population of spiders on insecticide treated and control plots are given in Table 3. Mean population after two sprays revealed that spider population was the maximum in untreated check (4.65 per ten plants) followed by spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 126 g a.i./ha (4.45 per ten plants), spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 135 g a.i./ha (4.30 per ten plants) and spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 144 g a.i./ha (4.28 per ten plants) treated plots.


 
Effect of spinetoram 6% w/v + methoxyfenozide 30% SC on coccinellids
 
Data on population of grubs and adults of coccinellids on insecticide treated and control plots are given in Table 4. Mean population of coccinellids., Menochilus sexmaculatus Fab. and Coccinella transversalis F. after two sprays revealed that coccinellid population was maximum in untreated check (2.3 per ten plants) followed by spinetoram 6% w/v + methoxyfenozide 30% w/v @ 126 g a.i./ha (2.15 per ten plants), spinetoram 6% w/v + methoxyfenozide 30% w/v @ 135 g a.i./ha (2.11 per ten plants) and spinetoram 6% w/v + methoxyfenozide 30% w/v@ 144 g a.i./ha (1.95 per ten plants) treated plots.


 
Studies on phytotoxicity of spinetoram 6% w/v + methoxyfenozide 30% w/v SC in greengram
 
Spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 144 g a.i/ha and spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 288 g a.i/ha did not cause any phytotoxic symptoms like leaf injury, wilting, vein clearing, necrosis, epinasty and hyponasty at any day after treatment on stems, leaves, flowers and pods of greengram. 

Out of eight treatments evaluated against lepidopteran pod borers viz., M. vitrata and L. boeticus, two sprays of spinetoram 6% w/v + methoxyfenozide 30% w/v SC @ 144 g a.i/ha and flubendiamide 34.35 SC @ 48 g a.i/ha from 45 DAS at 15 days interval proved to be most effective and no lethal effect was recorded to the coccinellid predators, M. sexmaculatus, C. transversalis and spiders. They did not cause any phytotoxic symptoms like leaf injury, wilting, vein clearing, necrosis, epinasty and hyponasty at any day after treatment on stems, leaves, flowers and pods of greengram.