Mustard aphid, Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae): Its management and impact on predatory fauna in rapeseed mustard under organic farming conditions

Rapeseed- mustard is an important source of edible oil but vulnerable to attack by various insect pests. More than three dozen insect pests are known to be related with rapeseed mustard crop in India. Among them, mustard aphid, Lipaphis erysimi (Kalt.) is a major pest on rapeseed-mustard. Bio-efficacy of PAU homemade neem extract (PAU HMNE) @ 5.0, 7.5 and 10.0 L ha⁻¹ along with standard check, Actara (thiamethoxam 25 WG) @ 100 g ha⁻¹ was tested against L. erysimi on gobhi sarson under organic farming conditions. All treatments were applied twice, first when aphid population reached at economic threshold level, ETL (50–60 aphids per 10 cm terminal portion of the central shoot of plant) and second after 7 days of first spray. Water spray and untreated control were kept for the comparison purpose. Three replications were kept for all the treatments. Aphid incidence was recorded on 10 cm terminal portion of central shoot from 10 randomly selected tagged plants per plot. On pooled mean basis, Actara 25 WG @ 100 g ha⁻¹ was found to be most effective against mustard aphid offering highest per cent reduction over control (PROC) viz. 85.01- 94.67 and 83.75–89.66% during 2020–21 and 2021–22, respectively, but it also registered highest predators’ mortality. In contrast, a locally prepared neem extract, PAU HMNE @ 10.0 L ha⁻¹ was next to record high PROC, i.e., 37.44 to 48.28% and 43.57 to 50.06% in 2020–21 and 2021–22, respectively, and highest predators’ population. A highest seed yield of mustard (14.80 and 16.85 q ha⁻¹) was marked in Actara 25 WG @ 10.0 L followed by PAU HMNE @ 10.0 L (13.83 and 16.24 q ha⁻¹) over the untreated control plots with lowest seed yield (11.30 and 14.60 q ha⁻¹) in 2020–21 and 2021–22, respectively.