Field margins and botanical insecticides enhance Lablab purpureus yield by reducing aphid pests and supporting natural enemies

Abstract

Botanical insecticides offer an environmentally benign insect pest management option for field crops with reduced impacts on natural enemies of pests and pollinators while botanically rich field margins can augment their abundance. Here, we evaluated the non-target effects on natural enemies and pest control efficacy on bean aphids in Lablab of three neem-and pyrethrum-based botanical insecticides (Pyerin75EC®, Nimbecidine® and Pyeneem 20EC®) and determine the influence of florally rich field margin vegetation on the recovery of beneficial insects after treatment. The botanical insecticides were applied at the early and late vegetative growth stages. Data were collected on aphids (abundance, damage severity and percent incidence) and natural enemy (abundance) both at pre-spraying and post-spraying alongside Lablab bean yield. The efficacy of botanical insecticides was similar to a synthetic pesticide control and reduced aphid abundance by 88% compared with the untreated control.However, the number of natural enemies was 34% higher in botanical insecticidetreated plots than in plots treated with synthetic insecticide indicating that plantbased treatments were less harmful to beneficial insects. The presence of field margin vegetation increased further the number of parasitic wasps and tachinid flies by 16% and 20%, respectively. This indicated that non-crop habitats can enhance recovery in beneficial insect populations and that botanical insecticides integrate effectively with conservation biological control strategies. Higher grain yields of 2.55-3.04 and 2.95-3.23 t/ha were recorded for both botanical insecticide and synthetic insecticide in the presence of florally enhanced field margins in consecutive cropping seasons. Overall, these data demonstrated that commercial botanical insecticides together with florally rich field margins offer an integrated, environmentally benign and sustainable alternative to synthetic insecticides for insect pest management and increased productivity of the orphan crop legume, Lablab.

Life-table parameters, functional response, flight ability, and cross-generational effects of matrine demonstrate its safety to Hippodamia variegata (Coleoptera: Coccinellidae)

“…Yang et al (2019) demonstrated that use of broad-spectrum synthetic insecticides prevented noncrop habitats from improving the population density of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in wheat fields. In general, pest control benefits more from the use of more selective insecticides that have low toxicity to natural enemies because larger natural enemy population are preserved (Fang et al 2018, Torres and Bueno 2018, Machado et al 2019, Ochieng et al 2022). Our studies show that matrine is a natural enemy friendly insecticide that is effective against A. gossypii and safe to H. variegata even when used at higher concentrations than it recommended by product labels.…”

Four Most Pathogenic Superfamilies of Insect Pests of Suborder Sternorrhyncha: Invisible Superplunderers of Plant Vitality

“…Thus, for example, in the USA, the resistance of the A. gossypii to organophosphates and pyrethroid was recorded as early as 1992 [ 172 ]. Despite the growing resistance, large farmers are forced to continue using chemical means of protection, combining them with biological methods [ 173 ] and botanical insecticides [ 174 , 175 , 176 ].…”

Field margins and cropping system influence diversity and abundance of aphid natural enemies in Lablab purpureus

“…The treatments were laid out using a 2 × 2 factorial arrangement in a randomized complete block design (RCBD) with four replications, giving a total of 16 plots. The experimental plots measuring 10 × 10 m were isolated from each other by a distance of 20 m. Lablab is a short crop; the 20 m separation was adopted as the compromise distance in conformity with typical smallholder land holdings (field sizes) as reported by Ochieng et al (2022) that also minimizes insect movement between any two experimental plots. Lablab monocrop was planted at a spacing of 0.5 × 0.3 m. In the maize-lablab intercrop, maize was planted at a spacing of 0.75 × 0.3 m, 1 seed per hill and lablab was planted between the maize rows at an intra-row spacing of 0.3 m, 2 seeds per hill.…”

“…Agricultural systems that rely heavily on mechanization and synthetic inputs such as pesticides disrupt non‐crop habitats where such natural enemies of pests seek refuge (Balzan et al, 2016; Bommarco et al, 2013) This calls for approaches that will balance the benefit of agricultural intensification and restore biocontrol service through enhancing the role of natural enemies in pest management. Conservation of important biological control agents provide a sustainable pest management option that can reduce dependency on the application of synthetic pesticides (Ochieng et al, 2022).…”