Pest Dynamics under Conservation Agriculture based Cereal Systems of South Asia

Pests are the key yield limiting factors in agricultural production systems around the world. Their population dynamics are shown to vary with the modifications in agro-ecosystem, cropping system and management practices. Plentiful information is available on assessment of their seasonal population fluctuations mainly due to abiotic factors in conventional tillage (CT) based cereal production systems. However, while transitioning from CT based production systems to a more stable and ecologically sustainable conservation agriculture (CA)- based systems, the pest dynamics particularly in relation to biotic factors are not clearly understood. Therefore, we conducted a systematic study on pest dynamics under long-term CA in major cropping systems of North-West Indo-Gangetic plains. In our study, crop rotations, no-tillage and residue retention led to more diverse aerial and epigeic arthropod communities which seemingly increased biological control of pests through predation by natural enemies, that subsequently resulted in no significant increase of pests in the CA-based cereal systems. CA-based ricewheat (RW) system had the highest insect diversity than respective CT system and maize-wheat (MW) systems. In RW system, stem borers (+7.0% and -11.2%), leaf folders (15.6% and 4.8%), leafhoppers (-2.9% and -3.6%) and grain sucking insects (0% and -2.0%) were observed at tillering and grain filling stage, respectively under CA- based system compared to CT- system. Similarly, in MW system, stem and silk borers (-14.8% and -14.0%), defoliators (-4.6% and -36.8%), beetles (-22.9% and -4.2%), shoot fly (-9.2% and 0%) were recorded. The parasitoids and predators density under CA-based RW system was about 20 folds at tillering stage and 3.5 folds at grain filling stage, while, under CA-based MW system it was 6.4 times (at tillering stage) and 3.9 times (at grain filling stage) as compared to their CT counterparts. The increased density of both aerial and epigeic beneficial arthropod diversity perhaps yields in increased niche differentiation and consequently reduced herbivory in CA systems. The CA systems naturally conserve and foster beneficial biodiversity that potentially helps mitigating the populations of several detrimental arthropods by making production systems more amenable to biocontrol.