Reduced Incidence of Purple Blotch and Cercospora Leaf Spot in Garlic Through Relay Cropping and Spatial Crop Management

Abstract

Ecological pest management is an approach that uses compatible pest control techniques to promote sustainable production under varying environmental conditions. This study aimed to identify the effective management techniques and crop assemblages that sustain the performance of the garlic production system. The effectiveness of habitat management was evaluated using different relay cropping systems, planting distances, and trap and band crops to manage diseases, such as purple blotch (Alternaria porri) and cercospora leaf spot (Cercospora duddiae), and to improve yield. Results showed that planting six rows of garlic every two rows of tomato effectively controls purple blotch occurrence at bulb development (65.39%) and maturity stage (57.15%). Cercospora leaf spot was also reduced by up to 32.50% at maturity under a similar relay cropping system, followed by planting of six rows of garlic and one row each of tomato and corn. The inclusion of tomato and corn served as an effective biological control agent and a physical barrier because tomato exhibits antifungal properties and corn has tall height and broad leaves, which help reduce disease incidence and spread and lead to higher yields and net profits. These systems yielded 3.77 and 3.90 t ha^-1 , respectively. Planting distance also significantly influences disease incidence and yield. Those garlic plants planted at a distance of 20 cm x 15 cm produced the highest yield of 2.55 t ha-1 , with an increase of 18.43% compared to other distances. The use of trap and band crops, such as marigolds and corn, also decreases pest occurrence and improved crop quality as well as attract natural enemies and pollinators. Overall, the use of relay cropping, planting distances, and integration of band and trap crop reduces disease incidence and severity, increases yield and profitability, and enhances ecological stability. Thus, reduces the use of synthetic pesticide and promotes long-term sustainability and productive garlic farming.