Efficacy Of Seed Dressers And Resistance Of Sorghum Varieties In The Management Of Fall Armyworm

Abstract

Sorghum is a food security crop for millions of people in E. Africa but its production is negatively impacted by fall armyworm damage, leading to food insecurity. The aims of this study were to evaluate the efficacy of seed dressers and the resistance of sorghum varieties to manage FAW under field conditions. The study tested four seed dressers (Thiamethoxam, Imidacloprid, Lindane and Carbofuran) and screened five varieties of sorghum (Wagita, Seredo, Gadam hamam, KARI Mtama 1 and IESV24029SH) for resistance to FAW. A local check, Nakhadabo was included for comparison. The experiments were carried out at Kiboko and Alupe KALRO/ICRISAT Research Stations in a randomized complete block design in a factorial arrangement with 3 replications for two seasons of 2018/2019 respectively. The data collected included; dead heart symptoms, FAW leaf feeding damage, number of larvae per plant and days to 50% flowering, panicle damage symptoms, plant height and grain weight. Lindane (4) recorded the lowest dead heart symptoms compared to untreated controls (6.2). All seed dressers compared to untreated controls, recorded less leaf feeding damage. However, Lindane (9) was the most effective among the seed dressers on the leaf feeding damage. Seed dressers varied for the number of days to 50% flowering. Imidacloprid (147 days) showed earliness at Alupe, while Thiamethoxam (125 days) showed earliness at Kiboko. Lindane (3.3 larvae) and Thiamethoxam (3.9 larvae) recorded a lower number of FAW larvae per plant compared to other seed dressers and untreated controls. Lindane (5.5) was the most effective seed dresser compared to other seed dressers and untreated controls (7.4) on FAW panicle damage symptoms. Lindane (295cm), Carbofuran (296cm) and Thiamethoxam (296cm) recorded shorter plant heights compared to other seed dressers and untreated controls. Carbofuran (2.34g) recorded the highest grain weight per plot compared to other seed dressers and untreated controls. xviii Significant differences (P≤0.05) were observed among sorghum varieties, and KARI Mtama 1 (5) recorded the lowest dead heart symptoms compared to other varieties. Alupe recorded the highest FAW leaf feeding damage compared to Kiboko. Nakhadabo (4.2), KARI Mtama 1 (5.3) and Wagita (5.9) showed resistance by recording the less leaf feeding damage, while IESV24029SH (10), Gadam hamam (8.2) and Seredo (8.1) showed susceptibility by recording a higher leaf feeding damage. Alupe recorded a higher number of FAW larvae per plant compared to Kiboko. Nakhadabo (1.3 larvae), KARI Mtama1 (2 larvae) and Wagita (2.3 larvae) recorded a lower number of larvae per plant, whereas the other varieties showed susceptibility. Sorghum at Kiboko flowered earlier compared to Alupe, and Gadam hamam (52.3days) was the earliest at Kiboko, while Nakhadabo (67days) was the earliest at Alupe. Higher panicle damage symptoms were recorded at Alupe compared to Kiboko. KARI Mtama 1 (1), Wagita (1.3) and Nakhadabo (2.3) recorded a moderate resistance to panicle damage symptoms compared to other varieties. Plant height was higher at Kiboko, but lower at Alupe. Gadam hamam (103cm) and IESV24029SH (105cm) recorded shorter plant heights compared to other varieties. Grain weight was higher at Kiboko compared Alupe, and Wagita (3.6g) recorded the highest grain weight compared to the other varieties. The study has identified Thiamethoxam, Imidacloprid, Lindane and Carbofuran to be effective against FAW at vegetative stages of sorghum and development, and may be incorporated prior to planting to protect sorghum seeds from early FAW infestations. The study also identified varieties Nakhadabo, KARI Mtama1 and Wagita to be resistant to FAW feeding damage on sorghum and therefore, can be considered in the management of FAW where its infestations are high or anticipated during the growth periods.