Biocontrol Potential of Chitin and Chitosan Extracted from Black Soldier Fly Pupal Exuviae against Bacterial Wilt of Tomato.

Globally, Ralstonia solanacearum (Smith) is ranked one of the most destructive bacterial pathogens inducing rapid and fatal wilting symptoms on tomatoes. Yield losses on tomatoes vary from 0 to 91% and most control measures are unaffordable to resource-poor farmers. This study investigated the antimicrobial activities of chitin and chitosan extracted from black soldier fly (BSF) pupal exuviae against R. solanacearum. Morphological, biochemical, and molecular techniques were used to isolate and characterize R. solanacearum for in vitro pathogenicity test using disc diffusion technique. Our results revealed that BSF chitosan significantly inhibited the growth of R. solanacearum when compared to treatments without chitosan. However, there was no significant difference in the antibacterial activities between BSF and commercial chitosan against R. solanacearum. Soil amended with BSF-chitin and chitosan demonstrated a reduction in bacterial wilt disease incidence by 30.31% and 34.95%, respectively. Whereas, disease severity was reduced by 22.57% and 23.66%, when inoculated tomato plants were subjected to soil amended with BSF chitin and chitosan, respectively. These findings have demonstrated that BSF pupal shells are an attractive renewable raw material for the recovery of valuable products (chitin and chitosan) with promising ability as a new type of eco-friendly control measure against bacterial wilt caused by R. solanacearum. Further studies should explore integrated pest management options that integrate multiple components including insect-based chitin and chitosan to manage bacterial wilt diseases, contributing significantly to increased tomato production worldwide.

Effect of Moisture Stress on the Development of False Codling Moth Thaumatotibia leucotreta (Lepidoptera: Tortricidae) on Two Tomato Varieties.

False codling moth Thaumatotibia leucotreta (Meyrick) is a pest native to sub-Saharan Africa infesting over 100 plant species including tomato. Its survival and performance are influenced by changes in precipitation and stress-related biochemical changes in the host plant. Water availability for agricultural production continues to decline due to climate change affecting drought-sensitive crops like tomatoes. Little is known on host plant-insect interactions of T. leucotreta and tomato as influenced by moisture stress. Hence, our study tested the impact of different water holding capacities (WHC) (40%, 50%, 60%, 70%, and 90%) of plant growing media on the growth of Anna F1 and Yaye tomato varieties and the infestation rate and development of T. leucotreta on the two varieties. WHC significantly influenced the growth of Anna F1 and Yaye tomato varieties. WHC significantly affected stem girth of Anna F1 variety and leaf length, leaf width, stem girth, and plant height of the Yaye variety. For Yaye variety, T. leucotreta laid a significantly high number of eggs when grown at 70% WHC and had the highest pupation when grown at 60% WHC. The development of T. leucotreta as observed on wing growth was highest at 40% and 50% WHC for both Anna F1 variety and Yaye variety. Our study shows that the infestation of tomato by T. leucotreta is likely to be high when grown in water-scarce media. The results are useful for predicting possible future T. leucotreta trends with increasing water scarcity due to climate change and in designing pest management programmes.