Planting date effects on the dynamics of the cotton mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae), and the damage status of roselle (Hibiscus sabdariffa L.) plants in Luxor, Egypt

Abstract

Roselle (Hibiscus sabdariffa L.) is an important crop, but the cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), hampers its economic production. The purpose of this study was to assess the effects of different roselle planting dates on the abundance and damage status of mealybugs. The study was conducted during two growing seasons, 2022 and 2023, in a private farm of Balady roselle cultivar in the Esna region, Luxor Governorate, Egypt. Four different times, on April 14th, April 29th, May 13 th, and May 27th, we cultivated the roselle plants in the field. The findings showed that later roselle planting was associated with a higher percentage of damaged leaves and a higher density of mealybug populations. Using analysis of variance (ANOVA) and multivariate statistical analyses (Principal component analysis, dendrogram from cluster analysis, and hierarchical clustering), the results revealed a clear variation in P. solenopsis populations between planting dates within each season; the first planting date on April 14th was significantly different from all other planting dates. The early planting date showed a decrease in P. solenopsis population dynamics across both seasons compared to the late planting date. Furthermore, these results support the idea that a significant decrease in mealybug populations was associated with the early planting date of April 14th, while the insect population trend increased significantly with subsequent planting dates (The third and fourth planting dates) in both seasons. The heatmap and hierarchical clustering also supported similar relationships between planting dates that shared the seven assessed characteristics. The data from the similarity coefficient matrix was used to create a dendrogram. A dendrogram was constructed using the similarity coefficient matrix data. The early planting date showed a significant decrease in P. solenopsis numbers, percentage of damaged leaves, and all measures of dispersal and attraction, except for a higher non-preference index. Conversely, the fourth planting date showed the highest significant increase in P. solenopsis numbers, percentage of damaged leaves, and measures of dispersal and attraction, except for a lower non-preference index. These findings show that early roselle planting dates can be a useful tactic for sustainable crop management, as they can reduce cotton mealybug damage in an efficient, non-chemical way.