Population Dynamics of Heliothrips haemorrhoidalis (Thysanoptera: Thripidae) in Strawberry Cultivars in Southern Brazil.

Abstract

Heliothrips haemorrhoidalis is a polyphagous thrips species that has been reported as a potential pest in strawberry cultivation in Brazil. Since it has only recently emerged as a pest species in production areas, understanding seasonal trends in the species' activity is particularly important for designing management strategies. Therefore, this study aims to investigate the influence of climate factors (temperature and relative humidity) and six strawberry cultivars ('Albion', 'Aromas', 'Camino Real', 'Monterey', 'Portola', and 'San Andreas') on the population dynamics of H. haemorrhoidalis during the 2018-2019 and 2019-2020 growing seasons in southern Brazil. The greatest peak in thrips populations in the cultivars assessed occurred between January and March (summer) in both growing seasons. The relationship between the incidence of H. haemorrhoidalis and temperature was observed to be negative during the autumn, spring, and summer months but positive during winter. Relative humidity levels above 70% had a negative influence on the abundance of insects. Populations of H. haemorrhoidalis varied between the cultivars as follows: 'Aromas' > 'Monterey' > 'San Andreas' > 'Albion' > 'Camino Real' > 'Portola'. Cross-sections of strawberry leaves showed that 'Monterey' had the highest density of nonglandular trichomes/mm2 (7.26), while 'Portola' cultivar, the greatest predominance of glandular trichomes/mm2 (12.67), which may have contributed to the incidence of H. haemorrhoidalis. The demographic information presented on H. haemorrhoidalis in strawberry cultivars provides a starting point to better understand the insect's population dynamics. These results also indicate that climatic conditions are a limiting factor for the development of H. haemorrhoidalis.