LADYBIRDS IN CEREAL FIELDS IN THE REGION OF ZAGHOUAN IN TUNISIA

Abstract

An inventory of ladybirds was carried out in cereal fields in Zaghouan over three years to evaluate their seasonal apparition and their efficiency in decreasing aphid populations. Only two species, Coccinella algerica and Hippodamia variegata were identified. The delegation of Mograne was the most populated by ladybirds (64%). As the main result of the correlation analysis, the relationship between ladybirds and temperature was strong, especially during 2018 and 2019. The frequencies of morphs differed among years and seasons, and the number of individuals was more considerable with the aphids’ increased populations, especially in the spring (April and May). It coincides with the development of weeds in fields. H. variegata manifested with eighteen different morphs. According to the morphological criteria, the most common morph has 9 spots. Comparing the morphological criteria and genitalia, a sexual inversion was encountered, reaching 16.67% for males and 2.13% for females. It is supposed that the chemicals’ use and the temperature were the main factors that induce polymorphism and sexual inversion with H. variegata. The limited use of chemicals enhances the presence of ladybirds in fields in the Mograne region. Key Words: natural enemies, ladybird, cereals, Hippodamia variegata, Coccinella algerica.