Field evaluation of Cryptolaemus montrouzieri (Mulsant) (Coleoptera: Coccinellidae) as biological control agent of the mealybug Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae)

Abstract

Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is one of the latest invasive mealybugs in Europe. It causes severe fruit distortion and reduced fruit size leading into important economic losses in citrus. Cryptolaemus montrouzieri (Mulsant) (Coleoptera: Coccinellidae) is probably one of the most-used predators of mealybugs in biological control programs worldwide. However, its impact on D. aberiae is still unknown. Here, we conducted a two-year field study in nine citrus orchards located in eastern Spain in order to describe the population dynamics of D. aberiae and C. montrouzieri and evaluate the effect of the predator on D. aberiae using different approaches. Our results showed that C. montrouzieri and D. aberiae had two main synchronised population peaks per year: early spring and summer. Although D. aberiae and C. montrouzieri seasonal trends were synchronised, C. montrouzieri neither reduced mealybug density within the same year nor prevented fruit damage, which occurs early in the season. Moreover, D. aberiae population growth rates were not correlated with C. montrouzieri density. When two consecutive years were analyzed, the increase of D. aberiae in the second year was negatively correlated with the density of C. montrouzieri in summer of the previous year. Based on our two years of data, C. montrouzieri was not able to regulate D. aberiae on its own or prevent the damages produced by the mealybug but might become a valuable addition to the natural enemy guild when combined with other natural enemies and rational control measures.