Impact of seasonality and ladybird predators on the population dynamics of Mugo pine aphids

Pine-feeding aphid species cause considerable aesthetic damages and decrease the decorative value in the urban green spaces. In present study, aphids and associated ladybird predators were monitored on Pinus mugo Turra in Mashhad metropolis (Northeastern Iran) during four seasons in 2016. We aimed to evaluate the seasonal dynamics of pine-feeding aphid species and associated ladybird species in the urban green spaces along with determination their diversity and abundance. We identified four aphid species belonging to two genera of the subfamily Lachninae associated with eleven species of their natural coccinellid enemies. The highest numbers of aphid individuals were observed at the end of March till mid-August. Low numbers of coccinellids were present in March, but later (May–September) they exhibited a rapid increase, upon migration of aphids from the Mugo pine trees. Eulachnus tuberculostemmatus (Theobald) is considered as the dominant species, with a relative abundance of 32.97% whereas the highest abundance of aphids was detected in spring (45.84%). Cinara pinihabitans (Mordvilko) was the most common species in spring (43.06%) and summer (29.45%). Among the collected ladybirds, the seven-spot ladybird, Coccinella septempunctata L. was the dominant species with a relative abundance of 35.46% whilst the highest abundance of aphids was detected in spring (57.93%). C. septempunctata was the most prevalent identified coccinellid in spring (51.74%) and summer (21.51%), however, in fall and winter its presence declined (18.6 and 8.13% respectively). Scymnus nubilus (Mulsant) is reported as a new record for the Razavi Khorasan province exhibiting the lowest relative abundance (0.2%). Our results showed that ladybirds alongside high temperatures in the summer reduce the population growth of Mugo pine pest aphids in the urban green spaces of the target region. The potential importance of the ladybird dominant species as the effective biocontrol agents of aphids infesting Mungo pine trees could further trigger the reduction of insecticidal applications in parks and other green spaces.