Are the ladybugs Cryptolaemus montrouzieri and Exochomus quadripustulatus (Coleoptera: Coccinellidae) candidate predators of Toumeyella parvicornis (Hemiptera: Coccidae)?

Abstract

Background: Toumeyella parvicornis is an alien pest of recent introduction in Italy that infests stone pines (Pinus pinea L.), itsmain host plant in Europe. Infestations are currently controlled through endotherapic treatments, but the high costs and thelong-term inefficacy highlight the need for alternative control strategies applicable in natural systems as well. An analysis ofthe effectiveness of autochthonous and naturalized predators is the first step to achieve this goal. This work focused on twocandidate predators, Exochomus quadripustulatus and Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), that may potentiallycontrol T. parvicornis. The analysis was carried out under laboratory-controlled and semi-field conditions.Results: Laboratory tests were carried out to assess: (i) the predation rate of the ladybugs over different densities of pest preimaginalstages, and (ii) the effect of the presence of heterospecific and conspecific predators on the attractiveness of prey colonies.Semi-field experimentations were carried out by wrapping infested stone pine twigs with net sleeves and applying one ofthree treatments: (i) Exochomus quadripustulatus, (ii) Cryptolaemus montrouzieri, and (iii) control containing only the pest population.Both the ladybugs were attracted by T. parvicornis, offered as prey. Exochomus quadripustulatus was more attracted toconspecific and heterospecific ladybugs than Cryptolaemus montrouzieri and responded to prey more quickly.Conclusions: The results obtained could be useful for planning further experimentations to explore the potential use of thesepredators in biological control programs that may be applied in infested areas. Besides the use in an urban context, where pesticideuse is strongly limited, the release of natural enemies may help safeguard stone pine forests.