Insect-associated fungi from naturally mycosed vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae)

Vine mealybug, Planococcus ficus, is a major pest of grapevine, which is present in at least 39 countries. According to American Vineyard Foundation, P. ficus is in the top ranks among major insect-pests of grapevine. It is the ‘top priority concerns’ by grape growers and a ‘threat to the sustainability of wine industry’ demanding a ‘high priority research’. In Douro vineyards, it is considered as an occasional insect-pest; however, its importance is increasing in some localities. The present study investigates the occurrences of P. ficus-associated fungi. Vine mealybugs were observed in two of the four surveyed farms. Out of the 183 collected mealybugs, 58 were dead of which 25 had symptoms of mycosis and 13 were parasitised. Subculturing cadavers and subsequent pathogenicity test yielded 22 entomopathogenic fungi (EPF) including yeasts. The yeast Meyerozyma (=Pichia) guilliermondii, and the EPF Sarocladium kiliense and Purpureocillium lilacinum were the most abundant, i.e. representing 18.18% (N = 4), 13.64% (N = 3) and 13.64% (N = 3) of the isolates, respectively. Considering biological affinities, fungal families Nectriaceae and Microascaceae had the most similar count-data profiles. To our knowledge, this work reports the first isolations of EPF from vine mealybug worldwide; and Pseudocosmospora rogersonii in Europe and as EPF worldwide. The mortality rate originated by mycoses on P. ficus was significantly higher than by its parasitoids, suggesting that fungi as P. ficus biocontrol agents are relatively more important than considered before. Overall, this report provides new insights into the development of mycoinsecticides and conservation biocontrol strategies for P. ficus pest management.