Abstract
Pseudococcus comstocki (Hemiptera: Pseudococcidae) is a mealybug species native to Eastern Asia and present as an invasive pest in northern Italy and southern France since the start of the century. It infests apple and pear trees, grapevines and some ornamental trees. Biocontrol programmes against this pest proved successful in central Asia and North America in the second half of the 20th century. In this study, we investigated possible biocontrol agents against P. comstocki, with the aim of developing a biocontrol programme in France. We carried out systematic DNA-barcoding at each step in the search for a specialist parasitoid. First we characterised the French target populations of P. comstocki. We then identified the parasitoids attacking P. comstocki in France. Finally, we searched for foreign mealybug populations identified a priori as P. comstocki and surveyed their hymenopteran parasitoids. Three mealybug species (P. comstocki, P. viburni and P. cryptus) were identified during the survey, together with at least 16 different parasitoid taxa. We selected candidate biological control agent populations for use against P. comstocki in France, from the species Allotropa burrelli (Hymenoptera: Platygastridae) and Acerophagus malinus (Hymenoptera: Encyrtidae). The coupling of molecular and morphological characterisation for both pests and natural enemies facilitated the programme development and the rejection of unsuitable or generalist parasitoids.
Highlights
Pseudococcus comstocki (Hemiptera: Pseudococcidae) is a mealybug species native to Eastern Asia that has been present as an invasive pest in northern Italy and southern France since the turn of the century [1, 2], infesting apple, pear and ornamental trees of the genera Morus and Catalpa in particular
We present here (i) an overview of the classical biocontrol programme, which resulted in the field release of two natural enemies: augmentative biological control using French populations of A. malinus, and the introduction of exotic A. burrelli populations, (ii) the methods and results of the molecular and morphological characterisations carried out at each step in the classical biocontrol programme, and (iii) a discussion of the added value provided by the molecular identification methods
The mealybug identification obtained from Syria (P. cryptus) in 2009 led us to discard Syria as a source country for the importation of a natural enemy
Summary
Pseudococcus comstocki (Hemiptera: Pseudococcidae) is a mealybug species native to Eastern Asia that has been present as an invasive pest in northern Italy and southern France since the turn of the century [1, 2], infesting apple, pear and ornamental trees of the genera Morus and Catalpa in particular. P. comstocki causes economic losses, principally due to a decrease in fruit marketability as a consequence of the massive development of sooty mould on the honeydew excreted by the mealybug which accumulates on the leaves and fruits. In several infested orchards in southern France up to 80% of the harvested fruits are discarded when infestation rates are high and accumulation of sooty mould is severe on the surface or the carpel of the fruits Biological control is often used as an alternative to pesticides for the control of mealybugs [4]. This approach has repeatedly proven to be successful and safe for non-target organisms [5, 6]. Specific hymenopteran parasitoids have been used to control P. comstocki, including Acerophagus (= Pseudaphycus) malinus (Hymenoptera: Encyrtidae) in the former USSR [7,8,9,10,11,12] and in the USA [13, 14], and Allotropa burrelli (Hymenoptera: Platygastridae) in the USA [14, 15]
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