The status of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) in the UK, and its potential as a biocontrol agent of Panonychus ulmi (Koch) (Acari: Tetranychidae)
The non-native predatory phytoseiid mite \(Neoseiulus\) \(californicus\) has been found in recent years in UK apple orchards. The aims of this study were to determine whether this mite could establish in the UK and its potential as a biocontrol agent for \(Panonychus\) \(ulmi\). By reviewing the literature and examining specimens of \(N. californicus.\) it was concluded that taxonomic synonymies with \(Amblyseius\) \( californicus.\) \( Amblyseius\) \(chilenensis\) and \(Typhlodromus\) \( mungeri\) could be supported, but those with \(Typhlodromus\) \( marinus\) and \(Neoseiulus\) \(fallacis\) could not. \(Neoseiulus\) \(californicus\) was found in strawberry, hop, blackcurrant and apple plantations in the main fruit growing regions of the UK. Field and laboratory studies showed that \(N.californicus\) possesses the ability to diapause, is a chill tolerant species and can survive winter field conditions in the UK. \(Neoseiulus\) \(californicus\) was found to readily consume both \( Panonychus\) \(ulmi\) and \(Tetranychus\) \(urticae\) and consumed greater numbers of prey than the native phytoseiid \(Typhlodromus\) \(pyri\). Deutonymphs consumed an average of 1.8 and 1.6 immature \(P. ulmi\) stages per day respectively and an average of 2.6 and 1.4 \(T. urticae\) respectively. The total mean development time for \(N. californicus\) was 7.47 days and for \(T. pyri\) was 12.45, feeding on \(P.ulmi\). \(Neoseiulus\) \(californicus\) from USA, Spain and UK displayed differences in measurements of a selection of morphological characteristics, diapause ability (16, 0 and 960/0 diapause respectively), development times (shortest for USA and longest for UK), fecundity (0.82-0.97 eggs per day) and esterase banding patterns, indicating the existence of different detectable strains. In conclusion, \(N. californicus\) was found to be a component of fruit plantation fauna in the UK, has the potential to survive winter field conditions and readily consumes \(P. ulmi\) and \(T.urticae\).