Effect of relative humidity on the biology of the predatory mite Amblyseius largoensis (Acari: Phytoseiidae)

Abstract

ABSTRACTAmblyseius largoensis Muma (Acari: Phytoseiidae) is a common predator in the humid tropics, where it has been found in association with Raoiella indica Hirst (Acari: Tenuipalpidae), an important coconut pest. The objective of this study was to assess the performance of A. largoensis from Recife, Pernambuco, northeast Brazil (Atlantic Forest biome), under different levels of relative humidity (RH). Also, to analyse the world-wide distribution of A. largoensis. This phytoseiid was evaluated at the following development RH levels (20%, 36%, 56%, 65%, 72%, 80%, 89%, and 95%) and on reproduction RH levels (66%, 83%, 91%, and 98%) at 27°C. Amblyseius largoensis failed to complete development at or below 72% RH. Maximum population increase of the predator (about 26-fold in one generation) occurred at 91% RH. Only 7% of the records of the distribution of A. largoensis were from hot arid areas. The results suggested, that while the Recife population of A. largoensis is well adapted to survive high RH conditions, its efficiency as a biological control agent might be limited in drier inland areas. Thus, populations of A. largoensis that occur in drier areas of the world should be evaluated as to their potential as biological control agents of R. indica.