Phytoseiidae (McMurtry and Croft, 1997)

Sahraoui, H., Tixier, M. - S., Lebdi-Grissa, K. & Kreiter, S., 2014, Diversity And Abundance Of Phytoseiidae (Acari: Mesostigmata) In Three Crop Management Strategies Of Citrus Orchards In Tunisia, Acarologia 54 (2), pp. 155-169 : 164

Phytoseiidae species found and their biological control efficiency

Among the thirteen Phytoseiidae species collected in this survey, five were found in the three orchards: E. stipulatus , P. persimilis , N. barkeri , N. californicus and T. (A.) rhenanoides . The majority of these species are, according to McMurtry and Croft’s classification (1997), generalist predators that feed on a great variety of food sources including mites, insects, pollen ... This may explain their high abundance in absence of pest preys.

Euseius stipulatus was the dominant species on citrus trees in the three orchards. This species also prevails in other citrus orchards in Tunisia ( Sahraoui et al., 2012), Spain ( Pereira et al., 2006; Abad-Moyano et al., 2009, 2010) and in the Mediterranean citrus orchards in general ( McMurtry, 1977). Euseius stipulatus was found even when Tetranychidae were absent. This species is considered according to McMurtry and Croft (1997) as specialized pollen feeder (Type 4). Several authors reported that its development rate is higher fed on pollen than on phytophagous mites (i.e. Ferragut et al., 1987, Zhimo and McMurtry, 1990). Furthermore, some studies have shown that its occurrence could be related to pollen abundance ( Villanueva and Childers, 2004). The abundance of E. stipulatus in spring (in the three orchards) could thus be due to the presence of pollen. However, in orchard (1), this species was also abundant in December whereas pollen quantity was low. This species is also known to feed on Panonychus citri (McGregor) ( Ferragut et al., 1988, 1992), T. urticae ( Abad-Moyano et al., 2009) and eriophyid mites ( Ferragut et al., 1987). Its abundance in December could thus be due to the occurrence in orchard (1) of specimens of Tetranychus sp. , of eriophyid mites, or tydeid mites (which are abundant during this period) suggesting that this species could feed on these preys in citrus orchards. This species was present throughout the year during the surveys except in summer (July-August) when the temperature exceeds 30 – 35 ºC. Ferragut et al. (1987) showed that this species stops laying eggs at 32 °C.

Among the other Phytoseiidae species present on citrus trees, N. californicus and P. persimilis can be considered as good candidates for biological control of phytophagous citrus. Phytoseiulus persimilis is known as a specialist predator, especially efficient to control T. urticae in greenhouses all over the world ( McMurtry and Croft, 1997).

Neoseiulus californicus is reported to control mites of the family Tetranychidae ( Escudero et al., 2004; Greco et al., 2005; Katayama et al., 2006; Gomez et al., 2009), but can also consume other mite species as Phytonemus pallidus (Banks) ( Easterbrook et al., 2001) and small insects, as Thripidae (Rodriguez et al., 1992) .

Typhlodromus (A.) rhenanoides is a generalist species, but also reported to reproduce and develop on T. urticae and the red mite P. citri ( Tsolakis et al., 2012) , two pest mites of citrus in Tunisia ( Grissa and Khoufi, 2012).

In regards to N. barkeri , this species is known to control Frankliniella occidentalis (Pergande) ( Rodriguez-Reina et al., 1992) and Thrips tabaci (Lindeman) ( Hansen, 1988; Desgaard et al., 1992). Yet, these thrips species are commonly reported in Tunisian citrus orchards (Belaam and Boulahia, 2012).

Even if the three species P. persimilis , N. californicus and T. (A.) rhenanoides are known to feed on some citrus pests, their densities in the present surveys were too low to play a key role in biological control.