Neoseiulus barkeri Hughes, 1948

NovljanK, Monica, K, Tanja Bohinc, KreiterK, Serge, K, Ismail Döker & TrdanK, Stanislav, 2023, The indigenous species of predatory mites (Acari: Phytoseiidae) as biological control agents of plant pests in Slovenia, Acarologia 63 (4), pp. 1048-1061 : 1050-1051

Neoseiulus barkeri Hughes

Neoseiulus barkeri ( Figure 2 ) was first described by Hughes in 1948 based on the material collected from barley in England. It is a cosmopolitan phytoseiid species and its natural populations are reported in more than 50 countries on different continents including Australia,

Africa, Europe, and North America ( Milevoj 2011 ; Demite et al. 2023). In addition to its natural populations, N. barkeri has been commercialized for biological control of several thrips species, in particular onion thrips Thrips tabaci Lindeman and western flower thrips

Frankliniella occidentalis (Pergande) , and also tarsonemid mites ( Tarsonemidae ), since 1981

( Fan and Petitt 1994a ; Knapp et al. 2018 ; UVHVVR 2022b). It is also used against T. urticae in cucumber ( Fan and Petitt 1994b). Fan and Petitt (1994a) showed that augmentative releases of N. barkeri provided control of Polyphagotarsonemus latus (Banks) ( Acari : Tarsonemidae )

on peppers. The presence of N. barkeri in Slovenia was first confirmed by Kreiter et al. (2020)

based on a single female collected from a cucumber Cucumis (sativus L.) field in Bukovica village.

According to McMurtry et al. (2013), N. barkeri is a type IIIe generalist predator from soil-litter habitats. Besides its predation potential on thrips species, N. barkeri has also been used for the biological control of the broad mite P. latus in protected crops ( Fan and Petitt

1994a). In addition, laboratory and greenhouse experiments have shown this predator to be a successful biological control agent for the management of bulb scale mite, Steneotarsonemus laticeps (Halbert) ( Acari : Tarsonemidae ), a serious pest of amaryllis in European countries

( Messelink et al. 2012).

The juvenile period of N. barkeri , from the egg-hatching until the emergence of adults lasts

7-8 days at 25 °C. The lifespan of adult females is 55-70 days depending on the diet, while it is shorter for males (around 44-47 days). One adult female may produce 1.3 to 1.9 eggs per day, depending on the diet, and up to 56 eggs over its life span ( Momen 1995). When the adult females fed on T. urticae protonymphs, under laboratory conditions, consumption may reach up to 20.95 protonymphs/day and around 541 protonymphs for a total of 25.83 reproductive days ( Momen 1996).

Wu et al. (2016) also reported that releases of N. barkeri significantly reduced both larval and adult western flower thrips in greenhouse-grown cucumbers during the seven weeks of the study period. The same study also proved that the entomopathogenic fungi Beauveria bassiana

Bals.-Criv., which is often used by growers as a biological control agent against the same pest,

can cause up to 77.5% mortality in the predatory mites N. barkeri . The interactions between multiple natural enemies are important aspects of biological control and in case the interaction is unbeneficial, a different strategy should be applied in the release of multiple BCAs. Wu et al.

(2017) found that the single application of B. bassiana followed by the release of N. barkeri two weeks after spraying further suppressed F. occidentalis population in five weeks. According to the authors, while Beauveria bassiana reduced F. occidentalis populations by 70 and 64%, for the years 2013 and 2015, N. barkeri further reduced the pest populations by 72 and 75% in the same period, respectively.

Figures

Figure 2 Adult female ofNeoseiulus barkeriHughes (photo: Johan Witters).