Neoseiulus californicus (McGregor)

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 : 1053-1055

Neoseiulus californicus (McGregor)

Neoseiulus californicus , previously known as Amblyseius californicus ( Figure 4 ), was first described by McGregor in 1954 based on a single male collected from lemon in Whittier,

California, USA. Its natural populations have been reported in about 30 countries around the world ( Demite et al. 2023). It has been available in international markets since 1985 for spider mite control. Nowadays, together with other three phytoseiid mites species, namely

Amblyseius swirskii Athias-Henriot , Phytoseiulus persimilis Athias-Henriot , and N. cucumeris ,

it covers two-thirds of the entire arthropod biological control agent market ( Knapp et al. 2018).

However, there had been confusion concerning the true identity of N. californicus until its type specimen had been located by Beaulieu and Beard (2018). Although the latter authors figured out that the type specimen of N. californicus is identical to the male of N. barkeri , and the well-known species which is commercially available in international markets is identical to the N. chilenensis (Dosse) , they proposed to maintain the usage of the name N. californicus

(McGregor) for the species concept of Athias-Henriot (1977) ( Beaulieu et al. 2019).

In Slovenia, the species was first recorded in 2012 in Korte (Primorska region), and

Ljubljana areas on various crops, such as watermelon ( Citrullus lanulus [Thunb.] Matsum.

and Nakai), eggplant Solanum (melongena L.), and apple ( Malus domestica Borkh. ), both in the greenhouses and in the open fields ( Trdan et al. 2013). After that, its populations were found in many regions in Slovenia, such as in central Slovenia and Slovenian Istra, on many vegetables, fruits, and ornamental plants ( Milevoj 2011 ; Trdan et al. 2013 ; Bohinc et al. 2019).

The commercial products of N. californicus are available in the Slovenian market ( UVHVVR

2022d).

Neoseiulus californicus is a type II selective predator of tetranychid mites. It prefers to feed on spider mites ( Gomez-Moya et al. 2009), but can also consume other mite species of phytophagous mites of other families such as Eriophyidae , Tarsonemidae , and Tydeoidea, like for example the tarsonemid mite P. pallidus ( Easterbrook et al. 2001) , small insects such as thrips ( Rodriguez-Reina et al. 1992) and even pollen when prey is unavailable ( Rhodes and Liburd 2006 ; Ragusa et al. 2009) ( Figure 5 ). Therefore, in the absence of spider mite prey,

this species can survive by consuming other food sources such as thrips, molds, and plant exudates and nectars ( Malais and Ravensberg, 2004). This species develops faster when the temperature is warmer, with a lower temperature and minimum relative humidity threshold of around 10 °C and 60% ( Malais and Ravensberg 2004). Lebdi-Grissa et al. (2004) showed that N. californicus developed well at 24, 30, and 35 °C. The fastest juvenile development from egg to adult and the generation time decreased with increasing temperatures, with the best result

(3.9 days and 8.6 days) at 35 °C. However, the development parameters showed better results at 30 °C, with the highest net reproduction rate of 23 female progenies/female, survival of immature mites of 90%, and fecundity of 35.2 eggs/female. At 24 °C, the value of the female lifespan is the highest, which was 15.7 days. A similar result reported by Nguyen and Amano

(2009) stated that the mating duration is inversely related to the temperature for the temperature

18-30 °C. However, the optimum temperature for an egg-laying female was 25 °C, with a total of 46.1 eggs laid in a life cycle. In addition, previous studies reported that dry-adapted strains of N. californicus showed greater levels of tolerance to low humidity compared to the other phytoseiid species ( Walzer et al. 2007 ; Palevsky et al. 2008 ; Döker et al. 2016).

on Tetranychus urticae (red form) (photo: İsmail Döker).

According to Marafeli et al. (2011), although N. californicus can feed and reproduce in all life stages of T. urticae it prefers the larvae. The authors found that adult males, adult females, nymphs, and larvae of N. californicus consumed an average of 21.9, 34.2, 18.7, and 9.9 T.

urticae larvae per day, respectively. Adult females are found to be the most efficient predator with a predation rate of 86.3% out of 40 given prey. It can migrate from grasses to fruit trees or grapevines and vice versa ( Auger et al. 1999). It is a specialist predator of T. urticae on annual plants and woody species; and P of. ulmi and various Tetranychus spp. (and perhaps eriophyid mites) on trees and less frequently on grapevines ( Auger et al. 1999).

Figures

Figure 4 Adult female ofNeoseiulus californicus preying on a two-spotted spider mite immature (photo: Institut Agro Montpellier).

Figure 5 Eggs and adult females of a laboratory-reared population of Neoseiulus californicus feeding