Neoseiulus californicus (McGregor)

Vásquez, Carlos, Colmenárez, Yelitza Coromoto, Greco, Nancy & Ramos, Mayra, 2023, Current Status of Phytoseiid Mites as Biological Control Agents in Latin America and Experiences from Argentina Using Neoseiulus californicus, Neotropical Entomology 52 (2), pp. 240-250 : 246-248

Experiences with Neoseiulus californicus in Argentina

Neoseiulus californicus is distributed in Europe, Japan, South Africa Canada, North America, and South America ( Demite et al. 2022) and is used by augmentative releases in numerous countries, such as the Netherlands, Belgium, Spain, Israel, Japan, USA, Mexico, Brazil, Colombia, and Chile where it is massively raised and marketed.

Members of type II of the Phytoseiidae family have a preference for a broad range of tetranychid species, but they also feed and reproduce on mites of other groups, including Eriophyidae , Tarsonemidae , and Tydeoidea, and also on pollen ( McMurtry et al. 2013; Khanamani et al. 2017; Soltaniyan et al. 2018, 2020). Commercial Typha angustifolia pollen Nutrimite® is an acceptable food for N. californicus because it enables this predator to develop and reach adulthood, as well as reproduce and have viable offspring, although their performance is significantly higher when it feeds on T. urticae ( Pascua et al. 2020) .

Strains from different geographic areas often differ in some population parameters and tolerance or susceptibility to certain factors, such as drought, insecticides, and winter conditions. In Argentina, there are no biofactories that produce this control agent, but several studies that have been carried out on its ecology suggest that it is possible to implement conservation biological control strategies, particularly in strawberry crops in the horticultural belt of La Plata, Buenos Aires (34°56′00″S, 57°57′00″W). In strawberry greenhouses, Greco et al. (1999) found both T. urticae and N. californicus populations were widely distributed, although, in general terms, N. californicus exhibited an uneven aggregation than T. urticae . This would create refugees for the prey, thus increasing the persistence of the system. The high spatial coincidence of N. californicus with T. urticae indicates an important dispersal capacity of the predator, and a high ability to detect leaflets with prey ( Greco et al. 2005).

Several wild plants surrounding crops may provide temporary habitat and potential food sources for N. californicus in that region, in different seasons. Pollen from Urtica urens L., Lamium amplexicaule L., Convolvulus arvensis L., Sonchus oleraceous L., Galega officinalis L., allowed the development of N. californicus adult, but not a reproduction. Survival was 70–80% when fed on pollen from S. oleraceus , G. officinalis , and C. arvensis , 80–90% when fed on pollen from U. urens and F. x ananassa, and more than 90% when fed on T. urticae and pollen from L. amplexicaule . In autumn and winter, U. urens , L. amplexicaule , and S. oleraceous could promote the persistence of N. californicus when prey density in strawberry is low since this plant species provide supplementary food sources. In summer, pollen of C. arvensis and G. officinalis would contribute to the persistence of N. californicus when the strawberry crop is ending and offers scarce food resources. Although the pollen of these plants would not enable the predator population to increase, the presence of these plants in the vicinity of strawberries could contribute to the persistence of the N. californicus population and help to limit T. urticae growth when this pest begins to colonize the crop ( Gugole Ottaviano et al. 2015).

The ability to resist winter conditions and periods of starvation is another characteristic of this strain. Greco et al. (2006) found a survival of 62.5% after 96 h of starvation, and it has recently been observed that females can survive 10 days without food (Alonso, personal communication). Although total fecundity decreased due to a reproductive diapause during starvation, the number of offspring produced by females after the periods of starvation was not significantly different from those fed females, they leveled at approximately 2.9 eggs per female per day. Besides, the fecundity of individuals of this N. californicus strain decreased significantly under winter conditions, but reproductive diapause might not be observed. In the laboratory, individuals exposed to winter conditions throughout the life cycle exhibited a long pre-oviposition period, and low oviposition rate but did not diapause. After being kept under winter conditions from larva to adult, when individuals were transferred to the optimal spring temperatures and lighting, the pre-oviposition period was shorter, and the fecundity was higher than under winter conditions. When it remained under spring conditions from larva to adult and was then transferred to the winter parameters during the first 15 days of adulthood, the pre-oviposition period was long and the oviposition rate was low. Once the optimal conditions were restored, the daily fecundity became similar to that of the individuals remaining under optimal conditions throughout the life cycle ( Gugole Ottaviano et al. 2018).

All these features suggest that N. californicus is a good candidate for conservation biological control in La Plata, Buenos Aires. A management plan for T. urticae in strawberries, based on the natural control by N. californicus , and acaricide applications only when necessary was developed and validated ( Greco et al. 2011). The plan has two components: a sampling protocol and a decision chart. Systematic presence-absence sampling of active T. urticae and N. californicus was used to predict prey and predator densities relying only on the proportion of T. urticae -infested leaflets, once the occurrence of the predator was detected in at least one of them ( Greco et al. 2004). The decision chart was constructed taking into account the relative pest and predator densities and the pest’s rate of increase ( Greco et al. 2005). It determines the range in the proportion of T. urticae -infested leaflets that will require different actions: to use selective acaricides and re-check at 7 days, to take no action but re-check at 7 days, and to take no action but re-check at 14 days. The management plan is potentially effective and feasible, showing that natural populations of N. californicus can consistently produce strong top-down suppression of T. urticae . It was experimentally implemented in 11 commercial lots for 2 years, and it was found that spider mite densities remained low and similar to those of lots under conventional management. The management plan’s application reduced the usage of acaricides by 90% and needs much less time (25% less) than applying acaricide in an area of the same size ( Greco et al. 2011). This biological conservation method, which reduces the frequency of acaricide usage to conserve the predator, might be supplemented by occasional augmentative releases, as shown by the same proposal to abolish chemical control for T. urticae in strawberries.

Other helpful knowledge for biological control through this agent in integrated management plans is the compatibility between this strategy and others, such as the use of resistant cultivars to T. urticae . Gugole Ottaviano et al. (2013) found that Festival and Albion could be suitable strawberry cultivars used in T. urticae management programs that include biological control by N. californicus . Ultimately, two other aspects are being investigated: (1) dispersal based on resource availability and (2) intraguild predation by Orius insidiosus Say ( Hemiptera : Anthocoridae ), the main predator of Frankliniella occidentalis (Pergande) ( Thysanoptera : Thripidae ); to determine the compatibility of these agents for the control of two crucial strawberry pests.