Effects of sheltered ground habitats on the overwintering potential of the predacious mite Neoseiulus californicus (Acari: Phytoseiidae) in apple orchards on mainland Korea

Prediction of the potential distribution of the predatory mite Neoseiulus californicus (McGregor) in China under current and future climate scenarios

Neoseiulus californicus is a predatory mite with a wide global distribution that can effectively control a variety of pest mites. In this study, MaxEnt was used to analyse the potential distribution of N. californicus in China and the BCC-CSM2-MR model was used to predict changes in the suitable areas for the mite from 2021 to 2100 under the scenarios of SSP126, SSP245 and SSP585. The results showed that (1) the average of area under curve value of the model was over 0.95, which demonstrated an excellent model accuracy. (2) Annual mean temperature (Bio1), precipitation of coldest quarter (Bio19), and precipitation of driest quarter (Bio17) were the main climatic variables that affected and controlled the potential distribution of N. californicus, with suitable ranges of 6.97–23.27 °C, 71.36–3924.8 mm, and 41.94–585.08 mm, respectively. (3) The suitable areas for N. californicus were mainly distributed in the southern half of China, with a total suitable area of 226.22 × 10⁴ km² in current. Under the future climate scenario, compared with the current scenario, lowly and moderately suitable areas of N. californicus increased, while highly suitable areas decreased. Therefore, it may be necessary to cultivate high-temperature resistant strains of N. californicus to adapt to future environmental changes.

Predators and Parasitoids-in-First: From Inundative Releases to Preventative Biological Control in Greenhouse Crops

Repeated mass introductions of natural enemies have been widely used as a biological control strategy in greenhouse systems when the resident population of natural enemies is insufficient to suppress the pests. As an alternative strategy, supporting the establishment and population development of beneficials can be more effective and economical. The preventative establishment of predators and parasitoids, before the arrival of pests, has become a key element to the success of biological control programs. This “Predators and parasitoids-in-first” strategy is used both in Inoculative Biological Control (IBC), and in Conservation Biological Control (CBC). Here, we provide an overview of tools used to boost resident populations of biocontrol agents.

Overwintering of the Argentine strain of Neoseiulus californicus (Acari: Phytoseiidae)

Overwintering and diapause are variable among mite species and strains. The aims of this study were to determine whether certain crops constitute overwintering sites for the Argentine strain of the predator Neoseiulus californicus and whether females underwent reproductive diapause in winter. Neoseiulus californicus was recorded monthly on the vegetables tomato, sweet pepper, eggplant, and artichoke, and on strawberry, among other crops in Buenos Aires province, Argentina. This mite was found at a lower percentage of crops in the winter than in the other seasons. Since the predator was quite frequent on artichoke, this crop could constitute a refuge during adverse environmental conditions. The mite's frequency on several crops in other seasons and potential association with a strawberry pest is discussed. 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 higher than under winter conditions. When individuals remained under spring conditions from larva to adult and were then transferred to the winter parameters during the first 15 days of adulthood, the pre-oviposition period was long and the oviposition rate 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. Fecundity of N. californicus decreased significantly under winter conditions but reproductive diapause was not observed.

Rapid cold hardening response in the predatory mite Neoseiulus californicus

We investigated the rapid cold hardening (RCH) response in the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae). On direct exposure, ≤2 % of adult females survived -10 °C for 2 h. However, when acclimatized first at 5 °C for 1 h, 75 % of females survived. RCH could also be induced by acclimatization at 30 °C for 2 h or anoxia (oxygen-free nitrogen) for 1-2 h. All immature stages showed enhanced survival when acclimatized at 5 °C for 2 h before exposure to -10 °C. Acclimatization at 30 °C induced RCH only in eggs and deutonymphs, and anoxia was effective for eggs, larvae, and deutonymphs. The variability among immature stages may be attributed to the cost associated with the acclimatization treatments. Our findings suggest that RCH may promote the survival of N. californicus during unexpected changes in temperatures, and can be an important feature particularly when this natural enemy is introduced to non-native environments.

Desiccation tolerance in diapausing spider mites Tetranychus urticae and T. kanzawai (Acari: Tetranychidae)

We investigated the effects of changes in vapor pressure deficit (VPD) on the survival of diapausing (winter form) and non-diapausing (summer form) spider mites Tetranychus urticae Koch and Tetranychus kanzawai Kishida (Acari: Tetranychidae). Adult females of both species were kept without food at VPDs of 0.0, 0.4, 0.7, 1.5, 1.9, or 2.7 kPa for 3, 6, 9, 12, or 15 days at 25 °C. Diapausing females of both species kept at a VPD of ≥0.4 kPa for ≥6 days clearly tolerated desiccation. Under water-saturated conditions (VPD = 0.0 kPa), in which no desiccation occurred, diapausing females showed high starvation tolerance: 90 % survived for up to 15 days. No interspecific differences in tolerance to desiccation or starvation were observed under most conditions. These results indicate that diapause functions increase tolerance to desiccation and starvation. Such multiple tolerances to harsh environments might support winter survival in spider mites.

Cover crop mulch and weed management influence arthropod communities in strip-tilled cabbage

Cover crop mulch and weeds create habitat complexity in agricultural fields that may influence arthropods. Under strip-tillage systems, planting rows are tilled and preestablished cover crops can remain between rows. In field experiments conducted in Michigan in 2010 and 2011, a preestablished oat (Avena sativa L.) cover crop was allowed to grow between rows of strip-tilled cabbage and killed at 0, 9-14, or 21-27 d after transplanting (DAT). The effects of herbicide intensity and oat kill date on arthropods, weeds, and crop yield were examined. Two levels of herbicide intensity (low or high) were used to manipulate habitat vegetational complexity, with low weed management intensity resulting in more weeds, particularly in 2010. Oat kill date manipulated the amount of cover crop mulch on the soil surface. Later oat kill dates were associated with higher natural enemy abundance. Reduced herbicide intensity was associated with (1) lower abundance of several key cabbage (Brassica oleraceae L.) pests, and (2) greater abundance of important natural enemy species. Habitats with both later oat kill dates and reduced herbicide intensity contained (1) fewer herbivores with chewing feeding guilds and more specialized diet breadths, and (2) greater abundance of active hunting natural enemies. Oats reduced cabbage yield when oat kill was delayed past 9-14 DAT. Yields were reduced under low herbicide intensity treatments in 2010 when weed pressure was greatest. We suspect that increased habitat complexity associated with oat mulches and reduced herbicide intensity enhances biological control in cabbage, although caution should be taken to avoid reducing yields or enhancing hyperparasitism.

Environmental Engineering Approaches toward Sustainable Management of Spider Mites

Integrated pest management (IPM), which combines physical, biological, and chemical control measures to complementary effect, is one of the most important approaches to environmentally friendly sustainable agriculture. To expand IPM, we need to develop new pest control measures, reinforce existing measures, and investigate interactions between measures. Continued progress in the development of environmental control technologies and consequent price drops have facilitated their integration into plant production and pest control. Here I describe environmental control technologies for the IPM of spider mites through: (1) the disturbance of photoperiod-dependent diapause by artificial light, which may lead to death in seasonal environments; (2) the use of ultraviolet radiation to kill or repel mites; and (3) the use of water vapor control for the long-term cold storage of commercially available natural enemies. Such environmental control technologies have great potential for the efficient control of spider mites through direct physical effects and indirect effects via natural enemies.