Biocontrol in practice in Canadian floricultural greenhouses

The environment inside Canadian prairie greenhouses differs from greenhouses built in other northern latitude locations in terms of lighting, temperature, humidity, and photoperiod. Since the performance of biocontrol agents depends upon several interactive environmental variables, their effectiveness to control pests in a particular crop growing under certain climatic conditions does not directly translate to another crop or location. So, we analyzed research trials assessing the efficacy and compatibility of various biocontrol agents (Amblyseius cucumeris, Amblyseius cucumeris, Phytoseiulus persimilis, Encarsia formosa, Aphidius colemani, Aphidius ervi, and Steinernema feltiae) on key pests (Western flower thrips, two-spotted spider mites, greenhouse whiteflies, and aphids) of spring bedding plants grown in a commercial floricultural greenhouse. Were analyzed several compatible combinations of biocontrol agents and observed a significant reduction in pest densities and plant damage symptoms as compared to untreated control plants. The results demonstrate that P. persimilis controlled two-spotted spider mites successfully in calibrachoa crop. The combination of Amblyseius cucumeris and S. feltiae resulted in significantly better control of Western flower thrips than the use of Amblyseius cucumeris alone in sweet potato vine plants. The application of E. formosa and Amblyseius cucumeris individually reduced greenhouse whiteflies on calibrachoa plants as compared to control, but their combination performed better resulting in a significantly lower number of whiteflies on plants. Another combination of Aphidius colemani and Aphidius ervi controlled green peach aphids and foxglove aphids effectively on the pansy crop. The biocontrol agents were effective for managing a variety of pests in a commercial greenhouse setting.

Augmentative biological control in greenhouses in Japan.

In Japan, augmentative biological control is mainly implemented in greenhouses using arthropod natural enemies. Two imported natural enemy species, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) against spider mites and Encarsia formosa Gahan (Hymenoptera: Aphelinidae) against the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), were first commercialised in greenhouses in 1995, followed by the commercialisation of other exotic species. Exotic arthropod natural enemies are used to control both exotic and indigenous pests in greenhouses. Currently, the most popular exotic natural enemy species are predatory mites such as P. persimilis and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Recently, there has been a shift from using exotic to using indigenous natural enemies in greenhouses. Currently, the importation of generalist predators for augmentative biological control is very difficult in Japan. Several collaborative studies have been conducted in Japan to develop biological control using indigenous natural enemies. These studies developed innovative technologies, such as new banker plant systems based on combinations of two natural enemies or flightless Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Indigenous natural enemies have been commercialised following the registration of Orius strigicollis (Poppius) (Hemiptera: Anthocoridae). Biological control can be achieved using an indigenous strain of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) with a banker plant system, on which the bug can reproduce without alternative prey. Research and development of biological control using indigenous natural enemies should be continued in Japan.

Phototoxicity of Ultraviolet-A against the Whitefly Bemisia tabaci and Its Compatibility with an Entomopathogenic Fungus and Whitefly Parasitoid

Ultraviolet (UV) radiation significantly affects insect life and, as a result, has been widely used to control different invertebrate pests. The current results demonstrate that when Bemisia tabaci first instar nymphs are exposed to UV-A light for 12, 24, 48, and 72 h, their developmental and biological parameters are negatively affected by UV-A exposure; the effect increased with an increase in exposure time. We hypothesized that UV-A light is compatible with other biological control agents. Results showed that when the entomopathogenic fungus Cordyceps fumosorosea was applied to third instar nymphs of B. tabaci previously exposed to UV-A light, the LC50 was 3.4% lower after 72 h of exposure to UV-A light compared to the control. However, when the fungus was exposed to UV-A light, its virulence decreased with an increase in UV-A exposure time. The parasitism rate of Encarsia formosa against 24 h UV-A-exposed third instar nymphs of B. tabaci increased while the adult emergence from parasitized nymphs was not affected after UV-A light exposure. Parasitism rate was significantly reduced however following E. formosa exposure to UV-A light; but again, adult emergence was not affected from parasitized nymphs. The percentage mortality of E. formosa increased with increasing exposure time to UV-A light. The enzyme activity of SOD, CAT, GST, and AChE and the energy reserve contents were negatively affected due to UV-A exposure. Collectively, this study has demonstrated that UV-A light significantly suppresses the immune system of B. tabaci and that UV-A light is compatible with other biological control agents if it is applied separately from the biological agent.

Combining Banker Plants To Achieve High Pest Control Efficiency In Multi-Pest, Multi-Natural Enemy Cropping Systems

Banker plants increase biological pest control by supporting populations of non-pest arthropod species used as alternative hosts or prey by natural enemies. Due to the specificity of trophic interactions, banker plants may not efficiently promote natural enemies with different ecologies. Yet in most cropping systems different pest species are present together and require different biocontrol agents to efficiently control them. In the present study, we tested the combined use of two banker plants and their associated prey / host to enhance populations of the specialist parasitoid Encarsia formosa targeting the main tomato pest Bemisia tabaci, and a polyphagous ladybird Propylea japonica targeting the secondary pest Myzus persicae in tomato crops. In a laboratory and a greenhouse experiment, we measured the abundances of these four species using the Ricinus communis – Trialeurodes ricini banker plant system alone, in combination with the Glycines max – Megoura japonica system, or in absence of banker plants. We found that the first banker plant system enhanced populations of E. formosa, resulting in higher control of B. tabaci populations and the suppression of their outbreak in both our laboratory and greenhouse experiment. Conversely, abundances of P. japonica were not affected by this first system, but were significantly increased when the second was present. This resulted in high control of M. persicae populations and the suppression of their early and late outbreaks. Our study demonstrates the potential for combined banker plants to provide long-term, sustainable control of multiple pests by their target natural enemies in complex agroecosystems.