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.

Endophytic Colonisation of Solanum lycopersicum and Phaseolus vulgaris by Fungal Endophytes Promotes Seedlings Growth and Hampers the Reproductive Traits, Development, and Survival of the Greenhouse Whitefly, Trialeurodes vaporariorum

In the scope of mitigating the negative impacts of pesticide use and managing greenhouse whiteflies, Trialeurodes vaporariorum sustainably, 16 endophytic fungal isolates from five different genera (Beauveria, Trichoderma, Hypocrea, Bionectria, and Fusarium) were screened for their ability to colonise two preferred host plant species, namely, tomato (Solanum lycopersicum L.) and French bean (Phaseolus vulgaris L.), through seed inoculation. Seven and nine isolates were endophytic to P. vulgaris and S. lycopersicum, respectively, where significant differences in the endophytic colonisation rates were observed among the fungal isolates in P. vulgaris and its plant parts, with a significant interaction between the isolates and plant parts in S. lycopersicum. Hypocrea lixii F3ST1, Trichoderma asperellum M2RT4, Trichoderma atroviride F5S21, and T. harzianum KF2R41 successfully colonised all the plant parts of both hosts and therefore were selected and further evaluated for their endophytic persistence, effect on plant growth, and pathogenicity to T. vaporariorum adults and F1 progeny. The four endophytes remained in both host plants for the 5-week assessment with varied colonisation rates related to the strong interaction with the time, isolates, and plant parts in both hosts. The effect of the same endophytes on the different host growth parameters varied in P. vulgaris and S. lycopersicum, with T. asperellum M2RT4 not boosting the growth in both host plants while T. atroviride F5S21 resulted in enhanced shoot biomass in S. lycopersicum. T. atroviride F5S21 and T. harzianum KF2R41 inoculated S. lycopersicum plants and H. lixii F3ST1, T. asperellum M2RT4, and T. harzianum KF2R41 inoculated P. vulgaris plants had significantly lower oviposition, while nymph development in both hosts was significantly prolonged in all the endophytically–colonised plants. The endophytes H. lixii F3ST1 and T. asperellum M2RT4 significantly reduced the longevity/survival of the exposed T. vaporariorum adults and the progeny in both S. lycopersicum and P. vulgaris. The findings demonstrate the attributes of the various endophytes in host plant growth promotion as well as their effects on the life-history parameters of T. vaporariorum and could consequently be developed as potential endophytic fungal-based biopesticides for the sustainable management of the pest in S. lycopersicum and P. vulgaris cropping systems.

Compatibility of the fungus Lecanicillium muscarium and the predatory mite Amblyseius swirskii for their combined application against the greenhouse whitefly Trialeurodes vaporariorum

The present study evaluated effects of the fungus Lecanicillium muscarium (Ascomycota: Hypocreales) and an organic extract from its mycelium on the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) and its predator, mite Amblyseius swirskii (Acari: Phytoseiidae). Mites were exposed to fungal spores or organic extract prepared from L. muscarium mycelium. No negative effect was shown on the predator feeding on T. vaporariorum nymphs treated with fungal conidia at a concentration of 5 × 107 spores/ml; by day six the number of mite eggs and nymphs was 18.7 % higher than on leaves treated with Tween 80. In contrast, treatment of leaves with a 0.5 % alcohol extract derived from L. muscarium mycelium caused 35 % mortality of A. swirskii adults by day two. In a trial conducted in a commercial greenhouse on rose plants, the application of L. muscarium conidia followed by the release of A. swirskii suppressed T. vaporariorum more effectively than each of the control agents applied separately.

Vibrational communication and mating behavior of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)

The greenhouse whitefly (GW), Trialeurodes vaporariorum is considered one of the most harmful insect pests in greenhouses worldwide. The GW mating behavior has been partially investigated and its vibrational communication is only in part known. A deeper knowledge of its intraspecific communication is required to evaluate the applicability of control methods based on techniques of behavioral manipulation. In this study, for the first time, we provided a detailed ethogram of the GW mating behavior and we characterized the vibrational signals emitted during the process of pair formation. We characterized two types of male vibrational emissions (“chirp” and “pulses”), differently arranged according to the behavioral stage to form stage-specific signals, and a previously undescribed Male Rivalry Signal. We recorded and characterized two new female signals: The Female Responding Signal and the Female Rejective Signal. The mating behavior of GW can be divided into six different stages that we named “call”, “alternated duet”, “courtship”, “overlapped duet”, “mating”, “failed mating attempt”. The analysis performed with the Markovian behavioral transition matrix showed that the “courtship” is the key stage in which male exhibits its quality and can lead to the “overlapped duet” stage. The latter is strictly associated to the female acceptance and therefore it plays a crucial role to achieve mating success. Based on our findings, we consider the use of vibrational playbacks interfering with GW mating communication a promising option for pest control in greenhouses. We discuss the possibility to start a research program of behavioral manipulation to control the populations of GW.

A novel non-trichome based whitefly resistance QTL in Solanum galapagense

The greenhouse whitefly Trialeurodes vaporariorum is a major threat in tomato cultivation. In greenhouse grown tomatoes non-trichome based whitefly resistance may be better suited than glandular trichome based resistance as glandular trichomes may interfere with biocontrol, which is widely used. Analysis of a collection of recombinant inbred lines derived from a cross between Solanum lycopersicum and Solanum galapagense showed resistance to the whitefly T. vaporariorum on plants without glandular trichomes type IV. The resistance affected whitefly adult survival (AS), but not oviposition rate. This indicates that S. galapagense, in addition to trichome based resistance, also carries non-trichome based resistance components. The effectiveness of the non-trichome based resistance appeared to depend on the season in which the plants were grown. The resistance also had a small but significant effect on the whitefly Bemisia tabaci, but not on the thrips Frankliniella occidentalis. A segregating F2 population was created to map the non-trichome based resistance. Two Quantitative trait loci (QTLs) for reduced AS of T. vaporariorum were mapped on chromosomes 12 and 7 (explaining 13.9% and 6.0% of the variance respectively). The QTL on chromosome 12 was validated in F3 lines.