Evaluation of a guardian plant system to suppress Frankliniella occidentalis (Thysanoptera: Thripidae) in greenhouse ornamentals.

BACKGROUND: Western flower thrips (WFT), Franklinella occidentalis (Pergande), is an economically damaging pest of greenhouse ornamentals. A 'guardian plant system' (GPS) that targeted WFT was evaluated under controlled and commercial greenhouse conditions. This system used mycotized millet grains with the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin applied to soil of potted marigolds, Tagetes patula (L.), combined with the foliar-dwelling predatory mite Neoseiulus (=Amblyseius) cucumeris (Oudemans) in slow-release sachets under controlled greenhouse conditions, and with the addition of a pheromone lure under commercial settings. RESULTS: Significantly fewer WFT and less foliar damage on GPS was observed over the 10 and 12 weeks experimental periods compared to the untreated controls. Predatory mites were maintained up to 10 weeks with one release under controlled greenhouse conditions and 12 weeks with two releases in commercial greenhouses. In commercial greenhouses, greater numbers of WFT were found on marigolds than on crop plants within 1 m of the system. Fungal granules persisted for 12 weeks up to 2.5 × 105 CFU g-1 in the GPS soil. CONCLUSION: The use of biological control agents to suppress WFT within a GPS could be a useful IPM strategy for greenhouse production. The marigold GPS attracted WFT which were suppressed primarily through predation by foliar-dwelling predatory mites and to a lesser extent, infection from conidia produced by the granular fungal formulation in the soil. Further investigations into system deployment and fungal granular application rates and new fungal formulations are suggested to improve system efficacy. © 2023 Society of Chemical Industry.

Evaluation of the entomopathogenic fungus Metarhizium brunneum and the predatory mite Stratiolaelaps scimitus against Rhizoglyphus robini under laboratory conditions.

Rhizoglyphus robini Claparède (Acari: Acaridae) is a pest of bulbs, corms and tubers of several economically important crops. The biological control of R. robini has yet to be fully explored as an alternative to chemical pesticides. Entomopathogenic fungi in the genera Metarhizium (Hypocreales: Clavicipitaceae) are used for the biological control of several agricultural pests. The soil-dwelling predatory mite, Stratiolaelaps scimitus (Womersley) (Acari: Acaridae) is also frequently used alone or in combination with other biological control agents. There are few reports on the use of M. brunneum or S. scimutus against R. robini. The objectives of this research were to investigate the in vitro effect of different predatory mite ratios of S. scimitus on R. robini mortality and the combined use of a M. brunneum-based granule with S. scimitus as potential strategies to manage this pest. Mortality of R. robini in Petri dishes containing predators was significantly higher than without predators. When soil-filled containers containing R. robini were treated with both M. brunneum granules and S. scimitus, the lower densities of the bulb mite were obtained with the highest ratio of predator/prey mites. The number of bulb mites in the containers treated with only M. brunneum was significantly lower than the untreated control. These results demonstrate the potential for releasing of S. scimitus alone and in combination with M. brunneum granules to manage R. robini.

A Review of Commercial Metarhizium- and Beauveria-Based Biopesticides for the Biological Control of Ticks in the USA.

There is a need for the development of sustainable, nonchemical tick management strategies. Mycoacaricide and mycoinsecticide product development worldwide has focused primarily on fungi in the genera Beauveria (Hypocreales: Cordycipitaceae) and Metarhizium (Hypocreales: Clavicipitaceae). Microbial biopesticides containing entomopathogenic fungi have potential in tick management. However, despite considerable progress in the development of fungal biopesticides over the past 20 years, the establishment of commercial products available for use against ticks continues to be slow. We reviewed published scientific literature and compiled a comprehensive list of reports of the effectiveness of commercial biopesticides based on the fungal genera Metarhizium and Beauveria and registered for use in the USA against ixodid ticks under laboratory and field conditions. We also report on results when these biopesticides were used as a part of integrated tick management. Until efficacious fungus-based products become more available, tick management will rely primarily on synthetic chemical acaricides, with natural-product acaricides as the alternative.

First Report of the Bat Tick Carios kelleyi (Acari: Ixodida: Argasidae) From Vermont, United States.

The soft tick Carios kelleyi (Cooley and Kohls, 1941) is an ectoparasite of bats that can harbor bacteria known to cause disease in humans, such as Rickettsia spp., Bartonella spp., and relapsing fever Borrelia spp. Human-tick encounters may occur when bats occupy attics or similar dwellings with access points to human-inhabited areas. During May 2021, a partially engorged adult female C. kelleyi was collected from a Vermont home with an attic that was being used as a roost by big brown bats, Eptesicus fuscus (Chiroptera: Vespertilionidae). The source of the blood in the tick was the domestic dog, Canis lupus familiaris. Subsequently, eight C. kelleyi larvae were collected from a rescued E. fuscus adult. This is the first report of a soft tick species from Vermont and it is unknown how long C. kelleyi has been present in this state. Reports of C. kelleyi are on the rise across the northeastern United States but the implications for the health of humans, domestic animals, and bats in northern New England remain unclear. Bat management plans should consider the importance of bat exclusion in preventing tick encounters with members of the household and should include a tick monitoring component if bats are evicted.

Biological control of Western flower thrips, Frankliniella occidentalis using a self-sustaining granular fungal treatment.

Western flower thrips (WFT), Frankliniella occidentalis, is one of the most destructive pests of vegetables, fruits and ornamental crops worldwide, causing extensive damage by direct feeding of the crop and transmitting economically important viruses. Despite the successes of biocontrol agents to control WFT, more efficient and cost-effective ways must be found to encourage grower adoption of integrated pest management. A sustainable fungal treatment was developed to preserve fungal inoculum in potting soil and reduce thrips populations. Combining cooked, oven-dried millet with BotaniGard® (a commercial form of Beauveria bassiana strain GHA) to potting soil increased spore production and persistence of the fungus in the soil. In treated pots with millet, spore concentrations were 3-4 times greater after 30 days compared with spore yields at 10 days. The number of WFT adults was significantly lower in the marigold pots treated with GHA mix + millet than untreated controls, 12% and 10% in treated pots and 70% and 68% in untreated pots in sterile and non-sterile soil, respectively. Incorporation of millet in the potting mix enhanced the effect of the fungal treatments by providing a nutritive substrate on which the fungus could become established. This method is relatively inexpensive and easy for growers to use in greenhouses because granular formulations of B. bassiana are not commercially available.

Evaluation of spray applications of Metarhizium anisopliae, Metarhizium brunneum and Beauveria bassiana against larval winter ticks, Dermacentor albipictus.

Dermacentor albipictus (Acari: Ixodidae), the winter tick, is a one-host tick that parasitizes large ungulates. They can dramatically affect moose, Alces alces (Artiodactyla: Cervidae), causing significant physiological and metabolic stress and mortality among heavily parasitized individuals. Entomopathogenic fungi in the genera Metarhizium (Hypocreales: Clavicipitaceae) and Beauveria (Hypocreales: Cordycipitaceae) are promising tick biological control agents. We examined the pathogenicity of experimental and commercially formulated isolates of M. anisopliae, M. brunneum and B. bassiana sprayed at concentrations of 106, 107 and 108 conidia/mL against the larval stage of D. albipictus and assessed the efficacy of spraying the commercial product Met52®EC, containing M. brunneum, strain F52, under laboratory conditions. Results showed larval D. albipictus mortality was significantly higher and occurred earlier when treated with M. anisopliae and M. brunneum isolates compared to B. bassiana at 106, 107 and 108 conidia/mL. Mortality was observed as early as 3 days in the M. anisopliae and M. brunneum treatments and after 6 days in the B. bassiana treatments. After 21 days, larval mortality ranged from 74-99% when ticks were treated with M. anisopliae and M. brunneum isolates at 106, 107 and 108 and conidia/mL. In contrast, mortality of ticks treated with B. bassiana ranged from 30 to 64%. When larvae were treated with the commercial product Met52, mortality was ~ 45% after 3 days and ~ 96% after 9 days. These results demonstrate the effectiveness of M. anisopliae and M. brunneum against D. albipictus.