Studies on indirect infection of Trypodendron lineatum Oliv. with Beauveria bassiana (Bals.) Vuill.

Abstract

The transfer of infection of B. bassiana from contaminated male T. lineatum to non‐contaminated females, as well as the effect of B. bassiana treated timber to the breeding activity and the mortality of young beetles in contaminated soil after immigration for hibernation was investigated. Breeding activity of non contaminated females is reduced by 20 % if placed together with contaminated males. Treated timber shows fewer holes of brood systems and less breeding activity than non‐treated one. The beetles were infected to a higher degree if the soil was contaminated and not the timber. Spraying higher concentrations once or lower ones twice gives mortality rates of up to 100%. Application of spore dust gives lower mortality rates than application of water diluted spores if the concentration on the soil surface is the same. Sterile soil shows after spore contamination a higher mortality rate than non‐sterilized soil. Investigations were completed with observations on the migration flights of hibernated beetles in spring, the hatching of young beetles out of the brood systems, their phototactic behaviour and their distribution in the soil after immigration for hibernation. Zusammenfassung Untersuchungen über eine indirekte Infektion von Trypodendron lineatum Oliv, mit Beauveria hassiana (Bals.) Vuill. Die Infektionsübertragung von kontaminierten Männchen auf nicht kontaminierte Weibchen, die Wirkung von B. bassiana‐behandeltem Rundholz auf das Brutgeschäft von T. lineatum und die Mortalität von Jungkäfern in kontaminiertem Uberwinterungssubstrat wurden untersucht. Die Brutleistung von nicht kontaminierten Weibchen wurde bei Ansatz mit kontaminierten Männchen um 20 % reduziert. Kontaminiertes Rundholz zeigte weniger Einbohrungen und geringere Brutleistungen als Kontrollstämme, wobei dieser Unterschied bei Lagerung im Bestand wesentlich stärker ausgeprägt war als bei Lagerung im Sägewerk ohne Beschattung. Bei der höchsten Sporensus‐pensions‐Konzentration von 5 × 107 Con/cm2 Stammoberfläche wurde eine Verringerung der Brutleistung um 44.89 % im Vergleich zur Kontrolle erreicht. Die Wirkung auf die Käfer war bei Kontamination des Uberwinterungssubstrates größer als bei Kontamination von Rundholz. Bei einmaligem Sprühen von 1 × 107 Con/cm2 Bodenoberfläche oder zweimaligem Sprühen von 1 × 106 Con/cm2 Bodenoberfläche wurden Mortalitätsraten bis 100 % erreicht. Ausbringung von Sporenstaub ergab bei gleicher Konzentration an der Bodenoberfläche eine um 39.60 % geringere durchschnittliche Mortalität als Sprühen einer wässrigen Suspension. In sterilem Boden lag die Mortalität um 18.88 % (nach Suspensionsbehandlung) und 14.21 % (nach Staubbehandlung) höher als im nicht sterilisierten. Die Untersuchungen wurden mit Beobachtungen zum Schwärmen der Altkäfer im Frühjahr aus den Uberwinterungsplätzen, dem Schlüpfen der Jungkäfer aus den Brutsystemen und dem anschließenden phototaktischen Verhalten sowie ihrer Verteilung im Boden nach Einwandern in das Überwinterungssubstrat ergänzt.

Extremely low infection levels of pathogens and nematodes in Trypodendron spp. (Coleoptera: Curculionidae)

“…In laboratory tests, Novák & Samsinakova (1962) found that B. bassiana caused 100% mortality of T. lineatum larvae in 6 to 8 days and 100% mortality of adults in 12 days. The latter authors also found that the effects of temperature, humidity, spore formulation, and spore dose on the infection of T. lineatum by B. bassiana were similar to those reported by Pražák (1988Pražák ( , 1991Pražák ( , 1997 for other bark beetle species, but different test conditions caused 36% to 55% mortality in most cases, while only a few experiments lead to mortality rates higher than 80% (Pražák 1988(Pražák , 1991(Pražák , 1997. Novák & Samsinakova (1962) reported that male beetles inoculated with B. bassiana transmitted the fungus to healthy female beetles and that the transmission reduced the number of eggs laid by 20%.…”

“…Novák & Samsinakova (1962) reported that male beetles inoculated with B. bassiana transmitted the fungus to healthy female beetles and that the transmission reduced the number of eggs laid by 20%. Application of B. bassiana spores to the bark surface reduced the number of egg niches by up to 44% depending on the spore concentration, and treatment of soil caused 88 to 100% mortality of hibernating offspring beetles (Pražák 1988).…”

Potential of Beauveria bassiana (Hyphomycetes: Moniliales) for controlling the white pine weevil, Pissodes strobi (Col., Curculionidae)

“…Soil application of pathogenic fungi has also been considered for the control of other insect pests that spend part of or all of entire life cycle in the ground. Treating soil with B. bassiana instead of treating timber induced a higher degree of infection in young hibernating striped ambrosia beetles, Trypodendron lineatum , which resulted in mortality rates of up to 100% (Prazak 1991). In addition, Metarhizium anisopilae (Hyphomycetes) applied on the soil at a low conidia rate provided respectively 82% and 97% of mortality in second and third instar June beetles, Phyllophaga anxia (Poprawski and Yule 1991).…”

Efficacy of native entomopathogenic fungus, Isaria fumosorosea, against bark and ambrosia beetles, Anisandrus dispar Fabricius and Xylosandrus germanus Blandford (Coleoptera: Curculionidae: Scolytinae)

“…They also stated that some treated females had 100% infected broods. Treated male adults transferred fungal inocula to untreated females which reduced their breeding activity by 20% (Prazak 1991). In summary, EPF did not only cause mortality of adult beetles outside in the host trees but also decreased beetles' population through infecting next-generation broods in the galleries.…”