Agricultural and Forest Entomology (2009) 11, 255-263

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Nadir Erbilgin, Thomas R. Gordon, David L. Wood and Andrew J. Storer (2009)
Bark beetle-mediated fungal infections of susceptible trees induce resistance to subsequent infections in a dose dependent manner
Agricultural and Forest Entomology 11 (3), 255-263
Abstract: 1 Experiments were conducted to determine whether propagule loads on the twig beetles Pityophthorus setosus and Pityophthorus carmeli (Coleoptera: Scolytidae) influence the pathogen infection of the host tree in the Monterey pine-Fusarium circinatum system.
2 On an average, F. circinatum was isolated from 2.6% and 3.3% of trapped P. setosus and P. carmeli, respectively, although the isolation percentages varied over the season, being highest in the spring and lowest in late summer and fall for both species. Mean pathogen load was 13.4 and 22.6 propagules per beetle, on P. setosus and P. carmeli, respectively, and decreased from May to November for both species. The pathogen was also isolated from approximately 55% of both beetle species that emerged from infected branches. Mean propagule load on emerged P. setosus and P. carmeli was 39 and 66.5, respectively.
3 On the basis of these data, beetle species were treated with one of three propagule loads (low, medium, high) and caged onto live branches to determine whether they could transmit the pathogen. At all propagule loads, both species transmitted the pathogen, and transmission percentage and lesion length, a measure of tree susceptibility, were positively correlated with propagule load.
4 To investigate further whether the previous transmission by beetles could affect response of the same trees to subsequent infection with F. circinatum, different branches were inoculated on the same trees used in the transmission study, and lesion lengths were measured. Lesion lengths were lower on trees that had been previously exposed to beetles treated with high or medium propagule loads than on trees that had previously been exposed to beetles treated with low propagule loads. This suggests that the initial infection by beetles carrying high or medium propagule loads induced resistance to subsequent infections of the host, whereas infections caused by beetles with low propagule loads did not.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Nadir Erbilgin, Thomas R. Gordon

Research topic(s) for pests/diseases/weeds:
transmission/dispersal of plant diseases
population dynamics/ epidemiology

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Fusarium circinatum Pine (Pinus)
Pityophthorus setosus Pine (Pinus)
Pityophthorus carmeli Pine (Pinus)