Application of methyl jasmonate to grey willow (Salix cinerea) attracts insectivorous birds in nature
It has been suggested that insectivorous birds may be guided by herbivore-induced plant volatiles (HIPVs) to herbivore-rich trees with herbivorous damage. The HIPV production in plants is partly mediated by the jasmonic acid signalling pathway. Methyl jasmonate (MeJA) was proved to be a suitable agent for the induction of HIPVs similar to those induced by herbivorous insects in many plant species. We studied the effects of methyl jasmonate on volatile emission and natural enemy attraction using mature grey willow (Salix cinerea) under natural conditions in the Czech Republic. We treated 12 experimental shrubs with 30 mM MeJA and completed the experiment with 12 control shrubs. We monitored attacks by natural predators with artificial plasticine caterpillars which were checked daily. Birds most often pecked the caterpillars exposed on MeJA-treated shrubs and this attractiveness differed significantly from the control. The attractiveness of MeJA-treated shrubs did not differ significantly from control shrubs for arthropod predators. Spraying MeJA on grey willows resulted in significantly higher production of α-pinene, β-pinene, 3-carene, limonene and β-ocimene. There was a marginally significant positive correlation between the predation rate by birds and relative change in α-pinene emissions.
Mrazova, A., & Sam, K. (2018). Application of methyl jasmonate to grey willow (Salix cinerea) attracts insectivorous birds in nature. Arthropod-Plant Interactions, 12(1), 1-8.
Probability of a predation event on plasticine caterpillars exposed on control and MeJA-treated willow shrubs in total (a) and during the four experimental days separately (b). Difference between the two treatments in part (a) F 1,22 = 8.43, P = 0.008. In part b day 1 = 24 h after the first application of methyl jasmonate (MeJA), day 2 = 48 h of the experiment and 2 applications of MeJA, day 3 = 72 h of the experiment and three applications of MeJA, day 4 = 96 h of the experiment and four applications of MeJA. Significantly different results for control vs. MeJA-treated shrubs within a day are marked by asterisks (**P ≤ 0.01), and the other differences are not significant
Probability of a predation event on plasticine caterpillars on control and MeJA-treated willow shrubs in birds (a) and in arthropods (b). In part b day 1 = 24 h after the first application of methyl jasmonate (MeJA), day 2 = 48 h of the experiment and 2 applications of MeJA, day 3 = 72 h of the experiment and three applications of MeJA, day 4 = 96 h of the experiment and four applications of MeJA. In both parts: *P ≤ 0.05; ***P ≤ 0.001, P = 0.058, other differences between control and MeJA-treated trees are not significant
Mean change in VOC emissions (in a and b with different y-axis scales) between the MeJA-treated and control (unsprayed) shrubs of grey willow (Salix cinerea) 24 h after the single application of MeJA. The x-axes show the individual compounds, and the y-axes show relative emissions. Note differences in the span of y-axes in two (a and b) parts of the figure. In both parts: **P ≤ 0,01, ***P ≤ 0,001