25 Flashcards
Why are there outbreaks of Bark Beetles killing huge abundance of trees now?
Climate change is altering the distribution of these beetles and pushing them more north and in higher elevations to trees that are unresistant to them.
In natural diverse systems, pine beetles culled old/sickly trees and?
Served as dynamic agent that opened forest gaps promoting seedling germination and succession.
!!!But now, pine beetles culled trees that lack defences. This results in?
*Climate change mediated hotter and drier summers which stress trees and compromise defences.
*Longer summers double beetle fecundity through allowing multiple generation per year
*Milder winters reduce beetle mortality…
What do the trees do when they are colonized by beetles? Attack stages of beetles on the trees
*The first line of defence are resin (sap). They then increase the production of the resin by the phytohormone (oleoresin production). This induces defences after damage to plant tissue by JA-induced increase oleoresin production. This occurs after the pioneer beetle female attacks the tree.
*Female beetle detoxifies terpenes and defecates by-products, which function as aggregation pheromones and attract more beetles. This is how the beetles can overwhelm the first line of defence.
*Beetle inoculate tree with blue-stain fungus, which induces SA response that inhibits JA-mediated defence induction in the tree
*Larvae emerge in an already weakened tree dig galleries across phloem, blue stain fungus grows into xylem: combined effect stalls defence induction and girdles tree, ultimately resulting in the death of the tree.
Different chemicals released by both trees and beetles during tree and beetle attack interactions? 4*
*Beta-myrcene emitted by tree attracts females as a kairomone
*Trans-verbenol emitted in female faces attracts males as a pheromone
*Exo-brevicomin emitted by males as aggregation pheromone
*Males emit frontal, mated females emit verbenone as an anti-aggregation pheromone (no new males can come since there are too many beetles)
Opportunities for pest control? 4*
Make traps that have beta-myrcene to attract beetles and they fall into the water. This work but not efficient if you have really big outbreaks since the whole landscape will smell like this. This only works if you have relatively low numbers.
Combining beta myrcene and trans-verbenol is more effective.
There are also the same traps combining beta-myrcene, trans-verbenol, and brevicomin, mass rapping of male and female beetles, but also the same problem if the whole forest smells like this.
Combined aggregation pheromone baits, which attract (pull) beetles. Verbenone anti-aggregation pheromone (push) in combination with non-host volatiles (double-push?) to all the trees to push them away.
How successful are push-pull strategies for pest control?
They are most effective and consistently effective. Pull only works sometimes. Success is plotted against increasing the number of beetles that release pheromones away from the traps.
Primary concept about push pull systems?
Repellant and attractive natural products (e.g., pheromones and kairomones) can be combined to function synergistically as push and pull respectively.
Second concept about push pull systems?
Repellent (push) and attraction (pull) of pests from crop plants can be accomplished by functional inter-(companion-) cropping
