Host Resistance Flashcards
What are semiochemicals
- signal chemicals
What are the types of semiochemicals?
Pheremone: same species signal. Things like alarm, aggression, aggregation, sex, trail marking and egg site marking. Anti aggregation (hotel is full folks).
Allomone: produced by species A and affects species B behaviour. benefits species A (repellents)
Kairomone: Produced by species A. Benefits species B instead (attractants).
How do patchily distributed species find eachother for mating?
Sex pheremones
What are some aspects of host attractiveness , defences.
- Preference: pests tuned into host and target them based on sight (silhouette and colour) and temperature (veg vs flower buds)
- Chemical odour is attractant, indifferent or repellent: alpha pinene - Fd beetle, ethanol: ambrosia beetle, turpentine: borers.
What is Antixenosis?
“Repulsion” or non preference. Repellents or deterrents usually.
What is chemotaxis?
Positive chemotaxis is attractant, negative chemotaxis is deterrent or repellent.
Example - beta pinene repels Fd beetle, marigolds are volatile repellents.
What are some morphological deterrents
- thick skin, fine hairs, surface waxes
What is antibiosis?
Increased insect mortality, reduced growth and reproductive success. Stronger allomones
Toxins: jugalone toxic to gypsy moth, nicotine and pyrethrums are natural insecticides, SS mimics juvenile hormone to prevent terminal weevil metamorphosis.
what are some physical antibiosis responses?
- overgrowth of tissue. (Variable in success)
- necrotic tissue surrounding egg
- adhesive coatings (gums)
- resin (pitching out bark beetles)
What are the 4 chemical signals that trees can send to bugs?
Preference
Indifference
Antixenosis
Antibiotic
What are some aspects of resilience?
- ability to withstand and recover from attack
- a factor of tree age and vigor (site conditions)
What is host pseudo tolerance?
Evasion of attack due to luck
-typically due to timing or rarity (susceptibility period short: shoot tip moths and terminal weevils)
Out of sync bud burst vs egg hatching in defoliators that require young tissue
Isolated or rare tree: species low in population have no pests because they can’t build up.
What is insect damage dependent on?
- host attractiveness and level of defences
- resilience (can it recover and survive)
What is a kairomone
Semiochemicals produced by trees that attract beetles (smell tasty).
