The avocado red mite,
Oligonychus yothersi (McGregor) (Acari: Tetranychidae), is a polyphagous pest that causes
damage to a wide range of plants. In Chile, is commonly found in avocado (
Persea americana
Mill.) orchards, and the
plant damage is expressed as a reduction of photosynthetic activity in leaves, causing defoliation of trees under severe
attack conditions.
Oligota pygmaea
(Solier) (Staphylinidae) and
Parastethorus histrio (Chazeau) (Coccinellidae) microcoleopteran
predators are found on ‘Hass’ avocado orchards, infested by
O. yothersi. This study investigated the role of
volatile compounds released by avocado in response to
O. yothersi infestation in the tritrophic interaction avocado-
O.
yothersi-
O. pygmaea-
P. histrio. Plant volatiles were collected from live plants by headspace technique on Porapak Q traps
and analyzed by gas chromatography coupled to mass spectrometry (GC-MS). In the chemical analysis, several chemical
groups were identified including terpenes, aromatic compounds, and green leaf volatiles. Eight chemical compounds
were detected only in the infested plants volatile profile, and differences were observed in the emission of 10 compounds
between infested and uninfested plants (P < 0.05). The behavioral responses of the insects to plant volatiles were evaluated
in a choice-test using a Y-tube as olfactometer. Uninfested plant volatiles were significantly attractive to
O. yothersi,
while infested plants volatile extract repelled the mites. Two compounds,
R-limonene and α-pinene, elicit an attractant
behavioral response from
O. yothersi.
Oligota pygmaea and
P. histrio females registered a strong attraction to volatiles
from infested plants, and the compounds (Z)-β-ocimene and methyl salicylate detected only in infested plant also were
attractive to predators.
