Acaricidal activities of Santolina Africana and Hertia Cheirifolia, two endemic plants of north Africa, on the two spotted spider mite (Tetranychus urticae)

The two-spotted spider mite, Tetranychus urticae Koch, is a worldwide pest which feeds
on a large variety of plant families. Because its resistance to acaricides is spreading
rapidly, the development of new biological control tactics for population management
is crucial. Plant extracts, such as Santolina africana and Hertia cheirifolia (Asteraceae),
may represent viable alternatives, since they are currently considered to be minimumrisk pesticides. Although these two plants are known for their biocidal properties, the
extract concentration that provides the most efficient control has not yet been
precisely determined. In this study, we conducted a series of laboratory experiments to
determine the susceptibility of adult females to different concentrations of S. africana
and H. cheirifolia extract. These plants were steam-distilled and sprayed using a Potter
spray tower. Mortality and fecundity were measured upon treatment with extract
concentrations ranging from 0.07 to 6.75 mg/L. Female mortality increased with
concentration, with LD50 values of 2.35 mg/L for S. africana and 3.43 mg/L for H.
cheirifolia, respectively Reduced fecundity was previously observed at concentrations
of 0.07, 0.09 and 0.29 mg/L .The chemical composition of the two oils were
characterised by GC-MS. The most abundant components of the S. africana oil were
terpinen-4-ol (44%), α- terpineol (11.31%) and borneol (6.73%). Camphor (15.11%),
terpinen-4-ol (14.2%), α- terpineol (9.3%) were characteristic of the Hertia oil.