Comparative toxicity study of different acaricides in laboratory preluding for field efficacy assessment against Tetranychus urticae (Acari: Tetranychidae)‎

الملخص EN

Toxicity and field studies were carried out on spirodiclofen, pyridaben, abamectin and hexythiazox against the developing stages of susceptible strain (SS) and field strains (FS) of Tetranychus urticae Koch.

(Acari: Tetranychidae).

Abamectin had the highest resistance ratios levels of 6 and 4.1 fold in adult and developmental stage respectively.

In adult stage, spirodiclofen and pyridaben had 1.2 and 1.1 fold, respectively.

Developmental stage had equal folds of 1.1 for spirodiclofen, hexythiazox and pyridaben.

In egg stage, hexythiazox, pyridaben and spirodiclofen had 1.3, 1.2 and 1 fold, respectively.

High relative resistances based on LC50s of abamectin were 357 and 171 fold for pyridaben and spirodeclofin, respectively in adult stage besides, 122, 9 and 7 folds for pyridaben, spirodeclofin and hexythiazox, respectively in developmental stage.

The field experiments throughout 4 weeks post treatments on green bean crop in season of 2017 showed that the highest overall reduction percentages in T.

urticae populations were occurred in spirodiclofen (55.90 %) and pyridaben (51.72 %) compared to abamectin (49.77 %).

Meanwhile, season of 2018, abamectin had the highest overall reduction percentages of 56.00 % compared to spirodiclofen (51.84 %) and pyridaben (49.40 %).

Hexythiazox had the lowest overall reduction percentages of 32.53 % and 36.17 % in seasons of 2017 and 2018, respectively.

The residual control activity in both seasons showed that spirodiclofen had delayed initiating effect (7- 28 DATs) ˃ pyridaben = abamectin (4 - 21 DATs) ˃ hexythazox (4 - 7 DATs).

Eventually, our study declared that spirodiclofen, pyridaben and hexythiazox were considered to be alternatives and complementary acaricides to abamectinin controlling different developmental stages of T.

urticae.