Neotropical Entomology (2005) 34, 991-998

Mário E. Sato, Marcos Z. da Silva, Adalton Raga and Miguel F. de Souza Filho (2005)
Abamectin resistance in Tetranychus urticae Koch (Acari: Tetranychidae): selection, cross-resistance and stability of resistance
Neotropical Entomology 34 (6), 991-998
Abstract: Studies on artificial laboratory selections with abamectin, cross-resistance relationships, and stability of resistance were carried out with Tetranychus urticae Koch to provide basic information for an abamectin resistance management program. Selections for resistance and susceptibility to abamectin were performed in a population of T. urticae, collected from a commercial strawberry field in the State of São Paulo, Brazil. After five selections for resistance and five selections for susceptibility, susceptible (S) and resistant (R) strains of T. urticae to abamectin were obtained. The resistance ratio (R/S) at the LC₅₀ reached 342-fold values. The toxicity of eight acaricides was evaluated in the R and S strains, observing significant differences (at LC₅₀) between R and S strains for milbemectin, fenpropathrin and chlorfenapyr. Significant correlation was detected between the LC₅₀s of abamectin and milbemectin, indicating cross-resistance between these acaricides. No cross-resistance was detected for the acaricides fenpyroximate, cyhexatin, propargite and dimethoate. The stability of abamectin resistance was also studied under laboratory conditions. Abamectin resistance was unstable in the absence of selection pressure. For all studied populations (with 75, 50 and 25% of initial frequency of resistant mites), the percentage of resistant mites decreased to levels equal or lower than 15% in six months. The results indicate that milbemectin should be avoided for managing abamectin resistance in T. urticae.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Full text of article
Database assignments for author(s): Mário Eidi Sato, Adalton Raga

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tetranychus urticae	Strawberry (Fragaria)	Brazil (south)