The effects of petroleum oil and lime sulfur on the mortality of Unaspis yanonensis and Aculops pelekassi in the laboratory

Arrowhead scale (AHS), Unaspis yanonensis (Kuwana) (Hemiptera: Diaspididae), and pink citrus rust mite (PCRM), Aculops pelekassi (Keifer) (Acari: Eriophyoidae), are important arthropod pests of organic citrus orchards in Jeju. This study was conducted to evaluate the stage-specific mortality effects of petroleum spray oil (PSO) (AI 95%) and lime sulfur (LSF) (AI 22%) against AHS and PCRM in the laboratory. The developmental stages of AHS were divided into the 1st nymph, the three sub-stages of the 2nd nymph (N2a = early soft body, N2b = hardened body, and N2c = late apolysis), and the two sub-stages of adult females (A3a = early age, and A3b = middle age). The developmental stages of PCRM were divided into eggs, the 2nd nymphs, and adults. PSO 100× and LSF 80× resulted in high mortality against the 1st nymphs of AHS. The effects of PSO and LSF were significantly different among the application rates on 2nd nymphs of AHS and were higher on N2a. The PSO and LSF treatments significantly affected egg hatch rate of PCRM: LSF 50× (2.4%), LSF 100× and PSO of 50× and 200× (17.8% to 20.4%), and LSF 200× (39.0%). PSO and LSF also significantly affected the mortality of the 2nd nymphs and adults of PCRM. PSO and LSF resulted in low direct mortality on A3a and A3b of AHS, but induced an abnormal morphology. PSO treatment resulted in a loose attachment of AHS scale cover on the leaf surface and LSF treatment resulted in an abnormal or lacking scale cover.