Toxicity of insecticidal soaps to the A sian citrus psyllid and two of its natural enemies

The Asian citrus psyllid ( ACP ), D iaphorina citri K uwayama ( H emiptera: P syllidae), is an important pest of citrus because it transmits plant pathogens responsible for a serious disease of citrus known as huanglongbing. Conventional insecticides are frequently used to manage ACP . Insecticidal soaps (hereafter ‘soaps’) are an insect control option labelled for commercial use as well as for use by homeowners and organic growers. Soaps have been shown to be toxic to some insect pests and therefore might be an alternative to conventional pesticides for control of ACP , but the efficacy of soaps against ACP was largely unknown. Our objective was to test whether different concentrations of two insecticidal soaps, M ‐ P ede and S afer I nsecticidal S oap C oncentrate, caused mortality of ACP adults, nymphs and eggs. In addition, we tested whether these soaps were toxic to two natural enemies of ACP , adults of the lady beetle C ycloneda sanguinea ( L .) ( C oleoptera: C occinellidae) and the parasitoid T amarixia radiata ( W aterston) ( H ymenoptera: E ulophidae). Direct sprays of M ‐ P ede or Safer I nsecticidal S oap were acutely toxic to ACP adults (regardless of gender) and nymphs when applied in solutions of 0.8–2% in water. Insecticidal soaps were non‐toxic to eggs at rates of up to 2%. Residues of soap were less toxic to adult ACP than direct sprays, even when applied at concentrations of up to 4%. M ‐ P ede or Safer soap at high concentrations (for example, 2% v/v in water) may be an effective alternative to conventional pesticides to manage adult and nymphal ACP , although multiple applications may be needed if a target population includes eggs. A 2% concentration of either soap applied as a direct spray was non‐toxic to adult C . sanguinea but acutely toxic to adult T . radiata . Soaps therefore may be compatible with biological control of ACP by adult coccinellids but not the parasitoid T . radiata .