The Asian citrus psyllid,Diaphorina citri, transmits a phloem‐limited bacterium,Candidatus ‘Liberibacter’ asiaticus that causes citrus greening disease. Because juvenile hormone (JH) plays an important role in adult and nymphal development, we studied the final steps in JH biosynthesis inD. citri. A putative JH acid methyltransferase ortholog gene (jmtD) and its cognate cDNA were identified by searchingD. citri genome database. Expression analysis shows expression in all life stages. In adults, it is expressed in the head‐thorax, (containing the corpora allata), and the abdomen (containing ovaries and male accessory glands). A 3D protein model identified the catalytic groove with catalytically active amino acids and the S‐adenosyl methionine (SAM)‐binding loop. The cDNA was expressed inEscherichia coli cells and the purified enzyme showed high preference for farnesoic acid (FA) and homoFA (k_cat of 0.752 × 10⁻³ and 0.217 × 10⁻³s⁻¹, respectively) as compared to JH acid I (JHA I) (cis/trans/cis; 2Z, 6E, 10cis), JHA III (2E, 6E,10cis), and JHA I (trans/cis/cis; 2E, 2Z, 10cis) (k_cat of 0.081 × 10⁻³, 0.013 × 10⁻³, and 0.003 × 10⁻³s⁻¹, respectively). This suggests that this ortholog is aDcFA‐o‐methyl transferase gene (fmtD), not ajmtD, and that JH biosynthesis inD. citri proceeds from FA to JH III through methyl farnesoate (MF).DcFA‐o‐MT does not require Ca²⁺, Mg²⁺ or Zn²⁺, however, Zn²⁺ (1 mM) completely inhibits the enzyme probably by binding H115 at the active groove. This represents the first purified FA‐o‐MT from Hemiptera with preferred biological activity for FA and not JHA.

Rapid development of resistance in vector mosquitoes to synthetic insecticides is a major challenge for malaria control. The use of plant-derived essential oils (EOs) is an attractive strategy in controlling mosquito populations because they are environmentally safe and may have a lower chance of developing resistance. This study assessed the larvicidal activities of EOs from Lantana camara, Lippia multiflora, Lippia chevalieri, and Cymbopogon schoenanthus against Anopheles funestus and Culex quinquefasciatus. The 3^rd4^th instar larvae were tested using a World Health Organization (WHO)-modified protocol to evaluate larval mortality 24h after exposure to EOs and their binary combinations. Culex quinquefasciatus larvae were more susceptible to EOs than An. funestus larvae. For Cx. quinquefasciatus, the lethal concentrations at 50 mortality (LC₅₀s) of EOs from C. schoenanthus, L. multiflora, L. camara, and L. chevalieri were 23.32, 27.24, 38.54, and 54.11ppm, respectively; whereas for An. funestus, the EO LC₅₀s were 120.5, 67.5, 49.21, and 105.74ppm, respectively. Synergistic effects were observed using EOs from C. schoenanthus+L. multiflora (LC₅₀=44.05ppm) on An. funestus, while L. camara+L. chevalieri (LC₅₀=33.16ppm), L. chevalieri+C. schoenanthus (LC₅₀=12.08ppm), and L. multiflora+L. chevalieri (LC₅₀=20.61ppm) were synergistic for Cx. quinquefasciatus. These results indicate the potential of EOs derived from local plants and their binary combinations as botanical larvicides. The EOs could be used as future ecofriendly agents to control these vectors.