Repellency of 41 plant species to citrus psyllids

Huanglongbing (HLB) is the most devastating citrus disease worldwide. The
organism associated with the disease is spread by an insect vector,
Diaphorina citri, commonly known as Asian citrus psyllid (ACP). Current
management of HLB relies either on physical removal of the infected plants
or on chemical control of ACP. Both methods are costly and not overly
effective. In addition, public concerns regarding insecticide residues in
fruit have greatly increased in recent years. It has been hypothesized
that plant volatiles could act as repellents to ACP, thus reduce the
incidence of HLB. To test this hypothesis, the repellency of fresh tissues
of 41 aromatic plant species to ACP was investigated. The repellency of
individual species was determined using a Y-tube olfactometer. Our results
showed that volatiles of five plant species were highly effective in
repelling ACP with repellency as much as 76%. Among these, the tree
species, Camptotheca acuminate, and the two shrubs, Lantana camara and
Mimosa bimucronata, could potentially be planted as a landscape barrier.
The two herbs, Capsicum annuum and Gynura bicolor, could potentially be
used as interplantings in orchards. This is the first time that the
repellency of fresh tissues from a diverse range of plant species to ACP
has been determined. Although further field evaluation of various
interplanting regimes and landscape barriers are needed to assess their
effectiveness, our results showed that these aromatic species, being
highly repellent to ACP, offer great potential as more cost-effective and
environmentally sustainable alternatives to the current methods of
managing HLB.