Additive interaction between a root‐knot nematode Meloidogyne javanica and a root‐feeding flea beetle Longitarsus bethae on their host Lantana camara

Abstract

BACKGROUND Changes in plants induced by one species have indirect effects on interactions with other species, thus shaping their abundances. The root‐feeding beetle Longitarsus bethae released as a biological control agent for Lantana camara has established at a few sites in South Africa. Lantana camara plants infected with the root‐knot nematode Meloidogyne javanica often exhibit an increase in L. bethae abundance, suggesting that nematode‐infected plants could be enhancing the development of the beetle. This study investigated the interaction between L. bethae and M. javanica. RESULTS The study showed that galling by M. javanica occurred at the highest inoculation of 300 eggs of L. bethae per plant. Longitarsus bethae performed over twofold better on M. javanica‐infected L. camara roots compared with healthy roots, and 275 adult L. bethae progeny, with slightly larger body size, emerged from M. javanica‐infected compared with 167 adults that emerged from healthy plants. Fresh gall weight from treatments where both L. bethae and M. javanica were combined was 36% higher than that from M. javanica only, suggesting that the combination of both species induces more galling than the nematode does alone. The total biomass of plants with M. javanica only, L. bethae only, and the two species combined was reduced by 48%, 24% and 50%, respectively. CONCLUSION Meloidogyne javanica improves the performance of L. bethae, and combination of the two species has an additive negative effect on L. camara. The interaction between M. javanica and L. bethae could enhance the biological control of L. camara. © 2019 Society of Chemical Industry

Why fitness impacts of different herbivores may combine nonadditively, and why it matters to the ecology and evolution of plant-herbivore communities

“…The ecological relevance of how herbivore impacts combine is obvious, both from a basic and an applied perspective. For instance, information on nonadditivity could help inform policies on pest suppression in agricultural crops (Barber et al 2012;Gagic et al 2016) and strategies for biological control of weeds by herbivorous insects (Wooley et al 2011;Musedeli et al 2019). More contentious, however, is the issue of whether nonadditivity of herbivore impact is relevant to the evolution of host plants.…”

Interaction of tomato plants infected by the nematode Meloidogyne javanica on aboveground herbivore Tetranychus urticae and on behaviour of its predator Phytoseiulus macropilis

“…For example, one study showed that a root-eating flea beetle Longitarsus bethae performed better on Lantana camara plants infected with M. javanica than on plants with healthy roots (Musedeli, 2020). On the other hand, other study showed that soybean cyst root nematode Heterodera glycine negatively affects the above-ground leaf-chewing Spodoptera litura by increasing the developmental time and decreasing adult body weight .…”