Exclusion of Mediterranean ant species enhances biological control of the invasive mealybug Delottococcus aberiae in citrus

Abstract

BACKGROUND: Delottococcus aberiae is an invasive mealybug that produces severe damage in Spanish citrus. This mealybug has established a mutualistic relationship with native Mediterranean ant species that may limit biological control of this pest. Herein, we evaluated the effect of tending ants on the biological control of D. aberiae. To do this, we compared: (i) the density of D. aberiae, (ii) the density of its natural enemies, and (iii) the damage produced by the mealybug in trees with (control) and without ants (ants excluded with sticky barriers) in two citrus orchards across two consecutive years. RESULTS: Lasius grandis was the most abundant ant species in both orchards and represented more than 95% of the ants tending D. aberiae in control trees. Spiders and lacewings were the most abundant predators observed in mealybug colonies, and the exclusion of mutualistic ants increased their abundance. Moreover, in control trees, ant activity throughout the year was negatively correlated with the relative abundance of predators (number of predators per mealybug). No parasitoids were recovered during field experiments. Ant exclusion reduced the density of D. aberiae and the ratio of damaged fruit at harvest across years and orchards.CONCLUSIONS: This work corroborates the previous finding that D. aberiae benefits from its mutualistic relationship with L. grandis, probably because the presence of ants reduced the abundance of generalist predators. This mutualism can be disrupted using physical barriers on on the trunk. Further research should assess other methods of ant control that are more economic and feasible for citrus producers.

Exotic predators can sequester and use novel toxins from exotic non-coevolved prey

“…Nonetheless, the high and constant abundance of Cry. montrouzieri in cochineal colonies in our field study, compared to previous field studies upon mealybugs in crops from the same region [80,88,89], suggests that the ecological benefits of this diet are higher than the cost. The enhanced defence against ants and other antagonists may be one of these benefits.…”

“…In eastern Spain, Las. grandis is among the most abundant ant species [79,80], and its presence has a strong negative effect on coccinellids, especially on immature stages [59]. Ants can cause significant mortality of Cry.…”

“…First, the availability of cochineals throughout the year [69] provides Cry. montrouzieri with a stable food source, while the presence of mealybugs is more seasonal [90]. Second, some insecticides applied in crops harm Cry.…”

Mirmecofauna em plantas cítricas: guildas e avaliação da sua influência sobre populações de cochonilhas

“…Existem espécies de cochonilhas que provocam danos econômicos ao sugar a seiva das plantas cultivadas e também podem transmitir fitopatógenos e provocar o aparecimento da fumagina (Yamamoto et al, 2004;Monteiro, 2019). Estes hemípteros fitófagos ocorrem comumente em pomares de plantas cítricas no Brasil, como plantios de laranja, tangerina e limão, também sendo frequente se observar a associação com formigas que se alimentam do honeydew e, em contra partida, protegem as cochonilhas de predadores e parasitoides (Mansour et al, 2012;Monteiro, 2019;Plata et al, 2023;Marchiori et al, 2023). Cabe ressaltar que espécies do gênero Citrus são amplamente cultivadas no território brasileiro, possuindo elevada importância econômica.…”