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

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. © 2023 Society of Chemical Industry.

Persimmon orchards harbor an abundant and well-established predatory mite fauna.

Traditionally persimmon cultivation has been considered a minor crop in Spain, but in recent years this crop has experienced an important increase in both cultivated area and production. This increase has been mainly attributed to the widespread adoption of a new postharvest treatment which considerably extends the fruit commercialization period. The sudden expansion of this crop has not allowed time to correctly develop an integrated pest management (IPM) program. Consequently, chemical treatments have become the main strategy to lessen the impact of pests. Given the importance of phytoseiids in other Mediterranean fruit crops, where they are the basis of IPM, we sought to determine whether they could be similarly employed in persimmon crops. For this, we studied the predatory mite complex, the phytoseiid population dynamics and the potential prey for them during three consecutive seasons in four persimmon orchards, two of which managed conventionally, and two organically. Phytoseiids were abundant throughout the season, found on average at a density of more than 1 predatory mite per leaf. The most abundant species was Euseius stipulatus (57.3%) followed by Typhlodromus phialatus (24.8%), Amblyseius andersoni (17.1%) and Paraseiulus talbii (0.8%). Persimmon leaves provided a diversity of prey for predatory mites throughout the year, the most abundant being mealybugs, coccids, whiteflies and thrips. The abundance of predatory mites was significantly correlated to the abundance of potential prey available. From our results we anticipate that phytoseiids will be key actors in the development of persimmon IPM. Their role in this crop is discussed, as well as how to conserve their populations.