Eight years of antâexclusion from citrus canopies: effects on the arthropod assemblage and on fruit yield
2012
Piñol, Josep | Espadaler, X. (Xavier) | Cañellas, Núria
1 Ants are important generalist predators in most terrestrial ecosystems. However, because many ant species are also hemipteran mutualists, their role in agriculture has generally been considered to be negative for plants. 2 In the present study, we report an experiment in antâexclusion from tree canopies in an organic citrus grove with two main objectives: (i) to examine whether the absence of ants increased the abundance of some beneficial arthropods and reduced the attack of some pests such as aphids and (ii) to examine whether antâexclusion increased the fruit yield of citrus trees. 3 The exclusion of ants from tree canopies had positive effects on the arthropod assemblage and on fruit yield. However, the 8âyear duration of the experiment can be divided into two periods with contrasting results. In the first period, the arthropod assemblage was only slightly affected, except for a greater density of aphids in antâexcluded trees; in addition, fruit yield was higher in antâexcluded trees than in the control ones. In the second period, antâexclusion increased the abundance of most arthropod groups, although the previous positive effect on fruit yield was no longer observed. 4 There are two main conclusions of the present study. First, from an applied perspective, antâexclusion from tree canopies is not a sound management alternative in citrus plantations in the Mediterranean. Second, the 8âyear duration of the experiment highlighted the importance of longâterm experiments in community ecology and biological control because the effects observed in the first 4 years of the experiment were very different from what occurred subsequently.
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