Increased pollinator habitat enhances cacao fruit set and predator conservation

Abstract

The unique benefits of wild pollinators to the productivity of agricultural crops have become increasingly recognized in recent decades. However, declines in populations of wild pollinator species, largely driven by the conversion of natural habitat to agricultural land and broad-spectrum pesticide use often lead reductions in the provision of pollination services and crop production. With growing evidence that targeted pollinator conservation improves crop yield and/or quality, particularly for pollination specialist crops, efforts are increasing to substitute agriculturally intensive practices with those that alleviate some of the negative impacts of agriculture on pollinators and the pollination services they provide, in part through the provision of suitable pollinator habitat. Further, similarities between the responses of some pollinators and predators to habitat management suggest that efforts to conserve pollinators may also encourage predator densities. We evaluated the effects of one habitat management practice, the addition of cacao fruit husks to a monoculture cacao farm, on the provision of pollination services and the densities of two groups of entomophagous predators. We also evaluated the impacts of cacao fruit husk addition on pollen limitation, by crossing this habitat manipulation with pollen supplementation treatments. The addition of cacao fruit husks increased the number of fruits per tree and along with hand pollination treatments, increased final yields indicating a promotion of the pollination ecosystem service provided by the specialist pollinators, midges. We also found that cacao fruit husk addition increased the densities of two predator groups, spiders and skinks. Further, the conservation of these predators did not inhibit pollination through pollinator capture or deterrence. The findings show that, with moderate habitat management, both pollinator and predator conservation can be compatible goals within a highly specialized plant-pollinator system. The effectiveness of this habitat manipulation may be attributable to the increased availability of alternative habitat and food resources for both pollinators and predators. The results exemplify a win-win relationship between agricultural production and biological conservation, whereby agricultural practices to support vital pollinators and pollination services can increase production as well as support species conservation.

Oecophylla smaragdina ants provide pest control in Australian cacao

“…The low R. nitida densities in the ‘with cacao husk’ treated plots may be due to the dispersal of R. nitida beetles outside of the plots or due to within‐plot mechanism ( e.g ., unsuitable habitats for R. nitida reproduction and/or survival or increased predation on R. nitida beetles mediated by habitat‐related increases in predator densities). In a concurrent study, we found that in addition to increasing pollination rates, the addition of cacao fruit husks as mulch underneath trees increased the densities of native spider and skink predators (Forbes ). Thus, it is possible that increased native predator densities within the ‘with cacao husk’ treated plots helps to maintain low insect pest densities in the absence of the predaceous O. smaragdina ants.…”

The Ecophysiology of Abiotic and Biotic Stress on the Pollination and Fertilization of Cacao (Theobroma cacaoL.; formerly Sterculiaceae family)

“…The ecophysiology of pollination and fertilization of cacao beans is manageable by optimized agrocultural practices. Adequate midge breeding sites using cocoa pod and banana pseudostem can improve the insect population and subsequently increase pollination and fertilization [95]. This management practice is envisaged as the way to increase bean yield.…”

Evaluation of cocoa mirid (Distantiella theobroma Dist. and Sahlbergella singularis Hagl.) control practices in Cte dIvoire

“…As a result, reducing the dosage would decrease the impact of the contact insecticides on mirid predators leading to a higher amount of cherelles observed after treatments. Weaver ants Oecophylla longinoda and Oecophylla smaragdina have been suggested as key-predators to mirids in cocoa cropping systems in Cameroon (Babin et al, 2010;2011 and Australia (Forbes and Northfield, 2017), respectively. Those predatory ants will less likely be killed by insecticide products that do not contain pyrethroids and will consequently be able to maintain their populations to levels that are able to significantly reduce mirid numbers.…”