Abstract
The use of non-crop plants to provide the resources that herbivorous crop pests’ natural enemies need is being increasingly incorporated into integrated pest management programs. We evaluated insect functional groups found on three refuges consisting of five different plant species each, planted next to a maize crop in Lima, Peru, to investigate which refuge favoured natural control of herbivores considered as pests of maize in Peru, and which refuge plant traits were more attractive to those desirable enemies. Insects occurring in all the plants, including the maize crop itself, were sampled weekly during the crop growing cycle, from February to June 2011. All individuals collected were identified and classified into three functional groups: herbivores, parasitoids, and predators. Refuges were compared based on their effectiveness in enhancing the populations of predator and parasitoid insects of the crop enemies. Refuges A and B were the most effective, showing the highest richness and abundance of both predators and parasitoids, including several insect species that are reported to attack the main insect pests of maize (Spodoptera frugiperda and Rhopalosiphum maidis), as well as other species that serve as alternative hosts of these natural enemies.
Highlights
The use of non-crop plants to provide resources that pests’ natural enemies need, such as alternative prey, refuge, or additional food [1], is being increasingly incorporated into integrated pest management programs [2]
We evaluated insect functional groups found on three refuges consisting of five different plant species each, planted next to a maize crop in Lima, Peru, to investigate which refuge favoured natural control of herbivores considered as pests of maize in Peru, and which refuge plant traits were more attractive to those desirable enemies
Considering the limitations of this, or any, study including the location of refuge patches on the maize plots treated with pesticides, one of the most interesting results is that the presence of bracteal extrafloral nectaries seems critical for the presence of parasitoid natural enemies of maize pests
Summary
The use of non-crop plants to provide resources that pests’ natural enemies need, such as alternative prey, refuge, or additional food [1], is being increasingly incorporated into integrated pest management programs [2]. The most effective natural enemies of phytophagous insects are entomophagous insects, i.e., predators and parasitoids These natural enemies are more specialized than other biological control agents such as entomopathogenic fungi, since the host range they attack are usually rather narrow, especially parasitoids, so that they influence the community structure of herbivorous insects more than other unspecialized enemies [3]. Both functional groups have shown higher fecundity and longevity rates when feeding on other resources like nectar (floral and extrafloral) or pollen [1,4,5,6], which are not usually available in agricultural systems. Natural enemies have been shown to move from edge vegetation to the centre of a standing crop, enhancing natural control [7]
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