Crop protection

Broomrapes are parasitic plants that feed on another plant for water and nutrients, causing eventually important crop losses. Scientists Cartry et al. recently reviewed all the possible interactions of broomrapes with surrounding organisms in an agricultural landscape. From the knowledge of these interactions, management methods targeting the weak point(s) of this parasitic weed, may be set to regulate – not eradicate – broomrape populations below a tolerance threshold compatible with the agroecological production of foodstuffs.

The Miridae are a vast insect family, comprising both well-known plant pests and natural enemies. They interact often with plant fungal infections on many crops. Scientists Ratnadass and Deguine reviewed the bug – fungal pathogen – crop frameworks. They showed that their interactions are mainly shaped by the necrotrophic status of mirid bugs and by the biotrophic or necrotrophic status of fungal pathogens. They propose agroecological options to manage both types of aggressors.

Viruses limit maize production around the world. Scientists Clemente-Orta et al. developed predictive models at variable spatial scales for explaining the incidence of two closely related potyviruses: maize dwarf mosaic virus and sugarcane mosaic virus at three different landscape scale. They showed that early planting, the management of edges, and the presence of non-crop habitats are key factors of virus incidence.

The eggplant shoot and fruit borer is a major damaging pest in Asia. Most farmers control this pest by spraying insecticides every week. Researchers Nahar et al. observed from a participatory study that such a chemical method of control was not effective. In contrast, the use of pheromone traps reduced yield losses by 20-30% and cost less than conventional practice. The adoption of alternative techniques, however, is constrained by farmers’ knowledge of insect biology and ecology, and therefore requires support to farmers.

The ground wētā is an insect pest causing damages in New Zealand vineyards. Scientists Nboyine et al. analyzed plant DNA present in the feces of this insect and revealed that many plants may constitute their staple diet. They reckoned, therefore, that deploying non-commercial trap crops around vineyards, as a decoy to feed on, is particularly appropriate to control wētā, as this insect seems to be highly generalist in its feeding behavior.

The fruit fly Drosophila suzukii threatens worldwide fruit production. Its control relies mainly on the application of synthetic insecticides during the soft fruit ripening period. Scientists Dam et al. reviewed the natural compounds reported effective against D. suzukii. Even though several natural compounds show promising in vitro activity against this pest, knowledge of their effects on non-target organisms and their field-efficiency are often missing, limiting their wide-spread use.

Preserving remnants of the forest in agricultural landscapes supports biodiversity conservation and the provision of agriculturally-relevant ecosystem services such as pollination or biological control. In Brazil, scientists Medeiros et al. recently found that forests in the surrounding landscape reduce the occurrence of a widespread economic pest in sun-coffee monocultures by enhancing natural enemy diversity. Remnants of the forest maintain a permanent reservoir of natural enemies and therefore, these habitats should be protected.

Inter-cropping non-Bt-maize with legume crops increases the role of predatory arthropods in naturally regulating herbivorous arthropod pests. Scientists Nickson Otieno et al. recently observed stronger predator-herbivore interactions within maize intercropped than in monoculture fields, both in organic and conventional farming systems. The results are useful in prescribing field practices for sustainable small-scale agriculture from sub-Saharan Africa.

Smallholder farmers in low-income countries often use plant extracts (‘botanicals’) to prepare homemade pesticides. This practice has remained controversial due to a perceived lack of evidence that such home remedies are effective and safe. Scientists Dougoud et al. reviewed commonly used botanicals and found evidence that they can reduce pests and crop damage. However, results are highly variable, depending on how the homemade pesticides are prepared and used.