Dynamic and impact of major insect pests on Jatropha curcas L. in two cropping systems with contrasting characteristics in the province of Kinshasa (DRC)

The dynamic and impact of the major insect pests on Jatropha curcas L. were studied on two plantations located in the province of Kinshasa, the first in pure stand without irrigation (Mbankana site), the second under irrigation in combination with other crops (N'sele site). In Mbankana, after being planted during the long rainy season (October - December), the plants suffer significant attacks by crickets Brachytrupes membranaceus Drury (Orthoptera, Gryllidae), which cause a mortality rate of 10 - 40%. The first half of October and second half of December are the best planting periods when it comes to limiting these losses. At N'sele, cricket attacks during planting are controlled by the farmers who eat these insects. After being planted at both sites, the plants are attacked by leaf miner caterpillars Stomphastis thraustica Meyrick (Lepidoptera, Gracillariidae) and flea beetles Aphthona sp. (Coleoptera, Chrysomelidae), which consume the leaf blades and buds. The size of these two pest populations and resulting damage reach a peak during the wettest time of year.
On adult plants at N'sele, insect pests observed include flea beetles, leaf miners, and shield-backed bugs Calidea sp. (Heteroptera, Scutelleridae). These bugs cause damage to flowers and capsules. In the absence of insecticide treatments, yield losses reached 90% in Mbankana and 60% in N'sele. The discussion focuses on what causes the different pest impact levels recorded between the cropping systems and methods used to limit the main types of damage caused by insects on J. curcas in the Kinshasa region.