Research on the role of natural enemies in the management of Pistia stratiotes L. in Morocco

The invasive plant Pistia stratiotes L. has become a major concern in Morocco, despite strict regulations to prevent its spread. This study investigated the presence and impact of natural enemies on P. stratiotes in two locations in Morocco: Fez-Meknes (Fez river) and Rabat-Sale-Kenitra (Koreima dam). A total of 3354 insects, representing two orders and seven families, were collected from the study sites. The most abundant species observed in Fez river were Megasternum concinnum, Agrypnus rectangularis, Plagiodera versicolora, and Naupactus cervinus. Similarly, Megasternum concinnum, Naupactus cervinus, and Agrypnus rectangularis were the predominant species in Koreima dam. However, Neohydronomus affinis, a potential biological control agent observed in the Fez River, was absent in Koreima dam. The abundance of natural enemies was significantly higher in Fez river compared to Koreima dam, and their activity increased from January to July. The study also revealed the important role of natural enemies, particularly N. affinis and N. cervinus, in controlling and affecting the population of P. stratiotes. These natural enemies demonstrated the ability to feed on all stages of the plant. Furthermore, the diversity, richness, and evenness of insect species were higher in Fez river (H' = 2.056) compared to Koreima dam (H' = 1.917), indicating a greater insect diversity in Fez river. The findings of this study highlight the potential of biological control as an integral part of the integrated management plan for P. stratiotes in Morocco. The introduction of N. affinis weevils in 2012 marked the first implementation of a weed biological control program in the country. The study emphasizes the importance of continued research and monitoring to develop sustainable and environmentally friendly strategies for controlling the spread of P. stratiotes in Moroccan water ecosystems.