The short version of a long study: fifteen years of effort to control white grub pests (Coleoptera: Melolonthidae) and achieve the forest management objectives in the regeneration of the Mamora Forest in Morocco

Resumo

Pest control requires extensive knowledge of the biology of phytophages, predators, parasites and entomopathogens, especially in the context of a large-scale forest regeneration program, with the planting of 1500 ha / year of young seedlings in large plots. This paper summarizes the results of a study to control the polyphagous larvae of the endemic species Sphodroxia maroccana (Coleoptera: Melolonthidae), which cause major damage to the roots of seedlings of cork oak (Quercus suber L.) in regeneration plots in the Mamora Forest, Northern Rabat, Morocco. Fifteen years of study were necessary to fully understand the biology of S. maroccana, which is endemic to this forest and has become a pest locally, due to an imbalance related to excessive human disturbance of the forest ecosystem. Specifically, uncontrolled grazing eliminates most of the plants that normally grow under cork oak trees. Thus, the feeding by larvae is mainly concentrated on the roots of young cork oak seedlings, thereby seriously compromising forest regeneration. An annual survey of S. maroccana density in each plot in the entire forest identified the potential risks to seedlings. Understanding the movement of the pest in relation to the soil moisture profile was crucial to its management. The results were used to identify key issues for sustainable management of the forest, namely: i) reduction of current anthropogenic pressures; ii) better consideration of the biology of the pest in reforestation activities; iii) changes in plantation practices to reduce the impact of the larvae by controlling their populations, but without eradication; and iv) the use of chemical control only when absolutely necessary.