Marc Dorel

Effect of fallows on population dynamics of Cosmopolites sordidus: toward integrated management of banana fields with pheromone mass trapping.

1 The banana weevil Cosmopolites sordidus Germar (Coleoptera: Curculionidae) is the most serious pest of banana and plantain in most production areas, including the West Indies. 2 During a period of 2 years, we assessed the efficacy of a pheromone mass‐trapping control strategy of C. sordidus in field conditions in Guadeloupe at different cropping stages, both in sanitation fallows and in different ratoon banana crops. 3 In the fallows, catches peaked 3 months after beginning trapping and then decreased to zero after 9 months. By contrast, for the new plantations, the catches of C. sordidus increased after the 11th month and, in the older banana fields, there was no decrease in C. sordidus catches. The C. sordidus catches increased in the neighbouring banana plots, whereas they decreased in the fallows, and these catches decreased with the distance from fallow. 4 In conclusion, mass trapping with synergized pheromone traps within fallows should allow better sanitation of banana plantations. Yet, within the farms, fallows must not be located next to new plantations to avoid massive damage to the young plants. More generally, the present study emphasizes that the control of this insect should be managed at the farm scale and not at the field scale, with special attention being paid to the location of fallows.

Experimental approaches for agro-ecological management of black leaf streak in dry and humid tropical conditions

Black leaf streak (BLS), caused by the phytopathogenic fungus Pseudocercospora fijiensis, leads to leaf necrosis and often to a substantial reduction in fruit yield. It also causes the fruit to ripen early by reducing the time between harvest and the beginning of natural ripening, called green life (GL). The usual method of control is by spraying fungicides, but this type of management is challenged worldwide due to the high costs, regulation of products, environmental concerns and the development of resistance. Integrated pest control is an alternative management method based on the combination of agronomic practices that can slow down the development of the epidemic, and limit damage to the fruit. Two experiments were conducted in the Dominican Republic and Martinique, to evaluate the performance of an innovative prototype cropping system with no chemical control. This system is based on optimal growth management, to reduce stress and enhance the leaf emission rate, combined with the systematic removal of necrotic parts of the leaves, which strongly limits ascopore sporulation and reduces the effect of BLS on GL. Depending on the conditions and cycles, the reduction in bunch weight with the prototype system versus chemical control ranged from O to 15%. Bananas were harvested at the same physiological age in the prototype and in the control. The bananas harvested from plants with as low as zero leaves left at harvest retained a good aptitude for conservation, with up to 40 days of GL, on average. The limited impact on fruit weight observed suggests that physiological compensation phenomena through remobilization of resources inside the plant (stem, bunch, suckers) occur. Above all, the removal of necrotic leaves prevented a significant negative effect on early fruit ripening when the bananas were harvested at the correct physiological age, and enabled export of the fruit despite the small number of leaves remaining on the plant at harvest. These results offer perspectives for the development and transfer of alternative practices to chemical control.