Exploring biotic and abiotic factors influencing cucurbit-fruit fly damage and diversity in cucurbit crop production systems

Abstract Agricultural policies in Côte d’Ivoire have mostly been focused on staple food crops such as rice and cassava. However, a diverse range of vegetables is essential for the balanced nutrition and health of the population. Cucurbits, for instance, are a regular ingredient in local cuisine, yet this product is subject to high pressure from pests such as fruit flies (Diptera: Tephritidae). Farmers try to protect their crops against these pests by applying high uncontrolled doses of the few chemical pesticides available to them. This practice is ill-adapted for managing fly infestations and there are major harmful effects. From an agroecological perspective, alternative control methods have been developed such as prophylaxis and using specific attractants in insect trapping systems. It is, however, necessary to identify and quantify the targeted pest population(s) prior to implementing any control method. The present study involved cucurbit field sampling and farmers interviews and aimed to gain further insight into various factors could explain the observed fruit fly infestations and species diversity. 90% of the surveyed cucurbit plots were infested by fruit flies and a mean of 30.5% of the cucurbit fruits were damaged. We noted that this infestation rate was mainly dependent on the location and period of the year as well as the extent of crop protection and field management practices. We identified 5 cucurbit fruit fly species with Dacus ciliatus found to be present on 77% of infested plots (0.63 mean relative abundance). Depending on the dominant species on the target plot, the latter index generally correlated with the infestation rate, the period of the year or the number of days since the previous crop protection treatment. The overall species diversity also depended on the number of days since the previous crop protection treatment as well as the treatment frequency index throughout the crop cycle. A more in-depth analysis of the infestation level at the fruit scale revealed preferential differences in terms of fruit weight and competition according to fruit fly species involved. This study offers an update of the current cucurbit fruit fly pest status in a West African country following as follow-up to previous inventories. The findings indicated enhancing farmers’ knowledge on the pests in their cropfields and the chemical pesticides they apply, through more political support, could help them efficiently adapt their cropping system management.