Cage study of spinosad-based bait efficacy on Bactrocera cucurbitae, Dacus ciliatus, and Dacus demmerezi (Diptera: Tephritidae) in Reunion Island

On Reunion Island, Bactrocera cucurbitae (Coquillett), Dacus ciliatus (Loew), and Dacus demmerezi (Bezzi) cause severe damage to Cucurbit crops. The aim of the study was to test in field cages the effectiveness of Synéis-appat (Dow AgroSciences), a spinosad-based bait (0.02% of spinosad) on both attraction and mortality of young adults (6-9 d old) of these three species. The effects of gender were also evaluated for all species whereas the effects of protein deprivation were tested with B. cucurbitae only. For the first 15 min after application, significantly more B. cucurbitae adults (21.7 +/- 1.8%) were attracted to the bait than D. demmerezi (7.6 +/- 2.4%) and D. ciliatus (2.7 +/- 1.4%); the subsequent response (30-75 min after bait application) of D. demmerezi was statistically similar to that recorded for B. cucurbitae; whereas the response ofD. ciliatus to the bait was consistently significantly lower. Adult mortality was significantly higher for B. cucurbitae (94.6 +/- 0.7%) than for D. demmerezi (85.7 +/- 2.1%), and was significantly higher for the latter than for D. ciliatus (60.4 +/- 4.4%). Sex had no significant effect on the mortality rate for each species. The efficiency of the bait was the same for B. cucurbitae adults regardless whether or not the diet included proteins. Overall, Synéis-appat appears to be more effective against B. cucurbitae and B. demmerezi than against D. ciliatus. In Reunion Island, this bait could constitute a useful component in the framework of Integrated Pest Management.     

Maize more attractive than Napier grass as non-host plants for Bactrocera cucurbitae and Dacus demmerezi

Some species of fruit flies (Diptera: Tephritidae) shelter and roost in non-host plants surrounding crops. The aim of this study was to compare the attractiveness of two plants (Poaceae): maize, Zea mays (Linné) and Napier grass, Pennisetum purpureum (Schumacher) for two species of Dacini damaging cucurbits in Reunion Island: Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) and Dacus demmerezi (Bezzi) (Diptera: Tephritidae). Plants of the two plant species were established in pots and presented to adult flies in field cages. In each cage, a cohort consisting of adults of a given species, of known sex and age, was released. For each species, the experiment was replicated four times. The number of adult flies on the different plants as well as their location on the plant was recorded. Maize was more attractive to adults of B. cucurbitae and D. demmerezi than Napier grass irrespective of sex and sexual maturity. Most adults of both species were found under the leaves of maize and Napier grass. The effects of the date, time of day, age, and sex of flies on their attraction to plants are discussed. A possible application of this study would be to use maize as a border plant to apply bait for the control of fruit flies.