The beauties and the bugs: a scenario to design flower strips adapted to aphid management in melon crops

Flower strips appear as a promising lever to promote pest control but a careful selection of plant species is needed prior implementation to avoid possible negative side effects. In the case of open field melon crops, the main pitfall would be to generate aphid and aphid-borne virus reservoirs near the crops. Combining biotests in controlled conditions and literature, we assessed 18 candidate plant species, and discarded those posing a potential risk of hosting Aphis gossypii (melon pest and virus vector), Myzus persicae (virus vector) and/or viruses. Five plant species got through the selection process: cornflower, grass pea, sainfoin, salad burnet and sweet marjoram. Flower strips sown with a mix of these five plant species were evaluated in a five-year field experiment. They displayed a flowering continuum likely to provide a food resource continuum conducive to the development of natural enemies. Their potential to host natural enemies was compared to those of grass strips and bare soil via the monitoring of generalist and specialist predators within the different field margins and melon crop. Flower margins supported significantly more of these natural enemies than grass margins and bare soil. All predator taxa analyzed responded positively to floral resources displayed. Spiders were 2.8 times more abundant in pitfall traps placed in flower margins than in bare soil. Other generalists and aphid specialists collected using a vacuum sampler were respectively 16.4 and 14.8 times more abundant in flower margins than in the spontaneous vegetation near the bare soil. Concerning aphid specialists, vacuum samples were dominated by coccinellids, but interception traps set for weekly periods showed that coccinellid and syrphid fluxes were significantly enhanced near flowers margins. All prerequisites were gathered to promote biological control of aphids and viruses in melon crops.