CONTROLE DE ALGAS E MOSCAS, EM ESPUMA FENÓLICA, PARA ALFACE SOB SISTEMA HIDROPÔNICO DO TIPO NFT

Abstract

Insects and algae demonstrate adaptability in hydroponic environments. The presence of algae attracts two species of flies, Bradysia spp. (Diptera: Sciaridae) and Scatella stagnalis (Diptera: Ephydridae) known as fungus gnats and shore fly, respectively. These flies feed on algae, which can damage the rootlets of the seedlings and transmit pathogens to adult plants. Little information on the management of flies and algae is known, which is a paradox in relation to the expansion of plant cultivation under hydroponics in Brazil. The objective of this work was to evaluate the potential of hydrogen peroxide (H2O2) as an insecticidal agent (for control of flies) and sanitizing agent (for algae control). Entomopathogenic fungi have also been evaluated for being a more sustainable form of pest management. The experiment was conducted in a commercial hydroponic system under a randomized complete block design, with 5 treatments and 4 replicates. The treatments, sprayed on the phenolic foam plates, immediately after seed deposition, were H2O2 (T1), Beauveria bassiana (T2), Metarhizium anisopliae (T3), Spinosad (T4) and water (T5) as a control. Parameters related to the quality of lettuce seedlings (Brida cv.), the presence of flies and the evolution of algae in the phenolic foam plates (though the scale of notes) were recorded daily. H2O2 and Spinosad affected the germination of lettuce seeds, but were able to amortize the presence of adult flies on the phenolic foam plates. The treatments with fungi and only water were those where the highest number of larvae of both species of flies was observed, compared to H2O2. No larvae of fungus gnats and shore fly were found in phenolic foam cells sprayed with Spinosad. However, lettuce seedlings from Spinosad sprayed plates were those with lower fresh weight. For the other treatments, including H2O2, the fresh weight of the lettuce seedlings was higher. H2O2 severely retained algae infestation in phenolic foam cells over a 15-day observation period. The present work makes the light of knowledge the potential that H2O2 can play as a sanitizing agent (for algae control) and an insecticide (for control of fungus gnats and shore fly) in hydroponic environments.