The corn leaf aphid is considered an important pest associated with maize. This study aimed to discover the trophic associations around Rhopalosiphum maidis in Manabí, Ecuador. Maize leaves were sampled to determine the numbers of parasitized aphids, and the identities of predators and parasitoids. Nine taxa of natural enemies were detected: the primary parasitoid was Lysiphlebus testaceipes Cresson, 1880 (Hymenoptera: Braconidae); the hyperparasitoid Syrphophagus aphidivorus (Mayr, 1876) (Hymenoptera: Encyrtidae); the predatory hoverfly Ocyptamus dimidiatus (Fabricius, 1781) (Diptera: Syrphidae), four species of coccinellids, Cheilomenes sexmaculata (Fabricius, 1781), Cycloneda sanguinea (Linnaeus, 1763), Hippodamia convergens Guerin-Meneville, 1842 and Paraneda pallidula guticollis (Coleoptera: Coccinellidae) and an assassin bug, Zelus sp. (Hemiptera: Reduviidae). A parasitoid, Pachyneuron formosum Walker, 1833 (Hymenoptera: Pteromalidae) emerged from hoverfly pupae. This study reports the presence of the parasitoids S. aphidivorus and P. formosum in Ecuador for the first time. These results increase the knowledge of a four-trophic level relationship (host plant – pest – parasitoids, predators – hyperparasitoids) in a maize agroecosystem as a fundamental basis for biological control programs.
Melon is attacked by pests such as the whitefly, Bemisia tabaci (Gennadius), the cotton aphid, Aphis gossypii Glover, the flower thrips, Frankliniella occidentalis (Pergande) as well as Diaphania worms that can affect yield and crop productivity. To control it, frequent spraying of organo-synthetic insecticides is carried out, which can generate ecological imbalances. During two productive cycles, experimental plots were established to test the effect of an organo-synthetic insecticide and a botanical one on some pests, a natural enemy and on melon productivity. The treatments tested were, 1. Organo-synthetic insecticide: lambda-cyhalothrin + thiamethoxam. 2. Botanical insecticide: azadirachtin. 3. Untreated plot. The populations of A. gossypii, B. tabaci, F. occidentalis, percentage of fruits damaged by Diaphania spp. (% FDD), and the effect on parasitism in B. tabaci (% PBT), as well as on yield (t.ha-1) and crop productivity. The populations of A. gossypii, B. tabaci, F. occidentalis, fruits damaged by Diaphania spp. (% FDD), and the effect on parasitism in B. tabaci (% PBT), as well as on crop yield and productivity. The % FDD, the populations of A. gossypii and F. occidentalis did not show differences between treatments. The yields were higher in plots treated with azadirachtin, where there were lower populations of B. tabaci and higher % PBT. Productivity presented a negative correlation with the populations of B. tabaci. Despite the control exerted by azadirachtin on B. tabaci, there was a decrease in productivity, which added to the damage of Diaphania spp. suggest the importance of these pests and for their management other alternatives should be tested that reduce populations to levels that do not affect yield and at the same time guarantee sustainable production.
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