Efeito dos insecticidas botânicos no controlo da lagarta do funil do milho (Spodoptera frugiperda) na cultura do milho

Abstract

The maize funnel caterpillar (LFM) is an invasive and polyphagous pest native to the American continent, where it has more than 350 hosts in addition to maize, its main host. It was detected in Africa in 2016 and particularly in Mozambique in 2017. Chemical insecticides have been most commonly used to control this pest, causing serious environmental problems. Many alternative methods have been recommended and studied, including botanical pesticides. The aim of this study was to evaluate the effect of botanical insecticides on the control of the maize funnel caterpillar (Spodopter afrugiperda). The experiment was set up in the FAEF experimental field from January to June 2023, using a causalised complete block design (DBCC), with 4 treatments and 4 replications; 1 - Control, 2 - Azadirachta indica leaves, 3 - Biol (mixture of Aloevera leaves, Calatropis procera, Tefrosia purpurea and Canavalia ensiformes seeds, pirip (Cyperus giganteus) and tobacco (Nicotina tabacum) and 4 - Calatropis procera leaves. In terms of level of infestation, the control treatment recorded the highest level of infestation (86.7 per cent compared to other treatments such as Calatropis procera (77.9 per cent), Biol (72.9 per cent) and Azadirachta indica (71.2 per cent), but all the treatments differed statistically from each other. As for the level of damage, the control treatment had an average scale of 5 (moderate damage on the damage scale) meaning that the plants had holes in the leaves and a completely destroyed funnel. The Azadirachta indica, Biol and Calatropis procera treatments scored 3 (low damage), meaning that the plants had small circular lesions and some long ones on the funnel leaves. All the treatments differed statistically in terms of damage level. The control treatment had a statistically lower maize grain yield than the botanical pesticide treatments. However, the botanical treatments did not differ statistically in terms of grain yield. As for the estimated yield losses if the botanical insecticides had not been applied, the Azadirachta indica treatment had a yield loss of around (19.4%), Biol (22.32%) and Calatropis procera (17%). The application of the treatments proved to be beneficial in controlling LFM, since the B/C ratio is greater than 1. Higher net returns were found when using Biol, since it has a higher benefit/cost ratio.(TRADUÇAO NOSSA)