Seletividade De Misturas De Herbicidas E Inseticidas Em Tanque Aplicadas Em Híbridos De Milho

Abstract

RESUMO - A associação de herbicidas e inseticidas é uma prática comum entre os agricultores, entretanto, muitas vezes pode provocar injúrias à cultura do milho. O trabalho teve como objetivo avaliar a seletividade de herbicidas em mistura em tanque com inseticidas de diferentes grupos químicos, no crescimento inicial de hibridos de milho. Dois experimentos foram conduzidos separadamente em estufa plástica com dois híbridos de milho (30F35 e 2B-710), utilizando como unidades experimentais vasos com duas plantas nos estádios fenológicos V3 e V6. O delineamento experimental foi o inteiramente casualizado, com cinco repetições. Foram avaliados 31 tratamentos, representados pela aplicação de seis herbicidas (atrazine, nicosulfuron, foramsulfuron + iodosulfuron, mesotrione, carfentrazone e 2,4-D, nas doses de 2000; 37,5; 36+2,4; 144; 10 e 1000 g ha-1, respectivamente) isolados e em mistura com quatro inseticidas (permethrin, methomyl, chlorpyrifos ethyl e novarulon, nas doses de 26,9; 64,5; 240 e 15 g ha-1, respectivamente) e uma testemunha sem aplicação. Avaliou-se a intoxicação das plantas aos 7 e 14 dias após a aplicação (DAA), o teor de clorofila das folhas, número médio de folhas por planta, massa seca da parte aérea e das raízes aos 14 DAA. Os resultados foram variáveis em função do híbrido e estádio fenológico na aplicação, sendo as misturas menos prejudiciais ao milho quando aplicadas em V3. Os tratamentos com atrazine foram os que menos afetaram o crescimento inicial dos híbridos. As misturas nicosulfuron + chlorpyrifos ethyl, mesotrione + chlorpyrifos ethyl e 2,4-D + chlorpyrifos ethyl foram as que mais prejudicaram o híbrido 30F35. Por outro lado, a mistura carfentrazone + chlorpyrifos ethyl foi a que mais afetou o crescimento inicial do híbrido 2B-710.Palavras-chave: fitointoxicação, antagonismo, estádio de desenvolvimento, Zea mays. SELECTIVITY OF HERBICIDES AND INSECTICIDES TANK MIXTURES APPLIED IN MAIZE HYBRIDS ABSTRACT - The association of herbicides and insecticides despite often cause damage to the corn crop is a common practice among farmers. This study aimed to evaluate the initial selectivity of herbicides in tank mixture with insecticides from different chemical groups in maize. Two experiments were carried out in plastic greenhouse, using as experimental units pots with two maize hybrids (30F35 and 2B-710) in V3 and V6 phenological stages. A completely randomized experimental design was used, with five replications. Thirty-one treatments were represented by applying six herbicides (atrazine, nicosulfuron, foramsulfuron+iodosulfuron, mesotrione, carfentrazone and 2.4- D) isolated and in combination with the four insecticides (permethrin, methomyl, chlorpyrifos ethyl and novarulon) and a check without application. The phytointoxication was evaluated at 7 and 14 days after application (DAA), the chlorophyll content in leaves, total number of leaves, dry mass of the aerial part and roots at 14 DAA. The results were dependent of hybrid and corn stage in the application, and mixtures were less harmful when applied in V3 stage. The treatments with atrazine affected less the initial growth of the two hybrids. The mixtures of nicosulfuron+chlorpyrifos ethyl, mesotrione+chlorpyrifos ethyl and 2.4-D + chlorpyrifos ethyl were the most prejudicial to the hybrid 30F35. In addition, the carfentrazone + chlorpyrifos ethyl mixture was the most harmful to the initial growth of the hybrid 2B-710.Keywords: phytointoxication, antagonism, development stage, Zea mays.

The Use of Herbicide Safener Increases the Selectivity of Nicosulfuron to Maize Crops

“…This was expected, since the hybrid used is tolerant to nicosulfuron and the rates used are within the recommended rates. Maciel et al (2018) treated maize plants of the hybrid 2B-710 with nicosulfuron applied single at the V6 stage and found low toxicity levels, reaching 5% and 3% at 7 and 14 DAA, respectively, and no effect on plant height in relation to the control. Tolerant hybrids are little damaged by nicosulfuron; these plants have the cytochrome P450 monooxygenase enzyme that detox nicosulfuron molecules (Powles & Yu, 2010;Nadula et al, 2018;Ye et al, 2019).…”

“…The CYP P450 activity is suppressed when malathion is added to the applied solution, making a tolerant cultivar, susceptible to the herbicide (Paporisch & Rubin, 2017). The maize hybrid 2B-710 treated with nicosulfuron combined with the organophosphorus insecticide chlorpyrifos presented 24.4% higher phytotoxicity and 37% lower plant height at 14 DAA ISSN 2166-0379 2020 when compared to plants treated only with nicosulfuron (Maciel et al, 2018).…”

“…Herbicide and insecticide can be applied simultaneously in post-emergence, which made this tank mixture practice frequent due to the lower application cost; however, mixtures of nicosulfuron with organophosphorus insecticides, such as malathion, can reduce the herbicide selectivity to crops, causing yield losses (Maciel et al, 2018). Organophosphorus insecticides reduce the maize tolerance to herbicides of the sulfonylurea group by inhibiting cytochrome P450 monooxygenase enzymes (Kreuz & Fronn-Pfister, 1992).…”

Glufosinate, nicosulfuron and combinations in the performance of maize hybrids with the pat gene

“…In experiment II, differences were seen in the injury caused by the two products based on nicosulfuron. Any difference in the commercial product, or dose or concentration of the oil/adjuvant in the application mixture can affect the level of selectivity of nicosulfuron in maize (MACIEL et al, 2018). The selectivity of this herbicide among hybrids is variable, and may be affected by the stage of plant development (MEYER; PATAKY; WILLIAMS, 2010).…”

Physiological characteristics of corn intercropped with different arrangements of palisade grass plants

“…Although nicosulfuron is selective to corn, this is directly linked to the choice of the correct hybrid, the stage of the application, and the dose used. Furthermore, applications of organophosphate insecticides or nitrogen fertilization at intervals close to the application of the herbicide can compromise the selectivity and cause phytointoxication even in hybrids with tolerance (Devkota et al, 2013;Guerra et al, 2010;Maciel et al, 2018).…”