Hospedabilidade de plantas daninhas a Meloidogyne spp. e interação entre herbicidas e nematicidas para a cultura de cana-de-açúcar
Giraldeli, Ana Ligia
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The sugarcane has great economic importance in Brazil. To keep productivity several biotic and abiotic factors can positively or negatively influence. Among them, weeds, nematodes and synergistic action between pesticides to control both can be cited. Thus, the present work aimed at studying possible common weeds in the mechanized harvesting system that can serve as hosts for the root knot nematode: Meloidogyne incognita and / or M. javanica and study the interaction between herbicides and nematicides used in the groove planting of sugarcane. Two experiments were carried in a greenhouse at the Agricultural Sciences Center (CCA-UFSCar), Araras, SP. The first experiment evaluated the host status ten weeds, as follows: Ipomoea triloba (Dammer), Merremia aegyptia (L.) Urban, Luffa aegyptiaca Mill, Euphorbia heterophylla L., Ricinus communis L., Crotalaria spectabilis Roth, Mucuna aterrima ( Piper & Tracy) Holland, Chloris polydactyla (L.) Sw., Digitaria horizontalis Willd., Urochloa decumbens (Stapf) RD Webster and the control (tomato Santa Cruz Kada) when inoculated with M. incognita or M. javanica in a completely randomized design in a factorial 11 x 2, with six repetitions. The plants were inoculated with 2.000 eggs and J2, and there were three plants per plot (6.000 eggs and J2 per pot - repetition). Sixty days after inoculation (DAI) the plants were removed and evaluated according to the reproduction factor (FR), final nematodes population (PF) and reproduction index (IR). In the second experiment the effect of interaction between two nematicides applied in contact with the stalks was evaluated. The nematicides tested were: benfuracarb (5,0 L ha-1) and carbofuran (50 Kg ha-1), and the herbicides applied preemergence of culture were: sulfentrazone (1,6 L p.c. ha-1), diuron + hexazinone (2,5 Kg ha1), saflufenacil (0,14 Kg p.c. ha-1) and amicarbazone (1,5 Kg p.c. ha-1). The experiment was carried in a completely randomized design in a factorial 15 x 5, with four replications in three sugarcane varieties (RB867515, RB975952 and RB975201). The first factor was corresponded to the 15 treatments and the second, to the five evaluation periods. Evaluations of intoxication symptoms were performed at 7, 15, 30, 45 and 60 days after emergence (DAE) of culture. In the last assessment biometric parameters height (cm), leaf area (cm²) and dry biomass of the aerial part (g) were evaluated. Regarding to the host status of weeds, it was found that L. aegyptiaca behaved as host of both nematodes, with FR > 1, higher than the control. The D. horizontalis was classified as host of M. incognita and non-host of M. javanica. C. spectabilis had the lowest FR and PF. R. communis and I. triloba present galls when inoculated with M. incognita, but were not considered host for presenting FR < 1. None of the weeds tested was considered immune, that is, with RF = 0. Regarding the interaction of herbicides and nematicides in all treatments, plants recover 60 DAE, and in treatments with the use of sulfentrazone increase in symptoms of poisoning was observed. As for the biometric parameters evaluated at 60 DAE, there was no statistical difference only in the variety RB867515 for height. In this case, the treatments amicarbazone / benfuracarb and amicarbazone / carbofuran plants were higher than the control and other interactions.