Interferência das plantas daninhas e níveis de infestação do percevejo Thlastocoris laetus (Mayr, 1866) (Hemiptera: Coreidae) na cultura do abacaxi (Ananas comosus (L) Merril)

Abstract

The knowledge of the critical period of weeds in the crops is a useful tool in the decision making of the necessary period of control of these plants, both biologically and economically. The objective of this research was to define the critical period of prevention of weed interference in the pineapple crop (Ananas comosus (L.) Merril) and the levels of infestation of the pineapple (Thlastocoris laetus (Mayr) stink bug in the crop in the Vila do Engenho, municipality of Itacoatiara, AM, in the agricultural years 2016 and 2018. The experimental design was a randomized complete block design, in a 2 x 15 factorial arrangement with four replications, with two treatments: control and cohabitation with weeds and 15 growing periods of 30 days after. The experimental treatments consisted of two groups, one of control and the other of coexistence of the crop. In the control treatments, manual weeding (with hoe) and mechanical weeding (with brushcutter) were used for growing periods, and at the end of each period weeds could be developed in the experimental plots. In the coexistence treatments, from the weeding, weeds lived with the crop for growing periods, and at the end of each period, the control was performed with mechanical weeding and chemical in the plots, which remained clean until harvest. The herbicide Paraquate dichloride at the dose of 300 g ha-1 of active ingredient (a.i.) was used to control weeds. The productivity and the accumulation of Proline were used to determine the critical period considering losses of 5 and 10% in the crop yield. The characteristics analyzed were the biometry of the plant, physical-chemical analyzes of the fruits, quantification of chlorophyll a fluorescence, chlorophyll a, b, total (a + b), chl a / b ratio, macro and micronutrient contents in leaf D and T. laetus concentration in plant structures: leaves, peduncle, fruit, crown and cub. The critical period of prevention of interference in function of productivity considering levels of 5 and 10% of losses were 259 and 204 days, respectively, and 388 and 366 days for the same levels, when proline was used as indicator. The biometric characteristics of the plant, the physical aspects of the fruit and the total acidity (TTA) levels of the soluble solids (TSS) and the TSS / ATT ratio were altered by the longer periods of living with the weeds. In the same way, the greater periods of coexistence resulted in losses in chlorophyll a fluorescence and promoted changes in chlorophyll a, b, total (a + b), chl a / b and carotenoids, as well as imbalance in nutrient levels in leaf D pineapple, leading to lower concentrations than those recommended in the literature. Removal of weeds caused an increase in the level of T. laetus infestation and the main insect attack niche is the fruit. The population dynamics of the species is influenced by the precipitation and the phenological phase of the crop and presents larger populations at the end of the vegetative growth and at the time of the fruiting.