Pakistan Journal of Biological Sciences

Year: 2021 | Volume: 24 | Issue: 11 | Page No.: 1119-1129
DOI: 10.3923/pjbs.2021.1119.1129

Indaziflam: Control Effectiveness in Monocotyledonous and Eudicotyledonous Weeds as a Function of Herbicide Dose and Soil Texture

Paulo Vinicius da Silva , Henrique Rodrigues Milagres Viana, Marcelo Rafael Malardo, Maxwel Coura Oliveira, Roque de Carvalho Dias, Estela Maris Ináci, Patrícia Andrea Monquero and Pedro Jacob Christoffoleti

Abstract: Background and Objective: The indaziflam herbicide has efficiency in the control of monocotyledons weeds and is recommended for some eudicotyledonous species. However, the efficiency of the control can vary to the detriment of the species, dose and soil texture. Therefore, the objective of the present work was to evaluate the effectiveness of the control of indaziflam herbicide for weeds species Mucuna aterrima, Sorghum halepense, Ipomoea purpurea, Rottboellia exaltata, Urochloa decumbens, Merremia aegyptia, Cenchrus echinatus, Digitaria horizontalis, Panicum maximum, Tridax procumbens, Urochloa plantaginea and Eleusine indica, besides elaborating the calculation of DL₈₀, DL₉₀ and DL₉₅ of the product in two types of soil. Material and Methods: Thus, experiments were carried out in a greenhouse, isolated for each weed species, in a completely randomized experimental design, with four replications and a 10×2 factorial scheme, with ten doses of the herbicide indaziflam (0 D, 1/16 D, 1/8 D, 1/4 D, 1/2 D, D, 2 D, 4 D, 8 D, 16 D, being D = 100 g ha^–1), applied in pre-emergence and two contrasting soil textures (clayey and sandy). At 7, 14, 21, 28, 35, 42, 49 and 56 days after weed emergence (DAE), visual control assessments were performed and in the last evaluation, the dry mass of the aerial part was performed. Results: The weeds of the Poaceae family showed greater susceptibility to the indaziflam herbicide, on the other hand, the Mucuna aterrima, Ipomoea purpurea and Merremia aegyptia weeds required a higher dose of active ingredient to be controlled efficiently. Conclusion: In general, the current study concluded that a lesser amount of active ingredient was needed in sandy soil than in clayey soils to promote adequate weed control. Therefore, the difference in the susceptibility of the studied plants as function of dose indaziflam, weeds species and soil texture.

Keywords: Lethal dose, residual, texture and alkylazine

INTRODUCTION

The herbicide indaziflam has as its mechanism of action the inhibition of cellulose biosynthesis, belonging to the chemical class called "alkylazine"¹. In Brazil, this product is registered for banana crops (Musa spp.), coffee (Coffea spp.), citrus (Citrus spp.), Palm oil (Elaeis guineensis), cashew (Anacardium occidentale), sugarcane (Saccharum spp.), coconut (Cocos nucifera), guava (Psidium guajava), apple (Malus domestica), mango (Mangifera indica), grape (Vitis, vinifera), eucalyptus (Eucalyptus spp.) and pine (Pinus spp.)². The indaziflam application for weed control must occur in raining season and/or with humid soil and the recommended dose varies from 75-100 g i.a. ha^–1, being this difference in detriment to the soil type (sandy or light <15% of clay, sandy-loam or medium -15-35% of clay and clayey or heavy >35% clay)³.

Regarding persistence, indaziflam has a high residual period in the soil, being more than 150 days⁴. However, Alonso et al.⁵, alert to the fact that this period may possibly be less than 150 days in tropical regions due to high temperatures and abundant rainfall. Regarding its physical and chemical characteristics, indaziflam has low solubility in water (2.8 mg L^–1) and high know (2.0 a pH = 2.0, 2.8 at pH = 4, 7 and 9), this product has wide spectrum of weed control, monocotyledonous and eudicotyledonous species and in Brazil, the positioning of indaziflam is aimed at pre-emergence applications of weeds³.

This information can be confirmed in the data provided in Agrofit², which indaziflam has recommendation of control for nine weed monocotyledonous species (Panicum maximum, Urochloa decumbens, Digitaria horizontalis, Urochloa plantaginea, Eleusine indica, Commelina benghalensis, Cenchrus echinatus, Digitaria insularis and Lolium multiflorum) and six species of eudicotyledons weeds (Bidens pilosa, Euphorbia heterophylla, Sida rhombifolia, Amaranthus deflexus, Conyza bonariensis e Amaranthus hybridus). However, there is a recurrent report of the efficacy of controlling indaziflam over other species that do not have a manufacture’s labeling recommendation^6-9.

Amim et al.⁶, proved high efficacy of indaziflam in the control of monocotyledons weeds, since evaluating the efficiency of this herbicide in weeds pre-emergency, found out indaziflam was more efficient in the control of D. horizontalis, P. maximum and Rottboellia cochinchinensis species. In clayey soil, R. cochinchinensis was efficiently controlled from 50 g ha^–1 dose of indaziflam. The control of E. heterophylla and Ipomoea grandifolia by indaziflam was more efficient in the loam-clay-sandy soil, with averages of 73.58 and 79.09% of control at 40 days after the application of the treatment (these numerical values do not take in consideration the dose of the herbicide, because it is about a factorial interaction of two factors dose×weeds species). These results also demonstrated a variation in the effectiveness of indaziflam to the detriment of the type of the soil to be applied and the weed species to be controlled.

Therefore, indaziflam presents a wide variation of information in relation to the recommended dose of the product, in detriment to the type of soil and the weeds species to be controlled in addition to number of other plants that are efficiently controlled by indaziflam, however, do not demonstrate information about the recommended dose, if doing necessary researches to answer these questions.

Based on the above considerations, the objective of present work was to evaluate the efficacy in the control of indaziflam herbicide for weeds species Mucuna aterrima, Sorghum halepense, Ipomoea purpurea, Rottboellia exaltata, Urochloa decumbens, Merremia aegyptia, Cenchrus echinatus, Digitaria horizontalis, Panicum maximum, Tridax procumbens, Urochloa plantaginea and Eleusine indica, besides elaborating the calculation of DL₅₀, DL₈₀, DL₉₀ e DL₉₅ of the product in a soil with clayey and sandy texture.

MATERIALS AND METHODS

The experiment was conducted in a greenhouse of the Plant Production Department at (ESALQ/USP), from August 2016 to January 2017.

Experimental design: The experimental design used was completely randomized and followed the factorial scheme 2×10, with four repetition, two soil texture and ten doses of indaziflam herbicide applied in pre-emergence. This factorial was assumed in an isolated way for each of the 12 weed species. (Mucuna aterrima (Piper and Tracy) Holland (MUCAT), Sorghum halepense (L.) Pers. (SORHA), Ipomoea purpurea (L.) Roth. (PHBPU), Rottboellia exaltata (Lour.) Clayton (ROOEX), Urochloa decumbens Stapf. (BRADC), Merremia aegyptia (L.) Urb. (IPOPE), Cenchrus echinatus (L.) (CCHEC), Digitaria horizontalis Willd (DIGHO), Panicum maximum Jacq. (PANMA), Tridax procumbens (L.) (TRQPR), Urochloa plantaginea (Link) Hitch. (BRAPL) e Eleusine indica (L.) Gaertn. (ELEIN)). The seeds were acquired in the specialized company Agroscosmos Ltda, specialized in selling seeds of weed.

The experimental units consisted of polyethylene pots with a volumetric capacity of 10 L of soil. The pots were filled with a clayey soil and a sandy texture, from the arable layer, which were sieved and collected from an area with no history of herbicide use and previously characterized in relation to their chemical and physical in the laboratory of soil from ESALQ/USP. The analysis of these soils can be observed on Table 1.

After filling the pots with the sandy and clayey soil, respectively, the weeds were sown individually in the experimental units, that is, each pot received the sowing of only a single species of weed, in the amount of enough seeds to obtain 5 weeds per pot, the seeds bought have already been characterized in terms of their germination by Agrocosmos Ltda., so the following amount of seeds were used for each specie: M. aterrima, I. purpurea and M. aegyptia and 0.48 g of seeds, S. halepense, 0.51 g, R. exaltata, 0.31 g , U. decumbens, 0.62 g , C. echinatus, 0.36 g, D. horizontalis, 0.11 g, P. maximum, 0.88 g, T. procumbens, 0.34 g and U. plantaginea, 0.58 g and E. indica 0.35 g.

The sowing was carried out on the day of application of the herbicide’s treatment, the sowing depth varied according to the size of the sides, this way, the smaller seeds were positioned more superficially at 0.5 cm of soil depth (D. horizontalis, C. echinatus, R. exaltata, P. maximum, T. procumbens, E. indica), the seeds of U. decumbens and U. plantaginea, were sown at 1cm of depth and the larger seeds were positioned 2 cm deep (M. aterrima, I. purpurea and M. aegyptia).

After sowing the weed, the herbicide indaziflam (D = 100 g i.a. ha^–1) was applied to the experimental units in two different doses: 1/16 D, 1/8 D, 1/4 D, 1/2 D, 1 D, 2 D, 4 D, 8 D, 16 D and 0 D that represented the witness without herbicide application.

The application was performed with the support of a backpack sprayer pressurized with CO₂, provided with a spray bar containing two Teejet TTI 110.02 fan nozzles and with an application volume of 150 L ha^–1, with a pressure of 2.0 kgf cm^–2. The environmental conditions at the time of the application were relative humidity of the air of 70.2%, temperature of 25°C and the wind speed of 2.0 km h^–1.

Right after the application, all the pots were transported to the greenhouse, where they received a water layer proportional to a precipitation of 30 mm, using a sprinkler irrigation system (1 L min^–1). This quantity was assumed because, according to Maciel and Velini¹⁰, 20 mm of rain are needed to transpose high solubility herbicides from the soil surface to the place where the seeds are placed in the greatest depth, in the case of highly lipophilic herbicides, such as indaziflam, this value can be higher. After this rain simulation, the irrigation was turned off for 24 hrs and after a period of 24 hrs it was switched on, receiving daily watering shifts of 10 mm of water, aiming to keep the plants alive and without hydric stress.

At 7, 14, 21, 28, 35, 42, 49 and 56 days after weed emergence (DAE), visual assessments were carried out based on the criteria of ALAM¹¹, which uses a percentage scale of scores, in which 0 (zero) corresponds to the absence of control and 100% absolute control of weeds. At 56 DAE the aerial part of the weeds was cut close to the ground and then packed in paper bags and taken to a greenhouse with forced air circulation at a constant temperature of 60°C for 2 days to obtain the dry mass.

The dry mass data were corrected to percentage values, assuming that the plots that remained without herbicide (witness) demonstrated a dry mass reduction equal to 0% and the other treatments as a result of the reduction imposed by the herbicide in comparison to witness.

Control data and dry mass reduction (%) collected were subjected to analysis of variance by the F-test. When significant, the averages were compared using the Tukey test, using the statistical computer program AgroStat^®. Then, the quantitative data were adjusted to the logistic type of nonlinear regression model, proposed by Streibig^12,13 for control (1) and for residual dry mass (2):

where, y is the control or the residual dry mass, x is the herbicide dose herbicide (g i.a. ha^–1), P_min is the minimum point of the curve and a, b and c are estimated parameters of the equation, so that a is the amplitude between the maximum and minimum points of the variable, b is the dose that provides 50% of the response of the variable and c is the slope of the curve around b.

The logistical model has advantages, since one of the integral terms of equation (b) is an estimate of the value of DL₅₀ or GR₅₀¹⁴. The DL₅₀ (lethal dose for 50% of the population) or GR₅₀ (growth reduction of 50% of the population) is the herbicide dose in grams of active ingredient per hectare, which provides the value of 50% of control or reduction of weed growth¹⁴.

Although one of the parameters of the logistical model (b) is an estimate value of DL₅₀ and/or GR₅₀, it was decided to also perform the mathematical calculation of this estimate as well as for the estimate of DL₈₀, DL₉₀ and DL₉₅ and GR₈₀, GR₉₀ and GR₉₅, using the inverse equations (control (3) and residual dry mass (4), based on the discussion proposed by Carvalho et al.¹⁵:

RESULTS

Regarding the control, all the weeds listed in the Table 2 were controlled efficiently. The control percentages for E. indica showed no significant difference, however, the control was 100% for two soils, from the lowest dose (1/16 D). The D. Horizontalis control showed no significant difference in the factor interaction, however, the averages were superior to 80% in all doses. P. maximum and T. Procumbens species demonstrated difference in the control percentages depending on the type of soil, therefore, for both services, the control was higher than 90% in the sand soil from the dose of 1/16 D, whereas for clayey soil, it was efficient from the dose of 1/8D.

In relation to C. Echinatus, there was no significant difference, however, an efficient control was observed from the dose 1/4D, for both soils (clayey and sandy). Although U. plantaginea hasn’t showed difference in control due to the soil texture, in the analysis of Table 2 it is possible to observe a control percentage of 81.7% in sandy soil at the dose of 1/4D and of 100% from the dose of 1D for the clayey soil, whereas in the commercial dose 1D in both soils the control was equivalent to 100%. Thus, the control was more than 80% efficient, starting from a lower dose in the sandy soil when compared to the clayey soil (Table 2).

In the analysis of Table 3 for E. indica, it is possible to observe that the reduction in dry mass has not showed significant difference in the factor interaction and had 100% reduction from the 1/16D dose, regardless the soil (clayey and sandy).

D. horizontalis had a dry mass reduction above 80%, starting from the dose 1/16D, for both soils (clayey and sandy). The P. maximum e T. procumbens weeds as well as in the control data, had a control reduction above 90.0% for the sandy soil from the dose of 1/16D and 80.0% for the clayey soil. For C. echinatus, a reduction in dry mass above 90.0% for both soils (sandy and clayey), from the dose of 1/4D. The U. Plantaginea specie, presented 83.8% of reduction of dry mass in sandy soil at a dose of 1/4D and of 100% from the dose 1D for clayey soil.

The control data for a second group of weeds was demonstrated in Table 4. For M. aterrima specie there was not significant difference in the control, however it was only considered adequate, i.e., above 80%, from the doses of 4D and 8D, for sandy and clayey soil, respectively. For S. halepenses, the application of indaziflam in sandy soil required a dose of 1/8 to promote a control considered adequate (81.7%), whereas in the clayey soil the control was only considered efficient a dose of 1/4D (80.0%). For I. purpurea, there was not statistical difference observed, however, the control was efficient from the commercial dose recommended (1 D), with 83.3 and 100% for sandy and clayey soils, respectively.

The R. exaltata specie was controlled with percentages superior to 90.0% regardless of the type of soil, starting with the dose of 1/4D. For U. decumbens, the control did not present significant difference in the factor interaction but this was effective, above 80.0% from the dose 1/2D, regardless of the soil texture. M. aegyptia, was not efficiently controlled by the herbicide indaziflam since the control was only effective from the dose of 4D (Table 4).

For all weeds in the second group (M. aterrima, S. halepense, I. purpurea, U. decumbens e M. aegyptia), the reduction in dry mass presented significant difference as represented in Table 5. For M. aterrima an efficient reduction of dry mass, superior to 80% was observed from dose of 4D for sandy soil and dose 8D for the clayey soil. For S. halepense was observed a reduction of 89.1% for dose of 1/8D and 85.4% for dose 1/4 D, for sandy and clayey soils, respectively. For I. purpurea, from dose 1D the reduction in dry mass was superior to 80.0%, regardless the soil. R. exaltata, presented a reduction in dry mass reduction above 90.0% for both soils analyzed (sandy and clayey). For U. decumbens, the reduction in dry mass from dose 1/2D was above 85.0%, regardless the soil type. For M. aegyptia, a reduction in dry mass of more than 85.0% was observed for both soils, from dose 8D.

The Table 6 demonstrated the data inherent to DL₅₀, DL₈₀, DL₉₀ e DL₉₅.

Based on DL₉₀, the indaziflam herbicide cannot be recommended for an adequate control of M. aterrima and M. aegyptia, because regardless the soil type, clayey or sandy, the minimum dose for the control of 90.0% of the plants in the pot was higher than the recommended dose range of indaziflam for all the cultures, which varies between 75-100 g ha^{–1 3}.

For I. purpurea, the dose for control of 90.0% of the plants in clayey soil was 105.7 g ha^–1, that is, higher than the maximum recommended dose³, thus also it would not be included in the control spectrum of the indaziflam herbicide. The weeds U. plantaginea and U. decumbens required a dose greater than 50 g ha^–1 in sandy soil. The remaining S. halepense, R. exaltata, C. echinatus, D. horizontalis and T. procumbens, the required dose to control 90.0% of the population was less than to1/2 D (50 g ha^–1), regardless the soil texture. It is noteworthy that for E. indica, in both soils and for P. maximum, in sandy soil, it wasn’t possible to perform the calculation of DL₅₀, DL₈₀, DL₉₀ e DL₉₅ as the control was equivalent to 100% in all analyzed doses, it is not possible to calculate according to the adopted parameters (Table 6).

Regarding GR₅₀, GR₈₀, GR₉₀ and GR₉₅ data, for reduction of dry mass, the data can be observed in Table 7. For the species M. aterrima and M. aegyptia, both in the clayey and sandy soil, the minimum dose for the 90.0% reduction in dry mass, the recommended dose of indaziflam (maximum dose 100 g ha^–1) was higher³.

As for the species I. purpurea, the reduction of 90.0% of the dry mass of this specie was obtained with 135.3 g ha^–1, also outside the recommended dose of indaziflam. For all other species studied, the dose of indaziflam was within the product’s range recommendation.

DISCUSSION

The E. indica weed was the plant most easily controlled through the indaziflam herbicide, because regardless of the type of soil in which the herbicide was applied, the control was 100% from the lowest dose of 1/16D. Although the factorial interaction of the statistical analysis did not include the weed factor and consequently it is not possible to establish a comparison of susceptibility to the indaziflam herbicide among the weeds, we can assume that E. indica was the specie most susceptible to the indaziflam herbicide as it was not possible to perform the calculation related to DL and GR, since at the dose of 1/16D (6.25 g i.a. ha^–1) the control was 100%.

Malardo et al.¹⁶, evaluating the efficiency of the indaziflam herbicide in the pre-emergence of the weed Eleusine indica (crowfoot grass), obtained a percentage of control close to 100.0% in applications in a clayey soil without the presence of sugarcane straw and with sequential rain simulation of 20 mm. The D. horizontalis, can be considered the second most susceptible plant to the indaziflam herbicide, because for both sandy and clayey soil, the dose required to promote a control of 90.0% of the plants was less than 4.5 g i.a. ha^–1. Panicum maximum had a high susceptibility to control through indaziflam, in which was not possible to calculate the GR for the sandy soil, since, from the lowest dose 1/16 D (6.25 g ha^–1), the control was 100%, while the clayey soil GR₉₅ was 26.3 g ha^–1.

Amim et al.⁶, evaluating the efficacy of indaziflam applied in pre-emergence of weed in soils with different textures, found that D. horizotalise P. maximum species were also more susceptible to indaziflam, corroborating with the data obtained in the present experiment.

Species: Tridax procumbens, Sorghum halepense and Rottboellia exaltata, presented a DL₉₀ with doses within the recommended range of the herbicide in pre-emergence, regardless the soil texture. These plants, according to information in the leaflet for both commercial products registered for indaziflam (Esplanade and Alion), have no mention of control through this herbicide².

These results reinforce the idea that being an herbicide recently placed in the market, there is still a lack of information inherent to the correct spectrum of weed control through the indaziflam herbicide, because the results obtained showed the efficiency of this herbicide on a great number of weeds higher than reported in the literature of plants susceptible to this product.

Weeds: Sorghum halepense, Ipomoea purpurea, Panicum maximum, Tridax procumbens and Urochloa plantaginea presented significant difference due to the soil texture factor, because in sandy soils the dose required for the adequate control of these species was lower than the dose required for the control in clayey soil. These results indicated that for the positioning of the herbicide indaziflam in pre-emergence condition, there may be a need for dose adjustment (increasing) the dose in clayey soils and/or with a higher percentage of organic matter, thus aiming at a compensation between the amount of herbicide absorbed to the soil matrix and available in solution for absorption by weeds.

This difference in the results due to soil texture was expected on account of physical and chemical characteristics of the indaziflam herbicide, which presents higher Kd, low Koc and high Know (equal to 2.88)³, these parameters may have favored the adsorption of indaziflam in sandy soil and/or with organic matter, decreasing thus the amount of herbicide available in soil solution and consequently susceptible to be absorbed by weeds resulting in effective control.

Sebastian et al.⁸, studying the influence of soil properties on the effectiveness of controlling the indaziflam herbicide on Kochia scoparia L., confirmed that is necessary a concentration of herbicide 10-100 times higher to produce a 50% growth reduction (GR₅₀) in a soil with 16.8% of organic matter compared to a soil with 0.4% organic matter.

Alonso et al.⁵, analyzing the dynamic of indaziflam in soils with different physical and chemical characteristics, also found that the influence of organic matter in the sorption process, where higher percentages of organic matter resulted in higher amounts of adsorption (Kd) and consequently, lower availability of herbicide in soil solution.

Thus, the higher adsorption of indaziflam herbicide in clayey soils and/or with higher percentage of organic matter can affect the effectiveness of weed control through the application of commercial dose and/or refer the application of a higher dose of this herbicide as a compensatory form of control.

This behavior was confirmed by Amim et al.⁶, through the application of six doses of indaziflam (0, 30, 60, 90, 120 and 150 g ha^–1) in pre-emergence condition in three soils with contrasting physical and chemical characteristics (sandy, clayey and clay-sandy-loam). Under these conditions, the authors found that the soil factor influenced the efficacy of the soil. The species D. horizontalis and P. Maximum were effectively controlled in all soils. For E. heterophylla and I. grandifolia, the control was more efficient in the loam-clay-sandy soil. Reinforcing the greater efficiency of indaziflam in the control of monocotyledonous weeds.

In this experiment the Sorghum halepense, Rottboellia exaltata, Cenchrus echinatus, Digitaria horizontalis, Panicum maximum and Eleusine indica plants required a maximum of 1/2 D (50 g ha^–1) to result in an effective control. All these plants have as common characteristic that they belong to the Poaceae family, showing high susceptibility of plants of this family to pre-emergence control through the indaziflam herbicide.

This high efficiency of indaziflam in the control of monocotyledonous weeds was also confirmed by Sebastian et al.⁸, evaluating the control of six annual winter graminea using indaziflam, the authors obtained the following values of GR₅₀ for the following evaluated weeds: Downy brome (0.23 +/- 0.07), Feral rye (0.56+/-0.06), Japonese brome (0.19+/-0.05), Jointed goatgrass (7.37+/-3.58), Medusahead (0.36+/-0.09) and Ventanata (0.44+/-0.09). In other words, the authors also found out values well below the recommended dose of indaziflam to promote a control of 50% of infesting community of these species, indicating a high susceptibly to weeds of Poaceae.

However, it is noteworthy that the species Urochloa decumbens and U. plantaginea, even being in the same Poaceae family were only controlled in both soils (clayey and sandy) from the recommended commercial dose (100 g ha^–1). Thus, plants of this genus may require a higher dose than the necessary for the other plants from the Poaceae for an efficient control, reinforce these two species Urochloa decumbens and U. plantaginea were controlled within the recommended dose.

This result can be justified due to fast and high root development of Urochloa decumbens. This behavior results in less water and nutrient absorption capacity, since the older roots tend to become more lignified quickly resulting in less permeability and less absorption of herbicides, present in soil solution^17,18. In addition to this fact, indaziflam has a high value of adsorption coefficients (Kd)⁵ resulting in less mobility of this herbicide in the soil (indaziflam leaching), thus the new roots emitted, less lignified and with a larger area absorption, tend to be positioned below the treated area of the herbicide, justifying this need for higher doses of indaziflam to obtain an adequate control percentage.

The same justification based on fast root development can also be expanded to U. plantaginea as according to Carvalho et al.¹⁹, this plant shows a high initial increment of biomass allocation to the root system (60% at 35 days after emergence).

In relation to eucotyledoneous weeds, in the present experiment a control considered excellent, with GR₅₀ of only 3.5 e 2.4 g ha^–1, for clayey and sand soil, respectively. In addition to presenting GR₈₀, GR₉₀ and GR₉₅ below 24 g ha^–1, that is, value well below the recommended dose range of the herbicide (75-100 g ha^–1). This result can be justified by the Tridax procumbens weed specie, presenting superficial germination and small seeds, with a mass of achenes ranging from 0.64-0.68 g²⁰, which may have favored fast absorption of indaziflam, resulting in adequate control.

Similar results were obtained by Sebastian et al.⁷, which carrying out an experiment in a greenhouse in order to study effectiveness of control through the of GR₅₀ calculation by applying the indaziflam herbicide in pre-emergence, for eight eudicotyledonous weeds with small seeds Verbascum thapsus, Dipsacus fullonum, Rumex crispus, Linaria dalmatica, Centaurea diffusa, Halogeton glomeratus, Conyza canadensis and Carduus nutans), obtained the maximum of GR₅₀ value of 1.33 g ha^–1.

However, other species of eudicotyledonous weeds presented different response to control through indaziflam, since M. aterrima and M. aegyptia, regardless the soil type, required a much higher dose than recommended (D = 100 g ha^–1), to promote 95% control. I. purpurea in application of indaziflam in clayey soil, also required a higher dose than recommended to promote an effective control of this weed.

In relation to M. aterrima, this less effective control can be attributed to seed imposed by impermeability of the husk to water, which at the expense of the hardness of the integument at the expense of the deposition of waxy substances of the outer layer of the paralyzed cells, pericarp and nucellar membrane^21,22. According to Abud, Reis and Teófilo²³, the primary root of Mucuna aterrima presents an expressive development, being in its largest proportion thick and lignified with thinning at the end, in relation to the seedling, 10 days after sowing it presents root system with an average length of 22.9 cm and aerial part with an average length of 22.3 cm, this behavior of the root system may also have influenced the less effective control of this species.

The weed seeds of the Convolvulaceae family, both belonging Merremia genus and to the Ipomoea also present dormancy due to the formation of a palisade layer of microsclereids or Malpighi cells impregnated with suberin, cutin and lignin, of little affinity with water²⁴, this results in imperviousness of the integument to water²⁵.

This physiologic aspect of the M. aterrima, M. aegyptia and I. purpurea seeds results in less permeability of the seeds to water and consequently reduces the entry of the herbicide into the seed by absorption and/or imbibition, culminating in less control of this specie. Thus, these three eudicotyledonous species, which have as common characteristic, large seeds and with a thicker coat, have greater difficulty in being controlled by indaziflam.

Thus, aiming at an efficient control of eudicotyledonous weed, of difficult control, such as M. aterrima, M. aegyptia and I. purpurea, it may be necessary to associate with another product directed to the control of broadleaf weeds, aiming at this forms the increase of the control spectrum. Within this perspective, a product that can be an alternative is the mixture of indaziflam+metribuzim, in which the metribuzim presents a controls spectrum for eudicotyledonous weed, also recommended to control the species of the genus Ipomoea³.

CONCLUSION

Thus, weeds present a difference in susceptibility to control through indaziflam herbicide and weeds of the Poaceae family required a lower dose of indaziflam to result in adequate control, however, species of Urochloa genus needed a dose one slightly higher in relation to the other Poaceas, possibly to the detriment of the more aggressive root system. In the species of eudicotyledonous weed, the indaziflam was inefficient in controlling in most situations by applying the commercial dose. Then, indaziflam presented a greater control spectrum for monocotyledonous weeds than eudicotyledonous.

SIGNIFICANCE STATEMENT

This paper to evaluate the efficacy of pre-emergent herbicides (indaziflam) in control of different species. In this manuscript, we show weeds of the Poaceae family were more susceptible to the herbicide indaziflam, in contrast, eudicotyledonous species required a higher dose to be efficiently controlled. Difference in susceptibility of the studied plants as a function of indaziflam dose, weed species and soil texture was observed.

ACKNOWLEDGMENT

We would like to thank the São Paulo Research Foundation (FAPESP) for the financing and support of this research (Process: 2015/14833-0).

REFERENCES