Worldwide, maize is one of the species with a great biological diversity, occupying the third in importance in area planted only after wheat and rice crops (^{SAGARPA-SIAP, 2014}). Mexico is ranked as the seventh largest producer of maize in the world, currently producing 23 273 256.54 million tons of grains of this species on an area of 7 426 412.19 hectares equivalent to 3% of world production (^{SAGARPA-SIAP, 2014}).

Maize is the most important crop in Mexico as it is used for human, animal and industrial consumption. (^{SAGARPA-SIAP, 2014}).

Several factors contribute to the post-harvest losses of this grain, with 5-10% of world production being lost due to pests, which is equivalent to the amount of grain needed to feed 130 million people annually (^{Casini et al., 2008}). S. zeamais maize weevil (Coleoptera: Curculionidae) is considered one of the most important pests that affect the grain of this crop when it is stored; in Latin America, between 30 and 40% of maize production is lost during storage. ^{Cerna et al. (2010)}; ^{Lagunes (1994)} mention that S. zeamais is one of the species of weevils that causes more losses in grains stored in the world; its control is mainly based on synthetic products, which are less effective as time goes by.

To minimize these losses, chemical pesticides are commonly used, where mixtures of insecticides and fungicides are used in order to protect the seeds during storage; however, chemical products and applied doses can cause seed toxicity, as well as frequently leading to resistance problems, environmental contamination and residues in food (^{Silva et al., 2003}). An alternative to this problem is the use of natural products derived from plants, which are generally biodegradable and do not produce imbalance in the ecosystem (^{Iannacone et al., 2001}; ^{Iannacone et al., 2003}). For this reason and in order to contribute to the search for natural products, nine vegetable powders were evaluated against the attack of S. zeamais adults in stored maize, looking for an alternative in the control of stored grain pests.

The study was carried out in the laboratory of Toxicology of the Department of Parasitology of the Autonomous University of Agraria Antonio Narro.

The plant material used was provided by the toxicology laboratory, each plant species (Table 1) were separately sprayed on an electric mill and subsequently filtered with a 250 μm sieve in order to achieve a fine and homogeneous powder. Finally, they were stored at room temperature in ziploc bags identifying them according to the species of the plant in question.

Table 1 Vegetable species evaluated for the control of Sitophilus zeamais Motsch., in grains of stored maize. 

As a substrate, white maize was stored with soft to semi-crystalline characteristics produced in the southeast of Coahuila in the spring-summer 2014 cycle, free of chemical treatments and impurities.

The methodology proposed by ^{Lagunes and Rodríguez (1989)} with slight modifications was used, which consisted of placing 300 g of maize with the doses of 1, 2 and 3 g of vegetable powder in 500 ml plastic containers to make a mixture of each treatment. After mixing, each container was infested with 30 adult S. zeamais insects.

In order to determine the powders effect on each treatment, the variable mortality was measured, which was evaluated 15 days after exposing the insects to treated maize. The living and dead adults of each treatment were quantified according to whether or not they showed coordinated movements at the touch of a dissecting needle (^{FAO, 1980}).

The statistical model consisted of a completely randomized model with 10 treatments and 3 replicates and a total of 30 experimental units, including the control. With the results obtained and observing that the control showed no more than 12% mortality, the mortality correction (MC) was performed using the ^{Abbott formula (1925)}: 𝑀𝐶=((%𝑚𝑢𝑒𝑟𝑡𝑜𝑠−%𝑡𝑒𝑠𝑡𝑖𝑔𝑜)/(100−%𝑡𝑒𝑠𝑡𝑖𝑔𝑜))∗100,, for its normalization the percentage values were transformed to arcoseno 𝑥/100 Afterwards, they were submitted to analysis of variance (Anova) to indicate the difference between the treatments and the Tukey test (p≤ 0.05) was applied for the separation of means, for which the software Statistical Analysis System (^{SAS, 2002}) was used.

The results of the mortality rate of the powders on S. zeamais are shown in Table 2, as proposed by ^{Lagunes (1994)}, who indicates as promising only those treatments with a mortality higher than 50%, it can be pointed out that two of the nine powders evaluated meet this criterion. The best results were obtained with black pepper powder and rude pepper with mortality rates of 68.84 and 60.42, respectively.

Table 2 Mortality of S. zeamais adults in stored maize grains treated with vegetable powders at doses of 3 g. 

The results obtained are consistent with the findings of ^{Salvadores et al. (2007)} who reported that the highest mortalities were obtained with Piper nigrum L., with control percentages between 65.6 and 97.6 respectively. Paula et al. (2002) reported that the metabolites, piperine and piperidine, isolated in Piper nigrum L., showed a control of 97.5%. ^{Scott et al. (2004)} worked with three extracts of plant species of the piperaceae family (Piper nigrum L.) in the control of five orders of insects mentioning the isobutyl amine (amides) as the secondary metabolite that acts as neurotoxic and insect repellent.

On the other hand, ^{Park et al. (2002)} mention amides in the genus Piper of the family Piperaceae, as secondary metabolites with insecticidal-acaricidal activity. Ruta graveolens L. (ruda) presented a control percentage of 60.42%, similar to that reported by ^{Silva et al. (2003)} with 60.5% control. In addition to the above mentioned treatments, the thyroid, mint, cinnamon, clove, chilli, rosemary and garlic powders showed control percentages lower than 50%, which agrees with ^{Silva et al. (2003)}; ^{Salvadores et al. (2007)}; ^{Silva et al. (2005)}; ^{Castillo et al. (2012)}. Of the evaluated treatments, black pepper and rude powder exceeded the threshold of mortality proposed by ^{Lagunes (1994)}.