Introduction

Pecan nut is a very important economic activity in northern Mexico and the southern United States. The five main producing states in the United States were: Georgia, Texas, New Mexico, Arizona, and Louisiana and Oklahoma, tied for fifth place (^{USDA-NASS, 2011}) and in Mexico the states of Chihuahua, Sonora, Coahuila, Durango and Nuevo Leon. The production of this nut in Mexico has increased by about 80% in the last thirteen years (2003 to 2015) currently reaching around 110 thousand tons.

The planted area reached 104 thousand hectares in 2013 (^{Secretaría de Hacienda y Crédito Público, 2014}). The cultivation of walnut in Mexico is of interest since in recent years it has positioned itself as an important player in the pecan nut market by occupying second place as a producer and first as a world exporter. The per capita consumption in Mexico is around 0.65 kg (^{Baca, 2007}), while in 2007 in the United States of America the reported consumption was around 0.752 kg and in 2010 0.964.

The oldest archaeological evidence of its collection by humans for subsistence dates from 8 000 years before Christ (AC) during the archaic period of America, in the Modok Rock settlement, current state of Illinois-USA (latitude 38° north), corresponding to the northernmost limit of its geographical distribution. Archaeological evidence of its westernmost distribution dates back to 8 000 years ago recovered from Baker Cave in Val Verde County (longitude 101° west), in the state of Texas in the USA.Its eastern boundary has been found in the state of Alabama in the USA (longitude 87° west), related to the Midwest Mississippi culture of the years 1050-1250 BC. To the south, the species is currently distributed to the state of Oaxaca in Mexico (latitude 17° north), although its historical limit of geographical distribution to the south is not supported by archaeological evidence if it is by genetic variation in plastids, which suggests that they are not the product of a recent introduction in the area (^{Gauke et al., 2011}).

^{Gray (1973)} states that pecan walnut is native to the southeastern United States of America and northern Mexico, and that the first commercial plantations began in 1871 in the United States of America and the pioneer introduction of commercial plantations in Mexico was made in 1904, in the state of Nuevo Leon. Currently, pecan nut production comes mostly from plantations instead of natural forests, in the 2009-2011 period, 82% of US production was obtained from improved cultivars (^{Graham, 2013}). The geographical distribution of pecan nut cultivation in North America is shown in Figure 1.

Figure 1 Geographic distribution map. The blue scale is directly proportional to the production in tons of pecan nut for the year 2014 (^{Suárez et al., 2015}). 

The main pests of this crop in Mexico are caused by the nut-boring worm Acrobasis nuxvorella (Neunzig), which affects a wide range of cultivars in a large geographical area, with a high level of affectation. It affects the two main varieties (Western and Wichita) grown in Mexico. This insect, when completing four generations per year, is responsible for losses of up to 80% of the fruits, negatively hitting the profitability of the crop.

Another insect that affects production is the rue auger worm (Cydia cariana), which is also found in most producing areas of Mexico. During the 2008 cycle it caused losses of 8.4% of the production of the state of Durango (^{SENASICA 2009}). ^{Del Toro (2013)}, mentions that harmful organisms affect the productivity of walnuts and their control implies 15% of the production cost of the crop. Mexico and the United States of America are the main producers of pecan nut, contributing about 93% of world production and the rest South Africa, Australia and Perú. Mexico is the world’s first exporting pecan nut.

In 2016, the combined pecan nut production of these two countries was 271 000 t, of which Mexico participated with 52%, this presents an annual growth rate in production of 15.6%, while in the United States of America it was of 12.4%, ^{Comité Mexicano del Sistema Producto Nuez, AC (2017)}. Potential markets with a strong real demand for pecans, such as Japan and Europe, could be an important opportunity to increase Mexican exports, diversifying the US market, traditionally the one preferred by Mexico.

Recent commercial results show that China, including Hong Kong, is a space with substantial growth over the past five years, which has become the second international market for American pecans. The quality of the nut is mainly considered by the percentage of almond, the size of the fruit, color, damages of the almond and others of minor importance. The almond content produced in the region in the varieties studied is good, considering that the majority of native trees yield above 40%.

In most varieties the nut size tends to decrease in older trees (^{Arreola et al, 2002}). In Mexico for the year 2016, the states with the largest area planted were Chihuahua, Coahuila, Sonora and Durango, as can be seen in Table 1.

Because in these states it is where most of the pecan nut is produced in Mexico, the present study had as a general objective to conduct a study of the functioning of this productive system in the main representative areas of the crop and thereby detect the areas of opportunity or actions that must be carried out to strengthen the national nut producer sector both in the field of production and marketing, for which three zones were chosen: the Comarca Lagunera located in the states of Coahuila and Durango; the municipality of Jiménez, Chihuahua and that of Hermosillo, Sonora. Table 2 shows the area sown and harvested from pecans in the study areas, ^{SIAP-SAGARPA (2017)}.

It is noted that the Comarca Lagunera, although it has a larger surface area than Hermosillo Sonora, has lower total production due to the lower yield per hectare. Likewise, a lower rural price is observed for this area, probably due to the lower nut quality. Jiménez Chihuahua has the highest production potential, since the potentially harvested area is high.

Materials and methods

To characterize the pecan nut production process, two surveys were designed, one to producers and the other to marketers-processors, which were applied in each of the three producing regions, the gathering of field information for the Comarca Lagunera it was carried out in the months of October to December 2014 and for Hermosillo, Sonora and Jiménez Chihuahua in the months of June, July and August of 2015, due to the availability of time, economic and personal resources for it.

The second survey consisted of questions that served as an interview guide applied to these companies, the first section gathered information number of years of operation; the main business and headquarters of the same, sources of nut supply and destinations of fresh and processed product, annual volumes handled, types of product made with the nut, markets, prices and volumes sold, sources of financing and support needs for Strengthen your competitiveness. From the information obtained, the corresponding section was described. In the Comarca Lagunera two companies were interviewed; in Hermosillo, two and in Jiménez five. It should be noted that the total population of companies by region is unknown.

In order to determine the number of producers to be surveyed in each of the regions, the register of producers that manage local plant health boards, dependent on SAGARPA in each region, was used, where once the sample was obtained, the sample size was calculated, using the following simple random sampling formula (^{Fuller, 2009}).

Where: N= population size; n= necessary sample size; d= precision of the estimate or the distance that you want the estimator to move away from the parameter (population proportion), in most cases d is less than 0.1, it is recommended to calculate the sample size for different values of d . S= standard deviation of the population, known or estimated from previous studies. t= value of the tables of t; α= significance level of α, the most common is to set α= 0.05

For the calculation of the variance (S²) it was established in 13.022, obtained from data from a previous sampling in which the sale price of the nut was taken as a reference. The degree of confidence used was equal to five percent. The survey applied to producers included 23 questions, the analysis and processing of the surveys was done with the Microsoft Excel program. The sample size for each region is shown in Table 3.

The weighted price of the kilogram of pecan nut, was obtained by multiplying the value in pesos per kilogram of walnut by the percentage of each form of marketing adding up all the ways of marketing the nut that the producer had, since there are producers who sell in different percentages and at different prices your harvest.

Results and discussion

The first difference found in the study regions refers to the surface of the orchards, according to the register of producers, the average size for the Comarca Lagunera, Hermosillo Sonora and Jiménez Chihuahua is 8.7, 215.8, and 50.4, ha, respectively. Another difference refers to the type of irrigation used in its cultivation. In Comarca Lagunera 92% of the orchards irrigate with water from the dam, in Jiménez, Chihuahua this type of irrigation is 15% and in Hermosillo, Sonora is irrigated only with water pumped from the subsoil.

The previous situation puts producers who have water at an advantage when the crop requires it (those of Hermosillo, Sonora); not so, those that depend on the water provision in the dams and the tanning that governs the irrigation in their area (Comarca Lagunera and Jiménez Chihuahua). Regarding the two varieties used in their orchards, one to pollinate and the other to be pollinated, it is observed that while in the Comarca Lagunera and Jiménez Chihuahua region the proportion of Western walnuts is greater (65.7 and 80.8% respectively), in Hermosillo, Sonora is smaller (24.7%), using the Wichita pollinator in the first zone and in Hermosillo, the Western.

Regarding yields obtained per unit area, the producers of the Comarca Lagunera registered the lowest (1.4 t ha^-1, while those of Jiménez, Chihuahua and Hermosillo, Sonora registered 1.7 and 2.7 t ha^-1) which can be attributed to the less frequent availability in the irrigation carried out as well as the less technical attention that the orchards receive, since they are producers with smaller surfaces than those managed in Jiménez and Hermosillo.

The age of the orchards is similar in the three zones (27 years on average). ^{Orona et al. (2013)} indicate that in the north of Coahuila the average age of commercial orchards established with varieties other than Western and Wichita is 21 years, same that registered a yield of 1.4 t ha^-1, indicating that technical advice helps improve Walnut productivity. Regarding the level of equipment for harvest and post-harvest, the Hermosillo region, Sonora, is the most equipped, as can be seen in Table 4.

Therefore, the lack of infrastructure is a point that needs to be addressed for the production of the nut, especially in the Lagunera Region. It should be noted that, in the Hermosillo region, Sonora the use of the nut dryer is a necessity, as it is a humid area located on the Pacific Coast, where defoliants are also used to harvest the nut, which increases costs of producer production.

The Hermosillo region has the lowest incidence of pests, followed by Jiménez Chihuahua and with more incidents and variety of these, the Comarca Lagunera. To reduce the problem of the husk borer (Cydia cariana) and nut borer (Acrobasis nuxvorella), in the state of Sonora there are actions that regulate the mobilization of vegetative material to the state, which prevents the introduction of these borers and other pests from various nut-producing regions. In the other two study regions, different species of Chrysopa and Trichogramma are released for the biological control of these borers.

The greater presence of pests in the Comarca is attributed to the less attention and technical assistance that the crop receives from the small producers that predominate in the area. The pests found here coincide with those reported by ^{Nava and Ramírez (2002)}; ^{Tarango (2005)}; ^{Aguilar (2007)}. In the last three years ^{Ávila-Rodríguez et al. (2015)}, found infestations and damages to the walnut foliage by a micro lepidoptera of the Coptodisca genus. Technical advice on the management of orchards is another marked difference.

Thus, while in the Hermosillo region, Sonora all producers receive technical assistance; in Jimenez, Chihuahua receives 66% and in the Comarca Lagunera, only 51%. Regarding being affiliated with some producer organization, it is observed that while in Sonora nine out of ten producers are; in Jiménez Chihuahua there are six out of ten and in Comarca Lagunera only 1.5 out of ten belong to an organization. The previous situation explains why the producers in the three regions studied have different levels of access to financial sources and technical assistance, being the organization of these which favors obtaining greater support.

Regarding ways to market the nut, in Hermosillo, Sonora is done in two ways: in bulk selected by size and selected packaged for sale to wholesalers; in Jiménez Chihuahua, apart from the aforementioned forms, it is selected, packaged and sold to wholesalers, and in the Comarca Lagunera, in addition to the forms marketed in Jiménez, Chihuahua, it is marketed husked and as standing gardens, this last form of nut sale It is done by producers who lack economic resources for the management of their crop, making it more practical to sell their garden before investing in it a resource that they do not have, thus ensuring a minimum income.

In receiving financing to produce it was found that the largest proportion of producers that receive it are those of Hermosillo, Sonora (55.5%). It is worth mentioning that in this region there are producers who do not receive it because they do not require it, their financial capacity is solved, while in Jiménez, Chihuahua and Comarca Lagunera this proportion is 25%.

The weighted price received by walnut producers in the Comarca Lagunera, Hermosillo, Sonora and Jiménez Region was 40.36, 73.1 and 61.03 pesos per kilogram, observing that these prices are lower for producers with smaller areas, which can be attributed to less bargaining power for the volumes sold, the quality of the nut sold or the type of buyer that is destined.

Marketers and nut processors in the study regions

Conclusions

In the characterization of the production system, similarities are found in the three regions regarding the age of the garden, although the Jiménez Chihuahua region has more years as a pecan nut producing area; the predominant sown varieties in the three sites are Western and Wichita with more than 90% although in different proportions per site; regarding the average yields obtained, these are higher in the Hermosillo Sonora region, followed by Jimenez Chihuahua and the lowest in the Comarca Lagunera, this situation of lower yields is explained by the lack of technical advice, lower producer organization and the lack of financing to produce.

Therefore, it is necessary to support the Comarca Lagunera more with producer organization, technical advice and financing. The ways of marketing the nut is greater in the Comarca Lagunera than in Jiménez, Chihuahua and Hermosillo, Sonora; in the latter region there are only two ways to market: in bulk selected by size and selected packaged for sale to wholesalers. The higher weighted price of walnuts received by Hermosillo producers is due to the way in which they market their product and the final market that their product has; in this case China, since the other two regions commercialize in greater proportion with marketers from the United States, who finally supplies the European and Eastern markets.

The presence and operation of marketing companies-processors in the Jiménez region of Chihuahua is greater and it was the state of Chihuahua where the first companies of this type were born, later extending to the rest of the country. The growing birth and proliferation of commercialization - processing companies are due to the growing market of pecan nuts in the world, identifying family-type companies that take advantage of these areas of opportunity.

The destiny of the pecan nut from the Hermosillo, Sonora and Chihuahua region towards the Chinese market represents a new business opportunity in Mexico and opens up the possibility of new markets. This situation favors Mexican producers, whose nut is sold directly to the Chinese market without triangulation by US marketers.

To reduce productivity gaps between larger and smaller orchards and between regions, it is important to support the weakest link, represented by small producers, with the implementation of: financing programs to produce and market, technical advice especially in the area of pests and diseases and training in the management of the garden, especially in irrigation management; and strengthen the infrastructure of the orchards for a better management of the nut and to be able to sell with greater added value.

In the comparison between regions if you want to match Sonora, it is necessary to improve especially in the aspects of organization, training and availability of financing, aspects in which it far exceeds the other two regions studied.