COVID-19 disease

The SARS-CoV-2 pandemic has transformed humanity. This virus is transmitted through particles expelled by sick people when sneezing or talking (^{Aguilar et al., 2020}; ^{MSE, 2021}). The most important preventive measures are maintaining social distance and the correct use of face masks. This implies avoiding physical contact and not participating in agglomerations of people (^{SSA, 2021}; ^{Hernández et al., 2020}). Even respecting these measures, the fear of contracting the disease prevails since it can cause respiratory problems and complications that can lead to the death of susceptible people or with chronic degenerative diseases such as diabetes, hypertension, and obesity (^{Díaz-Castrillón and Toro-Montoya, 2020}). In Mexico, COVID-19 was declared a health emergency in March 2020, the same month that the WHO declared it a pandemic. A year later, 1.9 million infected people and more than 160 thousand deaths had been recorded in Mexico (^{DOF, 2020}; ^{CONACYT, 2021}). At press time, these figures have increased by almost 100 and 80%, respectively. The 2020 GDP of Mexico fell by -8.5% and a timid recovery of 2.7 and 5.6 was forecast for 2021 and 2022 (Rivas-Valencia et al., Special Issue). It is estimated that the economic recovery will be slow. It may take three years to surpass pre-COVID-19 economic (^{González, 2020}). However, at press time, the Mexican GDP is growing at 5%, with a clear recovery in employment and consumption, which are close to pre-pandemic levels, thanks to a large GDP contribution from the agricultural sector in 2020 and 2021. There is no doubt that the health emergency affected agricultural production systems, mainly fruit production since harvesting, pest prevention and marketing require many workers. The present work aimed to provide information on the production system of guava fruits in Calvillo, Aguascalientes, the effect of the COVID-19 pandemic, and possible recovery strategies.

Productive system in Calvillo

Guava (Psidium guajava) is a fruit tree that grows in tropical and subtropical areas of the world. Most of the guava-producing area is in India, Pakistan, Brazil, Thailand, and Mexico (^{NHB, 2014}). In Mexico, it is one of the 12 most important fruit trees, with an annual production of close to 300 thousand tons from 22.1 thousand ha. The states with the largest guava-producing area are Michoacan, Aguascalientes, and Zacatecas, with 11.9, 6.2, and 2.5 thousand ha respectively. The productive system of Calvillo, Aguascalientes, is the most technologically advanced, with yields of 15 t ha^-1. Most of the guava production (80%) is consumed fresh within the country. The per capita consumption of guava in Mexico is 3 kg/person/year (^{Padilla et al., 2007}; ^{SIAP, 2021}). Guava is consumed for its flavor and pleasant aroma. Due to its nutraceutical properties, guava is recognized as an important source of Vitamin C and ascorbic acid (^{Hidalgo et al., 2015}); it is also used as an auxiliary treatment for gastric diseases and has even some anticancer properties (^{Pacheco et al., 2009}; ^{Sánchez-Zúñiga et al., 2017}).

The guava-producing area in Calvillo, which occupies 6268 ha, is the oldest in Mexico, going back more than 100 years. It accounts for 30% of the national production, with a commercial value of 300 million pesos (^{SIAP, 2021}; ^{Elizalde-González and Segura-Rivera, 2018}). Most guava orchards are located on slopes greater than 20% (^{Padilla et al., 2003}), in poor soils with a high content of calcium carbonates, alkaline pH, and 600-1800 meters above sea level. The planting density is 204-1000 trees per ha with a yield of 15-30 t ha^-1 respectively (^{Padilla et al., 2010}). The agronomic management of guava includes irrigation with micro-sprinklers and non-compensated sprinklers, annual trimming of mature shoots, chemical fertilization with NPK (1:1:1), application of organic fertilizer (20 kg/tree every two years), and control of pests and diseases using pesticides. Harvest takes place from September to December, after a water stress period locally referred to as period without irrigation “calmeo” (^{Reyes et al., 2003}; ^{Padilla et al., 2015}). Guava crops are attacked by various pest insects and diseases that can affect exports if guava shipments meet quarantine criteria. Pests and diseases can also affect the cosmetic value of guava fruits and reduce production (^{Vargas-Madriz et al., 2018}; ^{González et al., 2009}; ^{González -Gaona, 2002b}; ^{González-Gaona, 2002a}) (Table 1; Figure 1).

COVID-19 and agricultural production

Until the end of the first semester of 2020, no positive SARS-CoV-2 cases had been recorded in the municipality of Calvillo, Aguascalientes. The reported cases were of people who came from cities such as Aguascalientes and Guadalajara, or tourist areas such as Rincón de Guayabitos, Puerto Vallarta, and Manzanillo. Due to the low local incidence, it was considered a disease with little probability of affecting the Calvillo region. However, in the second semester of 2020, confirmed cases began to appear after the arrival of migrants from the United States. In January 2021, Calvillo was classified as a high-risk location, especially considering the index of active cases (^{GEA, 2021}). In mid-March 2021, 938 COVID-19 cases were reported, with 21 deaths, mainly among the elderly (^{GNCYS, 2021}). Many of those infected were asymptomatic, which contributed to increase the dispersal rate. Agricultural workers carried out their activities without face masks and without taking even minimal preventive measures. Young people met at parties without consideration for the sanitary guidelines established by the health authorities. On the other hand, companies, banks, restaurants, and grocery stores did comply with the preventive measures, establishing temperature screening practices, sanitary mats, mandatory use of face masks, and continuous use of alcohol-based gels (^{Official Gazette of the State of Aguascalientes, 2021}).

Agricultural activities were classified as essential by the federal government across the country. Thus, the production of guava did not face formal personnel restrictions. However, the COVID-19 pandemic did have an impact on guava production. Phytosanitary management activities were the first to be affected, mainly the sampling of pests and diseases. The detection of SARS-CoV-2 in more than 10 technicians from the State Plant Health Committee forced the imposition of quarantine until all PCR tests came back negative. This interrupted the activities and management measures against fruit flies and guava weevils, which are of quarantine and economic importance (Table 1, Figure 1). According to the State Plant Health Committee, most technicians had recovered and returned to work by the end of March 2021.

Figure 1 The management of the main diseases and pests of guava, such as the guava weevil (Conotrachelus dimidiatus), were affected by the COVID 19 pandemic. The guava weevil, for example, if not controlled, can damage up to 60% of the crop: External (A) and internal appearance of a damaged fruit (B) and size of the affected fruit (C). Adult weevils are difficult to observe, which is why guava fruits are checked (D) for feeding damage (E). Phytosanitary management activities start when the first fruits with oviposition damage are found (F). The application of chemical synthesis products (G) is the main control strategy. The COVID-19 pandemic affected the training of producers and technicians in these control strategies (H, I, and J). 

Guava producers usually hire five to seven full-time workers for pruning, fertilization, irrigation, weed control, and application of foliar fertilizers on their plots. Unfortunately, absenteeism due to quarantine restrictions and fear of contagion delayed most agronomic activities. Guava fruits are harvested manually twice a week for three months. The fruits are selected within the orchard. These two activities require the work of 10 to 15 people. The shortage of labor in the region forced producers to hire migrant laborers, mainly from the Pacific coast and “Huicholes” (indigenous people from the mountainous regions of Jalisco and Nayarit). This raised costs and increased the risk of spreading COVID-19. Most of these day laborers think their risk of becoming infected is nil because their activities are carried out in the open air. Thus, they do not follow preventive measures and prioritize financial gain over health (Personal communication from producers and technical advisers from Calvillo) (Figure 1).

An increased incidence of chronic kidney diseases has been reported in Calvillo, associated with overexposure to pesticides, mainly malathion and cypermethrin (^{Mendoza et al., 2015}). An alteration of the immune system has also been reported, predisposing the subject to other diseases and of course to COVID-19 (^{Corsini et al., 2008}). For these reasons, several studies have tried to obtain natural and biological alternatives for the control of pests and diseases in guava crops (^{González et al., 2020}; ^{Carrillo et al., 1993}).

COVID-19 and the supply chain

The health and economic crisis caused by SARS-CoV-2 affected supply chains at the global, national, and regional levels. It affected other productive activities too, such as negotiation and supply, development and production, transportation, storage, and distribution. This situation is a consequence of the logistical difficulties generated by the pandemic, particularly the restrictions on movement between and within countries, coupled with labor shortage problems caused by confinement measures (ILO, 2020).

The logistics of agri-food value chains include all the activities that make possible the flow of agricultural inputs and related products and services, such as transportation, storage, procurement, packaging, and inventory management. Efficient logistic systems are essential for the agri-food sector, especially in times of crisis, since any alteration can have a negative impact on the production and quality of food. Logistic problems have a differential effect, depending on the scale of each agricultural production system. Thus, large-scale agriculture could be the most affected, particularly in cases where production depends on a great variety and quantity of inputs such as seeds, fertilizers, pesticides, lubricants, and fuels. Small producers are less affected because some of their inputs are produced on their farms. However, they must also buy other inputs in local or regional markets, including fertilizers, pesticides, and fuels. The lack of these products and/or the delays in their supply affect producers in general (^{FAO, 2020}).

The basic inputs for guava production include fertilizers, organic fertilizers, and pesticides. In the case of technified producers, purchasing supplies in bulk helps somewhat to overcome input supply problems, even during the pandemic. Intermediate and traditional producers usually buy their inputs from local agro-input suppliers, and sometimes face difficulties to acquire some products due to lack of availability as a result of transport or production restrictions at the country of origin. Furthermore, none of the three groups of guava producers are protected by the economic policies of the Government, to the detriment of the production chain of guava fruits (^{Borja-Bravo et al., 2020}), which worsened during the COVID-19 pandemic.

COVID-19 and commercialization

The commercialization of guava fruits is carried out in collection centers such as ‘La Panadera’, from where it is distributed to the cities of Mexico, Guadalajara, and Monterrey. Shipments are not immediately paid, which in many cases affects producers directly. Furthermore, the price of guava fruits decreased due to decreased demand. The price per kilogram of premium guava decreased from MXN 10.83 to MXN 10.00 on average from January to March 2021 (^{SNIIM, 2021}). This is contrary to what normally occurs, with above-average prices during the months with the lowest market supply, from February to May (^{Ramos et al., 2017}). Another means of commercializing guava fruits is selling them in local markets and ‘tianguis’ (street markets). Unfortunately, adherence to the measures established by the health authorities resulted in the closure or reduction of both types of market. The Aguascalientes city council kept all markets and ´tianguis´ on pandemic alert during most of 2020 and until the writing of this study. The purpose of this alert was to avoid the spread of the disease. Preventive screening systems were also supervised and strengthened filters so that the population could make their purchases without putting their health at risk (^{AA, 2020}). All markets are working at 60% of their capacity and with a customer influx of less than 50%. This explains the reduction in sales of agricultural products in local and regional consumption sites.

Perspectives

Mexican people, especially those working in agriculture, do not have a clear understanding of the measures put in place to control this new disease. There is no doubt that accurate and timely information is the best strategy for mitigating the impact of the pandemic. It is also necessary to have a reliable, simple, and inexpensive screening test that allows increasing the number of outpatient tests. COLPOS developed a low-risk, inexpensive and practical qPCR test based on mouthwash. This test was proposed to SADER as an alternative for agricultural workers (G. Mora-Aguilera, 2021; Personal Communication). China and India have shown evidence that controlling polycyclic diseases, such as those caused by SARS-CoV-2, requires breaking the secondary cycles of infection (community contagion) for up to 15 days to eliminate infectious agents. This cannot be done without a policy that restricts the movement of people. However, movement restrictions are insufficient by themselves and have a high socio-economic impact. This is why vaccination is also being used as a mitigation strategy. Agriculture is an essential activity for Mexico and the world. Classifying it as essential and keeping it active was a successful decision, helping ensure food security during the pandemic. The Ministry of Agriculture (SADER) must prioritize the protection of technical personnel, farmers, advisers, and researchers involved in primary production processes, giving priority to the health of workers in the agro-food value chains and the health of consumers. Health authorities must continue to insist on the application of preventive measures such as the use of face masks, maintaining social distance, the use of alcohol-based gel, frequent hand washing, etc., to reduce the risk of infection by SARS-CoV-2, especially among the rural population, which does not have adequate access to primary and secondary health care systems.