Colombia, The Revenge

ARTICLE

All industries have faced setbacks in their early stages, learning over time until they reach maturity. The Hass avocado industry in Colombia, after several obstacles, is finally consolidating successful management practices to achieve growth and improve its production. Before the pandemic, many foreign companies viewed Colombia as a second Mexico, capable of supplying Hass avocados year-round to the entire world, raising expectations for developing projects in the country. But nature had other plans, giving a harsh welcome to all the new projects that had to endure the harshest winter in Colombian history, with two consecutive years of rain, and recently one of the most severe summers ever experienced. And it seems that this will be the trend for tropical avocados with global warming, where orchards without irrigation will lose productive potential and, due to increased stress, rapidly develop wood rot.

In the search for water, which Colombia has in abundance, many projects were located in high-altitude areas, some even too high, near the páramos (high-altitude Andean ecosystems) where sunlight is so low that avocado orchards developed a vicious cycle, unable to naturally induce flowering. The luckiest orchards survived, but had to wait more than four years for fruit to set, losing precocity and impacting the project's profitability. While higher elevations have fewer pests and diseases, they also offer lower yield potential; however, they have a commercial advantage: the mild climate allows for the production of stress-free fruit with better internal quality, which can be kept on the tree for longer periods, waiting for the optimal market window.

Lower elevations have greater precocity and a higher fruit set potential, with fruit set occurring in almost all flowerings, but when working without irrigation the plants produce a more stressed product similar to the Peruvian avocado, which presents serious condition problems.

Churchill defined success as the ability to go from failure to failure without losing enthusiasm. And that is how Colombia is currently consolidating the fundamental steps to begin the Revenge, which always comes.

1. Irrigation: Essential, especially at elevations below 2,000 meters above sea level, as summers will become increasingly longer and harsher. Irrigation is crucial not only for irrigation during the dry season but also for fertigation, since nutrient nutrition is very complex in soil so deficient in phosphorus, calcium, potassium, magnesium, zinc, and iron. Monthly manual fertilization, with its high inefficiency, results in weak trees susceptible to pests and diseases. Furthermore, fruit produced in malnourished orchards is of low quality, yielding small sizes and, even worse, very poor condition, leading to losses at the destination. It is very difficult for the Colombian industry to be competitive without investing in fertigation. Installing water storage tanks at water sources is necessary to achieve weekly applications in summer and every 15 days in winter, which is usually sufficient. If the winter is prolonged and harsh, foliar fertilization should be used, but fertilization should never be discontinued.

2. Soil Management: Avocado trees planted on coffee plantations survived, but orchards planted on cattle pastures with long-standing trampling experienced severe drainage and waterlogging problems due to compaction in the top few centimeters of soil. Currently, many orchards require complete restoration and have a high load of pathogenic microorganisms such as Phytophthora sp. and Fusarium sp., which must be brought under control.

The initial trials of raised beds have been very successful, effectively loosening the soil and mixing layers in areas with a poorer profile, thus facilitating drainage and oxygenation of the root zone. Once the raised bed is constructed, a period of soil profile maturation follows, during which rainfall compacts the soil, making it ready for planting after 2-3 months without erosion problems. In areas with Law 2 (a local agricultural law) where machinery is prohibited, the solution has been manual, using a rotary tiller along contour lines to subsoil the soil profile. This is then replaced with a moldboard plow to create a small raised bed. With the first winter rains, it is recommended to use a Hercules implement in low-lying areas that receive more moisture to ensure drainage around the weakest plants.

It is very common in Colombian soil management to find hand-dug trenches or half-moons placed over plants that, rather than draining, attract water, effectively becoming channels for moisture. Vertical trenches can help, but diagonal or horizontal ones only cause the death of surrounding plants.

Roads are also essential, as they not only allow the movement of machinery to facilitate harvesting but also help drain the soil. In some areas, hillsides have been observed to weep for more than a year due to the presence of significant underground moisture pockets. It is recommended to design the orchard, till the soil, build roads, and observe the water runoff after winter before planting, as most hillsides have geological faults that must be identified before cultivation.

3. Nurseries: These need to be addressed, as there is a great deal of informality in the Colombian nursery industry. Opinions on the ideal rootstock vary, but the results are clear and similar to those in other industries. The "criollo de tierra caliente" (hot-climate Creole) is a West Indian variety that performs moderately well in its native region. When taken to higher altitudes, it suffers from cold stress, grows poorly, and, like any good West Indian variety, does not tolerate excessive humidity. The "criollo de tierra fría" appears to be a hybrid with Guatemalan ancestry, exhibiting high heterogeneity. Thus, in cold and humid areas, the Hass rootstock is currently preferred, not because it is exceptional, but because there is no better option. With such a limited selection of rootstocks, designing successful orchards is challenging, but good results are being seen with Zutano, Semil, and clonal rootstocks. It is important to consider that clonal rootstocks have two grafts, and the level of specialization required to produce a good clonal plant takes time. Caution should be exercised when choosing a nursery, with Zutano and Semil rootstocks being the most prudent approach.

Another important factor is wood fungus, which is easily observed at the scion-rootstock union, requiring the use of fungicidal paint to sanitize this sensitive area. When using V-grooves or inlay grafts, it is more difficult to match the diameters, leaving too much air between the tissues and causing oxidation. The industry is reluctant to use side grafts, so it will take time to improve this technique. Finally, the grafting height is important, as the higher the graft, the weaker the budding of the scion, and vice versa.

Ideally, work with small plants to avoid root circling and facilitate their acclimatization in the field by performing a sanitary drenching when receiving the material from the nursery.

4. Pollinators: There is good overlap of male and female flowers in Colombia, with some variations depending on altitude, leading some to believe that pollinating varieties are unnecessary in this country. However, when summer arrives, the stress is so high that abortion can occur in small, medium, and large pre-harvest fruit, raising questions about the embryo's vigor in the face of water stress. In the field, the Edranol variety has shown poor effectiveness as a pollinator, while the Zutano variety has been very effective, as in several regions worldwide. This pollen contribution is important in Colombia for achieving vigorous hybrid fruit, since the embryo must withstand two summers between flowering and fruiting, producing stress hormones that cause abortion.

5. Growth Regulators: Lower elevations with higher temperatures and sunlight tend to be earlier, but higher elevations, which are cold and cloudy, require intervention to balance bud break, stimulating lateral branching to accelerate the onset of production. Management practices vary considerably depending on the temperature threshold, allowing for different planting densities for warm versus cold climates to prevent overcrowding.

Growth regulator applications should begin at planting, aiming to set the first few flowers within the first year. This may yield 2 to 3 fruits per tree, which isn't very productive, but strategically it's very important for opening the angle of insertion of the main branches, promoting an open canopy at an early age. If fruit set doesn't occur within the first year, branch pruning is recommended.

6. Girdling: At mid and low altitudes, branch girdling allows for modification of the crop's phenology, targeting the best commercial windows. It can be used to slow bud break, induce flowering, and promote fruit set, thus reducing fruit drop. At high altitudes, in cold and cloudy conditions, the results are highly erratic, showing improvement in 6 to 12 months depending on the length of the winter.

The thickness of the incision varies according to the level because the healing speed is different.

It is recommended to paint the wound immediately to prevent wood fungus.

7. Pests and Diseases: This is one of the areas in which agricultural professionals in Colombia have the most expertise. Learning is rapid, especially if investment is made in training to develop effective field monitoring equipment. Pests change from summer to winter, but mite infestations are becoming increasingly severe and persist for almost the entire season, with observed resistance to acaricides.

At the beginning of fruit set, pesticides with greater residual activity are used, but then as the fruit development progresses, care must be taken with the residues to avoid rejections at the destination.

The most important thing is to keep plants healthy and in good condition so that monitoring will be effective, allowing pests and diseases to be controlled in their initial stages.

Developing microbial consortia that stimulate root growth and also reduce soil pathogens is fundamental to achieving a healthy and productive orchard.

8. Pruning: In the tropics, under conditions of high relative humidity and cloud cover, plants grow weak and sluggish over time, failing to generate new roots and exhibiting accelerated aging by the seventh or eighth year, collapsing and dying quickly. Pruning and balancing the foliage with the root system helps the plant maintain its youthful appearance. Open foliage with better ventilation leads to fewer diseases, as light is essential, increasing the effectiveness of sprays.

The vast majority of orchards in Colombia either don't prune or prune poorly, performing only timid topping at higher elevations, maintaining a closed and dark canopy, and concentrating fruit set only on the periphery of the foliage. An open and well-ventilated canopy allows for an increase in the cubic meters of productive foliage, resulting in protected fruit without stress and with better post-harvest characteristics.