In an previous article, one of our readers asked in the comments section about "pre-emergent selective chemical herbicides for weed control for the cultivation of the agave, or the one that affects the crop the least, as well as of a fungicide to prevent or control fusarium". It seemed to us such a pertinent question, that we decided to give it an answer as a blog post, so that it remains at hand for any other reader who may have the same question.
Without further ado, this is the response of our experts.
In the case of the agave, several herbicides are used, both pre-emergent and post-emergent. We can find in the market different products that can be used in the crop and in the case of the pre-emergent, if they are applied to the ground exclusively, without wetting the agave leaves, they won't cause serious damage to the crop. However, there are no selective products for the agave and, if any of them is indeed absorbed by the roots (those with high solubility), they will affect and weaken the agave.
Those that have been used during different times and that have caused various damages such as chlorosis, weakening, reduction in growth rate, are:
Yet, if they are applied correctly and in the appropriate doses (correct calibration) the damages can be minor.
The phytotoxicity of some of these products can be reduced based on their application, looking for ways or adjuncts to reduce the wetting of the young leaves of the agave, since they are the ones that absorb the greatest amount of agrochemicals, unlike the older leaves.
So far, it hasn't been possible to demonstrate that Fusarium oxysporum is the only cause of the wilting symptom of the agave, although some species of Fusarium sp or strains of Fusarium oxysporum are invariably found in withered plants. In general, it has been observed that whenever aggressive herbicides or those that can damage roots are used, the plants show wilting symptoms after the third year (mostly at the fourth year).
When an agave plant is colonized by cerambycidae or white worm, or damaged by rhinoceros beetle between the first and third year, wilting symptoms are also detected around the fourth year. When a plant is affected by any of these insects and an aggressive herbicide (pre or post-emergent) is applied, the symptoms become even more evident and serious.
Various studies have found that the application of natural enemies to Fusarium, such as Trichoderma sp and Bacillus subtilis, reduces the colonization of Fusarium at the root. However, in many occasions the wilting doesn't decrease due to borer insects, herbicides or to the flooding of certain areas.
It's also been detected that applying compost fosters the development of microorganisms that are natural enemies of Fusarium sp.
In general, it's important to have an integrated crop management, considering that:
We hope that the questions of our reader were fully answered with this blog post. Subscribe to our blog about tequila production processes, so that you stay updated with our information. You can also come to Casa Sauza and take one of our guided tours so you can learn more about how our tequila is made, from the plantation of the agave, to bottling of the spirit.