Handbook of Vanilla Science and Technology

Between rows, weeding is performed with a hoe or machete. At the base of the plants themselves, weeds are carefully pulled out by hand in order to not disturb the shallow rooting structure of the vanilla plants. After removal, weeds that are annual herbs can be added to the mulch or composted and added later. Perennial weeds, such as Commelina diffusa and Syngonium podophyllum, are removed from the vainillal because they do not readily decompose. Weeds should be dealt with whenever they impede access to the vanilla plants and/or when support trees defoliate a disproportionate amount. In general, weeding is performed 3 to 4 times per year.

In shade houses, the rows between plantings are covered with milled “tezontle” (reddish, porous volcanic rock) or ground limestone, in order to prevent the growth of weeds.

1.7 SHADE MANAGEMENT (PRUNING OF SUPPORT TREES)

In vainillales with living support trees such as Erythrina sp. or Gliricidia maculata, shade is controlled by periodic pruning, usually 2 or 3 times per year. Pruning should be timed to take place in the rainy season (July-November) to avoid the development of diseases in vanilla due to inadequate sunlight. Shade levels are between 30 to 50% during the rainy season. In dry and hot times of the year (March-June), which coincide with flowering/pollination and fruit development, support trees should have a denser canopy to provide 70 to 80% shade, which conserves humidity, prevents burning from intense sunlight, and decreases the incidence of young fruit drop.

Pruning is accomplished by removing the thicker central branches and leaving the laterals in order to achieve a canopy in the shape of a parasol that also maximizes the equitable distribution of vanilla shoots. Branches are pruned with either saws or machetes, down to about 40 cm from where they diverge from the trunk. The thinnest of the cut branches are broken into longitudinal pieces and placed at the base of the support as an additional source of organic material. Thicker branches are removed from the vainillal entirely. Over-pruning results in sunburn to the vanilla plants, and should be avoided.

With orange tree supports, shade management also consists of eliminating young buds, which impede the growth of the vanilla plant. Shoots of the orange tree are pruned when they over-shade the vanilla, which are generally the unproductive or dry/dead shoots. This pruning is generally performed once to twice per year following flowering and the harvest.

1.8 SHOOT MANAGEMENT - LOOPING

The most common practice involving shoot management is “looping”, i.e. re-directing a growing shoot over a branch and towards the ground once it reaches the height of the first branches of the support tree. This practice maintains the height of the vanilla at roughly 2 m, facilitating hand pollination and harvesting. Another consequence of looping is hormonal induction promoting flowering and new shoot formation (usually just below the height of the fork in the tree where the shoot is bent). Shoots are managed so that they are equally distributed among the branches of the support tree such that no one shoot shades out another.

1.9 SHOOT MANAGEMENT - ROOTING

Once a shoot has been looped and has reached the level of the ground, a portion of it, usually 2 to 3 internodes long, is buried, leaving the growing apical meristem uncovered. This practice promotes root formation at the buried nodes. The shoot apex is fastened back to the support tree to continue growing. Rooting of shoots is performed every instance a new shoot has reached ground-level, helping to maintain the vigorous growth of the plant, which obtains more nutrients and is more resistant to F. oxysporum. In this way, rooting helps counteract the mortality of plants due to pathogens (Hernández-Hernández 2005).

1.10 MAIN VANILLA INSECT PEST

The “chinche roja” (Tenthecoris confusus Hsiao & Sailer [Hemiptera: Miridae]) is a small insect that passes through many life stages, including 4 instars. At the nymphal stage, it measures less than 5 mm in length (Figure 1.2). It is at this stage that it causes the most damage to vanilla. As an adult, the chinche measures 5 to 6 mm and is black and red, from where it gets its name (Perez 1990; Arcos et al. 1991; Sanchez 1993).

Fig. 1.2 The main vanilla insect pest, ''chinche roja'' (nymphal stage).

The chinche is the single most damaging vanilla pest, causing tissue damage in the leaves, stems, and fruits. The wounds left by the chinche allow for the colonization of fungus and bacteria that cause rot, wilting, and defoliation.