Handbook of Vanilla Science and Technology

The chinche is controlled when it is present at low population density, simply by killing them by hand in the early morning hours (when they are most present and least active). An organic control is prepared from 3 onions, 3 heads of garlic juiced in a blender, and a bar of pH neutral soap (in pieces), all dissolved in 40 L of water. The solution is left to sit for 48 hours and applied to the vanilla plants with a sprayer. Applied correctly, it is more effective at eliminating chinches than other insecticides (Hernández-Hernández 2008). 

An alternative organic control is oil from the neem tree (Azadirachta indica). The dosage is 4 mL of neem oil per 1 L of water. Neem oil is a natural insecticide that is biodegradable and non-toxic to beneficial insects and to humans.

Vanilla also suffers herbivory from caterpillars that occasionally damage floral buds.

1.11 MAIN VANILLA DISEASES

Root/stem rot (Fusarium oxysporum f. sp. vanillae) is a fungus that causes rotting of the roots, stems, and fruits, and plant mortality. It is found to some degree wherever vanilla is cultivated, principally where management is deficient and/or in plants that are bearing fruit. In Mexico, it is estimated to kill 67.4% of vanilla plants within 4 years of planting (Hernández-Hernández 2004).

When Fusarium infects the plant, it is very difficult or impossible to eliminate. Prevention is the best practice, and can be achieved by different techniques: using well-drained ground, planting only healthy and vigorous plants, ensuring the roots are always protected with a layer of organic material/compost, meeting nutritional requirements, looping and rooting shoots, avoiding over-pollination, regulating shade, and eliminating diseased plants or buds.

Fungicides may be applied during the rainy season, once to twice per month to prevent infection. Either carbendazim or Bordeaux mixture can be used, in the dosages indicated.

1.11.1 Anthracnose

This disease, caused by the fungus Colletotrichum sp., attacks leaves, fruits, stems, and flowers. It is identified by small, sunken spots that are dark brown. Infected fruits fall from the plant before they mature, and so overall yield decreases, sometimes by as much as 50%.

Anthracnose is prevented by ensuring that roots are healthy and that the plant is well-nourished. Fungicides can also be applied, such as inorganic copper oxy-chloride or Mancozeb at concentrations of 2 g/L in water or Bordeaux mixture. The application is done immediately after the cool winter winds (nortes) begin.

1.11.2 Rust

Rust (Uromyces joffrini) is identified by the presence of round pustules that are yellow-orange on the underside (abaxial side) of the leaves. As the rust develops, the pustules grow and merge together, eventually drying out the entire leaf. Rust is most frequently encountered in more traditional cultivation systems where there is little ventilation, excessive shade, and where precipitation is too great.

Plants infected with rust cease to develop, and so their productive capacity is reduced. Untreated, rust can defoliate entire plants or plantings.

When the symptoms of rust are first observed, growers immediately eliminate leaves, increasing the amount of light filtering to the plants. Bordeaux mixture or other products that contain copper are then applied weekly, at concentrations of 2.5 g/L of water. Infected leaves are taken out of the vainillal and buried.

1.11.3 Yellowing and pre-mature fruit drop

Yellowing and fruit drop of immature fruits manifest at high temperatures exceeding 32°C, and low relative humidity (<80%), during months of intense sunlight.

The fruit drop occurs 2 months after pollination, mostly in June, after a strong rainfall. Fruit drop varies from 15 to 90%, depending on the cultivation system.

In diseased fruits, two fungal species have been identified: Fusarium incarnatum-equiseti species complex and Colletotrichum sp. The Fusarium is the most commonly encountered, and is thus considered more responsible for causing fruit drop, but only under the environmental conditions cited earlier. In Mexico, these species have only recently been identified (Hernández-Hernández 2007). In India, other species of Fusarium have also been identified and reported to produced the same problem (Vijayan and Kunhikannan 2007), although Colletotrichum vanillae has also been isolated there as well (Anandaraj et al.2005).

During flowering and fruit development, growers should eliminate the stressful conditions that lead to fruit drop, by maintaining 50% shade and by misting plants. Vanilla should not be cultivated in areas with poor ventilation since this raises temperatures, and leads to problems of stress and pathogen development.