The presence of “El Niño” phenomena is not new in the southern hemisphere. Early this year, weather specialists announced high temperatures, rainfall and abnormal conditions in countries such as Chile, Argentina and Peru, just to name a few, and the spring rains affect cherry growers.

Some of the effects of this includes precipitation during the season of spring, something that worries the agricultural industry due to the consequences this can imply for orchards, cultivations, plantations and in general, to all the work done in the field.

With this in mind it is important to take into consideration the necessary actions to prevent irreversible damages and ensure a productive harvest.

First, we must not forget that rain and high relative humidity conditions in fruit that are about to ripen, alongside high temperatures, generates an increase in the internal pressure of the fruit, which can cause microfractures, the first sign before cracks and possible rottenness. 

But why that much damage? The reason is that the rain that falls over the fruit enters through the osmotic pressure differential inside them that, by this moment, present high content in sugar and other solutes.

Split

Splits is one of the main factors in the selection of fruit to export, discarding those that do not fulfill all the requirements. 

Different studies (Cristensen, 1996, 1998; Ellena, 2001; Lugli y Lugli, 1998; Sansavini y Lugli 1997; Rombolá et al, 2005) show the absorption of water as the main cause in the destruction of the external layers of the fruit. In addition, radicular absorption may result in splits when rain occurs after long periods of drought (Godini, 1997).

Challenging the rain

There are different management strategies that can minimize the split in cherries:

• Protective hydrophobic products: These are protective hydrophobic waxy films based on natural phospholipids or fatty acids that prevent water absorption, preventing fruit splitting.

• In Chile, for example, there are three proven alternatives, which have managed to reduce the incidence and severity of cracks due to rain. Its application should be done at the beginning of straw color/beginning of fruit veracity, considering that it should be done after the application of gibberellic acid.

• It is extremely important to achieve perfect coverage of the fruits, since its effectiveness will depend on the physical protection of the fruits; It is necessary to carry out successive and well-controlled applications to achieve the objective, ensuring that the products are applied to the fruit in a homogeneous manner, therefore tests must be carried out in the target areas, pedicellar cavity and stylar area, which is where the risks should be lowered since prolonged exposure to water in these sectors ends in a split.

• Pre-rain “saturation” irrigation: It consists of carrying out irrigation prior to rainfall in order to reduce the sudden absorption of water by the roots. In this way, it is possible to avoid an abrupt increase in the volume of the fruits, preventing splitting.

• How to do it? Short watering (2-3 hours) should begin about 48 hours before the rain, in order to reach a state of saturation of the soil in the first 20-30 centimeters of depth.

• This strategy should be repeated as many times as necessary in the event of possible precipitation. It is necessary to consider that if this strategy is put into practice very close to the rain, with 12 hours or less, it is advisable to continue watering while it rains. It is a very important strategy to prevent damage in orchards that have plastic covers.

• Ca Chloride (CaCl2): It has been determined that foliar application of calcium could reinforce the structure of cell walls, providing greater mechanical resistance to tissues. Foliar applications of salts such as CaCl2 (and other salts such as K Chloride, Mg Chloride) allow balancing the osmotic pressure between the interior of the fruit and the environment, limiting the absorption of water by the fruits.

• Constant and successive applications must be made before and during the rain episode, considering intervals no greater than 3 hours, in order to achieve the expected objective. Applications should be made in concentrations of 0.5% (500 g./100 L.) if the rain is less than 1 hour; If it is higher, a concentration of 1% CaCl2 should be used, that is, 1 Kg of Ca Chloride / 100 L of water.

• Constant and successive applications before and during rain at use concentrations of 0-5%-1% have proven favorable with proper operation. The operation is complicated because it requires a high demand for the use of machinery since it should be applied with maximum intervals of two hours in the same place while it precipitates to avoid the washing effect of the precipitation.

• Removal of water in the post-rain canopy: Removing water from the canopy of the plants once the rain is over, mainly from the pedicellar area of ​​the fruits, is essential; This task can be carried out with the use of helicopters or misting machines.

In the case of turbofoggers, which are originally used to carry out different applications in orchards, they must be unloaded to dry trees, in order to generate wind flows that allow water to be removed. They should be used at full power, never completely empty, but with a little water so that the machines do not run dry.

The first round should be quick and a second should be evaluated to be able to throw away all the water from the plants. A round with two pieces of equipment in parallel in adjacent rows, which causes the wind flows to overlap for better effectiveness and remove water from the foliage and fruit, can also be considered. Ideally, blowers should be used, since their way of applying air is much more efficient.

Under the same idea of ​​generating wind, helicopters must fly over the plants; The route and height of the helicopter must be designed and established based on its magnitude and power. It is important that when blowing the orchard floor, there is some humidity, in order to avoid raising dust that can be harmful to the fruit and the execution of the work.

The use of helicopters is high cost, but it has been shown to be effective in removing water from trees, preventing splits, especially those that are lodged in the pedicellar area known as crescent.

Additionally, frost control propellers can also be used as complementary methods, as they produce wind that allows the water on the fruit to drain, and which ultimately causes damage.

It is very important that in the event of a rainfall, the orchards have received the proper application of fungicides, always keeping in mind the tolerances, considering the little time left for the harvest.

Finally, it is key to mention that sensitivity to rain occurs from the straw-colored/beginning of color state. Below we share an image that makes it easier to identify this state.