In previous articles, we have talked about the importance and benefits of using agricultural plastics to protect and enhance fruit tree crops such as cherries, and grapes. This time we will refer to everything that has to do with the cultivation of kiwifruit under cover.
In addition to enhancing crops and providing the final product with better quality in terms of size, color and flavor, agricultural producers are increasingly relying on plastic covers to protect their kiwi crops from weather conditions.
Every year there is an increase in reports of extreme droughts, intense storms, fires, or floods, a situation that keeps farmers around the world on alert, as they have witnessed significant variations in the weather that have negatively affected their food production.
Why is it important to use plastic covers in kiwi cultivation?
Controlling the appearance of PSA bacteria or bacterial canker
In the specific case of kiwi cultivation, one of the main reasons for using plastic covers is the need to avoid or control the emergence of PSA bacteria or bacterial canker.
Bacterial canker destroys the nutrient and water absorption system, causing, in the worst-case scenario, the death of the plants, since there is no cure. Therefore, it is essential to avoid its spread and prevent it from contaminating the lands adjacent to the crop.
Generally, the symptoms of this bacteria are present during the spring and fall seasons when the rainy season begins, temperatures drop considerably, and humidity levels are higher.
There are countries such as Italy, and New Zealand where kiwi production has been affected because of the appearance of the PSA bacteria, causing them to enter a state of crisis due to the considerable losses caused by this disease.
Regardless of the geographical area in which the kiwi crop is located, this bacteria can appear if the conditions are right.
The impact of plastic covers on the kiwi crop is significant. Some trials have shown that by using a permanent tunnel it is possible to modify the intensity of light and the microclimate formed inside the structure, without compromising the integrity of the fruit or causing them to lose their properties.
“Covering a kiwifruit orchard with a protective canopy reduces the spread of PSA throughout the orchard when covers are constructed over vines with low levels of infection. The use of plastic covers ensures the production of the current and future kiwifruit without compromising the quality of the fruit,” according to information published on the website Research Gate.
Modifying the climatic conditions within the crop
The use of plastic covers in kiwi cultivation moderately increases the temperature, relative humidity, decreases radiation and reduces the wind inside the crop to almost zero. This reduces atmospheric demand and creates the ideal scenario for kiwifruit to thrive, as it resembles its climate of origin.
Warmer temperatures help limit bacterial growth, while plastic covers keep leaves dry, thus controlling the pathogen, which needs water and moisture to multiply and move.
When kiwi plants are in better growing conditions and not exposed to direct radiation, they usually require fewer nutrient inputs to obtain excellent levels of phosphate and nitrate. In addition, the warm environment helps them to cope with climatic shocks, especially in times of frost.
With no wind under the canopy, nor reaching the dew point, even when there’s rain, the PSA pathogen has reduced options to move and develop during critical periods. This allows the plant to get through seasons such as spring or fall with a minimal bacterial load.
Improving product quality
Thanks to the modifications of the climate generated under cover and the control of pathogens, the product obtained at the end of the harvest season are usually more homogeneous, uniform in size, shape, and of higher quality.
Advancing or delaying harvest
Also, agricultural producers use plastic covers to their advantage to advance or delay harvests, depending on the requirements and what they want to obtain during the growing season.
This benefit of advancing or delaying the harvest makes it possible to enjoy the product in seasons where it would not usually be available under conventional conditions, which could translate into higher yields of the kiwi crop under a canopy.
To learn more about this topic, we recommend reading our article on agricultural plastic covers.
On the other hand, we also suggest watching our webinar on plastic cover solutions for fruit trees.
If you would like to consult the type of plastic cover that is best suited to your kiwi crop, do not hesitate to contact our team.
What other measures can be applied to protect the kiwi crop from PSA bacteria?
Currently, many growers emphasize maintaining adequate control of plant material entering and leaving the kiwi fields, applying measures such as:
- Cleaning and disinfection of their tools to avoid contamination between plants.
- Crop protection through preventive applications of authorized pesticides.
- Continuously checking the crop for symptoms of infection on the leaves.
Another measure that can be implemented, especially when there are PSA-positive orchards, is to eliminate plant debris on the ground when pruning work is being done. In this way, a comprehensive management program can be prepared to allow the plant to be in a position to defend itself.
Types of structures in kiwi cultivation under cover
Before talking about the structures, it is worth mentioning that kiwifruit is a subtropical crop, so it should be planted in temperate climate zones.
It is important to protect the crop from the wind because the anchorage of the tree can be compromised, as well as the activity of bees for pollination or destruction of its bushy shrub.
With these considerations in mind, kiwi requires plant support structures with poles, usually made of concrete, and steel wires. Two types of structures are generally used to improve the quality and homogeneity of the product:
- Tunnel shape with metal arch.
- Roof shape, also known as T-bar system.
The T-bar system “uses T-shaped posts connected to each other by 3 wires. It is on these wires that the plants hanging in the middle of each post will be supported. They are located at an approximate height of 1.6 to 1.8 m. The plants need support twine to guide them to the top of the wire bower, and this support or tutor twine can be any of the existing ones in the market, or cords or wooden stakes,” according to information published on the website Infoagro.
It is recommended that the distance between the posts where the plastic cover will be placed is six meters so that the plants have enough space to thrive.
When producers want the male plants closer to the females, they guide them on a lower wire along the lines, adopting the Geneva Double Curtain formation (GDC).
Mostly LDPE-type covers are used, but some prefer raffia-type plasticized HDPE fabrics, especially in the case of roof-type structures. However, for both covers, it is necessary to place reinforcements on the sides so that they are well fixed and can withstand the wind or rain.
For further information, we recommend reading our eBook on fruit cultivation and the use of plastics to enhance production.
Markets where kiwi is grown
A bit of history
Although many people in the world tend to associate kiwifruit with New Zealand, since it’s the country with the largest production of this fruit, the truth is that kiwifruit cultivation originated in the mountains of China.
The cultivation of this climbing plant was spreading significantly to other parts of the world such as New Zealand, where in the early 20th century they managed to adapt it to the climate of the region, and later they gave it a more commercial vision of export and intensive cultivation.
In the 1970s a large kiwifruit production was achieved in the United States, and by the 1980s the fruit was already attractive in countries such as Brazil.
In Spain, by the 1960s, consumption was scarce and the few fruits that arrived were marketed at very high prices. Subsequently, it was decided to try and adapt kiwi cultivation in the region, and production was boosted in the 1980s. It is currently one of the most consumed fruits in the country.
Regardless of its variety, kiwi is becoming increasingly popular in different markets around the world and the cultivated area has been growing exponentially in the main producing countries such as New Zealand, Italy, and China.
In Chile, there is a new upturn in the crop with an estimated 7,500 hectares of fruit that is also produced in France, Greece, Spain, Turkey, and Iran.
“A large part of the annual production of Chilean kiwi is exported to 69 countries around the world, with the USA, Canada, Colombia, Italy, the Netherlands, Russia, and Spain being the main destination markets for different varieties such as Hayward, Jintao, Dori, Soreli, and Summer kiwifruit, mainly” according to information published on the website Red Agrícola.
Brazil also has a large number of hectares of kiwifruit cultivation, especially in areas such as Rio Grande, Santa Catarina, and Paraná.
However, the presence of poor weather conditions in early 2021 meant that some European production areas were impacted.
According to information reported on the website Fresh Plaza, producers in Spain fear that their production has decreased by up to 45%, while Italy forecasts a 60% decrease in volume compared to its peak productivity.
Elsewhere the outlook is more positive, with New Zealand expecting another record season, and China expecting a good domestic season. “Kiwifruit marketing is going well in Europe, with the Netherlands reporting a 47% increase in fruit sales, while in North America there is good demand, but some shippers fear that logistical problems could cause inconveniences later in the season, something that has also affected the Chinese market,” according to the information reflected in the article of Fresh Plaza.
If you need more information about the cover films that can best suit your kiwifruit crop, don’t hesitate to contact our team.