Kiwi is a very popular fruit, boasting numerous nutritional benefits , but at the same time it is also very vulnerable to various diseases . There are two varieties of kiwi; the most widely cultivated is known scientifically as Hayward (the classic green kiwi). This fruit grows in certain favorable environmental conditions : temperatures between -15°C and 20°C – 30°C; exposure to sunlight; and permeable and draining soil.
Despite these conditions, kiwifruit remains highly susceptible to disease . For this reason, the importance of prevention is emphasized. In this article, we will discuss the main diseases affecting kiwifruit and the most effective defense strategies.
Kiwi bacterial infection (PSA)
Kiwi bacterial blight , the acronym for which is PSA , identifies the bacterium responsible for the disease, Pseudomonas syringae pv. actinidiae . This disease affects both kiwi species and is therefore considered the most dangerous . Furthermore, it is also the most common disease in Italy.
What are the indicators of bacterial infection?
The most common symptoms are:
- Presence of necrotic spots on the leaves , which most often have a yellowish edge .
- Appearance of whitish or yellowish bacterial exudates .
- Possible internal darkening of the wood (visible when the branch is cut).
- Gradual withering of buds and young shoots , until they dry up completely.
- Areas of drying out on both branches and shoots.
- Collapse of the plant , in the more advanced stages.
It’s important to note that this disease is favored by cold, humid periods and can rapidly worsen following weather events that facilitate its spread . These include heavy rain, hailstorms, or frost . Another critical time is between fruit harvest and leaf fall . This, too, is a period characterized by rain and temperatures ideal for the bacterium. The latter, in fact, easily infiltrates through wounds caused by kiwi harvesting and the microlesions created by leaf fall.
During the winter months , reddish exudates may form, while in spring, flower dieback and blackening of the shoots can be observed. Leaf necrosis may also occur. In summer , however, the leaves show black-reddish spots , a clear sign of the presence of the disease.
If you spot a diseased plant , it’s essential to intervene immediately . How? It’s recommended to remove the affected branch or uproot the entire plant if the infection affects the trunk.
Defense strategies against bacterial infections
The most effective methods for combating bacterial blight in kiwifruit are monitoring and prevention . In the first case, targeted actions allow for timely intervention , thanks to which the spread of the bacterial blight is limited and damage to the plants is reduced. Furthermore, frequent monitoring allows for the identification of the most favorable climatic conditions for the development of the bacterium, mentioned above. Temperature is also a key factor in the spread of the bacterium: if it is between 15°C and 25°C, accompanied by rain , it will favor its development. Another element to take into consideration is the time period: the most favorable moments for the spread of the bacterium are from the beginning of the weeping phase until pre-flowering , a period in which rain often occurs and temperatures are low. In these conditions, branches and trunks with exudates can easily infect other plants, especially in the presence of wind and heavy downpours. The purchase of certified plant material also represents a method of defense against PSA. In addition, it is recommended to avoid excessive nitrogen fertilization .
Dark Spots on Kiwi Fruit: Causes and Symptoms
This disease manifests as dark , irregularly shaped spots on leaves and fruit . These spots can merge , forming large damaged areas that reduce the commercial quality of the product and hinder its growth . Among the main causes is the action of a pathogenic fungus, responsible for the disease, which develops in humid environments.
Fungal soil diseases: root rot and dieback
Among other diseases that can affect kiwifruit is root rot . Caused by the Phytophthora fungus, it damages the roots of the kiwifruit , limiting the absorption of water and nutrients. The first signs of the disease include discoloration of the leaves and a general slowdown in growth . In more severe cases, the plant can collapse. The fungus thrives in poorly drained and constantly moist soil. For this reason, good water drainage is strongly recommended and waterlogging should be avoided .
Armillaria mellea , commonly known as “honey fungus,” is another very dangerous pathogen for kiwi plants, but also for crops such as peaches, apricots, citrus fruits, olives, vines, and many others. As for defense, there are no chemical treatments; therefore, the solutions are prevention and agronomic management . These include improving drainage , avoiding water stagnation , and excluding fresh organic matter . Finally, using biodisinfectants and antagonistic microorganisms (e.g., Trichoderma) is useful for limiting its spread and protecting healthy plants.
Physiological problems and nutritional deficiencies
Potassium, magnesium, and iron deficiencies are another cause of disease. Iron chlorosis , in particular, is caused by iron deficiency. It causes yellowing of the leaves . More precisely, it’s not a lack of iron, but rather the presence of a form of the mineral that plants are unable to absorb. Calcium plays a key role in this phenomenon: if present in large quantities, it promotes the formation of insoluble iron compounds .
To prevent this, you must first perform a soil analysis to assess the calcium level . If the disease is already present, however, it is essential to water the plants in spring and, if necessary, use fertilizers based on microelements and high concentrations of iron .
Kiwi Pests: What They Are and How to Control Them
In this section we will discuss the main insects that are harmful to kiwifruit, which include:
- Eulia : a moth whose larvae damage kiwifruit by attacking the peel , leaving scars . They can even cause rot . It is controlled using Bacillus thuringiensis .
- Metcalfa : An insect that produces honeydew , primarily responsible for aesthetic problems. This substance is also produced by aphids . Honeydew is nothing other than the secretion of these insects. In addition to aesthetic damage, honeydew can act as a substrate for fungal infections. It can be controlled with Marseille soap or sweet orange essential oil.
- White scale insect : especially dangerous for smooth-skinned kiwis . It can be controlled with mineral oil, manual cleaning, or fern macerate.
- Green leafhopper : it drains sap, causing yellowing and deformed leaves . The products used to remove it are the same as those used for the green leafhopper.
- Red spider mite : causes discoloration and cobwebs. Repellent macerates , such as garlic or nettle, are recommended.
- Noctuid larvae : they feed on young shoots. In this case, Bacillus thuringiensis is also being referred to.
- Halyomorpha halys : known as the Asian stink bug , it causes deformations , tissue necrosis , and pulp alterations , making the fruit unsuitable for sale . Specific traps and insecticides are necessary to eliminate this pest.
Strategies to reduce risks
In light of what has been said so far, the importance of prevention to protect kiwi plants is emphasized. Furthermore, kiwi cultivation requires constant attention , as the aforementioned threats can quickly compromise productivity and quality. Therefore, in addition to agronomic practices, it is essential to have accurate and timely information on the actual condition of the plants. Plantvoice was created precisely with this objective: the device, inserted into the trunk, detects the health of the plant in real time and constantly monitors its well-being. Thanks to the data it provides, it becomes possible to identify stress or imbalances and thus intervene at the most effective time. Plantvoice therefore represents an innovative tool for protecting kiwis and maintaining long-term productivity .
FAQ
- Why is kiwi particularly vulnerable to disease?
Kiwi is susceptible to disease because it requires specific growing environments, such as moderate temperatures, sun exposure, and well-drained soil. Despite these conditions, the plant is susceptible to several diseases that can compromise its health.
- How can I prevent kiwifruit bacterial infection (PSA)?
Preventing kiwifruit bacterial blight includes constant plant monitoring, the use of certified plant material, and plant protection during critical periods. It’s also important to avoid excessive nitrogen fertilization, which could encourage the development of the bacterium.
- What are the main symptoms of dark spot on kiwifruit?
Kiwi dark spot appears as dark, irregular spots on leaves and fruit, which can merge to form large damaged areas, compromising the growth and quality of the fruit.
- How can I combat parasites that damage kiwifruit?
Pests such as white mealybugs, green leafhoppers, and red spider mites can be combated using natural remedies such as mineral oil, Marseille soap, fern macerate, or repellents based on nettle and garlic.
Take care of your plants with Plantvoice .
