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Management of Banana as a “Fruit Tree” in the landscape

Posted on Jun. 27, 2024  /  Best Practices, Plant Pests, Arboriculture, Edible Landscapes  /  Subscribe 0

By: Alberto Ricordi and Amjad Ahmad

Banana one of the most common fruit trees in Hawaiian managed landscapes. It is commonly found in residential and institutional properties, such as school gardens. One of the main challenges for landscapers dealing with banana are maintenance of the “clump” or “banana mat” including suckers “keiki” and dead leaves, and banana bunchy top virus (BBTV) infected plants.

Banana in the landscape design

Fruit Tree: Banana is most commonly used in landscapes as a fruit tree.  It bears fruit in one to two years after planting, is readily available in local nurseries, and is relatively easy to eradicate if needed with the appropriate tools. It requires full to partial sun, consistent water supply for good production, and tolerates drought. It’s also very versatile when it comes to soil conditions, however, it does better in soils high in organic matter and not very windy condition.

Wind break, visual screen, and border plantings: Bananas may be used as windbreaks and border plants (Figure 1). However, unmanaged banana mats (mat is the term used for a bunch of banana plants from the same corm) can lead to pest and diseases, which will be discussed in more details below.

Figure 1. Banana used as an accent plant in a residential landscape. Note that one of the stems is touching the roof, which is a cause of concern for pest control. In this case, the banana bunch was harvested but the stem was not removed. Photo: Alberto Ricordi

Accent or Shade tree: Bananas can be quite attractive in a tropical landscape as an accent in the garden, especially in small to medium sized residential gardens. They can also be planted in groupings in larger landscapes. Banana mats can provide shade, however, the location and amount of shade is not consistent since fruiting stems are removed or left to die off after harvesting (Figure 2).

Figure 2. Banana used as an accent plant in a residential landscape, to also provide shade to the adjacent hot tub. Note that one of the stems, in the foreground, “re-sprouted”. Photo: Alberto Ricordi

Maintenance of the banana clump/mat
It is very important to trim the clump consistently. The rule of thumb is to keep three stalks: grandmother, mother, keiki (Figure 3). Once the “grandmother” stalk fruits are harvested, it should be removed, and a new keiki should be allowed to grow. Pay attention to the direction of the keiki. Remove keiki that does not grow in the desirable direction and to keep relatively consistent distance between banana mats. If properly removed, keikis can be replanted to start new banana trees.

Keikis should be removed from the base and preferably with some roots (Figure 4). They will continue to grow if the meristem (growing tip) is left attached to the tree. Re-grown stems from improperly cut stems or keiki tend to be weaker and produce smaller bunches.

Figure 3. A managed banana clump in a farm with the 3 stem practice: grandmother, mother and keiki. Photo: Amjad Ahmad

Figure 4. How to properly remove keikis, to allow propagation and prevent re-growth of the stem from the clump. This keiki was selected for removal because it was growing towards the hot tub steps, which would block access to the hot tub or cause damage to the steps or equipment if left unattended (A, left). Note that the keiki was removed with roots attached to it (B, right). A spade shovel or o'o bar with a flat end (Truper Bar-Post Hole Digger/Tamping Bar) are good tools for keiki removal for propagation.  Photos: Alberto Ricordi

Banana Bunchy Top Virus (BBTV)
A previous article on Banana bunchy top virus (BBTV) was published at LICH Magazine in July/August 2022.  BBTV is a plant pathogenic virus of the family Nanoviridae known for infecting banana plants and other crops. The virus is transmitted by the banana aphid (Pentalonia nigronervosa) and is also spread through infected planting material, such as keiki removed from infected corms. Therefore, pest control and use of clean starting material are very important (Figure 5).

Figure 5. Dr. Amjad Ahmad with virus free banana plantlets propagated via tissue culture. Source: CTAHR 2023 Extension Award

Once infected, plants do not recover, which shows the importance of preventive measures. Infected banana keiki may take up to 3 months (based on variety) to show infection symptoms (Figure 6). The typical symptoms of BBTV are very distinctive and readily distinguished from those caused by other viruses of banana. 
The most distinctive symptoms of BBTV are:
• Infected plants exhibit a rosetted or ‘bunchy top’ appearance (thus the name of the disease);
• Yellowing and curling of leaf margins on BBTV-infected banana;
• Stunted plants arising from infected suckers, and
• Dark green 'dot-dash' patterns in minor leaf veins forming 'hooks' where they enter the edge of the midrib.

As mentioned before, there is no cure for BBTV. Infected plants should be completely removed and a clean plant material should be planted. The longer infected plant left in an area before removal, the longer will be needed to replant banana in the same area due to the concentration of the infection in that area. Here are some methods to test for BBTV and properly remove infected plants:
1.    If an infection is suspected, a BBTV testing kit would confirm the visual diagnose (example of BBTV testing). However, this kit requires additional tools and is not suitable for individuals. Seeking a laboratory with testing capacity would be more suitable. Field scouting and testing suspected plants is very important, prior to using them for propagation (macro- and micro-propagation techniques) to ensure all propagated plant materials are disease-free.
2.    Removal of infected plants: remove all parts of the plant, including the “corm”, to prevent new shoots from growing (keep in mind, any keiki from an infected corm will most likely be infected too). Glyphosate may be used to kill plants via trunk injection using at the rate of 1ml of Roundup per 2 inches diameter of the banana pseudostem (trunk);
More information on BBTV is available in this CTAHR website.

Figure 6. Symptoms of bunchy top: bunchy growth, yellowing and curling leaf margins, and stunted growth. Photo: Amjad Ahmad

Pest control – (Conventional & Organic)

The use of crop protection chemicals may help to prevent and delay BBTV infection in a field setting. The banana aphid (Pentalonia nigronervosa) is the insect vector for BBTV. The use of crop protection chemicals (synthetic or organic) in a rotation, of at least 3 products, will prevent the banana aphid from developing resistance to the chemicals, allow chemicals to be used over a longer duration of time, and reduce the chance of reaching the maximum allowed rate or applications of each product (keep in mind, the label is the law, application of any chemicals has to follow the approved rates and number of applications per a growing season. For banana its 1 year). 

Table 1 present a list of pesticides’ active ingredients with products approved for management of aphids on banana fields and in the landscape. Plants which exhibit signs of BBTV should be removed immediately and destroyed (since no cure if plant become infected with the virus and banana keiki may take over a month to show symptoms). Consult your local Extension Agent for BBTV symptoms verification. Only clean, disease-free plantlets should be used for re-planting (propagation).

Disclaimer: Mention of a trademark or proprietary name does not constitute an endorsement, guarantee, or warranty by the University of Hawaii Cooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitable products. Pesticide use is governed by state and federal regulations. Read the pesticide label to be sure that the intended use is included on it, and follow all label directions.

Fertilizing

Banana is a rapid grower and a heavy feeder. It is very demanding of potassium. Fertilizer needs vary by soil and cultivar, however, an example of general recommendation is: 1/4 lb of 16–16-16 synthetic fertilizer, preferably in the slow release form, or 1/2 lb of Sustaine 8-2-4 organic fertilizer, peer year. Boron deficiency could show symptoms similar to banana bunchy top infection. A soil and tissue analysis are recommended for large plantings to identify issues related to nutrition. In high rainfall areas, you may want to consider splitting the application of fertilizer, to avoid the risk of leaching nutrient losses. Consult your local Extension Agent for assistance with soil analysis and management of soil health. 

The “banana heart”: to cut or not to cut?

One of the most frequent questions regarding banana trees in residential areas is if the purple “heart” at the end of the bunch should be cut or not. That section of the bunch is actually a part of the banana inflorescence. Once the fruits start of set, that part of the flower is not needed anymore. Therefore, the heart can be cut to reduce the number of debris and keep the landscape cleaner, as sections of the flower may drop until the bunch is ready to harvest. The banana heart can be used in cooking/baking as well. Another popular reasons for cutting the heart is to claim the bunch – if someone cut that section, it means the bunch is claimed and “not for grabs” (Figure 7).

Figure 7. Banana bunch with the entire section of the “heart”. The brown and purple section of the inflorescence, beyond the fruits, can be removed for easier management and to “claim” the bunch. The purple heart can be used for cooking and baking. Photo: Alberto Ricordi

Disclaimer:

Mention of a trademark or proprietary name does not constitute an endorsement, guarantee, or warranty by the University of Hawai‘i Cooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitable products. Before applying any pesticide, applicators must determine if the product under consideration is correct for the intended use site. Always read the container/package label to determine if the intended use site is included on the label. READ AND FOLLOW LABEL INSTRUCTIONS BEFORE PURCHASING AND USING ANY PESTICIDE PRODUCT.

References:

Amhad, Amjad, 2022. A Short Guide to the Diagnosis, Control & Prevention of Banana Bunchy Top Virus (BBTV), LICH Magazine July/August 2022.

Banana Bunchy Top Virus, College of Tropical Agriculture and Human Resources (website)

Alberto Ricordi, D. Arch. is an Assistant Extension Agent of Ornamentals & Landscape Program at The College of Tropical Agriculture & Human Resources, University of Hawaii at Manoa. Amjad A. Ahmad, Ph.D.  is an Associate Extension Agent of Sustainable and Organic Agriculture Program at The College of Tropical Agriculture & Human Resources, University of Hawaii at Manoa.

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