By ERNIE REZENTS
For The Maui News—
In my last article I focused on mango cultivars recommended for Hawaii and how the Rapoza and Fairchild mangoes should be planted in areas where rain and high humidity are normal during flowering time. I also said that I was not aware of a dwarf mango tree, well one of the nurseries I visited said that there is such a plant. The dwarf mango’s name was one I had not heard before and the salesperson did not know the fruit’s characteristics.
The mangoes we typically grow are not true when planted from seed. Only seeds of the polyembryonic type mangoes (those that produce more than one plant from a single seed) will produce plants that are true to the mother plant – common mango, Paris, Julie, Shibata, Kurashige, and No. 9 or Chinese mango. Therefore to obtain a young tree that is true to its mother, propagation needs to be made vegetatively by using a piece of the mother tree you want to duplicate. Grafting is the most common form of vegetative propagation of mangoes.
Even though cutting and air layering are methods of vegetative propagation mangoes are usually not propagated by these methods because of the resulting poor root system. In grafting, usually a seed of a monoembryonic mango is planted to serve as a root stock; when it has reached 3/8ths to 1/2 inch in diameter it is ready for grafting. A piece of the original tree is transferred to the root stock plant. It is this piece (the scion), bearing the genes of the desirable fruit tree, that will bear the name and fruit of your new tree.
Grafting techniques used are the side-tongue graft, side-wedge, splice, and cleft. A Honolulu propagator uses the approach or inarch method. In this method both stock and scion plants are on their own roots at the time of grafting. This requires that the mother tree have very low branches and young stock plants be raised to make contact with mother tree branches to be used in grafting. Both the mother tree and stock plant are given a tangential side cut and spliced together. Ties to hold the two together are usually nurseryman’s tape or raffia. For those wanting to do grafting, check how these methods are pictured and discussed in the library copy of Plant Propagation Principles and Practices by Hartmann, Kester, and Davies or some other reference. For the rest of us, buying a grafted tree from the nursery is easier and more guaranteed. Request the cultivar you desire and they will most likely be able to order it from the propagator. Grafted trees are usually shorter and bear mangoes from 3-5 years. Seedling trees usually bear in 5-7 years.
Planting and Watering.
Matured mango trees may occupy a space measuring 30 feet high by 30 feet wide. So check on overhead wires, underground pipes and utilities, buildings, and neighboring trees. The tree is kind of messy so plant it where leaf drop can be tolerated. Production will be better if the tree is in full sun and has some kind of a wind break – from a building or other trees. Most of the cultivars suggested for Hawaii will do better if planted in drier parts of the island so select your cultivar wisely. Dig a hole much larger and deeper than the container the young grafted tree is growing in. Some compost can be mixed in with the soil along with about 1/4th pound of fertilizer such as 16-16-16 . Do not overuse commercial compost made with sewage sludge due to possible burning. Even though the bag suggests one part compost to one part soil I would use one part compost to two parts soil at the most. Several persons told me that their trees died from using too much of a good thing. They exceeded the bag’s recommendation. Homemade compost without manure is safe, but I would still use it at the same ratio. Thoroughly mix the compost and fertilizer with the loosened soil and return enough soil to the hole so that the plant ends up growing at the same depth it was while in the container.
Remove the young tree from the container or mulch bag. Some people say that planting with the container will “force” the roots deeper. Containers restrict root growth. Loosening and amending the soil with organic material will encourage deeper rooting because oxygen and water can penetrate the soil more deeply. Because compacted soils limit air penetration roots grow nearer to the surface to obtain the required oxygen.
At the time of planting loosen the outer roots of the root ball gently to encourage outward and discourage circling growth. Plant the tree; firm the dry soil as you add it to the hole, but not to the point that air penetration is restricted. If you firm moistened soil it will compact and severely limit air penetration. Create a watering basin and water immediately. Add organic mulch/compost to the top soil but keep it away from the young tree’s bark. Water every 2 or 3 days depending on the season and soil type. After the first year, once a week watering may be sufficient. Matured trees need periodic watering especially if they are growing in a sandy soil or if there has been no rain. The planting technique described here can be used when planting all types of trees.
I think most of us do not use enough fertilizers yet we expect our trees to bear “bumper” crops. When we do fertilize we might over apply because we were negligent previously and try to make up. The amount of fertilizer you use will depend on the age of the tree, its health, and whether it is a heavy bearer. You can apply one pound the first year: one fourth pound at planting, another fourth after four months, and a half a pound at the end of 12 months. During the second, third, fourth, and fifth years apply two, three, four, and five pounds to match the age of the tree. Divide the amount into three or four portions and apply during the year. Mark this on a calendar so that you do not forget. Thereafter apply one pound of fertilizer per inch trunk diameter. Measure the trunk’s diameter at six inches above ground if the tree is smaller than four inches in diameter. If the tree is between four and eight inches in diameter measure the diameter at 12 inches above ground. For matured trees greater than eight inches in diameter, determine the trunk diameter at 54 inches above ground or just below where the trunk branches out (for a low branching tree).
When the tree is bearing fruit, divide the fertilizer to apply one half just before flowering and one half just after the crop has been harvested. Broadcast the fertilizer uniformly from the trunk out to the drip line and a little beyond. Water immediately and as needed thereafter to make the nutrients available to the tree.
Use fertilizers with a ratio such as 1:1:1 (15-15-15) or 1:2:2 (10-20-20).
Diseases and Insects.
Anthracnose, Colletotrichum gloeosporioides, is a dark colored fungus affecting flowers but more so fruit. Fruit with black spots on the rind most likely have anthracnose. Powdery mildew, Oidium mangiferae is a white (darkening to gray) fungus that affects leaves, flowers, and young fruit. It usually causes new leafy growth to twist, curl, and develop dark colored dead tissue. Flower clusters look gray and the fungus is easily seen. Both fungi will cause flowers and young fruit to drop. Sooty mold is a black fungus that is usually found on leaves infested with scales. Scales give off honey dew that the fungus lives off. Eliminating the scales by spraying Volck or agriculture fine oil is the answer. Scales, aphids, white flies, and mealybugs all exude honeydew on leaves and fruit which may lead to a black sooty mold problem. The recommended oil treatment is good for gardenias, citrus, etc., wherever sooty mold is a problem. Read and follow the directions listed on the container.
To cure powdery mildew apply one tablespoon baking soda with one tablespoon of Volck or agriculture fine oil per gallon of water. Spray the mixture on leaves and flowers on a weekly basis beginning when flowers first appear and until the small fruit have set. Apply Benlate or Benomyl, a commercial fungicide to control both powdery mildew and anthracnose. Two pounds of this fungicide can be purchased from United Horticulture Supply on Papa Place in Kahului (871-2622) . If smaller amounts are found at other stores you can buy it from there. You need to take precautions when using all chemicals (read the label) and maybe spraying just the lower branches will provide you with enough mangoes.
My problem (and probably yours) is primarily powdery mildew. I can use the safer baking soda cure. Benlate is probably more effective, but for the homeowner it is more hazardous.
The Mediterranean and Oriental fruit flies are a problem at times. Garden shops sell baits (sex hormones) that are used to attract male flies to a container containing an insecticide to decrease the fruit fly population. The products are methyl eugenol for oriental fruit flies and medlure for the Mediterranean fruit flies. Hang the container with the chemicals on some other tree to attract the males away from, rather than to, the mango tree. There is also a yeast product (Stahley’s bait) that is mixed with an insecticide that both males and females eat and die. Pick up and dispose all fallen fruit. Fruit fly larvae pupate in the ground prior to emerging as adults. Burying fallen fruit is therefore not the solution.
Adult weevils lay eggs on small green fruit before it is half grown. The eggs hatch and the larvae burrow into the soft seed and remain there until becoming adults. After the fruit has ripened and the flesh decomposed the weevils bore their way out. People eating mangoes are unaware of seed weevils because there is no evidence of their presence.
Because of fruit flies and the mango seed weevil, mangoes cannot be shipped to the mainland. The State has experimented radiating Haden mangoes and has successfully controlled the pests without affecting the fruit. The radiation plant is located on the Big Island. Whether mangoes are treated for export is to be worked out. I think Hawaii can consume all the fruit we produce. Some areas where flies and weevils do not survive the harsh winters (like Canada) already import mangoes without a quarantine. However our pests do limit exports of fruit and controlling or eliminating them would really open up agriculture opportunities.
This is the fun part. I obtained mangoes from Frank Swan of Maui Meadows, Maui Tropical Plantation, and Yee’s orchard in Kihei. I photographed them and my wife and I sampled them for fiber content, taste, seed size, and skin color. The results are:
|Keitt||Firm, flattened||Yes||Tart side||Very flat||Red blush with yellow/green|
|Golden Glow*||Long, firm||Low||Excellent, juicy||Very flat||Yellow|
|Irwin||Long, flattened||Very low||Good, velvety,|
|Mapulehu||Large with a nipple||Yes||Stronger taste, tart, juicy||Average||Red/yellow|
|Swann**||Long, firm||Yes||Tart, juicy||Flat||Red/yellow (Beautiful)|
|Fairchild||Long||Yes||Stronger taste, juicy||Average||Yellow|
* Golden Glow is a Yee mango and plants are unavailable.
** Indian and the Swann mangoes belong to Frank Swann. He bought the plants from Mr. Singh (Kihei Gardens and Landscaping) in 1985.
Of course an annual bearing cultivar would be preferred and disease resistance needs to be considered. All of the above are probably sensitive to Powdery Mildew and Anthracnose and therefore will do better in hot dry areas. Rapoza and Fairchild are recommended for wetter parts of the islands. I have not tasted Rapoza or the Gouveia mangoes yet. Gouveia is supposed to be the best tasting mango and is recommended for growing in hot dry areas.
Next time I will write about present unusual garden happenings. Are they due to El Nino?