Mangoes and/or Worms

Papayoulele writes: My mango tree’s been losing a lot of mangoes for a while and of course they’re far from ripe. I heard that it means they have a worm. Are all my mangos bound to fall like this before we can eat any of them? Any advice on what I should do?
You also pose a number of unasked questions. Before employing any suggested actions, ask yourself; ‘Did the mango set an unusually large crop of young fruit this season? Have you had a similar problem before? If so, was the ripened yield of fruit satisfactory?’
If yes is the answer to the above, I am happy to tell you to expect another satisfactory crop of good, sizeable fruit. If all conditions are favorable – eg: good weather at flowering, active nectar/pollen gathering by the bees, it is not unusual to ‘set’ many more fruits than the tree can possibly sustain.
To protect itself, there will be a natural shedding of immature fruit at a quite early stage. This protects the tree by reducing the weight of fruit against the possible risk of broken branches, with surviving fruits being generally larger and of better quality.
It is not uncommon for commercial orchardists to further ‘thin’ the fruit manually to ensure the crop is of a good marketable size, thereby increasing the financial return to the grower.
On the other hand – you must carefully inspect the fruit, the tree, and its leaves for any sign of infestation. Cut open some of the fruit (both fallen and still on the tree) to check the inside of the fruit. The most usual ‘worm’ is the larva of one of the fruit flies which can ‘sting’ the fruit, then lay an egg which hatches into the larva and begins to eat the fruit from the inside, eventually emerging as an adult fly.
As mangoes are rock hard at this stage, I do not expect you to find this is so. It usually occurs later in the development of the fruit and at a time when the ripening process is beginning. Fungal problems can also be an issue, but their development is usually associated with a break in the integrity of the skin. This is usually caused by rubbing or knocking against branches and shows up as splits in the fruit around which, white/grey/black moulds can develop. Affected fruit should be removed and destroyed as soon as the condition becomes apparent.
Contact me again for treatment options should the above conditions develop in the future.
John Haines writes: Still a tropical garden novice even after a few years living most of the year in Bali. Insect and disease control is a dilemma. I was using USA products from Ace Hardware but that source seems to have ended. Mealy bugs seem to be the most common problem. .
Inventory control always seems to be a problem here. Frustrating! Lack of supply now doesn’t necessarily mean future unavailability. In the meantime look closely at the labels – you may find the same items under a different brand name. Insecticides divide into two categories – systemic and contact. Systemics are absorbed into the sap stream and are effective for between 2-6 weeks. (For edible crops you must allow a similar withholding period.)
Systemics usually belong to the ‘omethoate’ family. If you see something like ‘dimethoate’ in the contents you can expect to get the same results. These are powerful garden chemicals; read instructions carefully and follow them exactly. Look in the next issue for more environmentally friendly solutions.
Contact insecticides must actually come into contact with the pests troubling you. Mealy bug is a form of the scale insect, and is a sap-sucker. It protects itself with this white, waxy, water-repellent covering. Any contact spray must have a wetting agent added to it (ie: dishwashing detergent).
Any oil based spray will do the job, and you can quite easily make your own using this recipe: Place 500g soft soap (eg: Wings) into a container. Measure a given quantity of kerosene and add gradually, a teaspoon at a time, to the soap. Work together with the (gloved) hand, adding by the teaspoon until no more can be absorbed. Remove any free kerosene by blotting it up with paper toweling/tissues. The mixture is now ready to dilute. Calculate the amount of kerosene used and record it for future needs. (Nb: the soft soap itself is a sufficient wetting agent.)

Dilute at 20 – 25 parts water for each part of the mixture for leaf spraying, or 10 to 15 parts to use for brushing scale or mealy bug from woody stems. The emulsion should always be made with clean water. Never spray emulsions in bright sunlight – wait for a cloudy day, or spray in the late afternoon. Emulsion sprays and bright sunlight combine to produce a phtyo-toxic burn.

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