DO IT YOURSELF PEST CONTROL

(One of a series of articles about growing fruit trees in Samoa, written by Digby Gotts and published in the 'Samoa Observer' between December 2000 and April 2001)

I suspect that the most important pest control system in anyone’s garden is his or her eyes. Perhaps it should come as no surprise that most plants are beyond help before they are given it, but you should be able to notice the changes in a plant, telling you that it is under stress, well before it actually falls over dead. The changes are often small, (faint cries for help), but obvious if you see your fruit tree as a living system, capable of health, sickness and death. Here are some of the symptoms I see often in Samoa and the possible cause and remedy for each.

Dying branch tips, spreading down the tree: Fungal disease, most probably a water borne fungus in the soil. Cut away and burn the dead wood and spray the tree with copper compounds. Plant another tree in a well-drained location.
Dying and pink patches on branches: Fungal disease, most probably an airborne fungus. Cut away the damaged wood, well below the disease, burn it and paint the living wood near the wound with white paint.
Flowers dying before the fruit appears: Fungal disease, most probably airborne with wind and rain. Encourage the tree to flower in the dry season by pruning at the appropriate time.
Some leaves wilting: Fungal disease, most probably first stages of an airborne fungus. Remove the branch and burn it as soon as possible.

Yellow patches on leaves: Nutritional deficiency in the soil. Fertilize with a micronutrient mix such as “Thrive”, or add compost made elsewhere (this helps to ensure that the missing element is brought in).
Overall pale yellowish tinge to the leaves: Nitrogen deficiency common on soils near the beach. Add fresh manure, compost or green leaf trash.
Deformed or crumpled leaves: Nutrient deficiency, possibly boron. Use a ready mixed nutrient spray or compost. This symptom is also caused by mites, which can be controlled by spraying the tree with soapy water.

Clusters of insects in the new growth: These will soon bleed the new growth dry, preventing a good flowering and fruit set. Splash or spray soapy water into the leaves to kill them.
Cracks in the bark: Severe infestation of mites. Use soapy water again to control their spread. Paint the damaged area with white paint with a little copper compound added to help prevent secondary fungal infections.
Fruit with rotten spots: The dreaded fruit piercing moth or fruit fly got to your fruit first. In future, pick when the fruit is a bit younger and ripen it inside, or cover the fruit with bags of newspaper, old mosquito netting or nylon stocking.
Tree not growing quickly: Look at the amount of shade. Many tropical trees need full sunlight. Is the tree growing in a filled area? The new soil could be just rocks and gravel, washed out of all nutrients. Use compost and manures.

The joys of soapy water!

Soapy water is not only a necessary part of family health, it can also be used as one of the main ways to control insect pests on your fruit trees. You will often see small black insects in the tips of growing shoots. These are commonly aphids, thrips and scale, feeding by sucking the juices from the plant. They are spread by ants, which collect the sweet honeydew produced by the aphids. By themselves they do very little damage, but they also encourage fungal disease and carry bacterial and viral diseases which can wipe out an entire crop. This whole problem can be simply fixed by throwing out your soapy water into the tree. The soap destroys the ability of the insects to breathe and then fertilizes the tree as it breaks down in the soil. The soap used could be any of the kitchen and laundry detergents or bathroom soaps used normally in the house. The soapy water can be simply splashed or thrown over the tree or sprayed for a more precise use of the mixture.

Leaf eating insects can make the leaves of your favourite plants look like lace work. Many of these are caterpillars, feeding furiously to grow up into moths. Large ones are easy to catch by hand. Literally pick them off and drop them into a bucket of soapy water to drown. The soap makes the water wetter, blocking their air holes more quickly.

Fruit flies damage many of the fruits grown in Samoa by laying their eggs just under the skin. The result is small rotten spots and nests of grubs making the fruit inedible. The main organic solution is to offer something more attractive to the flies, which can then trap them into water to drown. Female flies love water-soluble proteins, like Vegemite. So smear some inside a plastic drink bottle, add some soapy water, poke a few small holes into it and hang it inside your fruit tree. The holes should be small enough for the flies to enter but too small to allow bees inside, so no more than 3/16 inch. Four traps inside every tree will ensure that most of your fruit is left unstung. Paper bags over the ripening fruit and keeping the ground clean of rotting fruit will also help keep the flies from finding your tree.