Managing Pests and Plant Diseases 297
Look for pests
Plant-eating insects are a normal part of
farming. They cause little harm to crops as long
as they remain in balance with other types of
insects, especially those that eat pests.
Examine your crops regularly. This will help you
understand when to allow friendly insects to do their
work, and when you might need to spray with natural
pesticides or use other pest control methods. When you
look for pests and diseases, ask questions such as:
• Are pieces of the plant being eaten by an insect?
• Is damage increasing? Will it affect the crop yield?
• Are friendly insects keeping pests under control?
Watch what insects do to
see if they are damaging or
helping your crops.
Is it a pest, a friend, or harmless?
Sometimes the insects easiest to see are protecting plants by eating the pests.
Or, the plant may be at a stage of growth where it can withstand some pest
damage and remain healthy.
Worms are important for healthy soil. Bees, spiders, and most insects
that live in water (such as in rice paddies) are friends, and help control pests.
Also, small wasps or flies with long, thin tubes at their backside are probably
friends. It is best to leave insect friends alone so they can help your crops.
Watch the insects in your fields to know if they are pests, friends, or
harmless. If you are unsure about some insects, collect them in a container
together with some plant parts, and watch them for several days. If you
find insect eggs, watch what they hatch. If tiny worms or grubs (larva) are
released, they may be pests. If they release flying insects, they are often friendly.
The main ways pests damage crops are by sucking the liquid from them
and by eating them.
• Sap-suckers include aphids, scale insects and mealy bugs, leaf and plant
hoppers, white flies, thrips, mites, and nematodes.
• Plant-eating insects include caterpillars, slugs, snails, plant and pod borers.
If it is a pest, how can you get rid of it?
Once you know how the pest damages crops, you can use natural pesticides
(see next page) made for that kind of pest.
Once you know when the pest appears and how it relates to its
environment, you can use physical methods of pest control (see page 299).
Answers to these questions can help know how to control a pest: Where does
it come from? When does it damage crops? Does it appear in one form and
then change to another form (for instance, caterpillars turn into moths and
butterflies)? Is it food for birds, other insects, or field creatures?
A Community Guide to Environmental Health 2012