Dr Abe V. Rotor
Living with Nature School on Blog
Paaralang Bayan sa Himpapawid (People's School-on-Air) with Ms Melly C Tenorio
738 DZRB AM Band, 8 to 9 evening class, Monday to Friday
Field lecture, UST Graduate School students, Amadeo, Cavite; below,a colony of aphids, and a brood of borers on guyabano.
Entomology – the science of insects – is a subject I love to teach. But before I take up the subject of controlling insects, I would like to emphasize beforehand that insects in general are extremely useful to mankind and the environment. Contrary to what many people think our world could not be any better without insects.
We would be missing honey and silk, fruits and vegetables which insects pollinate, fish which feed on them, and the Monarch butterfly that meets us at the garden at sunrise.
On the other hand, we detest the presence of their destructive kin: the cockroach that roams and spreads disease, ticks that spoil a dog’s lovely look, caterpillars that defoliate our favorite tree, or simply the buzzing of a mosquito that interrupts a good rest.
If these negative traits are not enough to take arms against these pests, think that the most ferocious animal on earth is not the lion but the mosquito. With the diseases mosquitoes carry they have brought unimagined deaths and sufferings to mankind. It is said that death due to mosquitoes alone surpasses that which all wars in history have caused. Their most prominent victim is Alexander the Great who died of malaria on the banks of the Tigris-Euphrates River.
So here are strategies of war against our insect enemies.
A. Natural Resistance
There is perhaps no substitute to natural resistance – that which is carried by the genes in a plant or animal - in combating a pest or disease, and in surviving under harsh environment. Where do these genes come from?
Tomato resistant to borer (Heliotes). Amadeo, Cavite
Even before scientists came to the conclusion that resistance (and also susceptibility) is hereditary, early farmers were already adopting the principle in plant breeding and animal husbandry, these being the foundation of the first Green Revolution that brought agriculture to its golden age in the last millennium.
It is evolution that brought desirable genes together in a species. “Survival of the fittest,” Darwin’s general formula is the gradual pooling of these genes through time, thousands if not millions of years. This also explains why varieties and breeds native to a place are more resistant than their introduced (non-indigenous) counterparts. Wittingly or not, man has caused the elimination of resistance genes, even as he chooses those that directly contribute to his economic welfare.
In order to gain from this knowledge, one may look into the adoption of these two measures.
1. Choose plants and animals that are genetically adapted to the place. They have the natural resistance to pests and diseases, as well as unfavorable conditions prevailing in the area.
2. Maintain physiologic resistance by enhancing soil nutrients and proper cultural practices. Healthy plants have less pest and disease problems. This is also true with animals. This leads us to the next practical technology.
B. Proper Cultural Practices
If you see farmers planting and harvesting their fields at the same time, they are actually practicing a practical means of minimizing crop loss. Not only that the damage caused by a pest is spread out over the whole area, the insect’s life cycle is controlled, thus eliminating the possibility of pest and disease outbreak. There are of course other advantages of cooperative farming such as communal irrigation, mechanization and collective marketing which are the answers to the problem on economics of scale.
Blue bottle flies breed dead bodies of animals.
A key to control pests is to eliminate their breeding places, such as uprooting infested plants, or pruning affected parts, and then burn them. Plant trap crops ahead of planting time to attract the potential pest. The trap crop is then rouged and burned thus eliminating the threat. Eliminate weeds because they serve as alternate host. Now we understand why fields are left vacant after harvest and during summer. This allows the soil to rest, and to break the life cycle of pest and diseases.
C. Biological Control
It is a common practice to remove unsightly cobwebs. But come to think of it. We are destroying natural insect traps built by spiders. Inside warehouses spiders prey on weevils and moths that destroy grains and other commodities. So with mosquitoes and flies at some corners of the house. No radar system or other echolocation instruments can detect the fine web, which makes this indigenous trapping devise.
On plants stalk the preying mantis that snatches its victim with one deadly grasp. The spotted ladybug overruns a colony of aphids and has its fill, unless the red ants guarding the aphids come to the rescue. A nest of hantik up in the tree has an army by the thousands. They swarm on intruders and large preys such as caterpillars.
Under the microscope one could examine the unsuspecting Trichogramma. Mass culture and dispersal of this parasite wasp has benefited sugar and corn planters since its discovery in the fifties.
Bacillus thuringiensis or Bt, has become the most popular entomophagous bacterium against Lepidopterous pest which include rice stemborers and cornborers. Applied as inoculum, Bt can cause widespread epidemic on these pests on the field.
D. Practical Pest Control at Home
Here are pest control techniques you can adopt at home.
1. To control furniture weevil and moths destroying the felt and the wood of the piano, place a dozen well-dried black pepper (do not crush) in the piano chamber near the pedals. Pamita is a good repellant and has a pleasant smell.
2. Coconut trees whose shoots are being destroyed by rhinoceros beetle (Oryctis rhinoceros) can be saved with ordinary sand. If the trees are low, sprinkle sand into the leaf axils. Sand contains silica that penetrates the conjunctiva, the soft part of the body where hard chitinous plates are joined.
3. Bean weevil destroying stored beans, especially mungo, can be control by mixing a little ash of rice hull (ipa’) with the same principle as in rhinoceros beetle.
4. To get rid of nematodes in the soil, incorporate chopped or ground exoskeleton (skin) of shrimps into the soil, preferably mixing it with compost. Chitinase is formed which dissolves the cover of the egg and the body of the organism. Use poultry dropping to reduce nematode population.
5. To control cucurbit fruit fly, cover the newly formed fruits of ampalaya and cucumber with paper bag. Bagging is also practiced on mango fruits. Use newspaper (1/8 of the broadsheet) or used paper, bond size. Roll the paper, two inches in diameter, insert the young fruit, fold at the top and staple. Bagged fruits are clean, smooth and light green. Export quality mangoes were individually bag on the tree.
6. To discourage goats in nibbling the trunk of trees, paint the base and trunk with manure slurry, preferably their own. To keep termites away from mud-plastered walls, use termite soil (anthill or punso).
7. Raise ducks to eat snail pest (golden kuhol) on the farm. Chicken and birds are natural insect predators.
8. An extra size mosquito net can be made into a mini greenhouse. Here you can raise vegetables without spraying. You can conduct your own experiments such as studying the life cycle of butterflies.
9. There are plants that have repellant properties. Plant them around the garden. Examples are lantana (Lantana camara), chrysanthemum, neem tree, eucalyptus, madre de cacao (Gliricida sepium), garlic, onions, and kinchai.
10. To scare birds that compete for feeds in poultry houses, recycle old balls, plastic containers, styro and the like, by painting them with two large scary eyes, imitating the “eyes” on the wings of butterflies and months. Hang them freely where birds frequent the area. To scare off birds in the field, dress up used mannequins. They are more effective than the T-scarecrow. Cassette tapes tied along the field borders produce sound that scare maya and other pests.
E. Insects as Food
One practical means of insect control is by gathering them to supplement nutrition. Gathering of insects for food is not only confined among primitive societies but is still one of the practical means of controlling insects. Anyone who has tasted camaro’ (sautéed mole cricket) would tell you it is no different from a crustacean. Well, insects and shrimps belong to the same phylum – Arthropoda.
Locust may destroy crops, but in a way bring food to its victims. During a swarm, locust is gathered by the sacks and sold for food and animal feeds. So with gamu-gamu (winged termites) at the onset of the rainy season, which is also the time of emergence of salagubang, another insect delicacy. Other food insects are the grubs of kapok beetle, eggs of hantik, larvae of honeybee and cheese maggots.
F. When is a pest a pest?
When we see an insect, instinct tells us to kill it. It should not be. A caterpillar is a plant eater, but the beautiful butterfly that
emergence from it is harmless. In fact it is an efficient pollinator. Hantik ants make harvesting of fruits very inconvenient because of their bite and sting, but they guard the trees from destructive insects. Houseflies carry germs, but without them the earth would be filled with dead bodies of organisms. They are nature’s chief decomposers working hand in hand with bacteria. Termites may cause a house to fall, but without them the forest would be a litter of fallen trees.
It is natural to see leafhoppers on rice plants, aphids on corn, bugs in the soil, grasshopper on the meadow, borers on twigs, fruit flies on ripening fruits. These organisms live with us under one biosphere. And if the rule is for us to dominate them, for all we know they have been dominating the earth for millions of years, even before mankind was born.
There is no way to escape pesky creatures. Conflict arises where their populations overrun our crops, spoil our stored products, and threaten our health and welfare. We have set thresholds of co-existence. As long as they do not cross this line, I think it is all right to be living with them, to ponder at the beauty of their wings, the fire they carry, the song they make, the magnitude of numbers, or simply to marvel at the mystery of their existence. ~