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Chapter II
Review of Related Literature and Studies
In the scheme of life, plants are among the most important living groups without which
the human race would not survive. Plants are a major group of living things including familiar
organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, and mosses. About
350,000 species of plants are estimated to exist currently. As of 2004, some 287,655 species had
been identified, of which 258,650 are flowering and 15,000 bryophytes. Plants are mostly
autotrophs. Autothrops are organisms that obtain energy from sunlight or organisms that make
their own food. Most plants carry out a process called photosynthesis, which occurs in the
chloroplasts of plants. (Paralumun New Age Womens Village, 1999)
Plants have various uses -- it provides food, shelter for the different species of animals.
Its trunk can be used for buidling houses, the leaves may be used for medicinal purposes. These
are just a few of the things that plants can give to us humans. Because of its importance man
needs to take care of plants. Nowadays, a growing awareness of how plants can help save
Mother Earth has created an earnest desire among people to preserve, cultivate and nurture
plants. But like people, plants too can get sick. One common disease that beset plants is
powdery mildew. On top of such diseases, plants often fall prey to pests. There is a wide species
of pests that are known to have devastated crops. A very common destructive pest to plants are
Aphids.
Aphids, also known as plant lice, are small sap sucking insects. They are small plant lice
that feed on plant parts. Aphids are among the most destructive insect pests on cultivated plants
in temperate regions. The damage they do to plants has made them enemies of farmers, crop
growers and gardeners all over the world. They are very successful in wrecking plants. Fruits
where aphids fester are often stunted in growth. (University of Florida, 2011).
Aphids are distributed worldwide but they are usually more common in temperate
zones. (Tim Bailey, 2011) The Philippines, being a tropical country, gets its fair share of
aphids.
Most aphids are about 2.54 mm long. Green and black are the most common colors for
aphids. A characteristic common to all is the two tubes, called cornicles, on the back ends of
their bodies. The cornicles secrete defensive substances. In some species they are quite long,
while in others they are also very short and difficult to see. (Virginia Polytechnic Institute And
State University, 2002 )
Most aphid species have a wide range of host plants which include weeds, ornamentals,
trees, fruit and vegetable crops. ( Jim Chaput, 2011) Anise, chives, coriander (cilantro), garlic,
onions, petunias and radish are examples of repellent plants.
Aphids also have predators. Glacewings, ladybugs and their respective larvae have a
voracious appetite for aphids. Larvae from the syrphid fly also consume aphids. Hover flies and
praying mantis feed on aphids. ( Golden Harvest Organics LLC™, 1996-2011) Unfortunately,
these predators are themselves pests that can cause plants irreparable damage.
Aphids feed by sucking up plant juices through a food channel in their beaks. At the same
time, they inject saliva into the host. Light infestations are usually not harmful to plants, but
higher infestations may result in leaf curl, wilting, stunting of shoot growth, and delay in
production of flowers and fruit, as well as a general decline in plant vigor. Some aphids are also
important vectors of plant diseases, transmitting pathogens in the feeding process. A sticky glaze
of honeydew may collect on lower leaves, outdoor furniture, cars, and other objects below aphid
feeding sites. Honeydew coated objects soon become covered by one or more brown fungi
known as sooty molds. Crusts of sooty mold are unsightly on man-made objects, and they can
interfere with Photosynthesis in leaves. ( Virginia Cooperative Extension, 2002 )
Aphids cause damage by sucking sap from new growth. They tend to cluster at the
growth end of plants and attach to soft, green stems. As a result, the new foliage may look
crinkled or stunted, and the aphids are usually plainly visible around the stem. If the infestation is
bad enough, the plant will begin to drop leaves. Finally, like mealy bugs, aphids secrete
honeydew that encourages the growth of sooty mold and fungus. (Jon VanZile, 2011)
Due to the damage that aphids and similar pests can cause to plants and trees, men have
created various ways of combatting these pests. The means of fighting these pests range from
concocting home-made insect repellants to chemical pesticides ( Pest Control, 2011 )
One of the old-fashioned and commonly-practiced ways of getting rid of such pests is
subjecting
plants to smoke. A lot of people in our country still do this. They burn dying
leaves
weeds
and
under
trees
purportedly
to
eradicate
tree
bugs
and
pests.
Chemicals, when combined with cultural controls, are more effective in exterminating
pests (The Joe Gardener Company, 2010 ). However, chemical pesticides, even if they can
eliminate said pests faster, do more harm than good. Some leave toxic residue on the plants and
their fruits, and most, if not all, are harmful to the ozone layer and hazardous to the human
health. (National Center for Healthy Housing, 2011 ) The researchers, therefore, highly
recommend the use of home-made remedies against these pests. These remedies are
environmental friendly and do not contain toxic chemicals that are harmful to men especially
when
ingested
with
the
contaminated
fruit
or
vegetable.
The home-made remedies which are made the subject of this research are: sodium
bicarbonate,
garlic
and
vinegar
A common treatment for Aphids that is both said to be cheap and effective is Sodium
bicarbonate, which is also known as baking soda.
Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It
has a slightly salty, alkaline taste resembling that of washing soda. ( T. Lakhanisky, 2002
) Occurring both naturally and man-made, it was first discovered by the ancient Egyptians who
found it as a cleaning agent. It wasn’t until 1791 when a French scientist developed the first
chemical method of making Sodium bicarbonate. Commercially mined from nahcolite deposits
around the world, it can be created from what is known as the Solvay process where calcium
carbonate, ammonia, carbon dioxide, and sodium chloride are combined. Sodium bicarbonate is
extracted from the naholite using warm water. The end result of both processes is the white
powder that spread through many areas of daily human life. ( MemeBridge, 2011 )
Sodium bicarbonate can be an effective way of controlling fungus growth and in the
United States is registered by the Environmental Protection Agency as a biopesticide. ( Ask.com,
2011 ) Baking Soda kills pests. When they ingest it, gasses build up in their stomachs, which
causes the organ to explode, killing the insect instantly. ( Laurel Jones, 2010 )
Another known remedy for aphids is garlic.
Garlic ( Allium Sativum ) is a kind of
onion. It is native to Central Asia, and it has been used throughout its history for both culinary
and medicinal purposes. It grows in the wild in central and southwestern Asia. Garlics are easy to
grow
and
they
can
be
grown
year-round
in
mild
climates
(NCAT,
1997
).
Garlic plants are very handy because they are not attacked by many pests or diseases.
They are said to repel even rabbits and moles. Garlic is grown globally, but China is by far the
largest producer of garlic ( Zomobo, 2011 ).
When garlic is crushed, it yields allicin, an antibiotic and antifungal compound which can
also serve as a natural insecticide (Stephen Tvedten, 2009). Garlic naturally contains high levels
of sulfur and a few cloves crushed in water can be used to make a homemade spray (
greenpassion, 2010 ).
Organic gardeners have long relied on garlic as part of their pest-fighting arsenal. Since
garlic contains sulfur, which, apart from being toxic to pests, can also act as an antibacterial and
antifungal agent. Garlic is a very effective treatment in combating Aphids ( Demand Media,
1997
).
Another very good example of a treatment for aphids is vinegar. Vinegar is an acidic
liquid produced from the fermentation of ethanol in a process that yields its key ingredient, acetic
acid. It also comes in a diluted form. Vinegar has been made and used for thousands of years.
Traces of it have been found in Egyptian urns dating from around 3000 BC. ( Wikipedia, 2011 )
Vinegar can be used as an herbicide. Acetic acid cannot be absorbed into plant root
systems so the vinegar will kill top growth, but perennial plants will reshoot. The acetic acid
content found in most commercial vinegar solutions available to consumers for household use do
not
exceed
5%
(
The
Titi
Tudorancea
Bulletin,
1999-2011
).
Stronger solutions are available from some stores, but it should be noted that solutions of
10% and above require careful handling, because they are corrosive and damaging to the skin.
Vinegar contains five percent acetic acid and can be used to control weeds, especially those that
come up around sidewalks or pathways. For better results, pickling vinegar, which is closer to
20-percent acetic acid, can be used. Too much vinegar can also burn the plant. ( Home-AirPurifier-Expert,
2005
).
Using vinegar as a treatment for Aphids is not only non-toxic but also easy to come up
with. Gardeners can make up a mixture at home easily because the ingredients are not that hard
to find. It can cheaply and effectively solve aphid problem ( Demand Media, Inc., 1999-2011 ).
Most people nowadays avoid the use of chemicals for fertilizers or for pest control
because it has become common knowledge that these chemicals are harmful to both humans and
to Mother Earth.
In order to save one's plants from aphids it is better to resort to vinegar. Not only is this
mixture non-toxic but it is also easy to secure. One can make a batch of aphid control sprays out
of things one most likely have in one's house. The basic formula simply calls for water, dish
detergent, cooking oil and vinegar. Combine all these ingredients together to make a foamy
mixture and spray daily to control the spread of aphids. ( Pest Control Canada, 2010 )
Custard Apples are popular backyard fruits in the Philippines together with the banana,
the rose apple, the jackfruit and the guava. Custard Apples, also known as sugar apples or Atis
in the Philippines, have a lumpy green skin covering masses of sweet, scented white flesh. They
are multisectioned and are easily divided into two pieces by hand. Custard apples are quite
sweet, oftentimes with sugar granules. They can be used as base for a delicious ice
cream. Aphids are common pests of the atis but they are almost harmless to the tree and the fruit.
( Yahoo! Inc, 2011 )
This type of fruit grows in places with tropical or subtropical climates. It is quite a
prolific bearer, and it will produce fruit in as little as two to three years. A tree five years old may
produce as many as 50 sugar apples. ( Demand Media, Inc., 1999-2011 )
The Atis is very prone to getting infected by aphids since the plant and the pest both have
the same preferences in the climates and their surroundings.