PHYSICAL METHOD OF PEST MANAGEMENT

Sometimes the most efficient way to kill insects is to stomp on them, literally or figuratively. Physical control method can be as simple as hand-picking the bagworms from a juniper bush, cutting tent caterpillars out of a shade tree, or using a fly swatter and window screens to keep your home free of flying insects. Physical Pest Control is a method of getting rid of insects and small rodents by removing, attacking, or setting up barriers that will prevent further destruction of one's plants. These methods are used primarily for crop growing, but some methods can be applied to homes as well.

Physical control method of insect pest comprises a number of technologies, some of which are based on active methods: Thermal shock (heat), electromagnetic radiation (microwaves, infra-red, radio-frequencies), mechanical shocks and pneumatic control (blowing or vacuuming tools). In the field, physical barriers represent the only passive technique available. This method aims to reduce the pest population by using devices that affect their physical environment.

Methods

1.  1.   Manipulation of Moisture:

Drying of grains up to less than 10% moisture before storage is a very good practice to prevent insect pest damage and draining of standing water is most effective method of destroying mosquitoes.

1.  2.    Barriers

Row covers are useful for keeping insects out of one’s plants, typically used for horticultural crops. They are made out of either plastic or polyester. They are made thin and light to allow plants to still absorb sunshine and water from the air.

Diatomaceous earth, made from fossilized and pulverized silica shells, can be used in order to damage the protective cuticle layer of insects that have them such as ants. When this layer is damaged, the insects become vulnerable to drying out. Unfortunately, the effectiveness of Diatomaceous earth decreases if it is wet. Therefore, it must be used often.^[2] This method was used back in the 1930s and 1940s when farmers would run dust over their fields. This would have the very same effect as diatomaceous earth.

3.      Traps

Fly paper or sticky boards are devices used in order to capture insects as they land upon the surface of the trap. They are covered in a substance that attracts insects, but are actually very sticky or poisonous. These traps are commonly used for flies or leafhoppers.^[3] Fly paper and sticky boards, for example, are often used in greenhouses to control whiteflies or leafhoppers.   Fruit and shade trees can be protected from various pests (e.g., plum curculio, gypsy moth, and codling moth) by tying a band of folded burlap around the trunk with its open side facing down.   As insects climb up the trunk, they are waylaid in the folds of burlap which can be treated with insecticide or inspected daily to collect the pests.

4.      Manipulation of Temperature:

a)      Cold storage: Placing produce inside of cold storage containers lengthens how long the produce lasts while also hindering the growth of insects inside of them. Cold storage of agricultural products prolongs their shelf life and retards the development of insect pests.  Most of insects become inactive around freezing point. Cold storage of fresh and dry fruits or vegetables is practiced to avoid fruit flies and potato tuber moth (PTM) damage.

b)      Heat treatment: Another method to use is to heat, as it will kill the insect larvae in certain types of produce. Heat treatments are sometimes used in place of fumigation to kill insect larvae in certain types of produce.   Mangoes, for example, are submersed in hot water baths (115°F for 68 minutes) to kill the eggs and larvae of fruit flies (Tephritidae) prior to export.

c)      Thermal shock: This approach is nonetheless is based on the premise that the commodity or the crop to be protected will be less sensitive than the target pest to an abrupt change in temperature. Research on thermal sensitivity and physiological reactions to short duration thermal stresses is central to the development of control methods based on thermal shocks.

d)     Fire: For farmers, fire has been a powerful technique used to destroy insect breeding grounds. It is used to burn the top of the soil in order to kill the insects that lie there. Unfortunately, this can present some drawbacks. Fire can make the soil much less effective or get rid of the insects that are beneficial to the plants. Also, there is no guarantee that it will actually solve the pest problems since there may be larvae below the surface of the soil. Fire may not kill healthy larva and pupa of pests that overwinter beneath the soil but may kill beneficial insects overwintering near the soil surface.

e)      Flame throwers: Flame throwers are employs against locust, hoppers etc they may also be used for burning weeds, scrub vegetations and localized sterilization of the soil. A flame thrower is essentially a pneumatic sprayer in which the lance is modified into a burner. The tank is field with kerosene, which on burning produces intense heat. The burner is so enclosed that the flame is thrown upward. By providing a hood it can also be thrown downward.  In the 1950's and 1960's enterprising farmers in the Midwest built tractor-driven flame throwers that used liquid propane (LP gas) to ignite and burn off the stubble from corn fields in the hope that a variety of soil dwelling pests would be killed by the heat.

5.      Tillage: Tillage was one of the first methods for controlling soil inhabiting pest. Exposure of overwintering phases of various insect pest to the sunlight after tillage helps in killing the insects before they reach to active stage. Also some larva such a white grubs are also exposed out to sun and birds.

6.      Manipulation of light:

a)      Light traps: This types of traps are useful for controlling the phototropic insects like moths, beetles etc. Insects are attracted to light and they get entered to the trap. Light traps are also called as “Bug Zappers”.

b)      Visible light can be used in 3 ways in controlling insects:

                                                        i.            By producing photo taxis: (+)^ve phototaxis= attracting effect

(-)^ve phototaxis = repelling effect

                                                      ii.            By inducing diapauses

                                                    iii.            By modifying oviposition

7.      Use of Radiant energy:

Several avenues have been explored for applying the different forms off electromagnetic radiation as a tool for controlling insects. Non-ionizing electro-magnetic radiation kills insects by raising their internal temperature. The utilization of radio, micro wave and infra red frequencies is based on a principle similar to that of thermal shock method except that, with applications involving electromagnetic radiation, the transfer of energy occurs without using a heat transfer fluid. The technologies that harness electromagnetic radiation are often too expensive for use in the field.

The radiant energy which have been used in insect control are:

                    i.            Radio Frequencies

                  ii.            Infra-red light                      

                iii.            UV-light and Visible light

                iv.            X-ray                    

                  v.            Gamma-ray                                  

Some other examples of Physical pest control:

Simple entrapment devices work quite well to control some types of insects. Fly paper and sticky boards, for example, are often used in greenhouses to control whiteflies or leafhoppers.   Fruit and shade trees can be protected from various pests (e.g., plum curculio, gypsy moth, and codling moth) by tying a band of folded burlap around the trunk with its open side facing down.   As insects climb up the trunk, they are waylaid in the folds of burlap which can be treated with insecticide or inspected daily to collect the pests. Ditches or moats with steep vertical walls are occasionally used as barriers to keep crawling insects (e.g., chinch bugs or white fringed beetles) from migrating out of one field and into another. Pitfall traps are dug at 3-5 meter intervals in the ditch and filled with kerosene or creosote to kill the pests.

References:

Chattopadhyay.S.B.1993.Principles and procedures of plant protection.3^rd edition.Oxford & IBH publishing co.pvt.ltd.New Delhi

Keller.S,Yubak Dhoj G.C.2013.Crop pest of Nepal and their management

Pedigo.L.P.2002.Entomology and pest management.4^th edition.Prentice hall of India pvt.ltd.New Delhi.India