BEHAVIOURAL CONTROL BY USING PHEROMONES

PHEROMONES They are chemicals produced as messengers that affect the behavior of other individuals of insects or other animals. They are also called ‘ectoharmones’. The term pheromones was introduced by Karlson and Butunadt in 1959. It is derived from Greek words pherein=to tranfer+hormaein=to excite. Pheromones are usually wind borne but may be placed on soil,vegetation or various items.

Insect producing pheromone

GENERAL ROLE OF PHEROMONES They serve as means of communication between animals like light and sound by transferring information from one animal to another by smell or taste. They evoke specific behavioural, developmental reproductive responses in the recipients which helps in survival of species. A class of pheromones,sex pheromones,are mainly use in the behavioural control of insect pests. And also called attractants or sex lures.

Sex pheromones helping in mating

PHEROMONE USE FOR INSECT CONTROL The use of pheromones to control phases of lives of pest species is one method of pest management. Beet army-worms a serious pest of cotton produced in United States caused a great loss in many areas of Texas in 1995. The damage was due to success in disrupting mating procedures between male and female beet army-worms with sex attractants pheromones. In India the species Indian Meal Moths(Pantry Moths) are attracted to a pheromone in a small box lined with a sticky substance and are thus captured for disposal.

BEHAVIORAL OR PHEROMONAL CONTROL OF PESTS Pheromones are used to control the insect pests in the following ways: Killing Sterilization Mating disruption Monitoring

KILLING A trap containing sex pheromone is placed in a pest infested region.The males aggregate at the trap and are destroyed. The pheromone source could be living virgin females, extracts of such females ,or synthetic substituents. Pheromones emanating from the traps are to complete with the pheromones released by the wild females. The males gathered at the trap may be killed with insecticides or sticky material that immobilise them on contact. Natural pheromone of gypsymoth,Porthetria dispar,a pest of forest and shade trees can be used for its control.

Sticking trap that immobilize the male insects

A synthetic compound Gyplure,similar to the pheromone disparlure of gypsymoth,has become important in insect control. Synthetic attractants can attract both sexes,e.g.cuclure attracts the melonfly,Dacus. The normal effect of sex pheromone is to attract male mealworm beetles to the female,but it has been found that the first male to mate with female covers it with another pheromone which dissusdes other males from mating with her. This strategy ay conserve the energy of the female or have other benefits.

STERILIZATION Sterilization of males attracted to a pheromone trap is a better contol measure then killing the males. The males may be somehow guided to contact a chemosterilant kept near the pheromone trap and then to return to the field. Mating of sterilized males with normal females would produce nonviable eggs,and this will reduce rest population. In honeybee colonies,the queens secrete a glandular substance(a pheromone)that is passed among workers castes,and this secretion coordinates nearly all activities of workers.

MATING DISRUPTION If the air is flooded with synthetic pheromone the addition of natural pheromones by females would not be perceived by the males,which would fail to find and inseminate the females. The above method is called “male inhibition technique”. Pink bollworm,Pectinophora gossypiella,has been successfully managed in many countries by using controlled released formulations of it femles sex pheromone gossyplure. Control of Pink Bollworm Moth(lepidoptera:Gelechiidae)with insecticides and pheromones(Attracticide):lethal and sublethal effects of combinations of insecticides with pheromones for control of Pectinophora gossypiella(saunders).

Mating in ladybird & cockroach

These may depend on,among other factor,males freely contacting attracticide sources,insecticide-induced mortality,and sublethal interference with the mate-locating sequence in poisoned males. In flight-tunnel tests,males readily contacted pheromone sources containing permethrin,fenvalerate or cypermethrin and suffered significant mortality. Moreover,after 24 hours survivors were less likely to complete the normal behavioral sequence involved in sex pheromone-mediated mate location.

MONITORING Pheromone-baited traps can help detect both the presence and density of insect pest.This information can be used to forewarn an outbreak of important pests.

Pheromones baited traps

Pheromones are used by cats to mark their territory,these may be employed by males,available females or lactating mothers. The pheromones are secreted by cats as a means of communication and may be found in the urine. There is supposedly type of facial pheromone,but it hasn’t been scientifically proven that it exists. This pheromone is said to be released by cats when they rub their faces against surfaces or people,this is also a way to mark territory.