Pheromone traps for insect control in field crops

Pheromone traps are an excellent monitoring tool for insect infestation. They enable early detection and provide information on the intensity and type of attack. Farmers who do not use these instruments risk yield losses and unnecessary expenditure through the arbitrary usage of pesticides. In this article, we show you how to build a pheromone trap from a conventional plastic bottle - cheap as well as efficient. Farmers can easily inspect it, and empty out the dead insects as needed.

What is an Insect pheromone trap used for?

Pheromone traps bait and catch male insects with sexual attractants. Attracted by this, a sticky board (less effective in dusty environments!) or a bucket of water catches the insect. These types of traps are not used to control insects (females remain alive), but to detect the presence and quantity of them. Pheromone capsules are available for a large number of species, including:

• clothes moth   (tineola bisselliella)
• mediterranean flour moth (ephestia kuehniella)
• eggplant fruit   and shoot borer (leucinodes orbonalis)
• cocoa moth (ephestia elutella)
• Indian flour moth (plodia interpunctella)
• tobacco beetle (lasioderma serricone)
• carpet beetle   (anthrenus verbasci)
• confused meal beetle (tribolium confusum)

How to make a pheromone trap

Materials required:

• 3.5 litre plastic bottle
• knife
• detergent and water
• galvanized utility wire/cotton thread
• sex pheromone components, purchased commercially or obtained through extension offices.
• bamboo or wooden stake

To allow flies to enter inside the plastic bottle, select a bottle and make two angular holes with a hot knife on each side having a measurement of an equilateral triangle. Put the wire through to hang the pheromone bait. Fill about 2 inches of the plastic bottle with soapy water. Put the lure in the pheromone dispenser or suspend the pheromone capsule from the lid using string or wire. Use cotton or sponge strips and treat them with the pheromones.

Treatment is done in a vacuum and treated cotton strips are covered in airtight containers for 24 hours. You can use mineral water bottles, or a bucket that is clean.

After you have placed the treated cotton or sponge inside, close the container. Attach the trap to a bamboo, wooden stake or hang on a tree branch. If traps are used for monitoring the pests, 2-3 traps are enough for 1 hectare. For mass trapping, use 30-40 traps per acre.

The simplest pheromone trap can also be prepared using one-liter clear plastic bottles commonly used for beverages. Ten to twelve holes are made in the bottle trap, to allow insects to enter. The holes can be made with a small piece of heated metal. The pheromone dispenser has to be in line with the entrance holes inside the bottle trap. The lure should be suspended by a wire from the bottle cap. To remove any moths caught, a rectangular opening should be made in the lower part of the bottle.

Buy the pheromone that lures the pest you want to control. Always label the trap with the name of the species you are trapping, the date the lure was placed, and the name of the pheromones if you are using several in number. Change lures according to the manufacturer's recommendation (usually every 1-3 months) and properly dispose of the lure wrappers. The tiny amount of pheromone left near the traps will compete with your lure. Wash your hands between handling each lure. Minute traces of other chemicals can render the lures completely ineffective. Always remove all captured adult and insects during each visit. Discard them away from the field. Put the live ones into a bucket with soap solution to drown.

Insect pheromone traps are inspected at least 8 times a year, more often is better, and the trapped insects are then counted and the species determined. The results are recorded in the pest control program.

How to install traps

The trap should be installed in a maximum grid of 10m throughout the field starting 5m from the border and minimum 3m, to not interfere with the others. Implant a sturdy stick firmly in the soil to support the trap. Then use a wire or sturdy thread to tie the trap to the stick. The lure inside the trap should always be 15-50 cm above the crop canopy. This requires moving the trap higher as plants grow taller. In general, a height of 1.5m above the ground is suitable for most crops.

Replacing traps and lures

For delta and winged traps, their sticky surfaces get soiled due to dust and moth scales. If the surface is not sticky enough, additional moths will not be trapped. Check traps regularly and replace their sticky bottoms when needed. Intense sun, wind, and rain can destroy entire traps. If this occurs, replace them promptly. Funnel traps are more durable in the field, but their plastic bags can be torn. Replace damaged bags to prevent trapped moths from escaping. Most commercial lures contain 2 mg of pheromone chemical. Such lures usually remain effective for 1-3 months; therefore, replace lures at least once a month or three. This is valid for our homemade pheromone bottle trap too.

If you need more information on how to control a particular insect infestation, you can always contact Plantix Community Experts.