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Script 53.2

Notes to broadcasters

This script describes biological control of sweet potato weevils (Cylas formicarius) using big-headed ants (Pheidole megacephala). Big-headed ants are found in many tropical countries, but we recommend that you determine whether they are present in your region before broadcasting this script. If big-headed ants do not exist in your region, the method described here could be summarized as an example of the importance of beneficial insects – insects which eat and control crop pests.

Script

For more than 600 years farmers have known that some kinds of ants can help control pests in crops. In Cuba farmers use big headed ants to prevent a weevil from damaging sweet potatoes. Many Cuban farmers have passed on the secrets of this method to their chidren. Mariá Elena González Pellón, who is a member of the Farm Radio Network in Cuba, shared some of those secrets with us. Today I am going to share them with you.

If you grow sweet potatoes you will be especially interested in this. An ant – called the big-headed ant – eats weevils which are pests of sweet potatoes. These big-headed ants are found in many parts of the world. If they are found in your region, you can use them in your field of sweet potatoes for on-site, no-cost pest control.

If you are going to use big-headed ants for pest control you will have to know what they look like. Do you know an extension worker or an insect specialist who can show you which ones they are? There are also some things you can look for yourself if you are trying to find them.

Big-headed ants are a reddish-brown colour. They live in large colonies. That means there are many ants living together. The worker ants can be big (eight millimetres long) or small (2 millimetres long) but in both cases their heads are much bigger than their bodies. In fact their head is about one third of their total body length. So if you notice ants with very big heads, they could be the big-headed ants you are looking for.

Collecting the ants
Now that you have identified them, you need to make a trap to collect the ants. Find a place where you know the big-headed ants live. That’s where you will build the trap. The trap is easy to build. First make a pile of cut banana stems. Pile the stems up like a stack of wood. Add some food scraps to the pile to attract the ants. Then cover the pile with a damp cloth to keep it moist.

Check the pile every day. Keep it moist and continue to add scraps. When the ants find the trap, they will move their nest into the banana stems. It will take anywhere from one to four weeks for the ants to move into the trap.

When you see that the ants are living in the trap it’s time to move them to your field of infested sweet potato plants.Move the trap to the field in a clean sack. The best time is early in the morning or late in the evening, if after a rain, and about forty days after the sweet potatoes have been planted. The ants will make a new home in the new location.

To get good control of the weevil, you will need at least 100 traps on each hectare of sweet potato that you are growing.

How effective is the big-headed ant?
This method of controlling weevils in sweet potatoes works well. It is a cheap and safe way for farmers to save their sweet potato crops. Some farmers in Cuba calculate that this method costs four times less than the price of one pesticide treatment.

Acknowledgements

Contributed by: Mariá Elena González Pellón, Centro de Información Filial IDICT, Academia de Ciencias de Cienfuegos (Cienfuegos Academy of Science), Cuba.

Reviewed by: Dr. Hélène Chiasson, Ph.D. Research Entomologist, and Adjunct Professor, McGill University Montreal, Canada.