Part 1.6

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INTEGRATED APPROACH FOR THE CONTROL OF THE LARGER GRAIN BORER, PROSTEPHANUS TRUNCATUS (HORN) (COLEOPTERA: BOSTRICHIDAE) IN TOGO

D. AGOUNKE & M.A. BILIWA

National Plant Protection Agency, Lomé, Togo

Background

Our experience here is based on a series of research activities that were conducted from 1984 to 1995. The findings could directly help identify practical solutions to the problems posed by the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), a new pest of stored products. In fact, chemical control using the binary insecticide Deltamethrin (Pyrethroid) and Pirimiphos-methyl (phosphoric ester) was the first method suggested in order to avoid or reduce the severe losses caused by the larger grain borer. The results of the preliminary studies conducted after the initiation of chemical control led to suggesting another approach focused on classical biological control using an introduced predator, Teretriosoma nigrescens Lewis (Coleoptera: Histeridae). After analyzing all the results of these two methods, we are now able to refer to an integrated approach for the control of the pest complex of stored food products in Togo, and particularly for the control of P. truncatus.

Conclusions

Since the results of the studies carried out on P. truncatus in Togo have been widely published (see annotated literature published by GTZ), we shall only focus on the following salient points:

1.	Storage environment (controlled environment)
	Positive impact of the chemical control of P. truncatus and other storage pests in Togo.

	^*	Large-scale storage systems: fumigation using PH3
	^*	Smallholders' stores and grain traders' stores: sandwich treatment of traditional stores (maize with husks) and bags of maize grain using the proposed binary insecticide. Other active ingredients and formulations are being tested.

2.	Natural environment
	Impact of classical biological control on the control of natural populations of P. truncatus (introduction of T. nigrescens).

In total 138,700 individuals (T. nigrescens) have been reared and released throughout the country.

During the last phase of the rearing and release programme our country went through some socio-political unrest; therefore, we were not able to fully assess the impact of the releases on the populations of P. truncatus in their natural environment. Nevertheless, we can assert that T. nigrescens has established in Togo.

3.	An objective analysis of the two methods clearly points out the potential of a
	consistent integrated control programme combining - in the case of Togo - chemical control and classical biological control using the introduced predator T. nigrescens.
4.	Justification of our approach

	^*	Complementary nature of the two methods (storage environment and natural environment). In other words, the two methods produce synergetic effects.
	^*	Compatibility of the two methods:

^1.	No antagonism (two separate areas of application);
^2.	Positive socio-economic impact;
^3.	Positive impact on health and environment.

Finally, our proposal does not exclude any possible combinations with other thoroughly tested control methods.

We wish to thank the Federal Republic of Germany for their assistance through GTZ. We also thank all the institutions that have collaborated with our national program.

We wish to pay a special tribute to Prof. F. A. Schultz who was the first to give his scientific support to this first classical biological control attempt in the storage environment.