**5. References**


When trees are young, usually until one and a half years after planting in southern Vietnam, neonicotinoids by soil drench are expected to control psyllids effectively for two months after the application. Methidathion by spray can keep high residue effects for a half month for the control of psyllids on seedlings. This insecticide can quickly kill psyllids in 12 hr after their infestation on plants, and neonicotinoids did not attain such quick effect on the psyllid. This is the advantage in the use of methidathion. Dimethoate showed similar lethal effects on the psyllids as methidathion, although both its quickness and residue effects were inferior to those of methidathion. Field application of imidacloprid, methidathion, dimethoate, and the mixture of imidacloprid with any of the two organophosphates showed that these insecticides showed similar effects on the control of psyllids: their residue effect was maintained for less than two weeks and no insecticides succeeded in attained high lethal effect to eradicate psyllids on trees even in a couple of days after the spray. It should be noted that dimethoate could not control aphids as much as imidacloprid or its mixture with dimethoate but imidacloprid would lead the increase of scale insects after the application. The application of any insecticide examined in this study did not lead these pests to be eradicated for even one week after the application. These results indicate that the application of insecticides cannot be expected to attain perfect protection of citrus trees from CG infection once the tree grew. Furthermore, since nymphs could increase in two weeks after the application without elimination, even secondary infection would not be avoided when citrus trees have grown to a stage of fruit yielding. The application of insecticide would only reduce more or less the probability of the second infection of trees by CG in the

This study was performed under the collaborative research project, no. 3241, of Japan International Research Centre for Agricultural Sciences (JIRCAS) with the Southern Horticultural Research Institute of Vietnam (SOFRI). Prof. Emeritus Su, H.-J. at the Taiwan University provided us with precious suggestions in the study. Dr. Chau, N. M. supported our studies both officially and scientifically. Dr. Koizumi, M. and Dr. Kano, T. suggested us about works on citrus both in Japan and other countries. Dr. Yonemoto, M. and Mr. Ogata, T. at JIRCAS provided information necessary for citrus cultivation. Dr. Hoa, N. V. and Mr. Dien, L. Q. gave us information of citrus in Vietnam. Miss Nga, V. T. and Miss Oanh, T.T.K. helped our works both in laboratory and field. We would like to express our sincere thanks

Boina, D.R.; Onagbola, E.O., Salyani, M. & Stelinski, L.L. (2009). Antifeedant and sublethal

Gatineau, F.; Bonnot, F., Yen, T. T. Hong, Tuan, D. H., Tuyen, N. D., & Truc, N. T. N. (2010).

effects of imidacloprid on Asian citrus psyllid, *Diaphorina citri*. *Pest Management* 

Effects of imidacloprid and fenobucarb on the dynamics of the psyllid *Diaphorina* 

**3. Conclusion** 

orchard.

to them.

**5. References** 

*Science*, 65, 870-877.

**4. Acknowledgment** 

*citri* Kuwayama and on the incidence of *Candidatus* Liberibacter asiaticus. *Fruits*, Vol.65, pp. 209-220


**4** 

*Ghana* 

 **Use of Pesticides in the Cocoa** 

Cocoa, *Theobroma cacao L.,* is a major cash crop cultivated in the tropical regions of West Africa, the Caribbean, South America and Asia. In West Africa, where over 70% of the world's cocoa is produced – with about 21% coming from Ghana - it is a significant component of the rural economy, as the industry is dominated by large numbers of smallholder peasant farmers who depend on the crop for their livelihood (Acquaah, 1999; Appiah, 2004). Like all living organisms, the cocoa plant can also be attacked by a wide range of pests and diseases. When this happens expected production targets are not met, and the economies of the producer nations are adversely affected. Preventive and curative measures are therefore necessary in the cocoa industry to maintain and even increase output

While non-chemical means of managing pests and diseases in the industry are widely recommended for health and other reasons, the use of some amounts of chemicals in the form of fertilizers, insecticides and fungicides is unavoidable in the effective management of cocoa farms (Moy and Wessel, 2000; Opoku et al., 2007; Adjinah and Opoku, 2010). Their use is therefore expected to increase with time. Indeed in the twenty-year period from 1986- 2006, the use of fertilizer world-wide increased by almost 250% (UNEP, 1991). The same trend applies to pesticides, although they are more difficult to monitor partly because of the secrecy that goes with the continued production and use of banned substances. The trends suggest quite clearly however, that much of the increase in world food production can be attributed to the response of crops to increased use of fertilizers and pesticides (UNEP, 1991). Fortunately, there has always been a clear appreciation of the potential deleterious effects of the chemicals used in the cocoa industry since the 60s, and standards have been set by FAO and WHO for acceptable levels of residues in the beans exported to other countries. The goal of maintaining high levels of agricultural productivity and profitability while reducing pesticides use presents a significant challenge. There are repeated cases of excessive levels of pesticide residues being found in agricultural produce and the safety of these products has become an issue of concern. Recently, changes in regulations in the European Union (EU), North America and Japan have called for a reflection on crop protection practices in cocoa and other commodity crops (ICCO, 2007). The quality of cocoa

**1. Introduction** 

(Akrofi and Baah, 2007).

**Industry and Their Impact on the** 

**Environment and the Food Chain** 

*1University of Ghana, Department of Food Process Engineering, 2Koforidua Polytechnic, Department of Energy Systems Engineering,* 

George Afrane1 and Augustine Ntiamoah2

individuals of the Asian citrus psyllid, *Diaphorina citri* (Homoptera: Psyllidae). *Kyushu Plant Protection Research*, Vol.53, pp.95-98. (In Japanese with an English summary).
