Helopeltis pernicialis damage to a cashew crop was very serious in each of two years, resulting in no harvest unless the trees were protected either by pesticides or biological control agents. A control threshold was determined by a combination of the net income from increased yield and the frequency of insecticide use. A damage level of 1- 5% achieved the highest net profit. A damage level of 6- 10% resulted in yield that was over 73% of the yield of the 1- 5% damage level, but required one third less pesticide application. Therefore, it appears that 6- 10% damage level can be regarded as a control threshold for H. pernicialis . The pre-flowering flush appeared to be the most appropriate time to carry out the monitoring and spray programme to control H. pernicialis . Preliminary results showed that at the time when H. pernicialis caused serious damage to a tree without O. smaragdina nests, a tree with a constant ant population was only slightly damaged, andthe damage level never exceeded the control threshold of 6- 10%. It is suggested that O. smaragdina has high potential as a biological control agent.
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Peng et al. (1997) studied this question.
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