CONTROL THRESHOLD ANALYSIS FOR THE TEA MOSQUITO BUG, HELOPELTIS-PERNICIALIS (HEMIPTERA, MIRIDAE) AND PRELIMINARY-RESULTS CONCERNING THE EFFICIENCY OF CONTROL BY THE GREEN ANT, OECOPHYLLA-SMARAGDINA (HYMENOPTERA, FORMICIDAE) IN NORTHERN AUSTRALIA

Helopeltis pernicialis damage to a cashew crop was very serious in eac h of two years, resulting in no harvest unless the trees were protecte d either by pesticides or biological control agents. A control thresho ld was determined by a combination of the net income from increased yi eld and the frequency of insecticide use. A damage level of 1-5% achie ved 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. perniciali s. The pre-flowering flush appeared to be the most appropriate time to carry out the monitoring and spray programme to control H. perniciali s. Preliminary results showed that at the time when H. pernicialis cau sed serious damage to a tree without O. smaragdina nests, a tree with a constant ant population was only slightly damaged, and the damage le vel never exceeded the control threshold of 6-10%. It is suggested tha t O. smaragdina has high potential as a biological control agent.