THE OCCURRENCE OF INDIGENOUS HETEROPTERANS ON SUBTROPICAL FRUIT IN SOUTHERN AFRICA

With the recent intensification of avocado and macadamia production in South Africa, the monetary value of heteropteran induced crop losses exceeded USD$ 7 million/annum by 2011. Monetary value of heteropteran damage on smaller crops such as litchi, mango, granadilla and guava is difficult to quantify but is expected to be considerable. The coconut bug Pseudotheraptus wayi Brown (Hemiptera: Coreidae) is polyphagous and may be regarded as the main heteropteran pest of avocado, litchi, guava and mango. Although the two spotted bug Bathycoelia natalicola Distant (Hemiptera: Pentatomidae) has been recorded on avocado, it is relatively monophagous and is the dominant pest of macadamia in Southern Africa. Nezara viridula (L.), N. prunasis Dallas & N. pallidoconspersa Stal. (Hemiptera: Pentatomidae) are lesser important insects that can become problematic if conditions are suitable. Heteropterans are difficult to monitor because they are low density feeders (60-1200 individuals/ha) and are often heterogeneously distributed. Additionally these elusive insects are cryptically coloured and are able to migrate relative large distances between adjoining orchards with relative ease. Severity of attack is dependent on the phenological development of host plant(s). Monitoring and spraying according to predetermined action levels are the basis for any sound IPM program. Chemical control of these insects is fraught with problems because none of the current monitoring techniques are very effective. Growers adopted a prophylactic approach to spraying which resulted in the proliferation of secondary pests. Immigration of bugs into the orchards normally increases towards the end of phenological cycle of the fruit. Additionally field weathered residues of currently registered crop protection products are ephemeral and risks regarding exceeding maximum permissible residue levels, limits the use of these products late in the production season. Current solutions (pheromone research, modelling, alternative monitoring and alternative control options) to this conundrum are briefly discussed.