Insect-fungal ecology on selected new crops in South Africa

English: This study investigates insect-fungal-plant interactions on three new crops (viz. cactus pear, pistachio and pigeonpea) in South Africa. Isolation of Drosophila. melanogaster and D. hydei flies from cactus pear (Opuntia ficus-indicay orchards showed that these two species harbour fungi. Inoculations of specific fungi obtained from the two Drosophila species onto fruit and cladodes of cactus pear showed that some of the fungi had the ability to cause rot and may even be pathogenic. Scanning electron microscopy (SEM) confirmed the harbouring of fungi on the bodies by of the two Drosophila species and it also showed that most of the fungal propagules were present on the legs of the flies. An insect succession study showed that both Drosophilidae flies and Nitidulidae beetles play a vital role in the degradation of the fruit by contributing to the rate of fruit decomposition and by spreading yeasts and fungi that cause rot. Further to this a dissemination potential experiment with Drosophilidae also showed that these flies are capable of transmitting fungi, which are capable of causing rot on 0. ficus-indica fruit. Isolation of Nysius natalensis bugs collected in Pistacia vera (pistachio) orchards showed that this species harbours fungi. Additionally, isolation of the heads and faeces of Sparrmannia flava beetles collected in pistachio orchards showed that this species also harbours fungi. More specifically, both these species harbour fungi known to be pathogenic to P. vera. SEM of N. natalensis confirmed that they harbour fungi on the exoskeleton and that most of the fungal propagules were present on the legs of the insects. It was also shown that N. natalensis cause feeding lesions on pistachio nuts, thereby providing access for fungal infection. Analysis of N. natalensis confirmed that their numbers are higher in late summer and that cover crops and surrounding vegetation have an influence on their population dynamics. Analysis of S. flava showed that they have a peak season during summer and that their flight activity is influenced by a combination of temperature, rainfall, windspeed, soil type and lunar phases. Isolation of Clavigralla tomentosicollis bugs collected in a Cajanus cajan (pigeonpea) cultivation showed that this speceis harbours fungi. Some of these fungi are known to be pathogenic to C. cajan. Scanning electron microscopy (SEM) confirmed the harbouring of fungal propagules on the exoskeleton of C. tomentosicollis. It was also shown that fungal propagules were present all over the body, most importantly the mouthparts. A dissemination potential experiment showed that this species is capable of transmitting fungal proapgules to pigeonpea plants. C. tomentosicollis prefers some pigeonpea cultivars above others.