To maintain population numbers of pestiferous social wasps below threshold levels, repeated annual toxic baiting remains the most effective management strategy. However, a critical prerequisite for successful management and potential eradication is the development of reliable attractants for monitoring the occurrence and distribution of invasive populations. This study aimed to identify effective attractants for monitoring and controlling populations of the invasive Vespula germanica and Polistes dominula (Hymenoptera: Vespidae), which are currently confined to the Western Cape province of South Africa. The attractiveness of various carbohydrate-and protein-based attractants was evaluated using in a Y-tube olfactometer to assess the behavioural responses of field-collected foraging wasps. Vespula germanica exhibited the strongest attraction to cooked ham and weakest response to fruit juice (Minute Maid (R)), whereas P. dominula foragers showed a preference for odour cues originating from their own nest. However, the effectiveness of the tested attractants did not directly correlate with wasps' response time in the olfactometer. In addition, significant differences in preferences were observed between females with developed ovaries and those with undeveloped ovaries in both species. These findings highlight the complexity of foraging behaviour in invasive social wasps. Future research should prioritise the development of novel attractants, new combinations of existing attractants and the identification of specific chemical cues to enhance monitoring and control strategies.
Biopesticides are non-toxic and biodegradable, less likely to develop resistance to pests and break down more quickly than synthetic pesticides. Black soldier fly (Hermetia illucens L) frass, the solid waste of black soldier fly larvae, can be used as a potential biopesticide due to its high chitin content, which has insecticidal properties and stimulates plant defences. However, research is needed to understand its effectiveness. This study evaluated the efficacy of black soldier fly frass tea (BSFFT) and residues incorporated into the soil as a potential biopesticide of the green peach aphid established on Brassica oleracea capitata L seedlings. The BSFFT at different concentrations (15, 30 and 60 g l−1) and a frass soil amendment (50 g) were compared with that of diluted dishwashing liquid (15 g l−1) (positive control) and distilled water (negative control). Behaviour and mortality were observed over 48 hours. Responses were analysed using beta regression, revealing that Myzus persicae Sulzer behaviour and mortality varied significantly between treatments. Adult aphid mortality was significantly higher for diluted dishwashing liquid (83%), the 50g soil amendment (21%), 15 and 60 g l−1 (both 18%) BSFFT than that of distilled water and 30 g l−1 frass tea. In contrast, the 30 g l−1 BSFFT and 60 g l−1 (16%) frass tea foliar applications also functioned as a bio-repellent, with 16–17% of adult nymphs moving off treated plants. The additive effect of mortality and repellence reduced aphid numbers by up to 34%. Overall, BSF frass exhibits some pest control activity and, as an organic and sustainable input, may contribute to plant health in addition to reducing pest pressure.
Wasps of the family Scoliidae are parasitoid on larvae of several scarabaeid subfamilies, among which are the white grub pests of sugarcane. In the Kilimanjaro region of Tanzania, four scoliid species were identified as potential biocontrol agents of the endemic sugarcane pest Cochliotis melolonthoides (Gerstaecker, 1867) (Coleoptera: Scarabaeidae: Melolonthinae). Eight scoliid species were observed during 117 transects in the vicinity of northern Tanzanian sugarcane fields at various level of grub infestation. Male scoliids from the genus Megameris are accurate bioindicators of grub infestation, whilst female scoliids were mainly captured whilst feeding on flowers of Tithonia diversifolia. We suggest that Campsomeris mansueta (Gerstaecker, 1857) that was described as a C. melolonthoides parasitoid is a misidentification of Megameris soleata (Gerstaecker, 1871). The male of Megameris pseudofasciatipennis Betrem, 1972 is redescribed and synonymised with Megameris nigrocalcarata Betrem, 1972. To minimise misidentification and provide a common framework for future research, we provide images and illustrated dichotomous keys to identify the scoliid wasps associated with sugarcane fields of northern Tanzania, along with a preliminary illustrated key to East-African scoliid genera. The implications of these results for conservation biological control against white grub C. melolonthoides are discussed.
The Pine Emperor moth, Nudaurelia clarki (Lepidoptera: Saturniidae) periodically causes economic harm to pine plantations in South Africa, necessitating aerial insecticide applications. Despite numerous attempts in past investigations to find a cost-effective monitoring approach to inform precise timing of insecticide applications, none have been adopted in commercial pest management. The sex pheromone of N. cytherea, a close relative of N. clarki, was identified in 1973, and shown to be attractive to N. clarki in a recent investigation. The synthetic pheromone has shown promise as a potentially useful mass-trapping tool for integrated pest management of N. clarki in South African pine plantations. This study investigates the potential of using the known synthetic pheromone as a monitoring tool in historically infested plantations, and compares its sensitivity to previously captured iNaturalist citizen science data.
Macchiademus diplopterus (Distant) (Hemiptera: Blissidae), commonly known as the grain chinch bug (GCB), is a pest of grasses and grains in South Africa, with aestivating adults posing a phytosanitary concern on export deciduous fruit. Effective pre-harvest management measures for nymphs and aestivating adults are needed to reduce export rejections. Laboratory bioassays evaluated four entomopathogenic nematodes (EPNs) and fungi (EPF) isolates as potential biological control agents against nymph and aestivating adult GCBs. EPNs caused high infection-induced mortality in both life stages, with the local Steinernema yirgalemense (157-C) achieving consistently high infection in nymphs and adults. The commercial Heterorhabditis bacteriophora (Field bugs) also showed potential against nymphs. In contrast, EPF isolates were largely ineffective against adults, causing less than 12% mortality. For nymphs, high mortality but low infection in control treatments prevented conclusions regarding EPF pathogenicity. However, Metarhizium robertsii and M. anisopliae showed the highest colonization in cadavers. No significant differences were observed between in vitro and in vivo produced S. yirgalemense and H. bacteriophora for adults, while efficacy varied depending on isolate and production method for nymphs. Lethal concentration (LC) and effective concentration (EC) estimates confirmed the superior performance of S. yirgalemense in adults, with infection positively correlated with nematode concentration. This study is the first to report entomopathogen pathogenicity against nymph and aestivating adult GCBs of this species. Given the economic benefits of managing GCB in orchards rather than in grain crops, field evaluation of S. yirgalemense is recommended on deciduous fruit, where it could provide the first pre-harvest biological control option for this pest.
