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Producers in the Western Cape province of South Africa are looking towards a push-pull strategy to reduce oviposition damage to plums by western flower thrips (WFT). White clover, Trifolium repens L., a favoured host plant of WFT, was investigated as a possible trap crop to provide the “pull” element. The attractiveness of collected volatiles of white clover flowers and of unopened (balloon stage) and open plum (Prunus salicina Lindl. cv. Sapphire) blossoms to WFT females was determined, using a Y-tube olfactometer. E-β-Farnesene, a known attractant for WFT, was included as positive control. Clover flower and open plum blossom volatiles exhibited statistically significant attraction of 69% and 71%, respectively, to WFT females. E-β-Farnesene and balloon stage plum blossom volatiles attracted 63% and 65% of WFT, respectively. When compared directly, 69% of WFT females chose the arm with the plum blossom volatiles over the clover flower volatiles. The clear preference shown by WFT for plum blossom volatiles indicates the use of a semiochemical to deter WFT from the plum blossoms would be required to enhance the efficacy of white clover as a trap crop in a push-pull strategy. [ABSTRACT FROM AUTHOR]

The objectives of this study were the specific taxonomic confirmation of the main olive seed wasp (OSW) attacking commercial olives in the Western Cape, to investigate monitoring methods and seasonal occurrence of OSW, to determine the potential economic damage of infestations, and to ascertain the geographic distribution of OSW in the regions where olives are cultivated in the Western Cape. Morphological and molecular methods were used to identify all the species obtained from cultivated olives at two trial sites near Stellenbosch and Agter-Paarl. Eupelmus spermophilus Silvestri (Hymenoptera: Chalcidoidea) was by far the most frequent and widespread olive seed wasp. Monitoring with yellow sticky traps over three seasons indicated OSW presence in orchards when olives were small enough for OSW to oviposit in, but traps were not reliable indicators of OSW infestation levels. Prematurely dropped olives, collected from February until harvest over three seasons, and olives picked at harvest were examined for OSW infestation. Total yield for each data tree was recorded at harvest, and yield loss due to OSW infestation calculated. Economically significant yield losses occurred sporadically. Fruits collected from both cultivated and wild olive trees indicated that OSW occurs in most olive-growing regions of the Western Cape. OSW does not pose a significant threat to the local olive industry as a whole and cannot be considered a key pest of olives, but during some seasons it can affect production yields where wild olive trees are located near commercial olive groves. [ABSTRACT FROM AUTHOR]

Wild and cultivated olives in the Western Cape of South Africa are direct or indirect hosts to a high diversity of Braconidae and Chalcidoidea wasps. Olive-associated Braconidae are known to parasitise the larvae of Bactrocera oleae(Rossi), and probably also Bactrocera biguttula (Bezzi). The lifestyle of olive-associated Chalcidoidea is not fully understood, and may include phytophagous, parasitoid and hyperparasitoid species. Some chalcids could represent olive seed wasps (OSW), a generic term that designates the seed feeders responsible for losses in commercial olive production. In order to obtain direct DNA-based evidence for the lifestyle of four putative OSW – Eupelmus spermophilus Silvestri, Eurytoma oleae Silvestri, Eurytoma varicolor Silvestri, Sycophila aethiopica (Silvestri); and the parasitoid Neochrysocharis formosus (Westwood) – we developed a multiplex PCR assay comprising species-specific primers for each species. The assay was used to survey larvae collected from the seeds of wild and cultivated olives. Eupelmus spermophilus was the most abundant species in wild and cultivated olives, and may represent a threat to the local olive industry. Eurytoma oleae was found only within the seeds of wild olives, and may also represent an OSW. We found direct evidence supporting the potential agricultural relevance of S. aethiopica and E. varicolor as parasitoids of E. spermophilus. These results may inform strategies for the management and control of OSW in the Western Cape. [ABSTRACT FROM AUTHOR]

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) or western flower thrips (WFT), has become a global pest of economic importance. WFT is extremely polyphagous, attacking a wide range of host plants in both field and greenhouse production systems. Chemical control is the most frequently used method for the control of WFT, but their cryptic nature, which protects them from contact with insecticides, and their resistance to many insecticides, have become critical limiting factors in terms of control. This has led to heightened emphasis on biological control in integrated pest management (IPM) programmes for WFT. Most commonly used predators are relatively large and unable to enter the cryptic spaces inhabited by WFT, thus limiting their ability to reduce WFT populations. Entomopathogenic nematodes (EPNs) and fungi offer alternative biocontrol options that suit IPM programmes well. This review focuses on WFT and its management, with an emphasis on crops being grown under cover, and on the use of EPNs for biocontrol, from a South African perspective. [ABSTRACT FROM AUTHOR]

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an important field and greenhouse pest of many crops worldwide. To control F. occidentalis is extremely challenging, because of its cryptic behaviour, short life cycle, and resistance to many insecticides. The life history and success rate of WFT on chrysanthemum (Dendranthema grandiflora) leaflets and green bean pods (Phaseolus vulgaris) showed that more first instar larvae hatched, and developed faster, with a higher survival rate, on the former than on the latter, making chrysanthemum a more attractive and suitable host than were the green beans. A total of 11 local South African entomopathogenic nematode species and the exotic Steinernema feltiae, were tested, under laboratory conditions, for pathogenicity against WFT. Generally, Heterorhabditis spp. were more virulent than were the Steinernema spp. The study showed that locally isolated Steinernema yirgalemense (66 %), Heterorhabditis baujardi (67 %), and Heterorhabditis bacteriophora (60 %) had potential for the control of F. occidentalis, in terms of targeting its soil-dwelling stages. Results from the temporal development study showed that both S. yirgalemense and H. baujardi were able to complete their life cycles in the host, and to produce a new cohort of infective juveniles. [ABSTRACT FROM AUTHOR]

Grapevine leafroll is the most damaging grapevine virus disease in South Africa, and the primary vector of Grapevine leafroll-associated virus 3 (GLRaV-3) is vine mealybug, Planococcus ficus (Signoret). Preventing re-infection of newly planted, virus-free grapevines is critical to control and prevent the spread of leafroll disease. Results from a previous survey raised concern that mealybugs surviving on leafroll-infected root remnants in the soil could transmit the virus to newly planted grapevines. This study aimed to determine if P. ficus commonly occurs on grapevine roots in the Western Cape Province of South Africa, if and for how long it can survive on remnant roots in soil, and if it can transmit GLRaV-3 to healthy grapevines after surviving on remnant roots. Surveys to determine the occurrence of mealybugs on grapevine roots were conducted at different times of the growing season in vineyards near Robertson, McGregor, Montagu, Somerset West and Malmesbury over three seasons. A field trial was conducted on a sand-clay-loam soil with 23% clay and a sandy-loam soil with 10% clay over 12 months to determine survival of different life stages of vine mealybug confined on root sections from leafroll-infected Pinotage/R110 grapevines. Results indicate that P. ficus does not readily occur on grapevine roots in the Western Cape, and that it does not survive well on root remnants of grapevines for any length of time. Implications for planting virus-free grapevines in soil where leafroll-infected vines were removed, are discussed. [ABSTRACT FROM AUTHOR]

Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an exotic ladybird, first recorded in South Africa in 2004, where it was introduced factitiously. In this study the seasonal occurrence of H. axiridis and other coccinellids were monitored in four vineyards and the adjacent windbreaks over three growing seasons in the Western Cape Province, South Africa. Harmonia axyridis made up the highest mean number of coccinellids collected per site over the collecting period, followed by Hippodamia variegata, Cheilomenes lunata, Exochomus flavipes and Micraspis sp. No indigenous parasitoids were observed attacking H. axyridis. The numbers of H. axyridis on the vines were negatively correlated with temperature but positively with rainfall. In view of the migration of H. axyridis from the vines in December, they appear not to pose any risk of contaminating grapes during harvest and tainting wine as most wine grapes are harvested from January onwards. [ABSTRACT FROM AUTHOR]

Grapevine leafroll disease is widely accepted to be the most damaging grapevine virus disease in South Africa. The current industry strategy to limit leafroll infection in new vineyards includes treating newly planted grapevines with a systemic insecticide like imidacloprid and rogueing all grapevines that exhibit leafroll symptoms. A tendency by some producers to eschew rogueing and rely solely on imidacloprid applications to control vine mealybug and so protect new vineyards from leafroll infection gave rise to this study. Two bioassays were conducted to determine if Planococcus ficus (Signoret) nymphs can transmit grapevine leafroll-associated virus 3 (GLRaV-3) to potted indicator grapevines treated with imidacloprid applied through the soil five months before exposure to viruliferous mealybugs. Ten of 21 leafroll-free grapevines treated with imidacloprid tested positive for GLRaV-3 seven to eight weeks after being exposed to viruliferous first- and second-instar P. ficus nymphs. This means that the systemic applications of imidacloprid to newly planted, virus-free vineyards will not necessarily protect the vines from GLRaV-3 if they become infested by viruliferous vine mealybugs, although the insecticide provides effective mealybug control and helps to prevent the secondary spread of leafroll infection in these vineyards. To control the spread of leafroll virus to newly planted, leafroll-free vineyards, all grapevines that serve as sources of infection should be removed. Where this is not feasible, vectors should be monitored and controlled rigorously in infested and disease-free vineyards alike, while all infected grapevines should be removed from new vineyards as they begin to develop leafroll symptoms. [ABSTRACT FROM AUTHOR]

Arthropod-mediated dispersal of pathogens is known in many cropping systems but has never been demonstrated for grapevine trunk disease pathogens. Arthropods from vineyards were screened for the presence of pathogens associated with Petri disease and esca using cultural and molecular techniques. The ability of the most abundant pathogen-carrying species to inoculate healthy grapevine vascular tissues was also determined. Millipedes and ants were allowed to associate with a DsRed-Express-transformed Phaeomoniella chlamydospora, after which they were exposed to freshly pruned healthy grapevines under controlled conditions and wounds were monitored for subsequent infection. In addition, the possibility of millipede excreta, commonly found on pruning wounds in the field, to act as inoculum source was determined. A diverse arthropod fauna was associated with declining grapevines and many of these carried trunk disease pathogens. However, spiders, the ant Crematogaster peringueyi, and the millipede Ommattoiulus moreleti were the most abundant pathogen carriers. The ant and millipede species fed on pruning wound sap and effectively transmitted trunk disease pathogens. Millipede excreta contained viable spores of Phaeomoniella chlamydospora and may serve as an inoculum source. Numerous arthropods, including beneficial predators, are potential vectors of grapevine trunk disease pathogens. Our results highlight the need for an integrated approach, including targeted management of ants and millipedes at the time of pruning, to limit the spread of grapevine trunk diseases. [ABSTRACT FROM AUTHOR]

Western flower thrips (WFT), Frankliniella occidentalis (Pergande), on table grapes in the Hex River Valley was monitored and its seasonal occurrence was investigated over three seasons. At the start of the growing season, blue sticky traps suspended from the overhead trellising structure to hang outside and under the vine canopy yielded similar WFT numbers. However, as the season progressed and vine canopies became denser, more WFT were caught on traps hanging outside the canopy in full sunlight than on traps hanging under the vine canopy. Female WFT became active in the vineyards after bud break and their numbers increased rapidly during flowering, peaking between October and January and declining rapidly thereafter. WFT were present in pre-bloom inflorescences and shoot tips before flowering, which means that monitoring should commence as soon as the first inflorescences are formed. No consistent relationship was found between economic damage at harvest and WFT numbers on sticky traps during flowering and berry set. Sticky traps should therefore only be used to determine the presence or absence of WFT in vineyards. The trap results suggest that there could be a constant influx of thrips into vineyards from alternate host plants in the surrounding area during the growing season. In vineyards with a history of WFT damage, control measures should be considered as soon as WFT is detected in order to prevent halo spot damage. [ABSTRACT FROM AUTHOR]