Transmission of Grapevine Leafroll-associated Virus 3 by Vine Mealybug, Planococcus ficus (Signoret), to Grapevines Treated with Imidacloprid

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

Seasonal Occurrence of Western Flower Thrips, Frankliniella occidentalis (Pergande), on Table Grapes in the Hex River Valley, South Africa

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

Survival of vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), on grapevine root remnants in soil in the Western Cape Province, South Africa

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. Resultsindicate 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

Youth Migration and the Politics of Wellbeing: Stories of Life in Transition

Drawing on accounts of unaccompanied migrant young people becoming adult, this book offers a political economy analysis of wellbeing in the context of migration and demonstrates the urgent need for policy reform

Best interests, durable solutions and belonging: future prospects for unaccompanied migrant minors coming of age in Europe

This paper sheds light on the ambiguous position of children who migrate without a parent or guardian as they become adults in the European Union (EU). Through a critical analysis of three prevailing frames (‘best interests’, ‘durable solutions’ and ‘belonging’), which largely inform policy and practice related to this group, it explores the tension between policy assumptions and what we know of the lived experiences and aspirations of these young people. It ultimately reveals a policy framework shaped by a state-centric view of migration, a static conception of belonging and a bias towards a political preference for return. Such a stance underestimates young people’s agency and willingness to embrace risk in their efforts to secure a viable future. The net result is policy which fails to offer a ‘durable solution’ or act in the ‘best interests’ of individual migrant young people or of society as a whole

OLIVE FRUIT FLY: A threat to the South African olive industry?

Olive fruit fly (Bactrocera oleae) is the most serious pest of cultivated olives in the Mediterranean basin. to date we have not seen the same level of damage in south africa, but the question remained whether it poses a similar threat as the local olive industry expands. From this study it is clear that the climatic con- ditions during the period preceding harvest are un- favourable for rapid population growth of OFF in the Western Cape, in contrast to conditions in the coastal area of Trapani province in Sicily. Climate, and not parasitism, appears to be the main factor limiting OFF population levels in the Western Cape. While sporadic outbreaks of economically damaging OFF infestations can be expected in areas where the climatic conditions during a particular season or part of a season are favourable for OFF, the generally un- favourable climatic conditions mean that OFF is not expected to pose a similar threat to olive production in the Western Cape as it does in the Mediterranean basin

Facet recovery and light emission from GaN/InGaN/GaN core-shell structures grown by metal organic vapour phase epitaxy on etched GaN nanorod arrays

The use of etched nanorods from a planar template as a growth scaffold for a highly regular GaN/InGaN/GaN core-shell structure is demonstrated. The recovery of m-plane non-polar facets from etched high-aspect-ratio GaN nanorods is studied with and without the introduction of a hydrogen silsesquioxane passivation layer at the bottom of the etched nanorod arrays. This layer successfully prevented c-plane growth between the nanorods, resulting in vertical nanorod sidewalls (∼89.8°) and a more regular height distribution than re-growth on unpassivated nanorods. The height variation on passivated nanorods is solely determined by the uniformity of nanorod diameter, which degrades with increased growth duration. Facet-dependent indium incorporation of GaN/InGaN/GaN core-shell layers regrown onto the etched nanorods is observed by high-resolution cathodoluminescence imaging. Sharp features corresponding to diffracted wave-guide modes in angle-resolved photoluminescence measurements are evidence of the uniformity of the full core-shell structure grown on ordered etched nanorods