Browsing by Author "Platt, T."

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    Foliar application of steinernema yirgalemense to control planococcus ficus : assessing adjuvants to improve efficacy
    (South African Society for Enology and Viticulture, 2018) Platt, T.; Stokwe, N. F.; Malan, Antoinette P.
    The vine mealybug (Planococcus ficus) is regarded as a key mealybug pest of grapevines in South Africa, with entomopathogenic nematodes (EPNs) being touted as a potential alternative to chemical control, although their vulnerability to above-ground environmental conditions has limited their use. In this study, tests were conducted to assess the ability of adjuvants to increase the deposition of S. yirgalemense on grapevine leaves. The combination of Nu-Film-P® and Zeba® resulted in significantly more infective juveniles (30) being deposited per 4 cm2 leaf disc than with either the control (14.8), or with Nu-Film-P® (23.3), although not significantly more than with Zeba® alone (29.2). The ability of S. yirgalemense, in conjunction with the two adjuvants, to control P. ficus on grapevine foliage was then assessed under controlled conditions. The application of S. yirgalemense with both Zeba® and Nu-Film-P® to P. ficus on leaf discs in a growth chamber resulted in 84% mortality, significantly greater than that attained by the application of S. yirgalemense with either Zeba® (47%), or water alone (26%). Similar results were observed in a glasshouse trial, in which the combination of S. yirgalemense, Zeba® and Nu-Film-P® offered 88% control of P. ficus on leaf discs hung on potted vines, compared with the control that was achieved with S. yirgalemense with either Zeba® (56%) or water alone (30%). This study demonstrates the potential of a combination of S. yirgalemense with adjuvants to give significant control of P. ficus on grapevine foliage, compared with using EPNs alone.
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    Grapevine leaf application of steinernema yirgalemense to control planococcus ficus in semi-field conditions
    (South African Society for Enology and Viticulture, 2019) Platt, T.; Stokwe, N. F.; Malan, A. P.
    The vine mealybug, Planococcus ficus Signoret (Hemiptera: Pseudococcidae), is a key insect pest of South African grapevine. The ability of mealybugs to avoid or resist the action of chemical pesticides has led to the investigation of alternative control methods, such as the application of entomopathogenic nematodes (EPNs). However, EPN application faces challenges, due to the maladaptation of EPN species to aboveground conditions. In this study, the ability of adjuvants to improve the control of P. ficus in grapevine using an indigenous nematode species, Steinernema yirgalemense, was investigated. A trial was performed to assess EPN survival on grapevine foliage, when applied in the morning (high humidity / low temperature) compared with in the afternoon (high temperature / low humidity). In a semi-field trial, the combination ofadjuvants Zeba® and Nu-Film-P® resulted in 66% control of P. ficus after 48 h, compared to the use of Zeba® alone (43%), and EPNs alone (28%). Additionally, lower concentrations of EPNs showed predictably lower mortality rates of P. ficus. Significantly, higher EPN survival was recorded at each time interval in the morning, compared with the corresponding interval in the afternoon. This study demonstrates the ability of S. yirgalemense, when applied with adjuvants and at an appropriate time of day, to control P. ficus on grapevine, under semi-field conditions.
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    Potential of local entomopathogenic nematodes for control of the vine mealybug, planococcus ficus
    (South African Society for Enology and Viticulture, 2018) Platt, T.; Stokwe, N. F.; Malan, Antoinette P.
    Planococcus ficus, the vine mealybug, is the dominant mealybug pest of grapes in South Africa. To provide an alternative for chemical control, entomopathogenic nematodes (EPNs) were investigated as a biological control agent to be used in an integrated pest management system. Four local EPN species were screened for efficacy against female P. ficus, the most potent of which were Heterorhabditis noenieputensis, with 90% mortality, and Steinernema yirgalemense, with 63%. Since S. yirgalemense was previously shown to be highly effective against a range of pests, the effects of temperature and humidity on the infectivity of S. yirgalemense to female P. ficus were also assessed. The application of S. yirgalemense at 25°C yielded the highest mortality, of 72%, followed by 45% mortality at 30°C, and only 9% mortality when applied at 15°C. Steinernema yirgalemense performed best at 100% relative humidity (RH), resulting in 70% mortality. Decreasing RH levels resulted in decreased mortality (61% mortality at 80% RH, 40% mortality at 60% RH). As a soil-based organism, S. yirgalemense is most effective as a biocontrol agent of P. ficus under conditions of moderate temperature and high humidity. Its lethality to P. ficus, and its status as an indigenous species, indicate its promise as a potential biocontrol agent of the vine mealybug.