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The obscure mealybug, Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), is an important polyphagous, cosmopolitan insect pest of fruit crops, including apples, pears and grapes. The mealybug negatively affects fruit production both in South Africa and globally by feeding on phloem sap, excreting large amounts of sugar and water as a carbohydraterich sugary substance, known as honeydew, onto the leaves and fruit. Honeydew causes severe secondary damage, as it promotes the growth of sooty mould, which decreases the amount of photosynthesis, thus affecting the development of the host plant. Fruit consignments with fruits stained with sooty mould or suspected of containing live or dead mealybugs are rejected when exported, due to the strict phytosanitary standards. Managing mealybugs in agroecosystems is difficult, due to their small body size and cryptic nature. Currently, control relies on the use of chemicals and, to some extent, on biological control. However, using such methods has proven to be ineffective in the management of P . viburni. Entomopathogens, such as entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs), have been used across agricultural production areas to control awide range of agricultural pest insects. The current review provides an overview of the biology and control of P . viburni, with special reference to biological control using EPF and EPNs in South African orchards, in an integrated pest management system. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs), of the families Steinernema and Heterorhabditis, are insect parasites that have been successfully used as biological control agents of soil-based insect pests on the North American and European continents. The success of nematodes as biological control agents of the soil stages of pest insects has led to research into their use for control of above-ground insect pests. Laboratorybased studies have shown exceptionally good control, in most cases, against such pests as mealybugs, codling moth and leaf miners. As the life stages of the above-ground insect pests have not co-evolved together with those of EPNs, they are, generally, more susceptible than the soil-based life stages. However, EPNs are susceptible to desiccation and vulnerable to UV radiation, so that ensuring their survival beyond soil environments is problematic. The impetus to avoid environmental stressors can cause EPNs to seek sheltered, cryptic habitats on foliage, where their target insect pest (such as mealybugs) may be found. The current paper provides an overview of information on the application of EPNs as a biocontrol agent for the control of insect pests above ground and on foliage, with particular reference to research done in South Africa. [ABSTRACT FROM AUTHOR]

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 of adjuvants 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Woolly apple aphid (WAA), Eriosoma lanigerum, is an important pest of apples, occurring throughout the apple-growing regions of the world. Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have generated intensive interest as inundative biocontrol agents of pest insects. Considering resistance of WAA against certain insecticides and the inability of parasitoids to control the aphid successfully early in the season, EPNs offer an alternative biocontrol option. The susceptibility of WAA to seven indigenous EPN species was tested in laboratory bioassays in which Steinernema yirgalemense and Heterorhabditis zealandica were identified as being the most effective against the subterranean adult females of the WAA, with infection rates of 39%and 28 %, respectively. The effect of E. lanigerum size showed that the last instar is most susceptible to infection, whereas none of the crawlers were infected. Increasing the exposure time of the aphids and nematode concentration had no positive effect on the WAA infection rate. On evaluating the ability of infective juveniles of S. yirgalemense and H. zealandica to tolerate exposure to imidacloprid, both nematode species were found to be compatible at the recommended dosage, with no significant nematode mortality having occurred. Neither did imidacloprid affect the ability of the nematodes to infect their hosts after 24 h exposure. The associated bacteria, isolated from 12 EPN isolates, showed a visual inhibitory growth effect, when they were exposed to the haemolymph of WAA. From these results, it is concluded that, although S. yirgalemense showed some infection of WAA, its low mortality and inability to complete its life cycle within the host, limits its effectiveness as a biological control agent against the subterranean stages of WAA in apple orchards. [ABSTRACT FROM AUTHOR]

Eriosoma lanigerum, woolly apple aphid (WAA), is an important pest of apples in theWestern Cape province of South Africa and in other apple-growing areas of the world. The aphid forms densely packed colonies covered with white, waxy, filamentous secretions, on the above-ground parts and on the roots of apple trees. The management of WAA primarily entails the use of resistant rootstocks, chemical and biological control, or the integration of all three strategies. Although Aphelinus mali is a specialised parasitoid ofWAA, its level of control has been reported to be unsatisfactory as its parasitism is confined to the above-ground populations of WAA. Entomopathogenic nematodes and fungi that are important natural biological control agents of many insects and other arthropods are used to control a wide range of soilborne insects. The successful applications of these entomopathogens to control other soilborne insects raise the possibility of using them to target the subterranean populations ofWAA. The review represents a combination of previous and current information on management practices for the control of WAA and the potential of integrating biocontrol agents such as entomopathogenic nematodes and entomopathogenic fungi in a pest management system. [ABSTRACT FROM AUTHOR]

The indigenous soil-dwelling scale insect, Margarodes prieskaensis, can severely damage and even kill grapevines in the northern grape-growing regions of South Africa. There are no registered means of control, and soil applications of insecticides raise environmental concerns. Using local isolates of entomopathogenic fungi (EPF) that are better adapted to local conditions to target female margarodes could add a valuable biocontrol component to an integrated management strategy. The objective of this research was to evaluate the efficacy of a local isolate of Metarhizium pinghaense against M. prieskaensis females under field conditions. Dry conidia suspended in water and 0.05% v/v Tween 20, applied as a soil drench, achieved 19.1% and 17.7% infection of margarode females in the Northern Cape and Limpopo, respectively, in 2021. Conidia stored in canola oil, suspended in water and 0.05% v/v Tween 20 and applied as a soil drench achieved infection rates of 38.5% and 62.8%, respectively, at the same sites in 2022. These results confirm the importance of formulating conidia for protection against adverse environmental conditions to improve EPF efficacy in the field. This study is the first to demonstrate the efficacy of M. pinghaense against margarode females at the soil surface and confirms the potential of this EPF for the biological control of margarodes. [ABSTRACT FROM AUTHOR]