Archie K. Murchie

DETECTION OF RHOPALOSIPHUM INSERTUM (APPLE-GRASS APHID) PREDATION BY THE PREDATORY MITE ANYSTIS BACCARUM USING MOLECULAR GUT ANALYSIS

Abstract  1 A simple, yet sensitive polymerase chain reaction based technique was developed for the detection of the apple‐grass aphid Rhopalosiphum insertum in the gut of Anystis baccarum, a predatory mite.

The impact of fungicides to control apple scab (Venturia inaequalis) on the predatory mite Anystis baccarum and its prey Aculus schlechtendali (apple rust mite) in Northern Ireland Bramley orchards.

Abstract Apple scab is the most serious disease in Northern Ireland Bramley orchards. As a result, as many as 14 fungicide sprays can be applied each season to control the disease. Anystis baccarum is a commonly occurring predatory mite in the orchards. The effects of three commonly used fungicides (captan/penconazole, mancozeb and dithianon) on A. baccarum and the pest mite Aculus schlechtendali were investigated. On the mancozeb treated trees there were fewer A. baccarum and more A. schlechtendali compared to the other treatments, although the latter result was probably due to the condition of the leaves in this treatment. Dithianon had no detrimental effect on A. baccarum.

European Union policy on pesticides: implications for agriculture in Ireland

European Community (EC) legislation has limited the availability of pesticide active substances used in effective plant protection products. The Pesticide Authorisation Directive 91/414/EEC introduced the principle of risk assessment for approval of pesticide active substances. This principle was modified by the introduction of Regulation (EC) 1107/2009, which applies hazard, the intrinsic toxicity of the active substance, rather than risk, the potential for hazard to occur, as the approval criterion. Potential impacts of EC pesticide legislation on agriculture in Ireland are summarised. While these will significantly impact on pesticide availability in the medium to long term, regulations associated with water quality (Water Framework Directive 2000/60/EC and Drinking Water Directive 1998/83/EC) have the potential to restrict pesticide use more immediately, as concerns regarding public health and economic costs associated with removing pesticides from water increase. This rationale will further reduce the availability of effective pesticide active substances, directly affecting crop protection and increasing pesticide resistance within pest and disease populations. In addition, water quality requirements may also impact on important active substances used in plant protection in Ireland. The future challenge for agriculture in Ireland is to sustain production and profitability using reduced pesticide inputs within a framework of integrated pest management.

Differential emergence of Culicoides (Diptera: Ceratopogonidae) from on-farm breeding substrates in Northern Ireland.

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are vectors of a number of viral diseases worldwide. Following the unforeseen outbreak of bluetongue in northern Europe (2006–2009) there was a need to clarify on-farm breeding substrates utilized by temperate Culicoides spp. Six substrates (cow dung, cow slurry, horse dung, sheep dung, maize silage and soil) were investigated for Culicoides spp. emergence over a 31-week period. Overall, most Obsoletus group Culicoides emerged from the cow dung and the most Pulicaris group Culicoides emerged from the sheep dung. Furthermore, Culicoides of the Obsoletus group were found to be abundant in cow slurry and sheep dung. Temperature played a significant role in the emergence times of adult Culicoides. The Obsoletus group appear to have undergone 3 generations during the experimental period. The sex ratio of emergent Obsoletus group Culicoides was affected by substrate type, with a greater proportion of males emerging from cow dung and slurry compared with the other substrates.

A review of African horse sickness and its implications for Ireland

African horse sickness is an economically highly important non-contagious but infectious Orbivirus disease that is transmitted by various species of Culicoides midges. The equids most severely affected by the virus are horses, ponies, and European donkeys; mules are somewhat less susceptible, and African donkeys and zebra are refractory to the devastating consequences of infection. In recent years, Bluetongue virus, an Orbivirus similar to African horse sickness, which also utilises Culicoides spp. as its vector, has drastically increased its range into previously unaffected regions in northern Europe, utilising indigenous vector species, and causing widespread economic damage to the agricultural sector. Considering these events, the current review outlines the history of African horse sickness, including information concerning virus structure, transmission, viraemia, overwintering ability, and the potential implications that an outbreak would have for Ireland. While the current risk for the introduction of African horse sickness to Ireland is considered at worst ‘very low’, it is important to note that prior to the 2006 outbreak of Bluetongue in northern Europe, both diseases were considered to be of equal risk to the United Kingdom (‘medium-risk’). It is therefore likely that any outbreak of this disease would have serious socio-economic consequences for Ireland due to the high density of vulnerable equids and the prevalence of Culicoides species, potentially capable of vectoring the virus.

Evidence for monogeny in the brassica pod midge Dasineura brassicae

An unusual brood characteristic that has been found in the Cecidomyiidae is that of monogeny i.e., production of predominantly all male or all female broods (Matuszewski, 1982). Cecidomyiid midges that demonstrate monogeny include Dasineura alpestris Kieffer (Barnes, 1931), the hessian fly Mayetiola destructor (Say) (Painter, 1930; Stuart & Hatchett, 1991), the sorghum midge Stenodiplosis sorghicola (Coquillett) (Baxendale & Teetes, 1981), the rice gall midge Orseolia oryzae (Wood-Mason) (Sain & Kalode, 1988), the aphid biocontrol agent Aphidoletes aphidimyza (Rondani) (Sell, 1976), and the sow-thistle biocontrol agent Cystiphora sonchi (Bremi) (McClay, 1996). As the biological characteristics of the vast majority of Cecidomyiidae are poorly known, it seems likely that this reproductive strategy is reasonably common in this family although not completely ubiquitous: for example Barnes (1931) found no evidence of monogeny in Dasineura leguminicola (Lintner). The brassica pod midge, Dasineura brassicae Winnertz (Diptera: Cecidomyiidae), is a common pest of brassicaceous seed crops, in particular oilseed rape ( Brassica napus L and B. campestris L), throughout north-western Europe (Alford et al., 1991; Winfield, 1992). The female midge lays eggs in batches inside a seedpod which has been damaged in some way, normally by the feeding and oviposition activities of another pest, the cabbage seed weevil Ceutorhynchus assimilis Paykull (synonym Ceutorhynchus obstrictus [Marsham]) (Coleoptera: Curculionidae), which is concurrent on the crop (Sylvén, 1949). Dasineura brassicae larvae feed on the inner pod wall and infested pods become yellow, swollen, and discoloured before eventually splitting open about 14 days after the initial attack (Sylvén, 1949), causing a complete loss of seeds. Other studies have dealt with production of a female sex pheromone by D. brassicae (Williams & Martin, 1986; Isidoro et al., 1992; Murchie et al., 2001), with host plant suitability for egg and larval development (Åhman, 1985a,b, 1986; Hallberg & Åhman, 1987) and with the relationship between C. assimilis damage and D. brassicae oviposition (Sylvén & Svenson, 1975; Ferguson et al., 1995). However, little information exists on the characteristics of individual broods within pods, beyond estimates of typical clutch size. The aim of this study was to determine whether D. brassicae laid single sex broods (exhibited monogeny). In consequence, the relationship between larval brood size and the size of the pods into which they were deposited was also investigated.

Anystis baccarum: An Important Generalist Predatory Mite to be Considered in Apple Orchard Pest Management Strategies

The increasing concern over the continued use of pesticides is pressurising apple growers to look for alternatives to chemical pest control. The re-discovery, and subsequent conservation, of the beneficial predatory mite, Anystis baccarum (Linnaeus) (Acari: Anystidae), in Bramley apple orchards in Northern Ireland offers a potential alternative control component for incorporation into integrated pest management strategies. Anystis baccarum readily feeds upon economically important invertebrate pest species including European fruit tree red spider mite, Panonychus ulmi (Koch) (Acari: Tetranychidae) and show a level of compatibility with chemical pesticides. Recent mis-identification by apple growers of this beneficial mite species had resulted in unnecessary pesticide applications being applied within Northern Irish apple orchards. However, dissemination of information to the apple growers and promotion of the benefits this mite offers in apple orchards has helped to conserve its populations. Apple growers, across the United Kingdom, must be encouraged to be aware of A. baccarum, and indeed all predatory fauna, within their orchards and seek to conserve populations. In doing so, it will ensure that the British apple market remains an environmentally sustainable production system.

Black Border Increases Stomoxys calcitrans Catch on White Sticky Traps

Stable fly, Stomoxys calcitrans, is a biting fly that can cause severe irritation to livestock resulting in reduced productivity. The most common method of monitoring S. calcitrans is through the use of sticky traps and many designs have been developed using different colours and materials such as alsynite fibreglass and polypropylene sheeting. Laboratory experiments and some field experimentation have demonstrated that colour contrast can attract S. calcitrans. However, this response has not been fully utilised in trap design. To test that simple colour contrast could increase trap efficacy, white sticky traps were mounted on three differently coloured backgrounds (white, yellow, and black) and positioned at five sites on a mixed livestock farm. White sticky traps on a black background caught significantly more S. calcitrans than the yellow or white backgrounds. An incidental result was that Pollenia sp. were caught in greater numbers on the yellow framed traps. The reasons for S. calcitrans attraction to black–white contrast are most likely due to conspicuousness in the environment although the extent to which flies are using this feature as a host-location cue or a perching site are unknown.