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Plantwise Technical Factsheet

rose-grass aphid (Metopolophium dirhodum)

Host plants / species affected
Avena sativa (oats)
Beta vulgaris var. saccharifera (sugarbeet)
Bromus catharticus (prairiegrass)
Bromus rigidus (ripgut brome)
Dactylis glomerata (cocksfoot)
Eleusine coracana (finger millet)
Festuca (fescues)
Fragaria (strawberry)
Glyceria (mannagrass)
Hordeum (barleys)
Hordeum vulgare (barley)
Iris (irises)
Lolium (ryegrasses)
Musa x paradisiaca (plantain)
Phalaris brachystachys (short-spiked canarygrass)
Poa annua (annual meadowgrass)
Poaceae (grasses)
Rosa (roses)
Rosa rugosa (rugosa rose)
Secale cereale (rye)
Triticum aestivum (wheat)
Triticum turgidum (durum wheat)
Zea mays (maize)
List of symptoms/signs
Leaves  -  abnormal colours
Leaves  -  abnormal forms
Leaves  -  fungal growth
Leaves  -  honeydew or sooty mould
Leaves  -  yellowed or dead
Whole plant  -  early senescence
Description
Adults

Generally elongate and spindle-shaped. On the primary host, apterous viviparous females are green, and about 3 mm long, whilst on the secondary host apterous females are pale green or yellowish green, 1.6-3.1 mm long; both with a more brightly coloured green longitudinal stripe on the dorsum. Antennae mainly pale, with tips of segments III-V, segment VI near the primary sensoria, and the terminal process dark; legs, siphunculi and cauda pale. Alate viviparous females exhibit brownish heads, and parts of the thorax and antennae are also brown; abdomen with dorsal spinal cross bars; body 1.6-3.3 mm long. Oviparous females whitish, yellow or pink; rather small, about 1.9 mm long. Alate male similar to alate female, but more slender. Head, thorax and antennae dark; abdomen reddish with irregular cross bars; siphunculi and cauda rather dark.

Detailed morphological descriptions of the different morphs, are given by Heie (1994).
Prevention and control

Cultural Control

Delaying sowing until after the peak autumn flight can reduce virus incidence in winter cereals. Early maturation of winter barley crops provides some resistance to M. dirhodum via drying out of the leaves (Howard and Dixon, 1995).

Host-Plant Resistance

Significant differences in the resistance of winter wheat varieties have been reported (Auclair, 1989), and the ancient variety Einkorn (Triticum monococcum) has shown antibiotic resistance to M. dirhodum (Sotherton and Lee, 1988). Maize cultivars Blask and Bulat were identified as the most resistant in a study on the susceptibility of 12 maize hybrids to M. dirhodum in Poland (Pienkosz et al., 2005).

A study by Clayson et al. (2014) showed evidence of synergy between resistance in wheat cv. Rapier and the susceptibility of M. dirhodum to malathion, raising the possibility of using reduced concentrations of pesticides to control aphids on resistant crop cultivars.

Biological Control

Biological control has been attempted in a number of countries recently invaded by M. dirhodum. Aphidius ervi and members of the Aphidius rhopalosiphi/A. uzbebistanicus complex were introduced into southern Chile from France in 1976-1977, from where they may have spread to Brazil and Argentina (Botto and Hernandez, 1982). The establishment of Aphidius spp. was confirmed during the spring following their introduction, and levels of parasitism reached peaks of 14.7% (Norambuena, 1981). Similarly, stocks of the A. rhopalosiphi group were introduced into New Zealand (in 1985) and Australia (in 1986) (Stufkens and Farrell, 1987; Carver, 1989). In 1988-1989, the rate of parasitism by A. rhopalosiphi was estimated at Lincoln, near Canterbury, New Zealand, to be about 50% in winter barley and 100% in spring barley at the time of peak aphid numbers (Farrell and Stufkens, 1990).

In Australia, M. dirhodum was rapidly subjected to parasitism by Erynia neoaphidis and by A. ervi (Carver, 1989). However, artificially introduced E. neoaphidis was found by Wilding et al. (1990) to be too slow and unpredictable in its action to be likely to form a practical alternative to conventional insecticides for cereal aphid control in the UK.

In Brazil, the braconids Aphidius ervi, A. rhopalosiphi, A. uzbekistanicus and Praon volucre have successfully been used for the biological control of wheat aphids M. dirhodum and Sitobion avenae since the 1970s (Alves et al., 2005Sampaio, 2009).

In field studies in wheat in Argentina, the coccinellid predator Eriopis connexa showed a linear increase in numerical response to an increase in the density of aphids (including M. dirhodum) and was higher in higher plant diversity (HPD) plots with refuge strips than in lower plant diversity (LPD) plots without refuge strips (Tulli et al., 2013).

In a population dynamics model devised to provide a tool for integrated pest management in winter wheat, it was estimated that fungal diseases accounted for 75% of the reduction in peak density of aphids (Sitobion avenae, Rhopalosiphum padi and M. dirhodum) in western France and were the key factor acting on aphid dynamics in this region (Plantegenest et al., 2001).

Chemical Control

M. dirhodum can attack cereal crops in the early stages of growth, infesting stems and leaves prior to the emergence of the inflorescence. Greatest yield losses occur when the attack is during the period between tillering and the end of flowering. Control is usually carried out at the time of flowering, using aphid-specific products, for example pirimicarb, which are generally more selective in preserving natural enemies. Application of pirimicarb against M. dirhodum on barley in New Zealand at the flag-leaf extension stage of plant growth was more effective than an application in the stem extension stage (Stufkens and Farrell, 1986).

Maize seed treated with imidacloprid prevented mass propagation of M. dirhodum and reduced transmission of BYDV (Epperlein et al., 1997). Pyrethroids, such as alpha-cypermethrin, have been shown to be effective in reducing aphid numbers, although such products can reduce the natural enemy population. Poehling (1988) found that prophylactic insecticide treatments immediately before flowering were often too early to prevent a later aphid outbreak, and prevented invasion of the fields by syrphids and coccinellids.

Essential oils from Schinus areira, Rosmarinus officinalis and Tagetes terniflora showed biological activity against M. dirhodum in the laboratory and could be used as alternative chemicals in the management of the aphid (Chopa and Descamps, 2012).

Field Monitoring / Economic Threshold Levels

Suction traps are used to sample flying aphids, as a monitoring/warning system for migratory activity (Farrell and Stufkens, 1992). Cereal aphid flight was monitored by 12.2 m suction traps weekly for 8 years at Szolnok, Hungary, and at Rothamsted, UK. The peak flight occurred 1, 3 and 2 weeks later at Rothamsted than at Szolnok for Rhopalosiphum padi, M. dirhodum and Sitobion avenae, respectively (Basky and Harrington, 2000). Cereal aphids, including M. dirhodum, were monitored using suction traps and Lamber’s pan traps in the Czech Republic. Primary migration was at the end of June. The suction traps were 10-20 times more efficient than the Lamber’s pan traps (Patocková, 2011). Leather et al. (1984) suggested using spring counts of M. dirhodum on the primary host as an indication of the likelihood of an outbreak on secondary hosts the following summer. Mantel et al. (1982) recommended a threshold of 30 M. dirhodum aphids per flag-leaf for application of aphicidal sprays. However, the current UK spray threshold is two-thirds of shoots infested at the start of flowering, or 5 aphids per shoot (Duffield et al., 1997).

IPM

In a review of 33 years of research studies in Transylvania, Romania, recommendations for control of wheat aphids, including M. dirhodum, included: cultural control (avoiding early planting in the autumn, destroying wheat volunteers, adequate fertilization, use of good quality seed and integrated control measures against weeds, pests and diseases); the use of tolerant varieties and natural enemies; and the application of insecticides, with economic and ecological efficiency (Malschi et al., 2013). 

Impact

M. dirhodum is one of the most economically significant insect pests of wheat in Washington, USA (Pike and Tanigoshi, 1996) and was described by Feng et al. (1991) as abundant in a field survey of dryland and irrigated crops of small grains in Montana, USA.

In Chile, M. dirhodum population levels have exceeded those in its native (i.e. European) region, causing relatively severe outbreaks of Barley yellow dwarf virus on cereal crops (Sylvester, 1989).

Severe infestations of M. dirhodum develop on cereals in some years as a result of favourable climatic conditions and the absence of natural enemy control (Cannon, 1986; Dixon, 1987). Significantly higher populations of M. dirhodum are associated with nitrogen applications, although it is not clear whether this is a direct or indirect effect, for example due to changes in canopy structure (Duffield et al., 1997). In a field study in the UK, longevity of M. dirhodum was unaffected by five levels of nitrogen fertilization (from 50 to 250 kg N/ha). Aphid intrinsic rate of increase and fecundity increased with each level applied to 200 kg N/ha but there was a significant decrease in fecundity for the highest rate of fertilization of 250 kg N/ha (Gash, 2012).  

In addition to the direct damage caused by a drain of nutrients by phloem-feeding (and the development of saprophytic fungi on honeydew excretions, which accelerates the ageing of the plants), indirect damage occurs as a result of the transmission of viruses. In particular, persistent Barley yellow dwarf virus (BYDV), which typically produces symptoms of yellowing and dwarfing. In Italy, M. dirhodum is able to transmit BYDV from maize (on which it produced no symptoms), or wild grasses, and pass it on to wheat and barley (Suss and Colombo, 1982; Guglielmone and Caciagli, 1996). M. dirhodum was recorded as a vector of isolate BYDV-PAS (but not usually as a vector of isolate BYDV-PAV) on cereals and grasses in the Czech Republic (Jarošová et al., 2013) and as a vector of isolate BYDV-PAV on wheat and oats in Brazil (Parizoto et al., 2013).  

M. dirhodum was found to transmit a Spanish isolate of Sugarcane mosaic virus in a non-persistent manner (Angeles Achón et al., 2003). M. dirhodum is also a vector of Potato virus Y (Schröder and Krüger, 2014) and an inefficient vector of Zucchini yellow mosaic virus (Katis et al., 2006). M. dirhodum is an occasional inefficient vector of Plum pox virus (Gildow et al., 2004a,b) and was also found to be a vector of a new virus called rose spring dwarf associated virus (RSDaV) (Salem et al., 2008).

Holt et al. (1984) determined the effect of crop growth stage (G.S.) on yield reductions of winter wheat caused by M. dirhodum. Yield losses at early (G.S. 30-41), middle (G.S. 41-65) and late (G.S. 65-77) stages of crop growth were 5, 8 and 27%, respectively. Yield reductions of barley attributed to feeding by M. dirhodum in the Irish Republic were estimated at 0.32, 0.48 and 0.43 t/ha (5.2, 5.6 and 5.7%) in 1997, 1999 and 2000 (Kennedy and Connery, 2005).

Related treatment support
 
External factsheets
Bayer CropScience Crop Compendium, Bayer CropScience, English language
NIPI IPM guidelines, Queensland Department of Agriculture and Fisheries, 2014, English language
University of California IPM Pest Management Guidelines, University of California, 2007, English language
Sistemas de Produção Embrapa - Publicações eletrônicas, Embrapa, Portuguese language
Pennsylvania State University Insect Pest Fact Sheets, The Pennsylvania State University, 2010, English language
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