WEEDS, PESTS & DISEASES No. 78 May 2008 Hairgrass (Vulpia spp.). What do we know? A review of the literature.

Key Points • In New Zealand the common name ‘hairgrass’ combines three individual Vulpia species (Vulpia bromoides, V. myuros and V. Megalura). • The individual species are very difficult to identify, with the seed head being the easiest feature to separate the species. • Typically germination follows a 2-3 month dormancy which breaks when monthly rainfall exceeds evaporation. • Germination occurs both in light and dark conditions; however germination is more rapid and uniform in the light. • Seedling emergence from the relatively shallow depth of 5cm is considerably less than 0-1 cm. • An integrated approach including cultivation, chemical and crop rotation is required for sustained control of Vulpia spp. • The relationship between burial through cultivation on seed dormancy and viability is not clear and will be the focus of future FAR funded research. • Chemical control can be difficult and will continue to be a focus of FAR trial work.

Introduction Vulpia spp. has been increasingly common on Vulpia spp. are a problem in New Zealand in small arable farms in Canterbury in recent years. seed crops as they contaminate seed and reduce seed yield. As part of understanding annual grass weeds in Climate cropping rotations, a literature review on Vulpia Vulpia species can survive and reproduce over a hairgrass was undertaken. The aim of this review was wide range of climatic conditions; however to identify gaps in the knowledge which could allow Mediterranean type climates appear most FAR to establish research priorities. This update aims favourable. Cool winters followed by warm to summarise the international research on this annual springs and the absence of drought appear ideal grassweed and provide an understanding of biology so but both species have been collected in areas some control measures can be established. ranging from 200–1200mm annual rainfall (Wallace 1997). Plants are shallow rooted and Three Vulpia species are recorded as present in New therefore sensitive to drought however the annual Zealand. These are, Vulpia bromoides and V. myuros, lifecycle reduces the prospects of death during also known as squirrel-tail and rat’s-tail fescue drought. respectively, (Wallace 1997) and V. megalura (uncommon) (Edgar and Connor 2000). In New Soil type Zealand these three species are collectively known as Vulpia plants grow on a wide range of soil types Vulpia hairgrass, other common names include silver and fertility levels where soil pH ranges from 4.5- grass and silky grass. 9. Surveys in Australia have shown Vulpia to grow mainly on light to medium textured soils Vulpia spp. can often be confused with toad rush (slightly acidic), and characterised by low to (Juncus bufonius); however usually only under moist moderate phosphate and potassium status. soil conditions. It can also be confused with fine leaved Vulpia myuros (and most likely V. bromoides) has fescues e.g. chewings fescue (Festuca nigricans) or been shown to tolerate soils with low potassium, red fescue (Festuca rubra) etc. phosphorus and nitrogen status. At the same time Vulpia species have been shown to survive and 1. Habitat reproduce under higher fertility environments with low-inter species competition. Under high fertility, Distribution is usually on dry, open, infertile soils V. myuros and V. bromoides are likely to suffer while being abundant in waste places e.g. fence competition from species such as Italian ryegrass lines and light pastures throughout New Zealand. (Lolium multiflorum) (Wallace 1997); however ryegrass sowing rates on arable farms are unlikely to Phenology (progression to flowering and seed set) produce crop plant populations high enough to induce The conditions required for floral initiation include competition severe enough for Vulpia plant death. exposure to a period of cool conditions (vernalisation response). Vulpia bromoides appears to flower over a wide range of day lengths, between 8–16 hours. Vulpia bromoides can produce numerous ears at temperatures of 25/15°C (day/night temperatures) compared to very few by V. myuros under the same conditions. For any significant production of ears, V. myuros required exposure to short days (8 hours) and cool temperatures (18/10°C). In both species flowering was inhibited by high temperatures (28/20°C) (Dillion and Forcella 1984).

New Zealand conditions appear favourable for both species to produce large numbers of seed heads and therefore return high levels of seed to the soil seed bank. Flowering occurs in the spring with both species flowering at similar times. The period from flowering to seed maturity varies from Figure 1. Young Vulpia spp. plants photographed 120 seven to 30 days depending on environmental days after planting, FAR Arable Site 2007 conditions. Seeds are shed shortly after maturity and are dislodged by wind or mechanical/animal 2. Growth and development disturbance. Vulpia spp. are prolific seeders and will typically produce more seed than is required Perennation to maintain the current plant population. Vulpia myuros and Vulpia bromoides are true annuals and survive adverse conditions as seeds e.g. high Seed Dormancy temperatures and drought. Under favourable Seed dormancy occurs in Vulpia spp. and has conditions some plants may survive into the second been reported by various authors. It is common year. Vulpia species seed prolifically in late spring to for a 2-3 month after ripening period (dormancy) mid summer. to be required for germination to proceed under field conditions. This can be extended in dry Germination climates and where temperatures are high. Most shed seed is located near the soil surface (except Dormancy is usually broken when monthly rainfall on cultivated soils). Under field conditions the seeds of exceeds pan evaporation under Australian V. myuros and V. bromoides typically have a seed conditions (Wallace 1997). The majority of seed dormancy of between 2 and 3 months (Wallace 1997). germinates readily and uniformly assuming Typically germination takes place when rainfall dormancy is broken and soil moisture is adequate exceeds evaporation (March – May under New (Dillon and Forcella 1984). Zealand conditions). Dillon and Forcella (1984) showed that exposure to light during the germination 3. Chemical control phase increased the temperature range for optimum germination. However maximum germination Chemical (FAR trials) percentage was achieved over a wide range of FAR has conducted several herbicide trials where temperatures, from 12–23°C for both species in hairgrass has been included. Consistent darkness, and 12-31°C and 9-28°C in light for V. performers against hairgrass have been Nortron myuros and V. bromoides respectively. Light and Gardoprim. Other chemicals which have stimulated both species to germinate more rapidly and proved useful include Sencor, Teedal, Karmex, more evenly over a wide range of temperatures. Kerb Flo and Avadex.

Physiology Nortron at 2 l/ha provides an effective control Dillon and Forcella (1984) studied the growth rates of option in ryegrass seed crops when applied pre both hairgrass species over a range of temperatures emergence. Increased rates may provide longer and photoperiods. For the initial growth period (7–10 lasting control in high risk situations. weeks) high temperatures and long photoperiods led to the greatest growth rates. Both species responded in Gardoprim has shown good control in two very a similar manner, however V. myuros usually had a contrasting seasons at 1.5 l/ha. In 2005 (warm greater growth rate compared to V. bromoides. Overall and dry) efficacy was reduced when the rate was low temperatures (18ºC day temperature and 10ºC cut to 0.75 l/ha. In 2006 good control was shown night temperature, 18/10ºC), with 8 hour photoperiods at 0.75 l/ha under cold, wet soil conditions. were optimum for growth of Vulpia spp. Plants grown under these conditions were 50–100% larger when Kerb and Teedal are both registered for the compared to those grown under either 23/15ºC or control of hairgrass but have been inconsistent in 28/20ºC. FAR trials; perhaps this is related to application timing (see Arable Extra No. 76). Winter applications 4. Cultural control were more effective than set growth stage timings. These results are supported by international literature. Cultivation and seed burial Vulpia bromoides and V. myuros germinate over a Atrazine has shown promise in controlling hairgrass wide range of temperatures provided dormancy and could possibly be used in second year ryegrass, requirements of 2–3 months have been met. tall fescue and other tolerant crops. Germination is a biological process and temperature regulates the rate of germination Chemical (literature search) while darkness retards germination of V. Vulpia species are tolerant to many of the ‘grass killer’ bromoides somewhat more than V. myuros. herbicides and therefore may require other chemical Similarly the seedling emergence from a relatively groups. shallow sowing depth of 5 cm is much less than either 0 or 1cm (Dillon and Forcella 1984). The Simazine is effective against both V.myuros and V. inability of both species to tolerate relatively bromoides and has potential usage in grain-legume shallow burial is perhaps the main reason why and other crops. The rates suggested vary between these species are seen as an increasing problem 0.25 and 2.4 kg/ha active ingredient (a.i.) when applied in Canterbury as reduced tillage increases. Under during autumn under pre-emergence conditions in conventional systems burial through ploughing Australia (Wallace 1997). The large variation in results would reduce plant emergence. The necessity of is likely to be related to soil organic matter levels and light for rapid germination and emergence may soil moisture status. The rate required to control explain why minimal tillage and direct drilled crops hairgrass on soils with high organic matter levels will are at greater risk compared to ploughed areas. be higher compared to that of low organic matter soils. However it has been stated that ploughing alone Moisture is required to move simazine into the root does not give adequate control and a combined zone where it will have the greatest effect. FAR has no tillage/herbicide programme is required for large New Zealand data on the activity of simazine on reductions in plant numbers (Wallace 1997). hairgrass. The question which remains unanswered is does Most triazine herbicides will provide some control of burial maintain a dormancy so that when Vulpia and most pulse crops have triazine registration cultivation occurs at a later date, germination can e.g. Gardoprim in peas, Atrazine in linseed, Simazine occur. in Lucerne etc. In maize triazine products are registered for use in New Zealand (Bowran and Seed bank survival Wallace 1996). The soil seed bank appears to be short lived under appropriate soil moisture conditions. Clethodim (Centurion Plus) has been shown to reduce However a proportion (1-7% under grazing) can hairgrass dry weight by up to 80% when rates of survive for three years. Most seeds germinate greater than 0.1 kg a.i./ha were applied (Leys et al. readily and uniformly. This indicates that adequate 1988). FAR has no New Zealand data on the activity control can be expected from some cultivation of clethodim on hairgrass but other results in literature techniques (Wallace 1997). suggest control is variable. Grazing Paraquat is commonly used in conjunction with other Heavy grazing by sheep in the spring, prior to selective herbicides for the control of Vulpia spp. in flowering and seed set, can reduce seed returned some states of Australia (Bowran & Wallace 1996). to the soil seed bank. This is best followed up The use of Paraquat alone does not always result in with autumn grazing during plant establishment. high levels of control and surviving plants may still produce large quantities of seed. Paraquat may be Integrated mixed with Simazine to increase efficiency of both For optimum hairgrass control no single factor products. Paraquat is registered for “most annual and above is likely to succeed on its own and an perennial grasses” in white clover seed crops. Control integrated approach is likely to be necessary. The will be greater when plants are smaller. use of herbicides alone can give short term control but herbicide options can be risky or limited in Maltic and Black (1992) have shown Diuron gave 70% many monocotyledonous crops. Therefore crop control of Vulpia fasciculata (not present in New rotation plays a major role with options for control Zealand) in cereals when applied pre-sowing at up to around stale seedbeds, cultivation and crop 500g a.i. Greater control was provided when mixed selection which allows for chemical control. with Trifluralin. FAR data supports control from 800g Spring crops offer an additional control option with a.i/ha, with limited cereal damage when applied pre- the removal of established plants with either emerge in one of two seasons 2007 (FAR Arable Extra cultivation or Glyphosate (prior to planting). No. 67) while no control was shown in 2006 (FAR Increased crop competition can reduce the plant Arable Extra No. 60). Trifluralin has been shown to numbers of Vulpia, therefore row spacing, sowing provide approximately 70% control at rates which are rate and fertility levels can all play minor roles in used for ryegrass control. FAR has no New Zealand an integrated control approach. data on control or crop safety of these products.

Description and identification. (From Edgar and Connor 2000, Wallace 1997 and Lambrechtsen 1992) Hairgrass is a green to yellowish green, loosely tufted, erect, slightly hairy annual ranging from 5-60cm tall. The leaf blade is 2-20cm long, 0.5-3mm wide, upper surface with 5-7 veins, hairless or with very few scattered hairs, keel indistinct. No auricles present (figure 2). Ligule is very short, but distinct (0.5mm, rarely 1mm, long, membranous, greenish white) (figure 3). In Vulpia species the emerging leaf is rolled (figure 4). The leaf sheath is hairless or with very few scattered hairs, the base of leaf sheath sometimes has a reddish purple tinge. Vulpia can take many plant forms depending on crop or weed competition (e.g. figure 1).

The inflorescence is a panicle carried well clear of the flag leaf (V. bromoides) or partly included in the upper most leaf sheath (V. myuros), erect or slightly nodding, 1-10mm long (V. bromoides) or 5-35cm long (V. myuros). Inflorescence length may be reduced under adverse conditions (Cunningham et al. 1992). Inflorescence colour is green-purple. Spikelets comprise of 3-10 fertile florets, 7-16mm long. Florets, 5-9mm long without keel and 5 veined with one awn. Awn up to 13mm long. The glumes are unequal and Figure 4. Descriptions of vegetative tiller finely pointed and are the main determinant between characteristics (Source: Lambrechtsen, 1992) the two species. References Vulpia bromoides – lower glume 2-6mm long (0.5-0.75 Bowran, D. and Wallace, A. (1996). Chemical weed management of times the length of the upper glume), 1 vein. Upper Vulpia. Plant Protection Quarterly. 11: 211-212. glume 5-10mm long, 1 times the length of the adjacent Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. fertile lemma, 3 veined. Both glumes without keels. (1992). Plants of Western New South Wales. 153-154. Inkata Press, Melbourne. Vulpia myuros – lower glume 1-3.5mm long (0.15-0.4 times the length of the upper glume), 1 vein. Upper Dillon, S.P. and Forcella, F. (1984). Germination, Emergence, Vegetative Growth and Flowering of Two Silvergrasses, Vulpia glume 3-8mm long, 0.75 times the length of the bromoides (L.) S.F. Gray and V. myuros (L.) C.C. Gmel. Australian adjacent fertile lemma, 1-3 veined. Both glumes Journal of Botany. 32: 165-175. without keels. Edgar, E. and Connor, H.E. (2000). Flora of New Zealand, Volume V, Grasses. Manaaki Whenua Press, Lincoln, New Zealand.

Lambrechtsen, N.C. (1992). What grass is that? GP Publications Ltd, Wellington, New Zealand.

Leys, A.R., Plater, B. and Cullis, B. (1988). Response of six temperate annual grass weeds to six selective herbicides. Plant Protection Quarterly. 3:163-168.

Maltic, R. and Black, I.D. (1992). Integrated weed management systems for the control of sand fescue (Vulpia fasciculata) in barley in South Australia. Proceedings of the 1st International Weed Control Congress, Melbourne. 2:315-317.

Wallace, A. (1997). The biology of Australian weeds. 30. Vulpia bromoides ((L.) S.F. Gray) and V. myuros ((L.) C.C. Gmelin). Plant Figure 2. Anatomical features of a Gramineae plant at Protection Quarterly. 12: 18-28. the leaf axis (Source: Lambrechtsen, 1992) ©This publication is copyright to the Foundation for Arable Research and may not be reproduced or copied in any form whatsoever without their written permission.

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Figure 3. Type and size descriptions of grassweed ligules (Source: Lambrechtsen, 1992)