Nationwide Survey of Pests and Diseases of Cereal and Grass Seed Crops in New Zealand

Arable Crops 51

NATIONWIDE SURVEY OF PESTS AND DISEASES OF CEREAL AND GRASS SEED CROPS IN NEW ZEALAND. 2. FUNGI AND BACTERIA

M. BRAITHWAITE1, B.J.R. ALEXANDER1 and R.L.M. ADAMS1

1New Zealand Plant Protection Centre, MAF Quality Management, PO Box 24, Lincoln

ABSTRACT A national survey of seed crops was conducted by the New Zealand Plant Protection Centre (NZPPC) from October 1995 to February 1996. Approximately 85,000 plants were inspected at 332 sites in the main cereal growing areas of New Zealand. One hundred and eighty new host/fungal associations were recorded for barley, brome, oat, ryecorn, ryegrass and wheat. Of these 26 were primary pathogens able to cause plant damage. The most common new associations were of fungi causing root rot problems, especially Phytophthora, Pythium and Fusarium species. The fungus, Ceratocystis paradoxa was found for the first time in New Zealand at two sites in Dunedin where it caused leaf spotting on wheat. Of the fungi and bacteria previously known to occur on cereals and grasses in New Zealand, Fusarium species were the most commonly observed, primarily associated with foot rot. A number of fungi and bacteria previously recorded on these hosts in New Zealand, were not detected during this survey. New Zealand’s freedom from a range of important exotic fungi and bacteria was confirmed. Keywords: cereal, grass seed, survey, Fusarium, Ceratocystis.

INTRODUCTION From October 1995 to February 1996, the New Zealand Plant Protection Centre (NZPPC) conducted a survey of pests and diseases on four cereal and two grass seed crops. The survey was part of an ongoing plant pest and disease surveillance programme operated by the Ministry of Agriculture and Forestry (MAF). Such a survey aims to detect any pests/diseases new to New Zealand, as well as previously known pests and diseases with altered hosts or distributions. Comprehensive lists of organisms (pest lists) known to occur in New Zealand are important in setting quarantine import standards and negotiating trade conditions for export crops. This paper documents the primary fungal and bacterial diseases found during the cereal and grass seed survey. New organisms, new pest-host associations and distributions of fungal and bacterial pathogens on each crop are listed. Findings for insects and molluscs are recorded in Bejakovich et al. (1998).

METHOD Four cereal crops, barley (Hordeum vulgare), oats (Avena sativa), ryecorn (Secale cereale) and wheat (Triticum aestivum), and two grass seed crops, brome grass (Bromus spp.) and ryegrass (Lolium spp.), were included in this survey. The survey was designed according to the procedure given by Dymock and Holder (1996). Sampling occurred throughout crop development at 332 sites in the main cereal and grass seed growing areas of New Zealand. The number of sites was apportioned among crops on the basis of their hectares of production and import/export values of each crop grown nationally (Statistics New Zealand 1994). The sites were chosen from grower lists provided by MAF Quality Management field officers and relevant grower associations and supplemented by local knowledge.

Proc. 51st N.Z. Plant Protection Conf. 1998: 51-59

Sampling Sampling was designed to detect pests infesting greater than 1% of plants at a particular site with 90% confidence. To meet this criteria, 256 plants were examined in detail at each site for signs and symptoms of disease caused by fungi or bacteria. Specimens of stems, leaves and roots were collected for laboratory examination and fungal and bacterial identification. Identification and reporting Laboratory procedures utilising visual examination, culture plating and biochemical techniques were used for specific organism identification. Where possible, identifications were carried out to species level. The nature of each pest-host association was assigned according to the definitions in footnote 1, Table 1. Pest-host associations new to New Zealand were validated by another practising plant pathologist from New Zealand or overseas. Results were compared with lists of known pest-host associations and distributions prepared from published and unpublished sources (Anon 1981; NZ Plant Protection Centre records; Pennycook 1989) for each of the six crops surveyed. All records from this survey are available on the Plant Pest Information Network (PPIN) database (Beal 1997). RESULTS AND DISCUSSION The number and nature of organism-host associations for each of the surveyed crops are presented in Table 1. Fungal and bacterial associations with host plants were classified into 4 groups: primary, secondary, saprophyte and unknown as described in footnote 1, Table 1. Only pest-host associations classified as primary are discussed further in this paper. Records confirming known and 26 new primary pest-host associations and their distributions are presented in Table 2. Ceratocystis paradoxa, causing a leaf spot on wheat, was found in New Zealand for the first time during this survey. A further 180 new fungal associations were found during the survey.

TABLE 1: Number of association records for fungi and bacteria recorded for the four cereal and two grass seed crops. ______Nature of Barley Brome Oats Ryecorn Ryegrass Wheat Total association1 grass ______primary 29 12 10 5 13 26 95 secondary 18 7 10 6 12 22 75 saprophyte 31 2 13 16 13 35 110 unknown 113 3 7 6 12 14 55

Total 91 24 40 33 50 97 335 ______1 Primary = the organism is able to invade and gain sustenance from intact tissues of this plant (and may cause damage or disease to this host, possibly leading to economic loss); secondary pest = the organism attacks, and gains sustenance from, tissues of this plant once already impaired (and may then cause disease or damage to this host, possibly leading to economic loss); saprophyte = the organism gains sustenance from decaying tissues of this plant; unknown = the association between the organism and this host is unknown. Barley Of the primary fungal pathogens previously recorded on barley, the most commonly detected in this survey were Gibberella avenacea (38% of sites), Rhynchosporium secalis (28% of sites), Monographella nivalis (21% of sites), Gibberella zeae (14% of sites) and Pyrenophora teres (14% of sites). During this survey, several fungi were recorded for the first time on barley. Drechslera poae was observed at four sites in two locations, Wanganui and Wellington. This fungus was associated with a leaf spot and although it is not a recognised disease of barley (Mathre 1982), it could be significant during wetter seasons. Fusarium sacchari was detected at several locations in both the

North and South Islands. This fungus is part of the Fusarium foot rot complex which affects many cereal crops throughout New Zealand. A resurgence of the Fusariumfoot rot complex on cereals has been observed in the USA (McMullen et al. 1997) and observations on the incidence of Fusarium species during this survey indicate potential future problems with this disease problem. Phytophthora cryptogea, P. gonapodyides and P. megasperma,Pythium irregulare, P. rostratum and P. utimum were detected in both the North and South Islands. These soil-borne root rotting fungi can cause problems in heavy or wet soils. Pyrenophora semeniperda, associated with leaf spotting, was widespread on barley in both the North and South Islands. It is an important pathogen warranting further research. The significance of Pyrenophora avenae, which was detected on barley in Wanganui is unknown. TABLE 2: Distributions of primary fungal and bacterial pathogens recorded for four cereal and two grass seed crops (number of sites where pests found). ______Pest-host associations of barley Code1: HB WI WN NC MC SC DN SL Total No. of sites: 1 13 3 17 38 11 11 10 104 ______Fungal species

Previously recorded associations2 Ascochyta hordei 000010001 Cochliobolus sativus (Bipolaris sorokiniana) 010001013 Drechslera siccans 012000003 Gaeumannomyces graminis 000000011 Gibberella avenacea (Fusarium avenaceum)18289110039 Gibberella zeae (Fusarium graminearum) 0205404015 Leptosphaeria nodorum (Septoria nodorum) 000110013 Monographella nivalis (Fusarium nivale) 0512625122 Pseudocercosporella herpotrichoides 000000022 Puccinia coronata 000010001 Puccinia hordei 000011002 Puccinia recondita 000030003 Puccinia striiformis 000001102 Pyrenophora graminea (Drechslera graminea) 010000001 Pyrenophora teres (Drechslera teres)0001850115 Ramularia collo-cygni 000001012 Rhynchosporium secalis 00022040329 Sclerotinia sclerotiorum 000010001

New associations Drechslera poae 031000004 Fusarium sacchari 010110003 Phytophthora cryptogea 000100102 Phytophthora gonapodyides 000000101 Phytophthora megasperma 010200205 Pyrenophora avenae (Drechslera avenae) 010000001 ______

______Table 2 continued Code: HB WI WN NC MC SC DN SL Total No. of sites: 1 13 3 17 38 11 11 10 104 ______Pyrenophora semeniperda (Drechslera semeniperda) 0112312010 Pythium irregulare 010000102 Pythium rostratum 020000002 Pythium ultimum 000010001

Bacterial species

Previously recorded associations Pseudomonas syringae pv. atrofaciens 000110002 ______Pest-host associations of brome grass Code: HB WI WN NC MC SC DN SL Total No. of sites: - - - - 5 4 - - 9 ______Fungal species

Previously recorded associations Ascochyta sorghi ----30--3 Cercosporidium graminis ----01--1 Glomerella graminicola (Colletotrichum graminicola) ----10--1 Monographella nivalis (Fusarium nivale) ----32--5 Puccinia recondita ----01--1 Pythium ultimum ----10--1 Spermospora bromivora ----02--2

New associations Gibberella avenacea (Fusarium avenaceum) ----01--1 Ramularia collo-cygni ----01--1 Rhynchosporium orthosporum ----10--1 Thanatephorus cucumeris (Rhizoctonia solani) ----01--1

Bacterial species

Previously recorded associations Pseudomonas syringae pv. syringae ----11--2 ______Pest-host associations of oats Code: HB WI WN NC MC SC DN SL Total No. of sites: 1 1 1 2 362723 ______Fungal species

Previously recorded associations Ascochyta avenae 000001001 Gaeumannomyces graminis 000001023 Gibberella zeae (Fusarium graminearum) 001100002 ______

______Table 2 continued Code: HB WI WN NC MC SC DN SL Total No. of sites: 1 1 12362723 ______Leptosphaeria avenaria (Septoria avenae) 000000022 Monographella nivalis (Fusarium nivale) 000001102 Puccinia coronata 000013015 Pyrenophora avenae (Drechslera avenae) 000022015

New associations Drechslera poae 001000001 Puccinia recondita 001000102

Bacterial species

Previously recorded associations Pseudomonas syringae pv. coronofaciens 000021003 ______Pest-host associations of ryecorn Code: HB WI WN NC MC SC DN SL Total No. of sites: - - - - 9 1 - - 10 ______Fungal species

Previously recorded associations Cercosporidium graminis ----31--4 Monographella nivalis (Fusarium nivale) ----30--3 Puccinia recondita ----11--2 Rhynchosporium secalis ----10--1

New associations Gibberella zeae (Fusarium graminearum) ----10--1 ______Pest-host associations of ryegrass Code: HB WI WN NC MC SC DN SL Total No. of sites: - 1 - 5 16 4 3 - 29 ______Fungal species

Previously Recorded Associations Ascochyta sorghi -0-0620-8 Drechslera dictyoides f.sp perenne -0-1220-5 Drechslera siccans -1-0100-2 Gibberella zeae (Fusarium graminearum) -0-0001-1 Monographella nivalis (Fusarium nivale) -0-0200-2 Puccinia coronata -0-1410-6 Puccinia graminis -0-0100-1 Rhynchosporium orthosporum -0-0300-3 ______

______Table 2 continued Code: HB WI WN NC MC SC DN SL Total No. of sites: - 1 - 5 16 4 3 - 29 ______Septoria tritici var. loliicola -0-0300-3 Thanatephorus cucumeris (Rhizoctonia solani) -0-0200-2

New Associations Phytophthora megasperma -1-0000-1 Pyrenochaeta terrestris -0-0100-1

Bacterial species

Previously recorded associations Pseudomona syringae -0-0311-5 ______Pest-host associations of wheat Code: HB WI WN NC MC SC DN SL Total No. of sites: - 12 4 53 48 19 7 14 157 ______Fungal species

Previously recorded associations Ascochyta sorghi -00020002 Ascochyta tritici -00060006 Blumeria graminis -00010001 Claviceps purpurea -00000011 Gaeumannomyces graminis -000640515 Gibberella avenacea (Fusarium avenaceum) - 6 4 23 17 3 1 0 54 Gibberella zeae (Fusarium graminearum) -1010500016 Leptosphaeria nodorum (Septoria nodorum) -001440312 Monographella nivalis (Fusarium nivale) -617830126 Mycosphaerella graminicola (Septoria tritici) -002500512 Pseudocercosporella herpotrichoides -00110013 Puccinia recondita -10220117 Puccinia striiformis -003872222 Pyrenophora avenae (Drechslera avenae) -10000001 Pythium irregulare -11110004 Pythium rostratum -20000002 Sclerotinia sclerotiorum -00110002 Thanatephorus cucumeris (Rhizoctonia solani) -00014038

New associations Ascochyta avenae -00010001 Ceratocystis paradoxa (Chalara paradoxa) -00000202 Macrophomina phaseolina -10000001 ______

______Table 2 continued Code: HB WI WN NC MC SC DN SL Total No. of sites: - 12 4 53 48 19 7 14 157 ______Phytophthora cryptogea -01100103 Phytophthora megasperma -119000011 Pyrenochaeta terrestris -00200002 Pythium ultimum -10000001

Bacterial species

Previously recorded associations Pseudomonas syringae pv. atrofaciens -00012003 ______1 Two-letter district codes as after Crosby et al. (1976): HB, Hawke’s Bay; WI, Wanganui; WN, Wellington; NC, North Canterbury; MC, Mid Canterbury; SC, South Canterbury; DN, Dunedin; and SL, Southland. 2 Previously recorded associations not detected in this survey are not reported in this paper.

Brome grass The most common primary species detected on brome grass were Monographella nivalis (snow mould, 56% of sites) and Ascochyta sorghi (33% of sites). A number of primary pathogens were recorded for the first time on brome grass. In particular, the fungus Ramularia collo-cygni (formerly known as Ovularia hordei) was detected in South Canterbury. This fungus is commonly reported on barley causing late season leaf spotting and early leaf senescence. Significant yield losses have been attributed to R. collo-cygni on barley and the importance on brome grass warrants further investigation. Oats The most common primary species found were Puccinia coronata (22% of sites) and Pyrenophora avenae (22 % of sites). Two primary pathogens, Drechslera poae and Puccinia recondita were recorded for the first time on oats during this survey. Drechslera poae was recorded in Wellington causing a leaf spotting and may be significant in wetter seasons. Puccinia recondita was recorded from the North and South Islands but is unlikely to be significant because several other important rusts are already known to occur on oats. Ryecorn The most common primary species found was Cercosporidium graminis (40% of sites). One new primary association, Gibberella zeae (Fusarium graminearum), was found for the first time on ryecorn causing a crown and root rot. This pathogen is widespread and favoured by wetter seasons. Ryegrass The most common primary species was Ascochyta sorghi (28% of sites). Two primary pathogens, Phytophthora megasperma and Pyrenochaeta terrestis, were recorded for the first time on ryegrass. Both these fungi infect roots and are favoured by wet soil conditions. Wheat The fungus Ceratocystis paradoxa was recorded for the first time in New Zealand, associated with a leaf spot on wheat in two localities in the Dunedin area. This pathogen has a wide host range overseas. Since its importance on wheat in New Zealand is unknown, additional research is required. The most common primary species recorded on wheat were Gibberella avenacea (34% of sites), Monographella nivalis (17% of sites), Puccinia striiformis (14% of sites) and Gibberella zeae (10% of sites). Several fungi were recorded for the first time on wheat in New Zealand. Ascochyta avenae was detected in Mid Canterbury. Its effects are likely to be similar to a number of other Ascochyta species which cause late season leaf spotting on wheat in New Zealand. They tend to be weak pathogens, of only minor concern.

General comments A number of important exotic pathogens of cereals and grasses were not found. Similarly, some previously recorded endemic primary pathogens were not detected during this survey. Their absence could be caused by weather patterns, resistant cultivars and the widespread use of fungicide treatments for disease control. No smut fungi (Ustilago spp.) were observed on any of the surveyed hosts. Fungicide seed treatments appear to have reduced the incidence of these fungi to very low levels. Rusts were only prevalent on oats, ryegrass and wheat. Their occurrence can be seasonal, depending on weather conditions. It is possible that more widespread occurrence could occur in other seasons. Also, the widespread use of resistant cultivars and fungicides may have reduced the amount of disease. Of the primary fungi, those associated with root and foot rot symptoms were generally the most commonly observed during this survey, especially various species of Fusarium. As well as root rot, the fungi can also cause leaf blights and head scab. A resurgence of the Fusarium disease complex has been reported in the USA, resulting in significant yield losses in wheat (McMullen et al. 1997). Wetter seasons, reduced tillage practices and shorter crop rotations are possible reasons for this resurgence. In New Zealand, potential problems with Fusarium spp. in wheat were identified by Sayer and Lauren (1991) when they showed that levels of Fusarium spp. varied in wheat seed depending on the area of production. The incidence, spread and control of foot rot and head scab of wheat is currently of concern to the wheat growing industry and this survey has emphasised the importance of this disease complex in cereals. Research into the epidemiology and control of these pathogens is currently being undertaken.

CONCLUSION This survey has detected many new fungal pest-host associations and distributions for the crops surveyed and has highlighted the most predominant diseases on each host. This information will be useful for setting priorities for disease related research in the cereal and grass seed industries.

ACKNOWLEDGEMENTS We thank the following people who undertook the field sampling and laboratory identifications: Mike Dance, Stojan Ganev, Karyn Beal, Graham Page, Juliet Richmond, Karen Knight, Heather Pearson, Alan Flynn, Dan Pearson, Maurice O’Donnell, Peter Holder, Davor Bejakovich with assistance from MAF Quality Management Field Officers. We would also like to thank: Carolyn Whyte for statistical advice; Jocelyn Cowley for technical advice; MAF Regulatory Authority for funding this survey; The Foundation for Arable Research for providing lists of growers names; and the growers for allowing their crops to be surveyed.

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