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Plant Parasitic Nematodes Fact Sheet

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Plant Parasitic Nematodes Fact Sheet PAGE 1 PLANT PARASITIC NEMATODES FACT SHEET 2009 SOUTHERN AND WESTERN REGION Managing cereal cyst and root lesion nematodes Root lesion nematode (RLN, Pratylenchus species) and cereal cyst nematode (CCN, Heterodera avenae) are significant pests that feed on the roots of crop plants and cause yield loss. KEY POINTS Management of RLN and CCN ■ CCN has one life cycle per season whereas RLN is polycyclic with in winter crops three to five generations per year. ■ CCN hosts are restricted to ■ As a general rule, well-managed rotations with resistant or non-host break crops cereals and grasses whereas the are vital. Avoid consecutive host crops to limit populations. RLN host range is broader and ■ Choose varieties with high resistance ratings, which result in fewer nematodes includes cereals, oilseeds, grain remaining in the soil to infect subsequent crops. legumes, pastures and broad leaf and grass weeds. ■ Reducing RLN and CCN can lead to higher yields in following cereal crops. ■ A number of different RLN ■ Healthy soils and good nutrition can, to some extent, ameliorate RLN and CCN species are present, including damage through good crop establishment, and healthier plants recover more Pratylenchus neglectus, thornei, readily from infestation. penetrans and teres. ■ Nematode type and species will ■ Observe crop roots to monitor development of symptoms. affect choice of management ■ Weeds can host parasitic nematodes and control of host weed species and crop practices, particularly rotation volunteers is important. options. TABLE 1: REACTION OF MAJOR CROP AND PASTURE SPECIES TO PRATYLENCHUS NEGLECTUS, P. TERES AND P. PENETRANS P. neglectus P. teres * P. penetrans * SUSCEPTIBLE MODERATELY SUSCEPTIBLE RESISTANT SUSCEPTIBLE SUSCEPTIBLE Wheat Barley Field Pea Wheat Wheat Canola Oat Narrow-leafed lupin Barley Oat Chickpea Medic Faba and Narbon bean Oat Field pea Mustard Durum wheat Lentil Canola Faba bean Biserulla Common vetch Lathyrus Narrow-leafed lupin Trigonella Triticale Chickpea Rye Durum wheat Safflower Triticale Clover and Lotus MODERATELY SUSCEPTIBLE MODERATELY SUSCEPTIBLE Legume pastures** Narrow-leafed lupin Barley Field pea Canola Triticale * Information for P. teres and P. penetrans is based on samples received by AGWEST Plant Laboratories for diagnosis, combined with data from preliminary field and glasshouse trials. ** Clover, Bitter vetch, Yellow serradella, French serradella, Sulla and Lotus. Source: VA Vanstone, DAFWA. Level 1, Tourism House | 40 Blackall Street, Barton ACT 2600 | PO Box 5367, Kingston ACT 2604 | t. +61 2 6166 4500 | f. +61 2 6166 4599 | e. [email protected] | w. www.grdc.com.au PAGE 2 About the root lesion nematode Pratylenchus spp. are microscopic P. penetrans is rare in WA but can Pastures vary in their susceptibility worm-like organisms less than cause severe damage to some crops. to RLN and under some pastures, one-millimetre in length which feed nematode levels could increase and on root tissues. More than one RLN species can be become damaging to subsequent found in the roots of an individual cereals. Pastures should therefore be P. neglectus is the dominant RLN crop, although one species usually monitored for RLN as other crops are, species in all regions. In WA, at least dominates. as well as considering their place in the 60 per cent of cropping paddocks rotation for RLN management. French Species identification is important to are infested with one or more of the and Yellow serradella, lotus and sulla help management as some varieties, Pratylenchus species. In about 40 per varieties tested to date are resistant crops and plant types have different cent of cases the nematode is at levels to P. neglectus, whereas clovers and resistance or susceptibility to different capable of causing crop damage and medics can be more susceptible. yield loss of five to 15 per cent. members of the Pratylenchus family. For example field pea, lupin and faba Intensive cropping of susceptible crops P. thornei is found in South Australia, bean are resistant to P. neglectus but – particularly wheat – will lead to an Victoria, Queensland and NSW. This are susceptible to P. penetrans. Canola increase in nematode levels. Rotations species occurs rarely in Western is more susceptible to P. neglectus are the key to limiting nematode Australia. than P. thornei (see Table 1). multiplication and reducing future crop damage. P. teres and P. penetrans have both Although there is no truly resistant been identified in WA and research is variety of wheat, there is sufficient Several studies have shown the extent underway to learn more about these variation in susceptibility that variety of yield loss attributed to P. neglectus species and the rotations that will limit selection in rotations can be a useful or P. thornei is directly related to the their populations in cropping soils. tool in managing the impact of RLN. population density present at sowing. Forty per cent of RLN identified in WA is P. neglectus; 10 per cent Oat and barley varieties range from All species of RLN have a wide host P. teres and 10 per cent mixed species. moderately resistant to moderately range. susceptible to P. neglectus. RLN ABOVE AND BELOW GROUND: (Right) Symptoms of RLN on cereal root systems. Note discolouration of roots and reduction in lateral root growth. (Far right) Patchiness, stunting and yellowing of cereal infested with RLN. PHOTOS: VA VANSTONE, DAFWA The symptoms Above-ground symptoms are often nutrient deficiencies. Depending on chickpea can be severely stunted and indistinct and a poor diagnostic the extent of damage and the growing reduced in number. indicator. The first signs are poor conditions, affected plants may partly emergence and establishment, recover if the rate of new root growth The root cortex (or outer root layer) is stunting, cereals tiller poorly and exceeds the rate at which nematodes damaged and may disintegrate. plants may wilt despite moist soil. damage the roots. Diagnosis is difficult and can only Symptoms of nematode damage can To gain the full picture, an examination be confirmed with laboratory testing, be confused with, or exacerbated particularly to identify the species by, nutrient deficiencies. Nematodes of what is going on under the ground is needed. Primary and secondary as all RLN species cause identical, are usually distributed unevenly symptoms. across a paddock, resulting in roots of cereals will show a general irregular crop growth. browning and discolouration and there will be fewer, shorter laterals When roots are damaged by RLN, branching from the main roots. the plants become less efficient in Chickpea roots can show distinct dark taking up water and nutrients, and in brown-orange lesions at early stages tolerating stresses such as drought or of infection and the lateral roots of PAGE 3 The life cycle of RLN Management of RLN When a pasture is included in the cropping rotation, weeds strongly RLN is a migratory plant parasitic The most important management tool influence nematode populations at the nematodes, meaning they migrate is good rotations. In heavily infested end of the pasture phase. freely between roots and soil providing paddocks break crops should be grown the soil is moist. The life cycle of for one or two years to decrease the Manage volunteer susceptible crop RLN begins after the opening rains in population. Resistant varieties should plants that can harbour nematodes. autumn. Juvenile and adult nematodes be selected for the following years. rehydrate, become active and invade Nematodes cannot move great plant roots where they feed and Adequate nutrition (especially nitrogen, distances unaided. However, they multiply as they move through the root. phosphorus (P) and zinc) normally can be spread by surface water, and allows plants to better tolerate plant in soil adhering to vehicles and farm Individual eggs are laid within the root parasitic nematodes, although this does machinery. In uninfested areas, good from which juvenile nematodes hatch, not necessarily lead to lower nematode hygiene should be adopted. They can grow to adults and lay eggs. There reproduction. Field trials in areas also be spread in dust when they are in may be three to five cycles within the infested with P. neglectus have shown a dehydrated state over summer. plant host each season. As plants and yield losses for intolerant wheat ranged soil dry out in late spring, RLN enters a from 12 to 33 per cent when minimal dehydrated state called anhydrobiosis levels of P were applied but losses were and can survive high soil temperatures reduced to only five per cent with a high Cultivation and desiccation over summer. (50 kilograms per hectare) rate of P. Since RLN is vulnerable to death As nematodes feed and multiply, Weeds can play an important role through soil disturbance while in lesions and/or sections of brown in the increase or persistence of its dehydrated state, mechanical discolouration are formed on the plant nematodes in cropping soils. Thus, disturbance through tillage has been root. Other symptoms include the poor control of susceptible weeds considered as a method of reducing reduction in the number and size of compromises the use of crop rotations nematode populations. However, tillage lateral roots and root hairs. for RLN management. of dry soil is not an option in southern or western Australian farming systems Wild oat, barley grass, brome grass as this would expose the soil to wind and wild radish are susceptible to erosion and also result in the loss of P. neglectus. valuable soil moisture.
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