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Root-lesion nematode survey of Central Queensland

Key Messages

  • Root-lesion nematodes were found in 28% of the Central Queensland paddocks sampled.
  • Sowing resistant and tolerant crops like sorghum, maize and cotton or wheat varieties like Suntop or Gauntlet will maximise yield, minimise increases in RLN populations and new paddock infestations.
  • Regularly test your soil for RLN – Knowing what you are dealing with will allow you to manage it effectively.
  • Practise good farm hygiene to stop RLN spreading between farms and paddocks in soil attached to machinery or livestock.
  • Under-performing wheat varieties may be due to increasing RLN populations.

What is the problem?

OLYMPUS DIGITAL CAMERAThe root-lesion nematodes (RLN), Pratylenchus thornei and Pratylenchus neglectus, are commonly found in paddocks throughout the northern grains region. These microscopic worms invade, feed on and damage the roots of susceptible hosts, limiting the plant’s access to soil water and nutrients. Intolerant wheat varieties (e.g. Strzelecki) can lose up to 50% of their yield and industry-wide losses have been estimated at $47 million annually.

What did we find?

From 2010 to 2013 paddocks were surveyed to map the occurrence of RLN in the Central Highlands and Dawson Callide districts (Fig 1), including a major survey in July 2013 of 44 paddocks that were sampled to a depth of 90cm (0-15, 15-30, 30-60 and 60-90cm). Peak RLN populations can be found below 30cm. The results of this survey (Fig 1) show that overall 28% of paddocks had RLN with P. thornei the dominant species. The infested paddocks generally had low RLN populations and patchy distributions but approximately 5% of paddocks had populations above the estimated economic damage threshold for wheat.

Figure-1-

Fig 1: Occurrence of P. thornei and P. neglectus from 2010-2013 in (a) Central Highlands (46 paddocks) and (b) Dawson Callide (36 paddocks). Overall, RLN were found in 28% of Central Queensland paddocks with approximately 5% having RLN populations above the wheat damage threshold (2000/kg soil). Paddocks above this threshold were found in only the Dawson Callide.

How does Central Queensland compare to other regions?

RLN are a major problem throughout the northern grains region but CQ has a substantially lower incidence of RLN compared to other cropping regions (Fig 2). This is advantageous because effective management of RLN before populations increase and spread could ensure that they do not become the significant problem in CQ that they have become elsewhere.

RLN Survey Figure-2-

Fig 2: Occurrence of P. thornei and P. neglectus from 2010-2013 in (a) Central Queensland (82 paddocks) and (b) Southern Queensland (284 paddocks). RLN were found in 83% of Southern Queensland paddocks compared to 28% in Central Queensland. P. thornei is a major pest of wheat and chickpea and can reduce yields of intolerant cultivars by 50% and 20% respectively.

What does it mean for me?

Our survey has shown that better than 1 in 4 CQ paddocks have RLN. The populations are generally low and patchy, but eliminating RLN from infested paddocks is not achievable. Fortunately, effective management strategies have been developed that can minimise the losses RLN can cause. These are the three most important components of effective RLN management:

1) Test your soil for RLN regularly (every 2-3 years)

Surveying paddocks for P. thornei and P. neglectus is important to develop regional RLN management plans, but growers and agronomists are encouraged to regularly test for RLN, using the PreDicta B service (contact details below), to determine the best management plan for their paddocks. Check regional distribution maps (Fig 3) to see if RLN are in your district

RLN Survey Figure-3

Fig 3: The distribution of Pratylenchus thornei and P. neglectus in the Northern Region from 2010-2013. Green- no Pratylenchus; Red- P.thornei; Blue- P. neglectus; Yellow- P. thornei and P. neglectus. RLN results from the nearest towns can be accessed online through Google maps

2) Grow resistant crops and varieties

Growing P. thornei resistant crops like sorghum, maize, sunflower and cotton for 2 or more consecutive seasons will help reduce P. thornei populations.  When growing wheat choosing tolerant and resistant varieties like Suntop and Gauntlet will help minimise RLN populations and achieve yield potential in infested paddocks (please consult the Queensland wheat varieties guide or NVT online for further varietal information).

Growing susceptible crops like wheat, barley, chickpea, mungbeans or soybeans can quickly increase the RLN population in your paddock to damaging levels. If you suspect intolerant wheat varieties are under-performing this may be an indication of an increasing RLN population in your paddock.

3) Stop soil movement between paddocks and farms

Central Queensland paddocks are generally free of RLN and practising good farm hygiene is important to minimise the spread of RLN from infested paddocks. Washing soil from farm machinery (including contractors) will prevent soil movement between paddocks or farms and help to minimise the spread of RLN.

Further Information

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