The Ecology & Management of Serrated Tussock in Native Pastures

Warwick Badgery & David Kemp

The University of Sydney Orange

Background

• Grasslands with a high perennial grass density and high DM can limit serrated tussock invasion

• Flupropanate kills many native grasses and creates bare ground for serrated tussock to invade

• A system is needed that focuses on prevention of seedling recruitment and in many cases on selective control of adult plants

Seedling reinvasion after spraying

Bare ground left after spraying native pastures

No of Serrated Tussock Seedlings in Plots of Varying % Bare Ground

R2 = 0.6917

-5

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60 70 80 90

% Bare Ground

Cu

mu

lati

ve n

o o

f S

eed

lin

gs

0.0 0.5 1.0 1.5 2.0 2.5DM (t / ha)

0

5

10

15

20

25

See

dlin

gs /

25

cm2

Serrated tussock seedlings cannot establish where pasture cover and DM are high

Grigulis unpublished

A perennial grass dominated patch that has prevented invasion

The paddock on the left has prevented invasion with no control despite large seed inputs

Survey Objectives

• To determine farmers current management of serrated tussock

• To assess their knowledge and use of preventative treatments– grazing management, fertiliser, pasture establishment

• To assess whether their management is proactive or reactive

• To define the on-farm limitations to better management– money, landscape, knowledge, attitude.

The Survey

• Farms were selected at random within the serrated tussock area mapped in 1997

• 54 farmers surveyed– personal interviews

on the farm

Mean Property Conditions

Average size: 1546 haAverage rainfall: 680 mmSoil TypesBasalt 15 %Granite 44 %Shale 34 %Loams/Alluvial soils 7 %TopographyAccessible 73 %Inaccessible 27 %PasturesSown 34 %Native 53 %Degraded 13 %

Heavy (>50% of a paddock),

Medium (5-50% of a paddock)

Scattered (isolated plants)

How To Define Successful Managers?

• Identify properties that have successfully controlled serrated tussock under difficult conditions– Difficult conditions: present for >20 years, and on

neighboring properties

• Identify factors associated with successful management:– Physical: property conditions

– Management: actions & attitude

Classifying Properties

0 10 20 30 40 50 60 70Years Serrated Tussock Present

0.0010

0.0100

0.1000

1.0000

10.0000

Se

rra

ted

Tu s

s oc k

(%

)

YesNo

Neighbouring Infestations

Characteristics of Successful Properties

Response Successful Other

Cooma Region (%) 71.4 ± 18.4 25.5 ± 6.4

Average Rainfall (mm) 593 ± 48.4 693 ± 15.1

Shale Soils (%) 1.7 ± 1.7 37.2 ± 5.5

Accessible Area (%) 91.7 ± 5.0 70.6 ± 3.9

SR below normal (%) 55.3 ± 14.3 24.9 ± 3.8

Feed Livestock (%) 57.1 ± 20.2 88.6 ± 4.8

Steers (%) 28.7 ± 15.0 5.9 ± 2.3

Characteristics of Successful Properties

• Pasture management very important

• No serrated tussock control practices were found to be different

• Prevention is better than cure

Preventative Management

• A high awareness of key principles:– 87% were aware that serrated tussock seedlings

would not establish where ground cover is high

• A willingness to change management:– 71% said they would reduce grazing pressure to

limit serrated tussock invasion

• Very few actually make changes

Why Wont Farmers Change?

• Preventing plants is not as visually obvious as killing them with a herbicide

• Therefore management tends to be reactive rather than proactive

Grazing Management

• 81% of people used a set stocked system• Most rested some paddocks at times

– rests may be too short or not often enough?

• The obstacles to using more active grazing management were:– drought– cost of locking up country– fencing needed

Changing Farm Structure

• Control of serrated tussock is difficult under current farm structures– paddocks can’t be rested for long enough to let

desirable grasses become competitive– difficult to take paddocks out of use to

rehabilitate them– difficult to improve ground cover in autumn

Paddocks0 50 100 150

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50

60

Mob

s1:1

1:5

Property Structure

Management ChangeChange structure:

1. decrease the number of mobs / combine mobs2. subdivide paddocks if needed

• Less mobs that are larger means:– easier to budget feed and adjust stocking rates– paddocks are rested more often and for longer– it is possible to manage for herbage mass to increase

plant competition for tussock seedlings– better utilisation of forage– can see the feed available more readily– stock will be moved more often

What Do We Do with Areas Already Heavily Infested?

• Arable and reasonable soil fertility:– Sowing an introduced

perennial pasture is successful

• Non-arable, & / or low soil fertility & / or low rainfall– Currently no reliable long-

term control– Flupropanate used every 3

to 5 years– New answers needed!

New Research

Three aims:1. To determine the levels of competition required to prevent

serrated tussock invading in different areas of the landscape (i.e. ridge tops v lower slopes) and environments (i.e. low rainfall)

2. To establish perennial vegetation on difficult sites following serrated tussock control to prevent reinvasion (i.e. native grasses that are adapted to low fertility)

3. To find management techniques to weaken adult serrated tussock plants, to make them more susceptible to competition

Funded

Conclusion

• Continual effort is needed to keep serrated tussock under control– use plant competition to limit seedling establishment– spot spray adult plants

• The longer the rest period the easier it is to manage for pasture cover / competition– reduce mob numbers and improve rotations

• Decisions need to be made early in a drought– to avoid over-grazing / killing useful competitive grasses

• New research – aimed at managing serrated tussock in areas where we don’t yet

have effective long-term control