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A study of the biology and control of Anthriscus caucalis and Torilis nodosa in pyrethrum

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Rawnsley, Richard (2005) A study of the biology and control of Anthriscus caucalis and Torilis nodosa in pyrethrum. PhD thesis, University of Tasmania.

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Abstract

The Tasmanian pyrethrum industry has been operating on a commercial basis for 23
years and is now the second largest producer of pyrethrum (Tanacetum cinerariaefolium
L.) for natural insecticides in the world. The industry, with a annual farm gate value in
excess of $7 million, makes a significant contribution to the rural economy of Tasmania
(Australia). Currently, production involves 120 contracted growers and 1300 hectares of
land. To maintain its position as a world leader in the production of pyrethrum, the
Tasmanian industry must continue to improve production technologies and efficiencies.
An emerging area of concern is the management of weeds, with some weed species in
pyrethrum being particularly difficult to control. This includes weeds that are commonly
found in vegetable crops which are grown in rotation with pyrethrum as well as
relatively uncommon species; such as Anthriscus caucalis and Torilis nodosa. This
study investigated the biology and control of both A. caucalis and T. nodosa which
belong to the Apiaceae family.
A morphological examination highlighted easily distinguishable characteristics for the
identification of these relatively unfamiliar species. Anthriscus caucalis seedlings are
identifiable by their tri-pinnate compound leaves which are glabrous on top with
scattered hairs beneath. The fruit of A. caucalis is ovoid in shape and 2.5 to 3.5mm in
size with distinguishing hooked spines and a short beak. The pedicels have a ring of
hairs at the top. Torilis nodosa seedlings are identifiable by their deeply bi-pinnate
compound leaves and narrow linear lobes. The fruit of T. nodosa is ovoid in shape and
2.5 to 3mm in diameter and composed of 2 distinct dimorphic mericarps. The outer
mericarp has barbellate spines with the inner mericarp tuberculate.
A survey of pyrethrum crops revealed that the occurrence of these species was high,
occurring in 30% of pyrethrum crops, with A. caucalis being the more prevalent species.
As pyrethrum is a perennial crop which can be grown for up to five years, it was also
found that the frequency of occurrence of Apiaceae species increased with increasing
crop age.
Investigations into the germination characteristics of A. caucalis and T. nodosa revealed
that A. caucalis possessed an innate seed dormancy which was overcome by seed
scarification and dry storage at 20°C. Torilis nodosa displayed no innate seed dormancy.
Both species, A. caucalis and T. nodosa, were found to behave predominantly as winter
annuals, germinating in autumn and over wintering as small rosettes. Studies indicated
that T. nodosa has a transient to short term persistent seedbank, while A. caucalis has a
short to long term persistent seedbank. Anthriscus caucalis was found to undergo rapid
vegetative stem development during late winter early spring with flowering commencing
during mid spring. Seed maturation occurred in early summer. Tori/is nodosa was found
to produce procumbent stems in mid to late spring and flower approximately 6 weeks
later than A. caucalis with seed maturation occurring in mid to late to summer.
Studies into the chemical control of A. caucalis and T. nodosa identified a small number
of herbicides with potential for use in pyrethrum. Applications of dimethenamid at 3.6
kg/ha provided the most selective pre emergent control for both species, while
clomazone applied at 120.0 g/ha provided very effective control of T. nodosa. Imazamox
applied at 34 g/ha provided significant post emergent control of both species with
excellent selectivity for use in pyrethrum. A number of other herbicides were identified
as having activity on A. caucalis and T. nodosa, however lower levels of selectivity
limited their potential adoption for use in pyrhethrum.
This thesis has provided significant information to the pyrethrum industry on the biology
and competitive nature of the relatively unknown weed species A. caucalis and T.
nodosa. The thesis has also provided immediate short term weed control strategies and
enhanced the weed management options available for the industry.

Item Type: Thesis (PhD)
Keywords: Pyrethrum industry, Umbelliferae, Pyrethrum (Plant), Weeds
Copyright Holders: The Author
Copyright Information:

Copyright 2005 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

No consultation or copying permitted, without the permission of Botanical Resources Australia Pty. Ltd., until June 2010. Thesis (Ph.D.)--University of Tasmania, 2005. Includes bibliographical references

Date Deposited: 03 Feb 2015 03:15
Last Modified: 11 Mar 2016 05:54
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