Lychee Pepper
Spot in Australia
(Its Impact and Control)
A report for the Rural Industries Research
and Development Corporation
by Henry and Jenny Drew
December 2001
RIRDC Publication No 01/163
RIRDC Project No DRW-1A
ii
© 2001 Rural Industries Research and Development Corporation.
All rights reserved.
ISBN 0 642 58382 X
ISSN 1440-6845
Lychee Pepper Spot in Australia (Its Impact and Control)
Publication No. 01/163
Project No. DRW-1A
The views expressed and the conclusions reached in this publication are those of the author and not
necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person
who relies in whole or in part on the contents of this report.
This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the
Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the
Publications Manager on phone 02 6272 3186.
Researcher Contact Details
Dr Henry Drew
283 Hunchy Road
HUNCHY QLD 4555
Phone: 07 5445 0032
Fax: 07 5445 0940
Email: hjdrew@ozemail.com.au
RIRDC Contact Details
Rural Industries Research and Development Corporation
Level 1, AMA House
42 Macquarie Street
BARTON ACT 2600
PO Box 4776
KINGSTON ACT 2604
Phone: 02 6272 4539
Fax: 02 6272 5877
Email: rirdc@rirdc.gov.au
Website: http://www.rirdc.gov.au
Published in December 2001
Printed on environmentally friendly paper by Canprint
iii
Foreword
This publication considers the increasing importance of a new disease of lychees in Australia.
The disease, named Lychee Pepper Spot (LPS) for its distinctive blemish to the fruit, is caused by a
presumably new strain of anthracnose (Colletotrichum gloeosporioides) which also causes rots in
several other subtropical fruits.
The report highlights the results of a telephone survey of 100 lychee growers across Queensland and
northern New South Wales carried out in 1999, and of an off-season fungicide trial to control the
disease. It also reports the results of a residue trial required by the National Registration Authority to
facilitate the issue of an off-label minor use permit for mancozeb, which can be used as an alternative
to copper sprays.
The survey results indicate that the disease has spread rapidly since its first detection in 1982 and is
likely to reach all commercial lychee growers within the next few years. While losses across most
orchards are currently low, below 1%, losses in individual trees can reach 25% of saleable fruit. The
disease is particularly widespread and severe on the most popular commercial variety, Kwai May
Pink. To date grower efforts to control the disease have had little success.
The trial results indicate that off-season spraying will not be sufficient to control the disease if
conditions later in fruit development are conducive to disease development. The implications of this
are that the Australian lychee industry, represented by the Australian Lychee Growers Association,
must lobby for the registration or off-label approval of new more effective fungicides which can be
used closer to picking. This will entail generation of further residue data.
This publication is a wakeup call to the Australian lychee industry.
This project was funded from RIRDC Core Funds which are provided by the Federal Government.
The lychee industry also provided funds for the project.
This report, a new addition to RIRDC’s diverse range of over 700 research publications, forms part
of our New Plant Products R&D program, which aims to facilitate the development of new industries
based on plants or plant products that have commercial potential for Australia.
Most of our publications are available for viewing, downloading or purchasing online through our
website:
• downloads at www.rirdc.gov.au/reports/Index.htm
• purchases at www.rirdc.gov.au/eshop
Peter Core
Managing Director
Rural Industries Research and Development Corporation
http://www.rirdc.gov.au/reports/Index.htm
iv
Acknowledgements
We wish to gratefully acknowledge the financial commitment of the Queensland Fruit and Vegetable
Growers Lychee Sub-Committee and the Rural Industries Research & Development Corporation in
funding this research.
We would also like to thank:
• The Australian Lychee Growers Association Inc. Executive, past and present, for their support
and comment. Our particular thanks to past Secretary Rick Bronson.
• Bob and Jill Houser and Chris Salta for use of their trees for the fungicide trial and for
considerable assistance in both spraying and assessment.
• Dr. Helen Wallace, University of the Sunshine Coast, for assistance with the statistics of the
fungicide trial results.
• Janine Clark, Queensland Fruit & Vegetable Growers, and Pam Bowles, Queensland Department
of Primary Industries, for handling the Mancozeb off-label permit application to the National
Registration Authority.
• Dr. Chris Menzel and Don Hutton, Queensland Horticulture Institute, Nambour for many useful
discussions.
• All the lychee growers who responded to the telephone surveys and who sent nutrition
information.
v
Contents
FOREWORD ............................................................................................................. III
ACKNOWLEDGEMENTS ......................................................................................... IV
EXECUTIVE SUMMARY.......................................................................................... VII
1. INTRODUCTION ................................................................................................. 1
1.1 BACKGROUND........................................................................................................................................... 1
1.2 RELEVANCE AND BENEFITS ....................................................................................................................... 1
2. OBJECTIVES ...................................................................................................... 3
3. METHODOLOGY ................................................................................................ 3
3.1 CONFIRMING THE IDENTITY OF LPS .......................................................................................................... 3
3.2 INCREASING AWARENESS OF LPS.............................................................................................................. 3
3.3 DETERMINING THE EXTENT OF LPS........................................................................................................... 4
3.4 EVALUATING LPS CONTROL STRATEGIES ................................................................................................. 4
3.5 GENERATING MANCOZEB RESIDUE DATA .................................................................................................. 7
4. RESULTS AND DISCUSSION ............................................................................ 7
4.1 TELEPHONE SURVEYS................................................................................................................................ 7
4.1.1 General survey.............................................................................................................................. 7
4.1.2 Nutrition pair survey .................................................................................................................... 9
4.2 FUNGICIDE SPRAY TRIAL ......................................................................................................................... 10
4.2.1 First season................................................................................................................................. 10
4.2.2 Second season ............................................................................................................................ 11
4.2.3 Fruit assessment ......................................................................................................................... 11
4.3 MANCOZEB RESIDUES ............................................................................................................................. 15
5. IMPLICATIONS AND RECOMMENDATIONS .................................................. 17
6. APPENDICES.................................................................................................... 20
6.1 APPENDIX A. TELEPHONE SURVEY QUESTIONNAIRE .............................................................................. 20
6.2 APPENDIX B. PAIR SURVEY RESULTS ..................................................................................................... 23
6.2.1 Leaf analysis results. .................................................................................................................. 23
6.2.2 Soil analysis results. ................................................................................................................... 24
6.2 APPENDIX C. LPS FUNGICIDE TRIAL RESULTS (NUMBER OF FRUIT PER REPLICATE) ............................... 25
7. REFERENCES .................................................................................................. 28
vi
Tables
Table 1 The postal codes of growers contacted in the 1st telephone survey
Table 2 Fungicide trial treatments in 1999/2000 and 2000/2001
Table 3 Timing of sprays - 1999/2000 (1st season) and 2000/2001 (2nd season)
Table 4 Incidence of LPS in the different areas surveyed
Table 5 Reported losses in orchards with LPS
Table 6 Reported occurrence by variety in orchards with LPS
Table 7 Number of fruit by grade, picking date and treatment
Table 8 Percentage of fruit by grade, picking date and treatment
Table 9 Statistical tests of between subjects effects for percentage of fruit
Figures
Figure 1 Trial block plan with individual treatment colours and replicate numbers
Figure 2 The increasing number of cases of LPS noted since 1982
Figure 3 Flowering at 19/07/99
Figure 4 Fruit set at 17/11/99
Figure 5 Flowering at 9/08/00
Figure 6 Production (number of fruit per tree)
Figure 7. The increasing incidence of LPS with picking date: An illustrative comparison
between treatments 2. blue (Copper + Mancozeb) and 4. red (untreated)
Figure 8. Average percentage (six trees) of fruit with LPS on 28th January
Figure 9 Mancozeb decay in LPS trial lychees
Abbreviations
ALGA Australian Lychee Growers Association Inc.
CQ Central Queensland
FNQ Far North Queensland
IHD Institute for Horticultural Development, Victoria
LPS Lychee Pepper Spot
MRL Maximum Residue Limit
NSW New South Wales
NNSW Northern New South Wales
NRA National Registration Authority for Agricultural & Veterinary Chemicals
QDPI Queensland Department of Primary Industries
QFVG Queensland Fruit & Vegetable Growers
QHI Queensland Horticulture Institute
RIRDC Rural Industries Research & Development Corporation
SCSTFA Sunshine Coast SubTropical Fruits Association Inc.
SEQ South-East Queensland
WHP Withholding period
vii
Executive Summary
Lychee Pepper Spot (LPS) is a newly recognised disease of lychee fruit in Australia. The disease,
caused by Colletotrichum gloeosporioides, results in superficial skin blemish but has no effect on
either eating quality or, apparently, on postharvest rots and shelf- life. The same species of fungus
causes fruit rots in several other subtropical fruits including avocados and mangoes.
The first symptoms of LPS are brown pinhead-sized spots on the top or sides of semi-mature fruit in
areas of the canopy with overhanging branches. The spots do not increase in size but rapidly turn
black. More spots appear on the top and sides of the fruit and may by harvest cover 30-50% of the
fruit surface. LPS affects all lychee varieties. However it appears most severe on the increasingly
popular Kwai May Pink (KMP), which comprised 37% of existing plantings in 1992, and 50% in
1999.In 1999 KMP made up 58% of future planned plantings.
Initially many growers were unaware of the symptoms of LPS and it was considered as one of
several types of unspecified “blemish”. A preliminary factsheet with colour photographs of LPS was
prepared and distributed to growers to raise awareness of LPS prior to implementing a telephone
survey. The telephone survey of 100 lychee growers spread over as wide a geographic area as
possible was carried out in mid-1999. The survey found that the first reports of the disease were in
1982. By 1989 it was found in all the major growing areas including Northern New South Wales
(NNSW), South East Queensland (SEQ) and Far North Queensland (FNQ). By 1999 43% of growers
surveyed reported having LPS on at least one variety in their orchard.
The general picture from the survey was of hotspots of infection with some severely affected trees
and fruit, but with generally low levels across the whole crop. Of those growers who had LPS in their
orchards 8% reported losses of more than 60% in their worst trees but 70% reported losses of less
than 1% across the whole orchard. Thirty two percent of those surveyed believed that LPS produced
a noticeable increase in leaf loss and a decline in tree vigour.
A fungicide trial to test the effectiveness of a range of off-season (winter-spring) treatments was
carried out in 1999/2000 and repeated in 2000/2001 in a young orchard at Mooloolah in SEQ. All the
products tested, except foliar calcium, were registered for control of Colletotrichum spp. in other
crops. Fruit were harvested on the 13th, 18th and 28th January 2001. Unfortunately there was high
variability within treatments and none of them gave a statistically significant reduction in disease
incidence or severity compared with an unsprayed control. While the average percentage of fruit with
pepper spot symptoms was low in all treated trees over the first 2 picks at 0.6-7.7%, this rose
dramatically in the final pick to 9.8-17.0%. The untreated control was similar in the 1st pick but 5
and 10% higher in the 2nd and 3rd picks, respectively.
The project also involved collection of residue data for mancozeb. Whilst the trial did not prove the
efficacy of any winter-spring treatments the lychee industry has applied for an off-label permit from
the NRA for mancozeb to control pre-harvest rots, to augment the existing registration of copper
oxychloride and hydroxide for algal spot. The laboratory analysis of sprayed fruit showed that the
mancozeb residue levels at 7 and 14 days after treatment were 3.5 and 1.3 mg/kg, respectively. There
is no MRL for dithiocarbamates on lychees or tropical fruit (inedible peel) but based on the MRL for
berries and grapes of 5 mg/kg, and on a safety factor of 100%, it is likely that a withholding period of
10 days would be required. The Queensland Fruit & Vegetable Growers have applied to the NRA for
a permit.
While no fully effective off-season treatments for LPS were identified the project has identified
needs and opportunities for further research, extension and industry action. These are summarised in
the recommendations below.
viii
The project has resulted in five general recommendations:
RECOMMENDATION 1.
The ALGA should support the registration of cuprous oxide by lobbying the chemical companies
concerned.
RECOMMENDATION 2.
The high intensity use of foliar fertilizers, like Stopit (calcium) and Eco-Carb (potassium
bicarbonate), should be further investigated.
RECOMMENDATION 3.
Growers should target autumn leaf flushes, periods of wet weather and the second half of fruit
development. Spraying should be on a 2-3 weekly basis during risk periods up to 10 days before
harvest.
RECOMMENDATION 4.
The ALGA needs to support the development of proven programmes with approved products to
minimise the risk of desperate growers using non-approved products.
RECOMMENDATION 5.
The ALGA should support regular on-going surveys to quantify the effects of LPS on individual
growers and on the industry. These surveys could include other information such as production
figures and estimates of pest problems which are needed to better plan the future of the industry.
1
1. Introduction
1.1 Background
Lychee Pepper Spot (LPS) is a newly recognised disease of lychees in Australia. It was first noticed
in South East Queensland (SEQ) in a few orchards on the Sunshine Coast in 1993 1. The disease
causes superficial skin blemish to fruit but has no effect on eating quality or, apparently, on storage
life. Since its first occurrence the disease has got steadily worse in affected orchards despite some
attempts at chemical control.
The unusual development of the characteristic spotting caused by LPS led to a number of theories as
to the cause, but it was not until 1997 that a type of anthracnose fungus (Colletotrichum sp.) was
implicated. This identification work was carried out by Dr Hin Yip with private funding from Mr
Rohan Bosworth, a major Far North Queensland (FNQ) lychee grower (Yip, 1997). The
identification was confirmed by QDPI Indooroopilly, but the species of Colletotrichum had not been
firmly established (Coates, 1997). Anthracnose caused by Colletotrichum spp. is recorded as a
disease of lychees in Vietnam (Trung, 1999) but usually manifests itself there as a “rot” rather than as
a “spot” (Trung, pers.comm.)
First symptoms of LPS are brown pinhead-size spots or freckles, usually on the top of semi-mature
fruit in areas of the canopy with overhanging branches 2. Infected fruit are generally more common
on lower branches, but in severely infected trees diseased fruit occur at all heights. The spots do not
increase in size but rapidly turn black. The lesions are separate or coalescent. More and more spots
appear on the top and sides of the fruit and may by harvest cover 30-50% of the fruit surface.
Infections appear to overwinter on leaves and leaf petioles 3.
Conidial spores of Colletotrichum germinate only in water. Upon germination they produce an
appressorium and penetration peg and penetrate the host tissue directly, causing little or no visible
discolouration (Agrios, 1978, p.301). Then more or less suddenly, especially when fruits begin to
ripen, the fungus becomes aggressive and symptoms appear. In the case of LPS it would appear that
infections become contained to the small spots, and the spreading rots seen in other fruits do not
occur. This infection process has implications for appropriate control strategies.
1.2 Relevance and benefits
LPS was identified in the Australian Lychee Growers Association Inc. (ALGA) “Lychee Industry 5
Year Strategic Plan” as R & D Goal: 9 (Anon, 1998). A subsequent postal survey of lychee growers
by the ALGA rated LPS in the top four priorities and $5000 of grower funds was allocated through
the QFVG Lychee Sub-Committee to LPS research in 1998/1999 (Bronson, 1998).
The lychee industry in eastern Australia was estimated in 1996 to comprise of 250,000 trees more
than 5 years old producing 3000 tonnes of fruit per year (Greer, 1996). The QDPI estimate for 1992
was a total of 247,000 trees producing 1192 tonnes (QDPI, 1992). The large increase in production
between 1992 and 1996, without significant increase in tree numbers, is an indication of the high
number of young trees in 1992 which had yet to come into full production. Production by 2001 is
expected to be 5000 tonnes. Value of production was estimated at $5,000,000 in 1992 rising to
$9,000,000 in 1996. Over the same period exports increased from 54 to more than 250 tonnes, being
approximately 15% of production.
1 A “new” devastating type of anthracnose developed on cherimoya on the Sunshine Coast at about
the same time.
2 This type of pepper spot infection is also sometimes seen on avocados.
3 Coates has achieved infection of both leaves and leaf petioles with Colletotrichum isolates (Coates,
pers.comm.).
2
This research aimed to benefit the lychee industry in Australia by establishing the extent of the LPS
prob
