01 163

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