© Australasian Plant Pathology Society 2002 10.1071/AP02029 0815-3191/02/030303

Australasian Plant Pathology, 2002, 31, 303–304

AP02029A. W. Cooke and L. M. Coat es

DISEASE NOTES OR NEW RECORDS

Pepper spot: A preharvest disease of lychee caused by Colletotrichum gloeosporioides

A. W. CookeA and L. M. Coates

Queensland Horticulture Institute, DPI, 80 Meiers Road, Indooroopilly, Qld 4068, Australia.ACorresponding author; email: tony.cooke@dpi.qld.gov.au

Abstract. Pepper spot of lychee was found to be caused by Colletotrichum gloeosporioides.

Australia has a small but increasing lychee (Litchi chinesis)industry based mainly on the cultivars Kwai May Pink, Tai Soand Wai Chee. Over the past two decades, a preharvest, fruitspotting symptom of unknown etiology has been increasingin incidence in lychee orchards from the Richmond river inNSW to far north Queensland. Due to the small size of thespots the disease has been referred to as pepper spot(Bagshaw et al. 1995). Symptoms on fruit, leaves andpetioles appear as small, slightly raised dark spots (Fig. 1)that may coalesce on fruit to cover much of the surface.Lesions are more usually concentrated on the stem end andshoulders of the fruit. The disease can downgrade fruitquality and affected fruit are rejected during packing. Duringa survey conducted in 1999, fruit of cv. Kwai May Pink werethe worst affected (63%), but other cultivars includingBengal, Tai So, Salathiel, HaakYip, Wai Chee and Bosworth10 also showed fruit symptoms (Drew and Drew 1999).

In 1996, fruit with typical symptoms of the disease werecollected from Kurrimine in north Queensland, surface

sterilised with 70% ethanol and lesions plated onto potato-dextrose agar amended with 1% streptomycin sulphate.Isolation plates were placed in a black light incubator for 2weeks and colonies of Colletotrichum gloeosporioides grewout of the tissue. Several monoconidial isolates wereobtained and grown under black light for 3–4 weeks.Cultures did not produce the teleomorph (Glomerellacingulata).

One monoconidial isolate of C. gloeosporioides (BRIP22984a) was selected to confirm pathogenicity. Twelve-month-old marcotts of lychee cv. Kwai May Pink wereinoculated in a glasshouse using conidial suspensions (1.5 ×106 conidia/mL plus 1% Tween 80) by spraying with a handatomiser. Inoculated branches were covered with moistplastic bags for 48 h. Symptoms became visible on leavesafter 7 days and raised, dark lesions typical of the diseasedeveloped on leaves and petioles after 2 weeks.C. gloeosporioides was reisolated from the lesions.

This disease has not been reported from other lychee-producing countries. Working independently in northQueensland, Yip (1997) has also attributed this disease toinfection by C. gloeosporioides. It is interesting that a similar‘pepper spot’ disease has increased in recent years inavocado orchards and has also been attributed toC. gloeosporioides (Willingham et al. 2000). It is not knownwhether the avocado ‘pepper spot’ isolates will inducesymptoms in lychee or vice versa. Also, it is not knownwhether isolates of C. gloeosporioides which cause a majorpostharvest problem in lychee can induce preharvest pepperspot symptoms as shown for avocado (Giblin et al. 2001).

References

Bagshaw JS, Underhill SJR, Fitzell RD (1995) Lychees – disorders andinjuries. In ‘Postharvest Diseases of Horticultural Crops – Volume2, Tropical Fruit’ (Eds L. Coates, A. Cooke, D. Persley, B. Beattie,N. Wade and R. Ridgeway), pp. 43–44 (Department of PrimaryIndustries, Queensland)Fig. 1. Symptoms of pepper spot on lychee.

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http://www.publish.csiro.au/journals/app

Drew H, Drew J (1999) R & D Progress Report – Lychee pepper spot(LPS). Living Lychee 20, 16–17.

Giblin FR, Coates LM, Bentley S, Willingham SL, Irwin JAG (2001)Pathogenicity and diversity of Colletotrichum gloeosporioidesinfecting tropical fruit. Proceedings of 13th Australasian PlantPathology Biennial Conference, Cairns, 24–27 September, 2001,p 370.

Willingham SL, Cooke AW, Coates LM, Pegg KG (2000) Pepper spot:A new preharvest Colletotrichum disease of avocado cv. Hass.Australasian Plant Pathology 29, 151.

Yip HY (1997) Lychee fruit pepper spot. Living Lychee 11, 6.

Accepted 7 April 2002