Mango diseases in Egypt

Mango (Mangifera indica L.) is universally considered one of the most important fruit crop in Egypt. Egypt produces 232,000 tone of mangos annually and exports moderate amounts (1500 tones) to 20 countries in the near East and Europe, FAO, 2000. It is expected that commercial and backyard plantings of mango trees will continue to increase. Mango suffers from several diseases at all stages of its life. All the parts of the plant, namely, trunk, branch, twig, leaf, petiole, flower and fruit are attacked by a number of pathogens including fungi, bacteria and algae. They cause several kinds of rot, die back, anthracnose, malformation, scab, necrosis, blotch, spots, mildew, etc. This fact sheet concentrates on the symptoms of the important mango diseases, the weather conditions conducive to disease development, and methods for control. ANTHRACNOSE Anthracnose, the most important mango disease, is caused by the fungus Colletotrichum gleosporioides. Flower blight, fruit rot, and leaf spots are among the symptoms of this disease (Arauz ,2000). Infections on the panicles (flower clusters) start as small black or dark-brown spots. These can enlarge, coalesce and kill the flowers, greatly reducing yield. On leaves, anthracnose infections start as small, angular, brown to black spots. Depending on the prevailing weather conditions blossom blight may vary in severity from slight to a heavy infection of the panicles. Anthracnose is usually more serious in years when rain and heavy dews are more frequent during the critical periods of infection from the onset of flowering until fruit are about half size. Severe infection destroys the entire inflorescence resulting in no setting of fruits. Young infected fruits develop black spots, shrivel and drop off. Fruits infected at mature stage carry the fungus into storage and cause considerable loss during storage, transit and marketing . Varietal differences in susceptibility have been noted in Egypt. , which maximum damage was observed on Alphons, whereas variety Tommi and Fagr Kelan was recorded to be resistant (Table 1). Since the fungus has a long saprophytic survival ability on dead twigs, the diseased twigs should be pruned and burnt along with fallen leaves for reducing the inoculum potential. POWDERY MILDEW Powdery mildew is caused by the fungus Oidium. Although a somewhat sporadic disease, it can cause severe crop loss due to flower and panicle infection and subsequent failure of fruit set (Figure 2) (Nofal and Haggag Wafaa, 2006). The disease is reported to cause approximately 20 -80% per cent crop loss. Powdery mildew is common in all over Egypt as ElBehera , El-Fayum, El-Monefia forword by El Ismilia Governorates. Powdery mildew is one of the most serious diseases of mango affecting almost all the varieties as cvs. Alfonso and Seddek. Meanwhile, Zebda , Hendi besenara and and Awies cultivars are moderate infection than the other cultivars (Table 1). The characteristic symptom of the disease is the white superficial powdery fungal growth on leaves, stalks of panicles, flowers and young fruits. The affected flowers and fruits drop pre-maturely reducing the crop load considerably or might even preven the fruit set. Rains or mists accompanied by cooler nights during flowering are congenial for the disease spread. The fungus parasitizes young tissues of all parts of the inflorescence, leaves and fruits. Powdery mildew occurs in the spring and is particularly destructive in years when the weather is cool and dry. MALFORMATION Malformation is widely prevalent in Egypt where more than 80 per cent of the trees suffer from this malady (Table 1) (Ploetz et al., 2002). Malformation affects vegetative and floral tissues of mango. The malformed panicles remain unproductive and are characterised by a compact mass of male flowers, greenish in colour and stunted in growth. Apical or axillary buds produce misshapen shoots with shortened internodes and dwarfed leaves which are brittle and recurve towards the supporting stem. The main and secondary rachis are thick and short and bear flowers with relatively larger bracts, sepals and petals as compared to normal flowers (Figure 3). The malformed panicles remain intact on the trees for a considerable period. Compact leaves formed at the apex of shoot or in the leaf axil, to form the bunchy Agric. Biol. J. N. Am. , 2010, 1(3): 285-289 286 top seedlings and are usually shallow with few tertiary roots. Floral aggregation may also appear on shortened primary axil of the inflorescence, which is further branched to secondary and tertiary branches, on which flowers are borne in clusters and no fruit or very poor fruit setting is observed. Infected inflorescence remains green for long time; no malformed heads dry up in black masses but persist on trees. More important, however, is the affect of malformation on fruit set: fruit in affected panicles either do not set or abort. The tap root may be twisted and may show necrosis. Though research efforto made hitherts have not been able to ascertain its etiology, the complexity of the disorder is attributed cultural practices, nutritional, to many factors like, mites, fungal, viral, etc. hormonal imbalance. The fungus Fusarium subglutinans causes malformation. It is believed that the mango bud mite, Eriophyes mangiferae, is a vector of this pathogen that enhances infection by wounding host tissues while feeding on mango. The pathogen is spread by grafting and in infected nursery stock. Table 1. Susceptibility of fruti of different mango cultivars to anthracnose, Powdery mildew and Malformation Disease reaction: Cultivars Anthracnose Powdery mildew Malformation Alphonso *HS HS HS Timour HS S HS Sadeka MR HS HS Zebda HS M S Tommi HR HR HR Kett R HR HR Kent Hendi Khasa Hendi Sennara FagrKelan Awais R