The primary insect pests of mangoes are the mango fruit fly and the mango stone weevil. The two most serious fungal diseases of mangoes are powdery mildew and anthracnose.
1.1. Anthracnose
Caused by the fungus Colletotrichum gloeosporioides, is undoubtedly the most common and widespread fungus disease of mango and is a major factor limiting production in areas where conditions of high humidity prevail. The fungus invades inflorescences, fruits, leaves and twigs. Substantial losses due to this disease are recorded every year not only at premature stages of the crop but also during storage after picking.
Symptoms:
The signs are visible as small black spots which later get bigger. When the germ affects the flower, some may wither and die before fruit set. Infected young fruits show very small, brown or black, sunken spots. The disease goes into an inactive stage until fruits are harvested. Afterwards, the fruits develop round, black sunken spots and eventually the whole fruit rots.
Management:
To control untreated subjects used for comparison with those given a particular treatment the disease, orchard sanitation and pruning of dead twigs and branches which may harbour the fungus are the principal control measures used to reduce the source of a new infection cycle.
The widespread occurrence of the inoculum of the fungus makes it impossible to control the disease by pruning and the removal of dropped leaves alone. To be more successful, the above mentioned measures have to be supplemented by spray applications using Mancozeb, copper oxychloride, Maneb, Propineb, Benomyl etc.
It is recommended to start spraying at the stage of flower-bud formation. During flowering/fruit set and until the fruits have developed to half their size, spraying should take place at fortnightly intervals. After this, it is sufficient to treat the trees once a month. It is very important to apply a full cover spray for the first two applications.
1.2 Powdery Mildew
The powdery mildew disease, caused by the fungus Oidium mangiferae, is a serious problem in all mango-growing areas. Infections can result in complete crop loss and defoliation of trees. The disease favours cool and cloudy weather but also occurs in warm and humid climatic conditions. It attacks leaves, buds, flowers and young fruits. Infected tissues are covered with a whitish, powdery growth of the fungus. Mature spores are easily blown away by wind and produce a fresh infection, or they may remain dormant alive but not growing; a resting stage during the unfavourable season awaiting optimum germination conditions in the next season.
Photos: Powder mildew symptoms on inflorescence, young and older leaves
Management:
Chemical control:
1.3. Mango Fruit Fly
Different types of fruit flies are known to attack ripening mangos in almost all mango-producing areas. Yield losses of more than 50% have been reported. Ceratitis cosyra followed by C. rosa and C. capitata have been found to be the major pests of mango.
The females lay their eggs under the surface of the fruit skin. After hatching, the maggots penetrate the flesh and destroy the fruit from inside. The infested part becomes mushy and causes premature colouring of the already useless fruit.
Photos. Adult and larva of mango fruit fly (©A.M. Varela, ICIPE)
Management:
Non chemical method:
Chemical method:
1.4. Mango Seed Weevil
The weevil, Sternochetus mangiferae (F), is a common pest and can be found in all local mango-growing areas. It is spread mainly by transportation of infested fruits since the weevil develops within the mango seed and can therefore be transported easily from one locality to another unnoticed. The mango weevil does not usually damage the fruit and consequently is not a serious pest as far as local consumption of the fruit is concerned. However, this pest hinders the development of a fresh fruit export market because the leading import countries in the Middle East and other places maintain strict quarantine the prevention of importation or exportation of unwanted organisms into a territory regulations.
Infestation symptoms are most obvious within the seed where the weevil largely completes its life cycle. Externally the affected fruits appear normal, but very often are rotting from inside.
Photos: Larva and adult of mango seed weevil (©Peter A. Follet; Monique H & Biovision)
Management:
To date, chemical control untreated subjects used for comparison with those given a particular treatment measures against this pest have not proved economical. However, implementing the following three steps will definitely reduce the weevil population in the orchard.
AnchorAnchorAnchorSanitation of orchard and yard: The biggest source of infestation is dropped fruits or seeds lying around in which weevils can survive up to about 300 days. Therefore, regular removal and destruction of waste material up to the end of the harvesting period is very important and effective.AnchorAnchorAnchorAnchor
Treatment of trunk and branches: The most suitable stage for control is during the emergence and oviposition of the adult weevil. The first step to suppress the weevil population is implemented at the beginning of the mango flowering season by using preferably long-lasting contact insecticides. It is important to thoroughly wet (by spraying) the bark of the trunk.AnchorAnchorAnchorAnchor
Fruit treatment: After fruit set, carry out spray treatments mainly focused on single fruits using Cypermethrin, etc. mixed with a spreader/sticker material added to a spray to increase retention on plant foliage liquid. Repeat applications at intervals of 2-3 weeks and combine this with the control of anthracnose.
1.5. Mealybugs (Rastrococcus spp.)
They suck sap from tender leaves, petioles and fruits. Seriously attacked leaves turn yellow and eventually dry. This can lead to shedding of leaves, inflorescences, and young fruit. Mealybugs excrete honeydew on which sooty mould developed. Heavy coating with honeydew blacken the leaves, branches and fruit. This reduces photosynthesis, can cause leaf drop and affect the market value of the fruit.
A wide range of natural enemies attacks mealybugs. The most important are ladybird beetles, hover flies, lacewings, and parasitic wasps. These natural enemies usually control mealybugs.
However, mealybugs can cause economic damage to mango when natural enemies are disturbed (for instance by ants feeding on honeydew produced by mealybugs or other insects) or killed by broad-spectrum pesticides, or when mealybugs are introduced to new areas, where there are no efficient natural enemies.Insecticides do not generally provide adequate control of mealybugs owing to their wax coating.
Management:
1.6. Mango leafcoating mite (Cisaberoptus kenyae)
The mango leaf coating mite is tiny (about 0.2 mm), light colored and cigar shaped. It cannot be seen with the naked eye. The mites leave in groups under a white coating on the upper leaf surface. The white coating can be easily rubbed off by hand. Leaves covered with the white coating tend to turn yellow and drop prematurely. In general, the coating has minimal effect on fruit yield.
Management:
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