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Red banded thrips (Selenothrips rubrocinctus)

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The adult of the red banded thrips is reported as a pest of mangoes in Kenya (AIC, 2003). Adult thrips are dark brown, about 1 mm long. Immature thrips (nymphs) are yellow with a bright red band around the base of the abdomen. Nymphs and adults feed together, normally on the underside of the leaves. Attacked leaves become dark stained and rusty in appearance with small shiny black excreta present. Leaf edges are curled.

Several other species of thrips are found on mango flowers. However, not all of them are pests. Their role varies according to the species. Some species are present in large numbers in mango flowers, but there is no evidence of damage or crop loss. Some thrips species are considered important pollinators. Other species of thrips attack the mango fruit. Thrips feeding on the fruit surface causes a rough, greyish white discolouration.What to do:

• Conserve natural enemies. Predatory thrips and mites, anthocorid bugs among other natural enemies are important in natural control of thrips.

Mango leaf coating mite (Cisaberoptus kenyae)

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The mango leafcoating mite is tiny (about 0.2 mm), light coloured 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.What to do:

• Remove and destroy leaves with white coating.
• Usually no further control measures are needed.

Helopeltis bugs (Helopeltis schoutedeni and H. anacardii)

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Helopeltis bugs, also known as mosquito bugs or mirid bugs are slender, delicate insects, about 7- 10 mm long with long legs and antennae, the antenna being nearly twice as long as the body. The females are red and the males brown to yellowish red. They lay eggs inserted into the soft tissue near the tips of flowering or vegetative shoots. Nymphs (immature bugs) are yellowish in colour. Both adults and nymphs feed on young leaves, young vegetative and flowering shoots, and developing fruits.

Attacked leaves are deformed and show angular lesions, particularly along the veins, which may drop off, so that the leaves appear as if attacked by biting insects. Feeding on the stalks of the tender shoots causes elongated green lesions, sometimes accompanied by exudation of gum. Severely damaged shoots die back due to the effect of bug saliva in combination with fungi which enter the plant tissue through the feeding lesions and the subsequent development of numerous auxiliary buds causes a bunched terminal growth known as ‘witches broom’. In case of serious infestations the trees may appear as if scorched by fire. Bug feeding on developing fruits causes brown sunken spots. The growth of trees is seriously retarded and fruit formation is reduced.

What to do:

• Monitor the crop regularly. Helopeltis attack occurs very suddenly and great vigilance is very important to control this pest, particularly during the rainy season or when water is available leading to flushing (production of young shoots) when Helopeltis populations normally build up.
• Conserve natural enemies. Weaver ants build nests on mango trees providing good protection against this and other bug pests.
• Do not interplant mango with crops that are host for Helopeltis bugs, such as cotton, tea, sweet potato, guava and cashew.

Scales

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Scales are small (1 to 7 mm long), generally immobile insects, varying in colour and shape according to the species. Female scales have neither wings nor legs. They resemble small shells glued to the plant. Females lay eggs under their scale. Once hatched, the tiny scales (known as crawlers) emerged from under the protective scale. They move in search of a feeding site and do not move afterwards. They suck sap on all above the ground plant parts.

There are two main groups of scales on mangoes: soft and armoured scales. Soft scales excrete honeydew. The most common soft scales on mangoes are soft green scales (Coccus viridis), brown soft scales (Coccus hesperidum), and wax scales (Ceroplastes spp.). The most important armoured scale on mango is the mango white scale (Aulacaspis tubercularis). The body of this scale is reddish brown. Females are covered with a white round shell, while males have a small rectangular shell with two groves.

Feeding by scales may cause yellowing of leaves followed by leaf drop, poor growth, dieback of branches, fruit drop, and blemishes on fruits. Heavily infested young trees may die. In addition, soft scales excrete honeydew, causing growth of sooty mould. In heavy infestations fruits and leaves are heavily coated with sooty mould, turning black. This reduces photosynthetic capacity. Fruits contaminated with sooty mould loose market value. Ants are usually associated with soft scales. They feed on the honeydew excreted by soft scales, preventing a build-up in sooty moulds, but also protecting the scales from natural enemies. Armoured scales do not excrete honeydew.What to do:

• Conserve natural enemies. Scales are attacked by a large range of natural enemies, mainly parasitic wasps and predators (ladybird beetles, lacewings, etc). These natural enemies usually control scales. Outbreaks are generally caused by the use of broad-spectrum pesticides that kill natural enemies, and/or to the presence of large number of ants that feed on honeydew produced by soft scales or other insects (mealybugs, whiteflies, aphids, black flies).
• Spray if necessary with light mineral oils. However, care should be taken when using mineral oils, since at high concentrations, they may be harmful to the trees. Oil sprays should be carried out after picking and not during flowering or during periods of excessive heat or drought. Sprays should target young stages of the scales.
• To protect natural enemies spray alternate tree rows each season.
• At early stages of an outbreak cut and burn affected branches and leaves.

Mealybugs (Rastrococcus spp.)

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Mealybugs are small, flat, soft bodied insects covered with a distinctive segmentation. Their body is covered with a white woolly secretion. 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 blackens 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.

The latter is the case of two serious mealybug pests on mangoes in Africa: Rastrococcus invadens in West and Central Africa and Rastrococcus iceryoides in East Africa. These mealybugs, of Asian origin, were introduced into Africa, where they developed into serious pests since the natural enemies present were not able to control them. They cause shedding of leaves, inflorescences and young fruits. In addition, sooty moulds growing on honeydews excreted by the insects render the fruits unmarketable and the trees unsuitable for shading. They cause direct damage to fruits leading to 40 to 80% losses depending on locality, variety and season. Rastrococcus invadens was brought under control in West and Central Africa by two parasitic wasps (Gyranusoidea tebygi and Anagyrus mangicola) introduced from India (Neuenschwander, 2003).

Rastrococcus iceryoides is a major pest of mango in East Africa, mainly Tanzania and coastal Kenya. Although several natural enemies are known to attack this mealybug in its aboriginal home of southern Asia (Tandon and Lal, 1978; CABI, 2000), none have been introduced so far into Africa (ICIPE).

Insecticides do not generally provide adequate control of mealybugs owing to their wax coating.What to do:

• Destroy affected parts at the beginning of the infestation. Heavily infested branches may be pruned to control the pest, especially on the tender branches before flowering begins.
• Conserve natural enemies.
• Avoid excessive spraying and the use of broad-spectrum pesticides, since they may kill natural enemies.
• Control ants tending mealybugs – see also section on mealybugs on citrus datasheet.
• When necessary spray only the affected branches/trees (spot spraying). Mineral oils, neem products and soapy solutions (1 to 2%) are reported to give satisfactory control of mealybugs.

Mango seed weevil (Sternochetus mangiferae)

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It feeds on mango leaves, tender shoots or flower buds. Female weevils lay one egg on the young fruit leaving a small, dark mark on the fruit skin. The larvae burrow through the flesh into the seed and destroy it. The larva develops and grows in the mango seed. When the larva has grown up to an adult beetle, it tunnels through the flesh and leaves a hole in the fruit skin. The tunnel gets hard and the fruit cannot be sold anymore.What to do:

• Keep the orchards clean of all fallen fruit and plant material by collecting, burying or burning it.
• Sticky bands applied at the upper end of the trunk before it branches has been recommended to prevent weevils from migrating to branches for egg laying. However, there are some reports that, although these weevils are not strong flyers, they can fly, and could infest the trees in spite of the banding. A method for banding is described in detail under citrus trees/ants control.
• Scout fruit regularly and remove fruits with egg-laying marks and destroy weevils (larvae, pupa and adults) in mango seeds (stones).

Mango aphid (Toxoptera odinae)

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It is small (1.1 to 2.5 mm long), brown, black or reddish brown aphid covered with a light powdery dusting. Aphids live in clusters sucking sap on the underside of young leaves, on petioles, young branches and fruit. Their feeding causes slight rolling, or twisting of the leaf midrib. Sooty mould growing on honeydew produced by the aphids may cover leaves, twigs and fruit. Coating of the fruit with honeydew and sooty mould reduces its market value.What to do:

• Conserve natural enemies. Aphids are attacked by a wide range of natural enemies, which are very important in natural control of these pests. Click here for more on Natural enemies