26[7] Sooty mould [EIFS

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This leaflet is produced by the Ministry of Agriculture & Livestock, Solomon Islands, with support from
IPPSI: Improved Plant Protection in Solomon Islands, a project financed by ACIAR, the Australian Centre
for International Agricultural Research, Canberra. Authors: Helen Tsatsia, MAL & Grahame Jackson,
TerraCircle Inc.

Extension Fact Sheet 51:

Sooty Mould Fungi

Common name: Sooty mould

Scientific names: A number of sooty mould fungi have been identified in Solomon
Islands:

Aithaloderma citri (grapefruit)
Capnodium mangiferum (mango)
Capnodium sp. (pawpaw)
Chaetasbolisia microglobulosa (chilli)
Chaetothyrium setosum (coconut, kongkong taro)
Limacinula samoenesis (coconut)
Microxiphium spp. (chilli, coconut, oil palm)
Trichomerium spp. (coconut, oil palm)
Tripospermum fructigenum, (Pometia pinnata)
Tripospermum gardneri (oil palm, cocoa)
Tripospermum sp. (chilli)
Triosporiopsis sp. (pawpaw)

Hosts: Many plants develop sooty moulds when colonised by insects that produce
honeydew (photos above are: left, soursop; right, coconut). The sooty mould fungi
recorded in Solomon Islands and the host plants are given above. Most were recorded from
living leaves.

Damage

The fungi grow on the sugary substances that are produced by insects – mostly, aphids,
scale insects (photo, right: remains of the infestation on upturned leaf), and whiteflies - as
they suck the sap of leaves. The secretions are known as honeydew.

The insects that produce the honeydew are the real problem. They cause direct damage by
sucking plant sap, and often the cause of poor growth, and indirect damage by encouraging
sooty moulds. The fungi do little harm to the plant; they may block sunlight and cause the
leaves to yellow, but rarely stunt the plant.

Biology and Life Cycle

Insect populations increase rapidly when ants protect them from their natural predators and
parasites. Large populations of insects mean large amounts of honeydew, and heavy
coverage of leaves, and other parts, by sooty mould fungi.

Detection and Inspection

Look for sooty mould on new growth and leaves, since the insects involved in sooty mould
growths prefer soft tissue.

Management

All the methods used for treating sooty mould are aimed at controlling the insects that
secrete the honeydew. Without honeydew, there can be no sooty mould. However, the
insects may be protected from their natural predators and parasites by ants, so removing
the ants should be the first step, if they are present.

Cultural control:

• If ants are present, kill them with boiling water, without damaging the crop plants.

Without the ants, predators and parasites will bring about natural control.

• For trees, prune low branches and remove weeds to stop ants reaching the leaves.

Chemical control:

• Use soap sprays (5 tablespoons of soap in 4 litres water), or white oil to kill the sap-

suckering insects. These sprays work by blocking the breathing holes of insects
causing suffocation and death. Spray undersides of leaves: the oils must contact the
insects. White oil (petroleum jelly) can be obtained as a commercial product or made
by mixing together: 1 cup cooking oil; 2 cups water; 1 teaspoon dishwashing liquid.
Dilute the mixture at 3 teaspoons per half a litre of water and spray on the infested
leaves. The additional of malathion is useful against scales insects.

• Use synthetic pyrethroids (for example, lambda cyhalothrin or cypermethrin). READ

INSTRUCTIONS BEFORE USE.

• Try the Papua New Guinea derris variety or neem; get plants from MAL or the Kastom

Gaden Association, as well as the method for making the spray.