DiseasesCitrus greening disease

This disease causes sectorial yellowing of leaves. Fruits

are small and

lopsided. Tree

may blossom out

of season. It is

transmitted by

citrus pysllid.

Control• Control psyllids with insecticides.

• Plant seedlings from certifi ed nurseries.

• Rogue infected trees and disinfect budding tools

from one seedling to the next.

Citrus gummosis

Bark rots on the roots or the trunk and the branches. In

early stages of infections gum oozes from the infected

parts hence the name gummosis. Leaves start yellowing

and the twigs dieback and the tree eventually dries up

and die if untreated.

Control• Surgically remove the bark or burn it with blue fl ame

from a propane torch.

• Fertilize and irrigate the treated trees.

• Use tolerant rootstocks - Cleopatra mandarin.

• Weed from the tree trunk outwards.

• Avoid planting on heavy or waterlogged soils.

• Plant seedling with the bud union at least 6cm above

the ground level.

Management of citrus pests and

diseases

Kenya Agricultural Research InstituteP.O. Box 57811-00200, NAIROBI.

Tel: 254-20-4183301-20, Fax: 254-20-4183344Email: resource.centre@kari.org

Website: www. kari.org

Compiled by: Kega, V.M.

For more information contact:

Centre Director, KARI Katumani, P.O. Box 340- 90100, Machakos

Tel: +254 44 20495, 20395/8, 21638, 20422Fax: +254 44 21122

Email: karikat@wananchi.com

KARI information Brochure series / 16 /2008 Ksh. 20

Citrus greening disease symptoms

They produce a lot of honey dew leading to black sooty

mould development which eventually leads to twig

dieback and loss of fruits.

Control• Ring-band the tree trunk with insecticide to

discourage climbing attendant ants.

• Spot spray the heavily infested trees or alternate

rows paying attention to the underside of the leaves.

• Prune off heavily infested branches.

Citrus black fl y

These appear as colonies of black small insects on the

underside of leaves. A thin fi lm of wax covers them.

Control • A parasitic wasp normally keeps these pests in check.

In severe infestations sprays of contact or systemic

insecticides are effective.

Citrus soft scales

These are small motionless insects mostly found on the

young and succulent tissue on leaves, stems and also on

fruits.

Control• Ring band the trees

with anti-climbant

insecticide. This

discourages the

attendant ants from

climbing and attending the scale.

• Spray with mineral oil.

Russet mites

These attack the fruits resulting in silverfi sh colour

Bud mites

They attack the young buds and shoots resulting in

whitish to silverish small spots on leaves causing severe

malformation of leaves and spread to new growth.

Control• Avoid dusty conditions by siting orchards away from

roads.

• Plant wind breaks and in heavy infestations spray

with acaricides.

IntroductionCitrus yields are often low and fruits are of poor quality

due to pests and diseases. Information on common

pests and diseases and their management is important

for improved yields.

PestsMediterranean fruit fl y

These are brightly coloured fl ies that lay their eggs on

citrus fruits. The fruits develop spots and change colour

to orange or yellow when still immature and eventually

drop from the tree.

Control• Spray alternative rows with systemic insecticide and

insecticide baits.

• Systemic insecticides in honey or fermented juice are

also effective.

Citrus woolly aphid

These are small insects covered with curly white wool

hence the name woolly aphid.

Mediterranean fruit fl y

Woolly aphid on leaf

Russet mites on fruit

Citrus soft scales on leaf