Pest Management Series 2000/01 The Citrus Blackfly (C.B.F.) A Farmer’s Guide to Identification and Control Published and Printed by the Extension Unit Regional Administration South, Ministry of Agriculture, Land and Marine Resources, Kings Wharf, San Fernando, Republic of Trinidad and Tobago January 2000 Revised February 2000

Introduction

The Citrus Blackfly (C.B.F.) originated in Asia. It was first identified in the Caribbean in 1913 in Jamaica. It can now be found in many countries in the Caribbean and Central America. It was first observed in Trinidad in 1997 and has rapidly spread throughout the island.

The C.B.F. is a member of the "white fly" family. The adult is 2 mm long with slate-blue wings. It is usually found on the younger leaves.

Its life cycle is shown in figure 1.

Figure 1: Life Cycle of C.B.F.

The time from egg to adult varies between 43-125 days, shorter periods occur with higher temperatures.

Which plants do the C.B.F. attack?

Its main hosts are all types of citrus.

It also infests avocado, banana, plantain, coffee, guavas, mango, pawpaw, West Indian cherry, carambola, pomegranate, roses, hibiscus and gliricidia.

What are the symptoms of the C.B.F.?

UPPER LEAF SURFACE

1. The presence of copious sooty mould fungus on upper leaf surfaces.

UNDERSIDE OF LEAF

2. 20-30 eggs in a spiral pattern on under surface of the leaf. These vary from white to light yellow. See figure 2.

3. Nymphs (less than 1mm) brown to black. These feed on sap and excrete a sweet substance (honey-dew) which drops onto the upper surface of the lower leaves and fruits. This encourages growth of the fungus - black sooty mould, causing the blackened appearance.

4. Under-leaf patches of pupae are easily seen as oval shiny black structures with white fringes. (Figure 3).  After the adult emerges, the pupal case remains attached to the leaf.

5. The growing tips of the branches (young flushes) can also be severely infested causing stunting of leaves. This reduces the growth of the plant.

N.B.

Only leaves and fruits are affected; branches remain clean.  The adult C.B.F. remains on shady grasses under the affected tree, serving as an avenue to reinfest the tree.

How does the C.B.F. damage your crop?

It feeds on the soft parts of leaves

Excretes honey-dew on which black sooty mould fungus thrives

Leaves cannot breathe or produce food

Leaves drop causing "die-back" of branches

Tree is weakened thus affecting production and leaving it susceptible to other pests (e.g. green and black aphids, leaf miner) and diseases

New growth is reduced and therefore fruit production also declines.

How can I control C.B.F.?

Use an integrated approach combining cultural, biological and chemical control methods

1. Cultural control

Keep orchard clean from weeds by brushcutting and cutlassing

Prune all diseased and dried branches

Do all activities which encourage the growth of healthy plants e.g. fertiliser application and drainage

2. Biological Control

Two wasps have been identified for use. These are Encarsia perplexa and Amitus hesperidum. They should be available for release shortly. These wasps are about the same size as those used to control the Hibiscus Mealybug.

3. Chemical Control

Use citrole, a recently introduced bio-degradeable paraffin compound to control the C.B.F. It works by creating a film and suffocating the insect.

Citrole is environmentally friendly;

It has negligible effect on beneficial insects because it is non-toxic

It causes no long term effect on the environment because the properties of this chemical are disintegrated

No harvest interval is required. Fruits can be eaten just after application

Apply citrole at the rate of 10 ml in 1 litre. Spray (preferably with a mist blower) to allow complete coverage of all leaf surfaces.

Sooty mould will be controlled once insect level is reduced with the use of Citrole. Do not use a fungicide.

Other insecticides can be used as an alternative for chemical control, for example Neem-X, Actellic or Agricultural soaps e.g. Mpede

N.B.

All chemical control methods are short-term. Re-infestation will occur depending on the C.B.F. level in untreated areas. Repeat applications are necessary.

The assistance of staff from the Research Division and the Extension, Training and Information Services Division is gratefully acknowledged.

For further information please contact

R.A.S. - (868) 657-5189, (868) 657-5455
St. Patrick (E) - (868) 647-8460
St. Patrick (W) - (868) 648-2384
Victoria - (868) 652-2622/2033, (868) 655-3428
Nariva/Mayaro - (868) 644-2326

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