iCowApp – Page 60 – Portal for the icow Apps content

Avocado root rot

Avocado root rot (Phytophthora cinnamomi)

Credit: Biovision-Infonet

**Root rot of avocado** tree. Note sparse yellowish foliage.
(c) A.A. Seif, icipe

This disease can attack trees of any size and age. Leaves of infected trees are small, usually pale or yellow green, are often wilted and fall prematurely giving the tree sparse appearance. In advanced stages of the disease, branches die-back and fruit remains small and crop yield drastically reduced. Feeder roots get blackened, decayed and died. Infected trees die prematurely. The disease is prone in areas subject to flooding and in poorly drained soils. The fungus can be spread or introduced to new areas by use of infected seeds, infested soil, irrigation water containing spores of the fungus and infected seedlings. The host range of the fungus includes Acacia, Camellia, Casuarina, Cypress, Eucalyptus and Grevillea.

What to do:

Use diseased-free seed.
Treat seed for planting in a hot-water bath at 48 to 50 degree Celsius for 20 minutes. After the hot-water treatment, rinse the seed immediately with clean, cold running water and spread out to dry thoroughly on a clean surface not in contact with the soil.
Use clean nursery soil for container-grown plants. The soil should be well drained and carefully irrigated to prevent excessive moisture. Use tolerant/resistant rootstocks (e.g. “Duke No. 6” and “7”; “G 6”).
Remove diseased trees from the field.
Avoid movement of soil or water from diseased to noninfested areas.
Use cultivation equipment first in healthy portion of the orchard before use in diseased areas. Washed and dry cultivation equipment after use in diseased areas.

Avocado Scab

Scab (Sphaceloma perseae)

Credit: Biovision-Infonet

The fungus readily infects young, succulent tissues of leaves, twigs and fruits. Lesions appear as small dark spots, slightly raised, oval to elongated. These spots join up, giving a corky appearance to the surface of the fruits, impairing the appearance but not the internal quality of the fruit. Fruits are only susceptible when young until about half size development. The fungus requires moist conditions for sporulation and infection.

What to do:

Remove dead branches and twigs since they harbour the fungus.
Remove fallen rotten fruits from the field.
Apply copper-based fungicides re-flowering, at fruit formation, and after harvest.

How to make EM solution

Credits: Su Kahumbu

You will need the following

1 lt EM (There are many brands available, ask your agro dealer)

1 lt Mollasses

18 lt clean water

20 lt Jerry can or water bottle. NOTE: If using recycled container ensure it is cleaned and rinsed well. If it is contaminated the micro organisms may not grow well.

Pour the molasses into the 20 lt bottle

Add a little water to the molasses bottle

Shake the bottle

As you rinse the molasses bottle until it is clean add all the rinsed water to the 20 lt bottle

Add the EM solution

Shake bottle to mix the EM and the molasses

Check the bottom of the bottle. If it is clear the mixture has mixed well

Now fill the 20 lt bottle to the top with clean water

Keep filling until all the foam is out and there is no air left in the bottle

Seal the bottle tightly with a lid.

Leave this mixture in a cool place to ripen/ferment for about 7-10 days . It will change colour from dark black to orange/yellow and will smell like fermented beer. When it reaches this stage it is ready for use.

Compost Step-by-Step 1

Credits: Su Kahumbu

A pile of vegetative matter. Not compost.

Making compost is a good skill to have. You can make compost for your farm or to sell.

Any pile of vegetative trash can be turned into valuable nutritious compost.

Start by clearing an area 1 m wide by 2 m long

Sort pile of vegetative waste and select the largest driest pieces for the bottom of the compost pile.

Place this dry material in a layer about 4 inches thick across the entire 1 x 2 m floor plan.

Add a 4-5 inch layer of green material on top. These can be weeds, grass or vegetable waste.

Add a 4-5 inch layer of dry material, dried leaves are good.

Add a 3 inch layer of farm yard manure. This can be wet or dry manure and can be from all livestock species.

Try to keep the 1 m x 2 m shape by building upwards in a rectangular way.

Add wet or green materials between the dry layers, in this example banana stems are being used. Chop them up into pieces as seen.

Cover the wet material with 4-5 inches of dry material

Add another layer of farmyard manure. You can sprinkle a hand full of fire wood ash and a kilo of minjingu rock phosphate onto the pile too if you have it.

If you have grass or hay or straw that has been used in your livestock bedding, layer this too.

Try to ensue even spread of the materials you are using.

Add about 20 lt of water or EM (effective micro-organisms) sprinkled over every 5-6 layers to ensure all the layers get wet.

Dry manure needs quite alot of water. The aim is to have all the materials wet at the end of building the compost pile.

Keep building , alternating layers of 4-5 inches of green and dry/brown material and every 4 layers sprinkling a handful of fire wood ash and a kilo of minjingu rock phosphate if you have it.

The layers will be visible from the side of the pile.

Make sure you have added at least 40 lt of water or EM to your pile by the time it is about 3 feet high. Try to build it as high as your materials will allow. One meter high is a good height for a compost pile of 1m x 2 m

Drive a stick into the middle of the pile

Check to see if the stick is wet. If it is dry you have not added enough water

Cover you compost pile with banana leaves or hay or plastic sheeting to prevent it drying out.

Drive the stick back into the pile and leave it here .

In one week check the pile to see if it is heating up.

Do this by pulling out the stick and holding the compost end in your hand .

If it is warm your compost pile is doing well. If is is cold your compost pit is not working and you need to break it down and rebuild it again.

Leave the pile for one month checking each week to ensure it does not dry out. After one week turn the pile by mixing the outer sides into the middle of the pile. It will be about half the size. Reduce the size to 1m x 1m so that it can continue to heat up. If the surface area is too big the pile will cool down and will not breakdown efficiently.

For continuity, make a compost pile every week. This will ensure you always have compost ready for use and your farm crops and soils will be of very high quality.

Spider mites

Spider mites (Oligonychus spp.)

Credit: Biovision-Infonet

**Spider mites** (here on cotton leaf). They are very tiny (they rarely exceed a size of 0.5 mm)
(c) O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org

**Broad mite** damage (here on passionfruit)
(c) A.M. Varela, icipe

Attack by spider mites (Oligonychus spp.) produce circular necrotic spots covered by dense webbing. As mite populations increase feeding causes leaf drop. These mites are more damaging to ‘Haas’ variety; ‘Fuerte’ variety is less affected.

Feeding by broad mites (Polyphagotarsonemus latus) causes leaf distortion. These tiny mites (0.1-0.2 mm long) cannot be seen with the naked eye, and are even difficult to detect with a hand lens. An attack by the broad mites can be detected by the symptoms of damage. Their feeding produces discolouration, necrosis and deformation of tissues.What to do:

Conserve natural enemies. Mites are attacked by a range of natural enemies which can keep the pest under control provided that the natural enemies are not killed by application of pesticides.
Wash the leaves with water using high-pressure hoses. This helps to reduce mite populations.
Irrigate and fertilise adequately heavily infested trees to maintain the flush of new growth that occurs after leaf shed due to mite attack. However, care should be taken not to overfertilise trees to avoid promoting mite populations. Click here for more on spider mites

Bugs

Bugs (Coconut bugs, Helopeltis bugs, stink bugs)]

**Brown stink bug**. Real size: 6 to 15 mm long.
(c) A.M. Varela, icipe

**Helopeltis bug**. Real size: 7 to 10 mm long.
(c) F. Haas, icipe

Adult **coconut bug**
(c) A.M.Varela, icipe

Adult coconut bugs (Pseudotheraptus wayi) are brown in colour and 10 to 15 mm long. Nymphs are red brown to green brown in colour and have long antenna. The adults and nymphs of the coconut bug feed on young and mature avocado fruit. Bug feeding causes necrotic bruise-like depressions. A hard lump develops, which can be easily removed when the fruit is peeled.

Helopeltis bugs also known as tea mosquito or mired bug are slender, delicate bugs, about 7- 10 mm long and have long legs and antenna. The females are red and the males are brown to yellowish red. The bugs prefer to feed on young plant tissue piercing the shoots, stems, leaves peduncles, petioles and fruits. Their feeding causes brown necrotic patches. Attacked leaves present angular lesion, which often drop out leaving holes as it attacked by biting insects. Feeding on young shoots causes dieback of the shoots. Feeding on fruits causes first a dark water-soaked mark around the feeding puncture, turning into a lesion with a light brown centre and black edge. The fruit may exude sap that forms a whitish deposit as it dries.

Stink bugs are shield-shaped bugs variable in size (6 to 15 mm long) and colour (green to brown or reddish brown). They emit a characteristic unpleasant odour when disturbed. They usually feed on the developing fruit. The feeding punctures cause local necrosis resulting in fruit spotting, and deformation.What to do:

Conserve natural enemies. Weaver ants in particular, are efficient predators of bugs in the coastal areas of East Africa.

Thrips

Credits:Biovision-Infonet

Thrips-black tea thrips Heliothrips haemorrhoidalis and the red banded thrips Selenothrips rubrocinctus)

Credit: Biovision-Infonet

Immature stage of the **red banded thrips** (*Selenothrips rubrocinctus*). Note a bright red band across the abdomen of immature thrips. Real size: about 1mm long.
(c) A. M. Varela, icipe

Thrips are small, slender insects (1-2 mm long) with two pairs of fringed wings. Adult thrips attacking avocado are dark brown or black, and the immature stages are yellow in colour. The red-banded thrips can be distinguished by a bright red band across the abdomen of immature thrips.

Thrips are sometimes troublesome pests in avocado. They may cause damage to the leaves and fruit. Affected parts become whitish or silvery and are usually covered by dark-coloured droppings.

On fruit, feeding begins near the calyx, gradually producing a scar that can cover the whole fruit. Attacked fruits develop a leathery brown skin. Feeding is most common on young fruit; economic damage generally occurs on fruit up to 2 cm in length (2-3 weeks after fruit set). Older fruit with thicker skin is less susceptible to attack.

Thrips on Beans

Flower thrips (Frankliniella spp. and Megalurotrhips sjostedti)

Feeding by flower thrips causes scars and blemishes on leaves and pods. Flower thrips can be found feeding on young plants. They are less than 2 mm long. As soon as the plants start flowering, however, most thrips would be found in the flower buds, flowers and on the young pods. Heavy thrips feeding causes flower abortion and flower malformation. French bean pods become scarred (having a rough silvery surface) and malformed and are not marketable.

**Thrips damage** on bean pods
(c) A.M. Varela, icipe

What to do:

Conserve natural enemies. Thrips are attacked by predatory thrips, lacewings and predatory bugs. Control measures are rarely needed.

Scales

Credit: Biovision-Infonet

**Armoured scales** on avocado leaves.
(c) A. M. Varela, icipe

Scales are small, stationary brown greenish insects occasionally found sucking sap from avocado leaves. Soft scales such as Coccus spp. excrete large amount of honeydew, which lead to the development of sooty mould on leaves, branches and fruit. Honeydew attracts ants, which while feeding on the honeydew protect scales from natural enemies.

Armoured scales such as the coconut scale (Aspidiotus destructor) may encrust young twigs, leaves and fruit. They do not produce honeydew. Scales are usually not a problem in avocado orchards; however, damage can be serious on young tress and small twigs may be killed. Although the presence of scales on the skin of fruit does not cause internal damage, it may lead to rejection of fruit, especially if grown for export.

What to do:

Conserve natural enemies. Scales are usually kept under control by parasitic wasps, ladybird beetles and lacewings, provided no broad-spectrum pesticides are used and no ants are present. See more here

Fruit Flies

Credit: Biovision-Infonet

**Fruit Fly** (*Ceratitis fasciventris*) Adults are 4.5-6 mm long, brightly coloured, usually in brown-yellow patterns. The wings are spotted or banded with yellow and brown margins.
(c) R. C. Copeland, icipe

Avocados, especially thin-skinned varieties might be attacked by various species of fruit flies. Some fruit flies lay eggs under the skin of the fruit that is just beginning to ripen, but others attack young and old fruit. When the fruit reaches about the size of a golf ball a sting lesion appears as a slight puncture mark surrounded by a white exudate. As the fruit develops the lesion becomes dry and turn into distinct star-shaped crack on the skin surface.

What to do:

Practise orchard sanitation.
Practise monitoring.
Apply baits (see more under Fruit fly).

False codling moth

False codling moth (Cryptophlebia leucotreta)

Credit: Biovision-Infonet

The false codling moth is small (wingspan of 16 – 20 mm), dark brown to grey in colour. The moths are active at night. Female moths lay single eggs mostly on the fruit. After emerging from the egg, the young caterpillar tunnels into the fruit and the fruit sap thus liberated forms a typical white crystalline excrescence on the surface of the fruit. When moths lay eggs on young fruits the caterpillars usually die and thus large caterpillars are seldom found.

However, the caterpillars are able to develop if fruits are approaching maturity when infested. The young caterpillar is creamy-white with a dark brownish head. With age the body turns pinkish red. The fully-grown caterpillar is 15 to 20 mm in length. When mature the caterpillar leaves the fruit and pupates in the soil or beneath surface debris.

What to do:

Proper orchard sanitation in combination with natural enemies normally keeps this pest under control.
Infested fruits (both on the tree and fallen fruits) should be removed regularly (twice a week), and buried at least 50 cm deep, or dump in a drum filled with water mixed with a little used oil. The fruits should be left in the drum for 1 week.
This moth also attacks citrus, cotton, maize, castor, tea, guava and carambola fruits. Other host plants include wild guava plants, oak trees and wild castor . These other host plants should be included in the sanitation programme.
If possible, remove wild host plants from around the orchard.