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Pests and diseases in aloes

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Aloes and succulent plants are prone to attack by pests and diseases like any other plants in the garden 
Diseases can be prevented to a large extend by keeping plants healthy, which is fortunate as it is easier to kill the pests than to cure the diseases. Chemicals should be used with care as both the pests and diseases can become immune to a specific chemical if the dosage is not strong enough and too strong chemicals will kill plants especially aloes and succulentsOther methods to keep pests and diseases under control will be given.
pests  and diseases resurrecting an ailing aloe


mealy-bug root-bug aloe-scale mite weevils
aloe-cancer shield bugs rot rust leaf spots
A systemic insecticide is the modern way of killing mealy-bug, root-bug, mite, weevils, aloe-cancer(caused by a mite), shield bugs and any other insects.  Insects and mite have built up some resistance to these insecticides and because of the wide variability of the chemicals available in different countries, it is not possible to make recommendation.  Use what is recommended locally.
ants do not do direct harm to the aloes but they are very dangerous indirectly.  They carry the aphids into the crevices of the leaves or where the leaves overlap so that the bugs can not be seen.   The first sign is often when the rosette collapse due to rot.  Watch out for any movement of ants and follow their trail.  They will also heap sand up against the stem of the aloe where they keep their aphid or  mealy-bug farm.  Spread some naphthalene ( mothballs) into the top layer of the soil around the plants.  It will keep ants away. 
The plant sucking bugs and treatment.
mealy-bugs are small sucking white fluffy insects. The white waxy fluff protect the insects.
aphids are light green or sometime blackish insects. they are found on new growth of many plants in the garden.  Ants like the plant sucking insects, but they just love the aphids and take very good care of them by defending them against their natural enemies. All these plant sucking insects do not move about very much.  It is more often the ants that care for them and carry them to new pastures.  In exchange they excrete sweet liquid for the ants. Very interesting information about aphids
aloe-scale is a very flat oval shaped small sucking insect with a water resistant white covering. There is a reddish-brown larger aloe-scale which lives mainly on aloes.  Scale live close to each other forming patches that may cover the whole leaf (killing it) or if left untreated it may cover the plant.   The patches of white specks are obvious and unsightly.   They can do damage by weakening a young small plant, but they do not cause rot as easy as the aphids and mealy bugs.
Most garden poisons are very harsh on aloes.  If poison is necessary,  a very good method to kill aloe-scale is with the powder garden poison'. The main ingredient is chloorpirifos but in the powder it is not as harsh as the liquids on the aloes and it sticks to the scale where water just runs off.
Natural enemies of plant lice are ladybirds, lacewing larvae, hoverfly, parasitic wasps, spiders and other small hunters. 
No harsh poisons are needed.  Wash the lice of   off with a dish washing soap liquid - best is if it is a lemon or orange scented dish washing liquid.  A mild nicotine wash with a drop of soap is also very effective. Mix the nicotine water to look like weak tea.
root-bugs are small whitish sucking insects that live underground near the surface on the roots of the plant. The ants will also tend and protect them.  A give away sign is usually a mount of loose earth that the ants heap up around the aloe stem.   If the plant looks sickly dig just under the soil.  The soft white bugs are easily seen.   We do not use poisons on the other sucking bugs but in this case it is too difficult to reach the bugs.  Drench the soil with a mild system poison.
mite are very tiny but they can cause a lot of trouble.  The worst one in my opinion is the aloe-cancer mite.  aloe-cancer is caused by a mite that lives inside the plant.  This cause the cells to multiply and form ugly weird growths.  Cut out the affected part of the plant.  Paint with a small brush a concentrated system insecticide on the wound. Do not paint the plant, paint the concentrate lightly only on the wound. The cancer damaged part of the plant will die, so cut it out, that leaves less mite to kill.   Do not discard the mite infected plant materiel on the compost heap.  Discard it in a sealed plastic.
shield-bugs are seldom seen.   They are dark grayish color and about the size of a fruitfly.  The bugs are definitely large enough to be seen, but they hide in the debris around the plants from where they go out to suck the juice from the soft new growth in the center of the plant.  They run very fast and is deft in dodging under a leaf.  Small white dots on the leaves are a sure sign that they are there.  Shake a little anti-insect garden powder (sold as Blue Death in South Africa)  in the center of the growing point every 3-4 weeks to keep them away.   A week or so after applying the powder the new growth will obviously be without the tiny spots  and the snout beetle (weevil)will be kept at bay as well.  The snout beetle lays it's eggs in the center where the larvae bore down into the aloe.  Nothing is seen until the center collapse with more often than not,  the whole aloe rotting.
rot should be cut out.    Treat it with anti-fungus and leave to dry.  When an aloe looks sickly without any signs of something wrong on the outside, the roots are rotting.  Remove the plant (it will probably be loose in the soil) cut off the dying roots and leave the plant dry to form new roots.  Here is a very good blog on growing new roots on an aloe.
Rotting rosette is very easy to spot as the leaves will be loose.   Here again remove all rotting material.  You are lucky if you have a clean piece of the stem left over.  follow the instructions
You grow an aloe from a piece of stem, you can not grow an aloe from the leaf like in Gasteria and most succulents. That is a fact.
Prevention is not always possible but it will help a lot.
Ants and their pet plant lice should be kept away.  Make sure the plant has enough sunlight and free air.  A plant in the middle of daisies or grass (Oxalis is very bad over here) is prone to remain damp and rot.  Overall good drainage,  do it with rubble, stones, broken tiles, pottery.
rust and leaf spots  are caused by fungi or bacteria entering the plant.  
It will also start where water is standing in a leaf;  rotting leaves and debris in the crevices;  soft leaves due to too little sun;  sickly plants with unhappy root systems and other mishaps.  Treat with products against fungus and bacteria on the market.   The best remedy is prevention, but that is not always possible.  A plant is seldom killed by rust or leaf spot unless rot sets in.  It may not look good on plants on display, but in the garden it is just one of those natural markings.
Soil problem  -  Sickly plants may be due to poor soil or growing aloes that prefer basic soil in an acid medium.  Have the soil tested.  Adding dolomite gravel is never wrong. 



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