scale- identification, control and iradication

[Jamie]

we will take a look at scale next, these little bugs can be destructive in large numbers and are a common pest, but can be quite simple to control.
lets take a look at what they are first.

scale can vary in many different colours and size ranging from black, brown, white even pinkish in tone. they are a pest that is generally covered by a shell that protects them while there soft inner core sucks sap from the vascular tissue of the tree, this can be a big problem in large infestations.

scale-insects-2-la.jpg

scalewhite.jpg

1scale.jpg

There are two main groups of scale insects, both of which spend most of their lives as immobile adults under a coating, sucking the sap from stalks, leaves and stems. Hard scale (for example red citrus scale) has an oyster like coating and can be difficult to control. Soft scale (for example pink wax scale and soft brown scale) are usually found on the mid-rib of leaves and stalks of host plants. Most common is white wax scale, seen as large patches of white waxy material along the stems and shoots. The wax covers the insects which feed on the sap. The adult scale lays up to 1000 eggs that hatch into crawlers. These crawlers move to a nearby feeding site where they set up home feeding on the sap of the plant. It is at this crawler stage the scale is most vulnerable as there is no waxy coating to protect them.

control.

the easiest way to control these pests if infestation is minimal is to pick them of by hand, this will get rid of the adult scale, the juvenielle scale can be controlled by a contact insecticide, be wary of these as they can also kill the predatory insects such as the ladybeetle which will feed of them.
a systemic is a good way to break the life cycle if you are having constant problems with them.

i am a big believer that a healthy tree is insect and disease resistant, sometimes we cannot avoid this as pot culture can put stresses on the tree that we cannot avoid.

feel free to add to this as i would like it to be a reference for anyone who has the problems of pests and disease where they can come and look at the thread and know what to do without to much problem.

jamie


symptoms.

obviously they can generally be seen in there adult stages.
White patches on stems or pink or brown raised dome like structures on leaves and stalks about 3-5mm. Sooty mould grows on the honeydew the scale insects secrete. Scale can cause death of stems if infestation is heavy.

[Jamie]

i will put mealy bugs into the scale thread as they are a similar pest and can be treated with similar products and results.

These small, white, powdery-looking insects are sapsuckers that attack a wide range of plants, indoor and out.
Adults are generally 3-4 mm long. Ants can be responsible for moving them from plant to plant. The presence of mealy bugs will also encourage black sooty mould to appear on the leaves.

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Longtailed_Mealy_bug.jpg

along with scale ants are an indication you have an infestation of either scale and/or mealybugs. the ants will actually "farm" the scale/mealybugs to harvest the honeydue that the bugs excrete and will even go to lengths to protect them, the ants can also be responsible for moving scale from one tree to the next.
They generally prefer warm, humid, sheltered sites away from adverse environmental conditions and natural enemies.
Different species of mealybugs prefer different feeding sites - some species feed in and under bark, while others feed on fruits, flowers or seed heads.
Mealybugs can build up in huge numbers in a very short time and cause considerable damage. They feed by inserting their straw-like mouthparts, known as ‘stylets’, into plant tissue. Feeding damage can be either by direct removal of plant fluids and nutrients, and/or by the excretion of toxic salivary compounds into plant tissue.

Honeydew - the waste product of the mealybug feeding process - is a perfect growth medium for sooty mold fungi. These molds damage plants by covering leaves and reducing light available for photosynthesis.

Most mealybugs (especially pest species) have numerous, often overlapping, generations per year. Like all insects, their development is dependant on temperature: there is a threshold temperature for each particular species of mealybug, below which development either ceases totally (dormancy) or is slowed to a greater or lesser degree (quiescence). Just as there is a minimum threshold temperature, there is also a maximum threshold temperature, beyond which development is slowed or ceases all together.
If temperatures remain elevated for prolonged periods, insect mortality increases rapidly with a consequent crash in population size. Mild to warm conditions are therefore favourable for insect development, and mealybugs are no exception to this rule. Temperatures of about 25°C and a high relative humidity are optimum for mealybugs in Australia, and their populations reach peaks in spring and autumn.

Eggs can be laid singly or in clusters, and female Long-tailed Mealybugs have been recorded as laying as many as 200 eggs in a lifetime. Egg clusters are usually embedded in a cocoon of waxy filaments, with the structure varying between species, from tightly packed to loose.

control

Because mealybugs have high reproductive capacities and multiple generations in a year, they have the potential to become resistant to pesticides very quickly. The use of stronger and stronger pesticides breeds more and more resistant mealybugs, until the stage is reached where efficient and practical chemical control of the pest is no longer possible. Fortunately mealybugs can be controlled using ‘soft’ methods including biological agents and low-toxicity pesticides, most of which are readily available to the horticultural industry and the home gardener.

i find removal by hand can be quite effective for minimal infestation.

as stated before i am a firm believer that a healthy tree is more resistant to pest and disease than a stressed or unhealthy tree, being in a potted culture sometimes these things cant be avoided and treatment is necessary.

feel free to add anything to these articles as for the reasons stated in the last post.


jamie

[anttal63]

Ok now im pissed!!! This time of the year my callistamon's get scale which i will normally pick off. This year they have all been repotted, kickn ass and looking healthy. Checkn out wether or not they needed watering this morning as we have had lots of rain, i discovered they are all infested, still young not too many hard shells yet. The prob is i have too many too pick off these days. i have not used any pestacide in at least 2 years because i have enjoyed my trees looking healthier for it. But extreme circumstances need extreme measures. My first thought is to throw them all in the bin and be done with bottle brush once and for all, BUT....??? Any one got any good solid solutions? Experienced only please!

[anttal63]

OK! Well i got dishwashing liquid out, first i pruned and thinned everything back hard, then i mixed a little dish soap in a water spray and more in a tub of water. the trees got sprayed and the pots got dunked. I have also now placed in the airiest and sunniest pos i got but will have to move again if it gets too hot. We shall see now ?

[Jamie]

good work ant, let us know how this works, it can be a simple effective method for scale treatment that beginners can use if it is effective!


jamie

[Steven]

I've been farming a little scale colony on a PJ 'Little Ruby' that I keep segregated from the rest of my trees. The tree has always been susceptible to scale so rather than continuing to fight it, I have left them be. For the last 18 months I haven't had a scale problem on my others. Perhaps giving them their own area has kept them at bay?!

Here is a picture I snapped today with my new camera.

Scale.jpg

Regards,
Steven

[craigw60]

G'day Steven I am sorry mate but that is just too alarming for words
Craigw

[Dutchie_Boy]

Thanks, there is some good information there.

Commiserations on the infestation.

[Chris H]

Steven

Pick em off and spray with Pest oil immediately...

Otherwise Im spraying you next time you come over!