What is Scale?
Scale insect is difficult to spot, so look out for the symptoms of an attack i.e. sticky lower leaves, sooty mould and yellowing of top leaves. Underglass, scale is very particular to all types of citrus. Outside, keep a close watch on camelias, rhododendrons, azaleas and box.
There are a number of different species of scale, although they are all similar in appearance -they are unlike any other pest as they don't look alive at all.
They are motionless and are stuck firmly to the stem and the underside of leaves (often around the veins) from which they suck the sap. They are dome shaped, about 0.6cm fully grown, light brown when young but gradually darken as they mature. They feed on the sap of the plant, leading to a yellowing of the leaves and in extreme cases total defoliation. Scale insects produce large quantities of honey dew which drips onto the lower leaves. Initially clear and sticky, it is then colonized by sooty mould (pictured left), which is unsightly and reduces the ability of the plant to produce food, leading to further weakness and loss of vigor.
This mould and honeydew are the first signs of an attack. A female scale insect produces a mass of eggs i.e. between 500 and 2000! and then dies. The eggs are laid under the scale which protects them as they develop. The eggs hatch to produce a crawler stage which settles on a suitable part of the plant, starts to feed and becomes immobile. The length of the life cycle depends on temperature but at 20°c it normally takes 10 weeks from egg to adult.
How do I control Scale?
Controlling scale in your greenhouse or conservatory - spray your plants with scale nematodes at anytime as long as the temp is 14c.
Controlling scale outdoors - Permanent outdoors plants should be treated when the temperature is above 14C i.e. normally between April and September. Potted outdoor plants can be moved into a greenhouse or conservatory and treated at anytime.
Treating scale with nematodes:
1) Mix the nematodes with water and spray the infected plants, concentrating on the undersides of the leaves and stems.
2) Keep the foliage moist for 12 hours. This can be achieved by damping down the leaves with a gentle soft water spray, being careful not to wash the nematodes off, or by covering the plant with polythene (put the plant in a bin bag if small enough) for 12 hours following treatment.
3) The whole process is repeated 3 times at 21 day intervals.
Our price includes 3 introductions sent by 1st class post at 21 day intervals.
N.B. Please note that once the scale insects are killed, they will remain on the plant, which will often lead people to believe that the control is not working. The first indication that the control is working is that honeydew will stop being produced so if the mould is washed off - SB Invigorator is very good at doing this - it will not come back. The scale itself can be removed by hand.