Scales
Damage
Scales remove plant saps by using their sucking mouthparts. Leaves become stunted and turn yellow and the twigs and branches dieback. Some scale species produce honeydews which they secrete while feeding. Honeydews on fruits, leaves, twigs, branches, and barks attract black sooty molds to feed and grow, causing these plant parts to blacken.
Description
1. Armored scales (Diaspididae) Armored scales are small, about 3 mm long. Their colors vary from white, yellow, gray, reddish or purplish. Adults are oval or round, hard bumps, and sometimes bearing a nipple or
dimple in the center. They do not produce honeydews but they secrete armor wax in an oyster shell or circular pattern. They remain attached to the host plant when shells are lifted up.
2. Soft Scales (Coccoidae) The eggs are covered or found under the mother scales. Eggs hatch into crawlers (nymphs), which are flattened and looking like dusts on the plant surface. Adult females are either oval or round, soft, legless bumps, and are wingless. Males are tiny yellow-winged soft scales. Soft scales secrete honeydews which attract ants. The shells of the soft scales are not left on the plant when lifted up. The soft covering they secrete cannot be separated from the scale's body. Soft scales typically move between branches and leaves during their lifecycle.
Control measures
Other solutions
Horticultural oil sprays
Horticultural oils are concentrated and must be mixed with water. Spray 2% solution against insects and mites. To make a 2% solution, pour 1/3-cup oil into a 1-gallon container, and then fill with water to make a 1-gallon solution. For a 3% solution, start with ½ cup of oil. Apply successive sprays at least 6 weeks apart. You can apply 1% oil solution by mixing 2.5 tbsp of oil in 1 gallon of water.
Following the mineral oil spray, use a highpressure water jet treatment to dislodge dead scales from trees. It is important to remove the dead scales remaining on the plant because this will ensure protection against newly hatched scales. To dislodge living scales is to use a forceful jet of water to 'power wash' them from barks.
Application of Vaseline, camphor, eucalyptus oils should be tested on small area, prior to large scale spraying because some leaves are sensitive to these oils. If done for the first time, ask for assistance from your local agricultural office. Field Guide to Non-chemical Pest Management in Mango Production
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