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What is it?
Pit scales are of the aesterolecanium species. They are insects which appear to the untrained eye as merely bumps on the bark of the oak tree. Oak trees are also known by the name quercus, and there are varieties of oak trees for just about any climate including those which are hot, windy, moist or have a large amount of salty air. Pit scales attack oak trees in any of these climates and heavy infestations can kill off young trees in a short period of time.
What does it look like?
Aesterolecanium pit scales are very small insects. At their largest size, pit scales are no more than 1/12 inch across. Typically, oak pit scales are small and green, however there are some which have a more golden color to them All pit scales are very flat and only slightly rounded on their backs. These mostly flat insects often cluster on oak tree bark which gives them the appearance of bumps. More often than not, these bumpy patches of scales will cluster in areas of the bark which has been pitted previously. Damage from aesterolecanium often first appears as dying leaves, twigs and branches. Often the twigs and branches will turn brownish or die back entirely. However, the dead leaves will typically remain attached to the tree throughout the winter even though they turn brown and die. In the spring, if the oak tree has previously been infested with pit scales, the tree will not develop leaves on time. Typically the leaves will appear three weeks later in the growing season than they normally would have had the tree not been infested.
How does it manifest?
Aesterolecanium pit scales lay their eggs in both spring and summer. The oak pit scales then emerge as young scales which are called crawlers. When the crawlers hatch from the eggs they find a spot on the new growth which has developed on the prior years growth of new branches. The small oak pit scales are soft bodied and feed off the oak tree by inserting their mouth parts into the oak tree and sucking out the nourishing sap. In areas where the aesterolecanium pit scales feed pits tend to develop. This is the reason that aesterolecanium are known as pit scales. The bumps which appear occur when the pit scale crawlers legs atrophy after feeding and a hard shell forms over their bodies. This hard shell also crusts over their bodies and this is the region where adult female scales lay their eggs. These hard shelled areas provide shelter for the developing eggs and young crawlers and are what form the characteristic bumps which appear on the oak trees.
What can you do about it?
Young crawlers and pit scales are most active from mid-May to late June and this is the best time to utilize a chemical control. You will want to spray the oak tree with an insecticide that contains acephate. This wil help to control the aesterolecanium pit scale populations and prevent adult females from laying eggs which will develop into another generation of young pit scale crawlers. To prevent pit scales from over wintering, you may want to also spray the oak tree with an oil based spray and thoroughly cover the oak tree. This application can also be repeated in the early spring tohelp prevent the emergence of any pit scales which may have survived and over wintered.
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