The bright yellow blooms of goldenrods brought a stunning beauty to old fields and roadsides in September. Now, the plants have turned a dull, lifeless brown as winter takes hold.
Nevertheless, a field of dried-up goldenrods also has a special attraction this time of year — insect galls. Most goldenrods (Georgia has some 35 species) harbor the galls, each of which contains a wormlike larva of a certain fly or other insect.
The larvae, in turn, are important winter food for several creatures, especially downy woodpeckers and sometimes Carolina chickadees. Gray squirrels also may rely on the gall larvae in winter, especially during years when nuts, acorns and other favorite foods are scarce.
Galls are common — albeit abnormal — plant growths caused by the larvae of certain insects and mites. Many plant species attract gall-makers, but goldenrods seem especially alluring to them.
Goldenrod galls appear as round swellings as large as golf balls on stems.
The commonest goldenrod gall is made by the goldenrod gall fly. In spring, the female lays her eggs on the stem. A larva from a hatched egg chews its way into the stem and the gall begins to form. No one knows just how a larva causes a gall to start, but it may have something to do with the larva’s saliva, which may mimic plant hormones.
The larva stays in its gall the rest of the year and continues to develop. By late fall, it will be fat and ready to enter the pupal stage to develop into an adult fly, which will emerge the following spring. The gall itself will have hardened and become tough to open.
To make sure that it can exit the gall as an adult, the larva in late fall will tunnel almost to the outside of the gall, leaving just a thin plant tissue inside. This will allow it to pop out easily as an adult in spring — if it has not been eaten first.
This time of year, downy woodpeckers will peck into goldenrod galls to retrieve the fat, tasty larvae. Chickadees, lacking pecking ability, will literally tear the galls apart for the larvae. Squirrels will gnaw on the galls like nuts.
IN THE SKY: The Geminid meteor shower will be at its peak this weekend, producing about 50 meteors per hour. Look to the east from about midnight until dawn, said David Dundee, Tellus Science Center astronomer.
The moon will be full on Tuesday, Dec. 17 — the “Snow Moon,” as the Cherokee peoples called December’s full moon. Venus is in the west just after dark and sets about two hours later. Mars rises out of the east just before midnight. Jupiter rises out of the east at dusk and is visible all night. Jupiter will appear near the moon on Wednesday night, Dec. 18. Saturn rises out of the east a few hours before dawn.
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