GALL MITE
Eriophyidae
Euaresta stigmatica
Ambrosia ambrosioides
Chrysomelidae: Hispinae
Watercolor © Michael Plagens. The leaf at left-center shows the pale blisters caused by the gall mites. A fruit fly that feeds in developing seeds is shown at upper right. And a leaf-mining beetle is illustrated at lower right.
Hundreds of species of gall mites are found on a vast variety of plants. They are nearly microscopic, yet their feeding and secretions can cause very conspicuous swellings, blemishes, or witches brooms. Many of them are serious pests of crops and ornamentals.
Canyon Ragweeds are often found that have numerous pale green
warts on the leaf surface. These are caused by eriophyid gall mites possibly Eriophyes
boycei Keifer a species that has been recorded on ragweeds. The mites feed on the plant tissue from the inside of
the hollow blisters that are formed by the plant in response to secretions and
irritations of the mites. Breaking open the galls will reveal the mites visible
with a 20x magnifier.