Hi – I wondered if you could identify the above images? The first one was on an elm tree – the whole tree was coveredin them. The second one (Oak ‘eggs’) was on the leaf until it dropped off in the autumn – what happened then I don’t know. They started out bright red but by autumn were a very pale pink. Many thanks!
Both of your photos illustrate Galls, growths that occur on various parts of plants that are usually caused by an insect or mite. Wasps, Moths, Aphids and Flies can all produce Galls. According to the University of Kentucky College of Agriculture website: “Galls are irregular plant growths which are stimulated by the reaction between plant hormones and powerful growth regulating chemicals produced by some insects or mites. Galls may occur on leaves, bark, flowers, buds, acorns, or roots. Leaf and twig galls are most noticeable. The inhabitant gains its nutrients from the inner gall tissue. Galls also provide some protection from natural enemies and insecticide sprays. Important details of the life cycles of many gall-makers are not known so specific recommendations to time control measures most effectively are not available.” Galls are not harmful to the plant. Regarding your images, we are not entirely conviced that the tree you indicate is an elm is really an elm. Also of interest with the color change in the Oak Galls is this citation from Lutz’ Field Book of Insects: “Of the Galls caused by insects, Oak Galls have been used in dyeing, tanning, and the manufacture of ink.”
Hi Daniel – thank you very much for your reply. I thought they may be galls but wasn’t sure. The tree was identified by a wildlife trust (I work for them so quite a few people saw the leaves and said they were elm). However no one was sure what the ‘lumps’ were. Have a good Christmas Best wishes