Welcome back to Ask a Naturalist: your own personal “Google” for information on all things natural on PEI! Over the past week or so, I’ve posted about White Spruce (Picea glauca) tips, male cones, and female cones. A few people have asked me about another type of growth on these trees: this is a Spruce Pineapple Gall.
Galls are abnormal growths that can appear on any part of a plant and are usually caused by insects or disease. In this case, the culprit is the Pineapple Gall Adelgid (Adelges abietis), a small insect that was accidentally introduced from Europe to North America in the 1800s.
Immature female Pineapple Gall Adelgids overwinter at the base of buds on both our native and non-native species of Spruce. As temperatures warm in early spring, the females mature and each one lays dozens to hundreds of tiny eggs. These eggs hatch about a week later, and the resulting nymphs set up shop on a twig where they’ll feed on the plant juices and new growth. This irritation causes the new needles to swell and create a gall; the Adelgids thrive inside it, protected from weather and predators.
By late summer, the nymphs are ready to become adults and the Pineapple Gall opens up to look very much like a tiny version of its namesake fruit. Nymphs emerge and grow into winged adult females that fly to nearby branches or trees to lay eggs. These will hatch into overwintering nymphs and start the cycle again.
So, we have female overwintering nymphs that lay eggs that produce more females. Wondering where the males are? There aren’t any! This form of reproduction is called ‘parthenogenesis’ and while it may seem strange to us, it isn’t that uncommon in nature. Parthenogenesis has been documented in plants, invertebrates, amphibians, reptiles, fish, and birds.
Pineapple Gall Adelgids are minor pests overall, unlike the much more serious Hemlock Woolly Adelgid (Adelges tsugae). Although it hasn’t yet been found on PEI, Hemlock Woolly Adelgid is a threat to our native Eastern Hemlock (Tsuga candensis) and the PEI Invasive Species Council is encouraging landowners to monitor for it. You can learn more about Hemlock Woolly Adelgid and this important monitoring program here: https://peiinvasives.com/hemlock-woolly-adelgid/
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Very interesting! I've seen some similar things like this but will keep an eye out now for these ones.
Neat, will look out for them. Some what related- Spruce Burls, 'Encountered a Red Spruce tree with at least a dozen, pic attached. From my limited reading, they seem to be more common in NS than elsewhere. Pic May 31, Purcells Cove NS area. Of course they can make wonderful dishes, bowls etc. Are they common in PEI?