My Magnolia is a Sticky Mess!
Written by: Jake Kubisiak, Certified Arborist IL-1392A
It was a typical busy summer day last year when our office phone rang. On the other end was a concerned client; something was wrong. “In all my time living here I’ve never seen this before.” The beautiful and usually problem free Magnolia tree seemed to be having an issue. “There appear to be tiny ‘egg sacks’ under the branches, there are many bees flying around, and the ground is very sticky. The limbs and trunk are also dark and discolored. WHAT IS GOING ON!?”
A visit to the property for an inspection of the tree revealed the causal agent was an insect known as Magnolia Scale. The ‘egg sacks’ are the actual adult insects. It turns out this first call turned into many calls last summer and fall with concerns for Magnolia trees and a seemingly over-night explosion in population of this insect pest.
Magnolia scale is a bit of an odd insect. As an adult they cannot move, but rather spend all of their time stuck to a twig sucking out plant sap. The young scale are known as ‘crawlers’ as they very slowly move from their birth place on the twigs to the leaves. As fall approaches they move back to the twigs and re-position for spring the mating season. Pregnant females then begin the heavy feeding part of their life cycle. As they grow and feed they excrete a sticky liquid known as Honeydew. This sugary liquid attracts ants and bees as they feed on the substance. Often so much is produced that heavily infested trees may appear to have a little rain shower of dripping honeydew coming from the canopy. Honeydew drips on to the trunk and all areas around the tree and it is a great environment for the growth of sooty mold. Sooty mold is a black ‘dusty’ appearing fungal growth that discolors the tree’s stems and leaves, and the areas below. Sooty mold is not damaging to the plant directly although a heavy covering can lead to a loss of photosynthetic efficiency.
A few signs that Magnolia scale may be active in your tree:
- During summer – white bumps are found under the twigs.
- Normally light gray bark becomes black and discolored from sooty mold.
- Bees are found flying around the canopy and ants may be crawling on the stems and twigs.
- The ground and plants around the tree are sticky and shiny.
- Leaf size, flowering and vigor will be reduced when infested trees are stressed.
Scale insect populations can skyrocket with just a few individuals producing THOUSANDS of eggs. Predators feed on the immature stages of the insect and many do not survive and mature, but the strategy is to simply create enough eggs that some and occasionally many will survive to carry on. Left unchecked these tiny, but occasionally numerous pests can literally suck the life out of a favorite plant. The good news is that now more than ever our treatment ‘tools’ offer better options for eventual control. If you have a concern about the magnolia in the yard we are a phone call away. Winter offers a good time to ‘scout’ for this insect as the immature nymphs are more easily found without leaves. Contact your Wachtel Tree Science Certified Arborist for a visit to keep this beautiful spring flowering tree healthy and attractive.