Magnolia Scale

Magnolia scale is the largest scale insect in the United States. The host plants in our area are Saucer Magnolia (Magnolia soulangeana) and Star Magnolia (Magnolia stellata). The adult female scale is rounded, 3/8” in diameter and has a whitish waxy covering. Immature scale or “crawlers” are between 1/8” and ¼” long and dark slate gray.

SYMPTOMS

Magnolia scale is a sucking insect that attaches to twigs and stems and sucks out plant juices.  The insect secretes sticky honeydew (the polite term for excrement) onto the leaves on which unsightly black sooty mold can form. Heavy infestations cause deformed leaves, twig and branch dieback, and general weakening of the plant. Plants under stress or growing in shade seem more prone to attack.

LIFE CYCLE

Magnolia scale overwinters as mature “pregnant” females. Eggs are laid under the protective covering of the mother in late spring. By late August, the crawlers have hatched from the eggs and crawled out from the scale covering in search of feeding sites. Crawlers overwinter on the undersides of 1 and 2 year-old twigs.

CONTROL

Because magnolia scale has two distinct life stages, both the adult scale and the immature crawlers require control.

To treat your Magnolia Shrub, follow these steps:

• Use 3 ounces of concentrate per foot of plant height mixed with one gallon of water of the systemic Tree & Shrub
• For a 10-foot shrub, use the entire 32-ounce bottle of Bio-Advanced Annual Tree & Shrub Insect Control.
• Fill a 2-gallon bucket with 1/2 gallon of water, pour the whole bottle of insect control into the water, and then use the hose to top off with another 1/2 gallon of water. This method mixes the solution for you.
• Pour the entire bucket of the solution next to the trunks of the shrub at the root collar, where 60% of all root uptake occurs.
• This treatment will take 5-10 days to be absorbed into the shrub, and you will know it is working when the sticky "honeydew" stops.
• Plan to treat with this every year.
• The only times your should not treat is when the soil is frozen solidly or when there is standing water in the area where the application should be made.

Sometimes flies are attracted to the sugary "honeydew". For fly control, use the Bonide Mosquito Beater spray insecticide which you can attach to a hose and spray into the Magnolia Shrub, coating as many leaves and branches as possible. Use it 24 hours before people will be arriving or the morning of an evening event.

Additionally, Bonide Mosquito Beater Natural Granules, which come in a shaker jar, use eugenol herbs to repel insects for up to 3 weeks. Sprinkle it on lawn and garden areas around patios, outdoor bars, or anywhere people will be enjoying the outdoors to repel all flying insects.

Keep your trees healthy by applying a 2-3” layer of mulch (shredded or chunk bark, coarse compost), watering during dry periods, and pruning out dead wood.