Magnolia trees across Long Beach still feeling effects of infestation

In an attempt to curb the spread of the tuliptree scale, Long Beach is rolling out a new treatment plan to help the city’s trees.

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Daniel Green | Signal Tribune

Trees located along Magnolia Avenue appear to show signs of Tuliptree Scale infection. The City of Long Beach documented around 120 reported cases last year of the infection but currently has between 350-400 cases. Over time, this infection can lead to leaves turning yellow, dropping prematurely, or branch dieback–– where branches begin to slowly die.

As magnolia trees across the city continue to struggle with an ongoing infestation, Long Beach City staff are suggesting a new plan to save the city’s trees.

The infestation comes in the form of thousands of little insects known as the tuliptree scale (Toumeyella Liriodendri), a softshell insect that the City is trying to halt through a new treatment plan that will identify and help magnolia trees affected by the bugs.

According to a city memo from Feb. 26, the Public Works department identified various levels of infestation in 2,571 magnolia trees, out of the city’s 6,975.

The emergence of the tuliptree scale across Long Beach is not a new phenomenon. As previously reported in the Signal Tribune in September, the City of Long Beach documented 120 reported cases in 2018 but had reported 350-400 cases last year.

Magnolia trees infected with the scale can face serious health problems depending on the level of infection, such as defoliation, dieback or death.

Scale harm the magnolia tree by attaching themselves to the trunks and drawing sap out of the plant’s tissue–– depriving the tree of essential nutrients.

The effects of the scales’ feeding can be seen through an excess of sap excreted by the insects called “honeydew.” A byproduct that may be familiar to residents living near magnolia trees.

“It’s kind of like a free-flowing straw because the pressure of the sap inside the tree is what drives it into the bodies of the scale,” Brian Thorson, a botanical curator at Cal State University Long Beach, said. “So, they’re actually consuming an excess. That is what is secreted out onto the sidewalks, and people’s cars, and down the size of the trees.”

In addition to depriving the magnolia tree of its sap, the honeydew created by scale can lead to additional issues, such as black mold. Even though the mold is not directly harmful to the tree, it can prevent photosynthesis.

When the city first began trying to address the scale infestation, it began a treatment plan for infected trees that included inspecting, pruning, trimming and the removal of 93 sick trees.

City workers also began spraying trees with a specialized insecticide called imidacloprid, which the trees absorb through its roots.

To aid the treatment plan, officials reached out to the public to ask residents to water trees on their property regularly–– which helps the tree circulate the insecticide through its system.

However, the City found that the previous treatment plan was not as effective as they hoped for.

“With the trees that were more of a severe infestation and higher, we noticed that there was only a 25% to 30% improvement rate after that treatment,” Jennifer Carey, a community-relations officer for Long Beach, said. “So, based on that we kind of regrouped and developed a new treatment plan.”

According to the city memo, the Public Works Department has recommended the removal of 192 fully infected trees. The beginning of the work is scheduled for early March and is expected to take 45 days to complete.

The Public Works department is also advocating for a treatment program for the remaining 1,078 trees showing signs of scale infestation, with an estimated cost of $325,000. The City Council has allocated $100,000 in the Fiscal Year 2020 budget to fight the disease.

City staff has also asked the council to consider a balanced approach between removal and treatment, which will be determined based on the severity of the scale infestation.

“It’ll be on a case-by-case basis [depending] on how prevalent the disease is in the tree and where it is impacting the tree,” Carey said. “If there’s a risk of public safety, or we’re worried about a limb failure, or […] part of the tree falling and possibly injuring someone or […] causing property damage, we are recommending that those trees are removed.”

The department has also stated that it does not have an estimate regarding how many sidewalks in Long Beach will require pressure-washing due to honeydew from the scale. However, it believes that $50,000 is enough to support 400 sites.

The City is also considering replacing trees that were removed with alternate species approved by the city.