Impact of Crepe Myrtle Bark Scale (Acanthococcus Lagerstroemiae) and Sooty Mold on Flowering in Lagerstroemia Indica × Fauriei 'Natchez'

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ag Science and Natural Resources

Date of Award

5-25-2024

Abstract

Crepe myrtle bark scale (CMBS) (Acanthococcus lagerstroemiae) is an important pest of crepe myrtle (CM). Infestation results in the growth of sooty mold (SM). The combination of CMBS and SM is reported to cause stunted growth and reduced blooming. To explore the effects of CMBS infestation and SM growth, an experiment was conducted at the Texas A&M University-Commerce (A&M-Commerce) Crepe Myrtle Research Garden (CMRG). The CMRG includes 24 ‘Natchez’ crepe myrtle (Lagerstroemia indica × fauriei ‘Natchez’) divided equally across four blocks. Within each block, three were randomly selected and treated with dinotefuran in year one and imidacloprid in year two, while the remaining served as untreated controls. Trees were observed and scored for CMBS and SM using a scale of 0-10, with 0 indicative of no CMBS or SM, and 10 representing complete plant coverage. At blooming initiation, bloom number was estimated by dividing panicles into small, medium, and large clusters. Bloom clusters were counted weekly until no blooms were seen. Once blooming ended, fruit was removed from each tree and counted. During year one, on average across all weeks, treated plants had lower CMBS scores (5.8 versus 6.3), lower SM scores (5.7 versus 5.8), higher average bloom number per tree (442 versus 193), and higher average fruit number per tree (3,770 versus 998) than untreated controls. In year two, CMBS and SM scores were lower due to pre-season power washing, with treated trees receiving final CMBS and SM scores of 0.48 and 0.52, respectively, compared to untreated trees receiving CMBS and SM scores of 1.01 and 1.33, respectively on average across all weeks. Average bloom number per tree for treated trees in year two was 294, compared to 119 for untreated controls, and the average fruit number per tree for treated trees was 7,031, compared to 2,009 for untreated controls on average across all weeks. Across both years, the data support the conclusion that CMBS infestation, along with the corresponding presence of SM, decreases bloom number in CM.

Advisor

Derald Harp

Subject Categories

Horticulture | Life Sciences | Plant Sciences

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