Control of Tea Scale on ‘Pink Snow’ Camellia Using Root-absorbing Systemic Insecticides

 Charles P. Hesselein, Joseph R. Chamberlin, and Michael L. Williams

Tea scale (Fiorinia theae) (Figure 1) is probably the most common and damaging pest of camellias and dwarf burford hollies as well as a pest of many other ornamental and fruiting crops.

 Controlling tea scale can be particularly problematic because of the difficulty in contacting them with insecticide sprays. Factors which make spray contact difficult include tea scale’s habit of heavily colonizing the undersides of older foliage, the cottony, waxy coating exuded by the male insects, the armored cover over the female’s body which protects both her and her eggs, and nursery cultural practices which promote thick, difficult-to-penetrate plant canopies. In addition, this insect’s non-synchronous, year-round life cycle makes targeting the vulnerable crawler stage with one or two sprays impossible. Media-applied, root-absorbing systemic insecticides may be one way of overcoming the obstacles to insect/insecticide contact.

 Figure 1. A dwarf burford holly branch heavily infested with tea scale.

The objective of our test was to evaluate four media-applied systemic insecticides (Figure 2): four rates of Pinpoint 15G, Orthene TTO (OTTO) 75 SP (applied as a drench), Marathon 1G, and Marathon 60 WP (applied as a drench).

‘Pink Snow’ camellias (Camellia sasanqua ‘Pink Snow’) potted in a pine bark based medium in trade gallon containers were utilized for this study. The tea scale infested plants were obtained from a local nursery and were well established in their containers. Plants were treated on October 9, 1998 and the last data were collected on January 12, 1999 (95 DAT). To minimize insecticide loss through leaching, all treatments were applied or watered in with 4 ounces of water and plants were not irrigated for 24 hours following treatment. Plants were maintained under shade and irrigated as needed by overhead impact sprinklers throughout the course of the study.

No differences among treatments were detected until 14 DAT (Figure 2). The most effective treatments from 14 DAT through the conclusion of the trial were Pinpoint 15G at 0.5 and 0.75 teaspoon per pot and OTTO 75 SP treatments. The percentage dead adult female scale insects during the trial for the untreated control ranged from 20-29% while the percentage dead adult female scale insects in the most effective treatments ranged from 79% at 14 DAT to 98% at 95 DAT. The 0.25 teaspoon per pot Pinpoint 15G treatment also demonstrated some efficacy but was not as effective as the 0.5 and 0.75 teaspoon per pot Pinpoint 15G and OTTO 75 SP treatments. The two Marathon treatments and 0.125 (1/8) teaspoon per pot Pinpoint 15G proved ineffective for controlling tea scale.

Figure 2. Treatment-related death of adult tea scale insects.

Nursery producers have a difficult time controlling tea scale with conventional high volume insecticide sprays. This test demonstrates that even the low label rate of Pinpoint 15G (0.5 teaspoon) provides greater than 90% control of this insect.

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