Management of Cycad Aulacaspis Scale
(Aulacaspis yasumatsui)

By: Catherine Mannion, Department of Entomology and Nematology, University of Florida - IFAS

Objective

Evaluate insecticide treatments for the control of cycad scale

Target Pest

Asian cycad scale (Aulacaspis yasumatsui)

Plant

  • King Sago (Cycas revoluta) – 1 gallon containers
  • Plants were maintained in a greenhouse at approximately 78°C
  • Plants were irrigated as needed

Site

Tropical Research and Education Center, Homestead, FL

Treatments

No Treatment Active Ingredient Application Rate
1 Experimental product -- Foliar --
2 Organocide Fish oil Foliar 2.0 oz (59.1 ml) per gal
3 Merit 75WP Imidacloprid Foliar 0.1 tsp (0.14 g) per gal
4 Merit 75 WP Imidacloprid Drench 4 tsp (5.6 g) per 1000 sq ft
5 Merit 75WP + Organocide Imidacloprid + Fish Oil Drench + Foliar 4 tsp (5.6 g) per 1000 sq ft + 2.0 oz (59.0 ml) per gal
6 Distance   Foliar 0.1 oz (3.5 ml) per gal
7 Distance   Drench 0.08 oz (2.4 ml) per gal
8 Dimethoate Dimethoate Foliar 4 tsp (20 ml) per gal
9 Dimethoate Dimethoate Drench 2 oz (59.1 ml) per gal
10 Control -- -- --

Insect Infestation

Plants were infested with scale eggs and crawlers prior to application. At the onset of the test, cycad infestation among plants varied from low to high but in general was moderate. Plants were distributed so that varying infestation levels were in all treatments.

Treatment Application

  • Application date – 03/06/03
  • Foliar treatments were applied with a CO2 backpack sprayer with an 8003 flatfan nozzle; 25 lb psi.
  • Plants were sprayed until runoff (approximately 200 ml spray solution per plant).
  • All foliar applications were made at 3 week intervals (0, 3, 6, 9 weeks)
  • All drench applications were made once (no repeat application)

Experimental design and analysis

  • Five replications; completely random.
  • The data were subjected to ANOVA.

Evaluation

  • The test was evaluated every two weeks for 12 weeks
  • Female scale mortality, egg mortality and scale infestation on the foliage were evaluated for each plant.
  • Female mortality: Leaflets containing female scales were removed and examined under a microscope. Up to 20 live and dead female scales were evaluated. Not all samples contained 20 females. Percent mortality was determined.
  • Egg mortality: Leaflets containing female scales were removed and examined under a microscope. The eggs were examined for up to 20 live female scales. The percentage of females with live eggs was determined.
  • Infestation on foliage: The foliage was rated on a scale of 1 – 5 with 1 being a low infestation and 5 being a severe infestation.

Results

Female Scale Mortality (Table 1): The products that achieved excellent control of female scales were the foliar application of Organocide, the foliar application of Organocide in combination with a drench application of Merit, the foliar application of Distance, and the foliar and drench applications of Dimethoate. Most of the mortality of the combination treatment of Organocide and Merit was likely due to the Organocide because the drench application of Merit alone provided poor control. The above treatments caused significantly greater mortality at 4, 6, 8, 10, and 12 weeks after the initial application. The foliar application of Dimethoate provided the quickest control with the highest percentage of mortality two weeks after application.

Egg Mortality (Table 2): The foliar application of Dimethoate provided 100 percent mortality of the eggs. The foliar application of Distance caused 99-100 percent control starting 4 weeks after the initial application. The drench application of Dimethoate caused 100 percent control after 6 weeks. The foliar application of Organocide and the combination treatment of Merit and Organocide provided more than 97% control after two foliar applications of Organocide.

Plant Infestation Level (Table 3): There were no significant differences in infestation rating at 2 and 4 weeks after the initial application. After 8 weeks, the infestation level was significantly lower (less infestation) in the Organocide, Merit in combination with Organocide, the foliar application of Distance, and both applications of Dimethoate.

Table 1. Female Scale Mortality
    Percent Female Mortality (weeks after treatment)
Treatment Application 2 4 6 8 10 12
Experimental Foliar 0.0 d 8.0 c 11.0 b 2.2 c 19.0 b 5.8 c
Organocide Foliar 50.6 c 94.0 a 87.6 a 95.2 a 95.0 a 97.6 a
Merit Foliar 0.0 d 25.0 b 4.0 b 13.6 b 2.0 b 8.0 c
Merit Drench Foliar 0.0 d 0.0 c 1.0 b 0.0 c 2.8 b 39.6 b
Merit + Organocide Drench 60.4 c 94.0 a 93.0 a 96.0 a 99.0 a 99.0 a
Distance Foliar 0.0 d 100.0 a 99.0 a 94.4 a 95.2 a 100.0 a
Distance Drench 1.0 d 0.0 c 4.0 b 0.0 c 5.0 b 19.2 c
Dimethoate Foliar 97.0 a 100.0 a 100.0 a 100.0 a 100.0 a 99.0 a
Dimethoate Drench 82.8 b 95.0 a 92.2 a 95.8 a 98.0 a 92.5 a
Control -- 0.0 d 2.0 c 0.0 b 5.2 c 2.0 b 1.6 c

 

Table 2. Egg Mortality
    Percent Egg Mortality (weeks after treatment)
Treatment Application 2 4 6 8 10 12
Experimental Foliar 0.0 c 0.0 c 4.2 b 0.0 c 0.0 b 0.0 b
Organocide Foliar 5.0 c 0.0 c 70.6 a 89.0 b 100.0 a 100.0 a
Merit Foliar 0.0 c 0.0 c 0.0 b 0.0 c 0 0.0 b
Merit Drench 0.0 c 0.0 c 1.2 b 0.0 c 0.0 b 0.0 b
Merit + Organocide Drench Foliar 0.0 c 0.0 c 79.3 a 97.2 a 100.0 a 100.0 a
  Foliar            
Distance Foliar 0.0 c 100.0 a 99.0 a 100.0 a 100.0 a 100.0 a
Distance Drench 0.0 c 0.0 c 0.0 b 0.0 c 0.0 b 0.0 b
Dimethoate Foliar 100.0 a 100.0 a 100.0 a 100.0 a 100.0 a 100.0 a
Dimethoate Drench 43.0 b 60.0 b 100.0 a -- 100.0 a 100.0 a
Control -- 0.0 c 0.0 c 0.0 b 0.0 c 0.0 b 0.0 b

 

Table 3. Infestation Level
    Infestation Rating 1-5 (weeks after treatment)
Treatment Application 2 4 6 8 10 12
Experimental Foliar 3.8 a 4.6 a 4.8 a 4.6 a 3.8 a 4.0 a
Organocide Foliar 2.6 a 2.6 a 2.6 ab 2.0 b 1.4 b 1.2 b
Merit Foliar 2.8 a 4.4 a 4.4 ab 4.8 a 4.6 a 4.2 a
Merit Drench 3.0 a 4.0 a 4.4 ab 4.4 a 5.0 a 4.4 a
Merit + Organocide Drench Foliar 3.0 a 2.6 a 2.4 ab 1.6 b 1.8 b 1.2 b
Distance Foliar 2.4 a 3.4 a 2.4 ab 1.8 b 2.0 b 1.2 b
Distance Drench 2.4 a 4.6 a 4.6 ab 5.0 a 5.0 a 4.8 a
Dimethoate Foliar 3.0 a 2.4 a 2.2 b 2.0 b 1.6 b 1.8 b
Dimethoate Drench 3.0 a 2.6 a 2.2 b 2.2 b 1.4 b 1.6 b
Control -- 2.2 a 4.2 a 4.2 ab 4.8 a 4.8 a 5.0 a

 

Figure 1. Distance - foliarFigure 2. Organicide - foliarFigure 3. Merit - drench and organocide - foliarFigure 4. Dimethoate - drenchFigure 5. Dimethoate - foliarFigure 6. Distance - drenchFigure 7. Merit - drenchFigure 8. Merit - foliar

Figure 9. Experimental - foliarFigure 10. Control