Susceptibility of Selected Tea Shoots to Oviposition by Empoasca onukii (Hemiptera: Cicadellidae) and Feasibility of Egg Removal with Harvesting

Abstract

The Empoasca onukii (Hemiptera: Cicadellidae) female lays its eggs inside the epidermis of the tea plant shoots. This has led to speculation that shoot harvesting could represent a method of egg removal. To verify the validity of this hypothesis, we sought to determine which part of the shoot was used for the oviposition and how the value of the harvested shoot affects the cost of the egg removal. In this study, four tea cultivars were chosen to examine the preferences for the site of oviposition. In addition, a mathematical model was used to describe the correlation between the economic value of the selected shoot and eggs laid within the shoot. Our study revealed that the pest preferred the 3rd and 4th leaf order intervals of the shoot as the oviposition sites, and the oviposition preferences was dependent on the leaf order interval class across all tea cultivars. In addition, a significant negative exponential relationship was found between the economic value of the selected shoot and the percentage of the eggs laid within the shoot, indicating that egg removal through shoot harvesting was limited. The findings of this study could be used to better understand the role of shoot harvesting in egg removal and would provide new insights into the understanding of the incidence of this pest.

Keywords: leaf order interval; leafhopper; oviposition preference; pest incidence; shoot characteristics.

Figure 1

A typical newly growing shoot of the tea plant. The whole shoot was classed as the corresponding leaf order intervals according to the shoot harvesting method.

Figure 2

An egg of Empoasca onukii within the epidermis of the tea plant shoot.

Figure 3

Length of the different leaf order intervals of the tea plant shoot. Bars represent mean ± SE of 30 samples for each cultivar. Bars with the same letters indicate that means comparisons were not significantly different in the same leaf order interval class of the four cultivars (ANOVA, Tukey’s test, p > 0.05). (Original data: Table S1.)

Figure 4

Percentage of Empoasca onukii eggs in the different leaf order intervals of the tea plant shoot. Bars represented mean ± SE of the infested samples (n = 37, 35, 38, and 43 shoots sampled with a total of 172, 128, 111, and 171 eggs for Jinxuan, Jinguanyin, Yinghong-9, and Yunnandaye cultivars, respectively). Bars with the same letters indicate that means comparisons were not significantly different among the leaf order interval classes in a cultivar (ANOVA, Tukey’s test, p > 0.05). (Original data: Table S2.)

Figure 5

The relationship between the economic value of the selected shoot and the cumulative percentage of eggs of Empoasca onukii within the shoot. The figure shows the exponential model fitting the data for each cultivar: (a) Jinxuan, (b) Jinguanyin, (c) Yinghong-9, and (d) Yunnandaye.