A novel approach to the assessment of fruit damage caused by Carposina sasakii (Lepidoptera: Carposinidae) using pheromone trap catches in Korean orchards

Abstract

This study reports a model that utilizes pheromone trap catches to assess the fruit damage caused by Carposina sasakii. The model consisted of four steps: (1) obtaining influx population density using pheromone traps, (2) estimating the actual female population within a defined area using an estimated conversion rate, (3) calculating the total number of eggs using the oviposition model of C. sasakii, and (4) estimating the proportion of fruits infested with eggs (potential damaged fruits) using the relationship between mean egg density per fruit and the proportion of fruits infested with eggs. The relationship between mean egg density ($\bar{x}$) per fruit and variance (s ²) was well described by Taylor’s power law, and its parameters were successfully incorporated into the equation that estimates the relationship between mean egg density and the proportion of fruits infested with eggs. In peach orchards, the model accurately predicted the proportion of fruits infested with eggs at the beginning of C. sasakii emergence in early season, but overestimated it in the mid-season. The fitting ability of the model outputs largely increased when the factor of oviposition behavior of C. sasakii was incorporated into the simulation processes, applying the allocation module of total eggs between peaches and apples.

Appendices

Appendix 1

Equations used in the C. sasakii model. The same parameter symbols used in different equations may have different meanings and values depending on the corresponding equations (see Table 1 for the meaning of symbols).

Simple exponential equation

$$ y = a \cdot {\text{e}}^{bx} $$

(1)

Modified logistic function

$$ y = {\frac{100}{{1 + \left( {\frac{x}{a}} \right)^{b} }}} $$

(2)

Taylor’s mean-variance model

$$ s^{2} = a \cdot \bar{x}^{b} $$

(3)

Wilson and Room’s model

$$ P(I) = 1 - {\text{e}}^{{[ - x\,\ln (ax^{(b - 1)} )/(ax^{(b - 1)} - 1)]}} $$

(4)

The parameters of a and b are taken from Taylor’s model.

Appendix 2

See Table 4.

Table 4 Estimated fruit damages (%) caused by C. sasakii at different mean air temperatures and the number of males caught on pheromone trap in peach orchards