Meta-analysis of the damage suppression effect of a double-layer fruit protection bag on fruit bug injuries of loquat fruits and evaluation by explicit solution of odds ratio

In the cultivation of loquat (Eriobotrya japonica (Thunb.) Lindl.) in Japan, injury to fruit by fruit bugs, such as the brown-winged green bug, Plautia stali Scott (Heteroptera: Pentatomidae), is a serious problem. Bagging developing fruits with a double-layer fruit protection bag (“double bag”) prevents damage better than a single-layer bag. In 19 field trials using both types of bags from 2005 to 2015 under varying conditions of fruit bug pressure, we compared the effects of bag types on the harvest rate of saleable fruits and the suppression of injury. Meta-analysis of the relative effect of double bags gave an odds ratio of 5.57 for the harvest rate of saleable fruits, indicating the high effect of protection by double bag. Explicit solution of the odds ratio showed the effect as a function of fruit bug pressure. This method makes it possible to cost-effectively choose which bag to use according to the predicted emergence of fruit bugs each year.