Date Published: May 31, 2019
Publisher: Public Library of Science
Author(s): Souvic Sarker, Un Taek Lim, Maohua Chen.
Both Grapholita molesta (Busck) and Grapholita dimorpha Komai (Lepidoptera: Tortricidae) are important pests of pome and stone fruits. Mature fruits of peach and plum have been tested as food sources for G. molesta, but no studies have examined the suitability of immature fruits, which are the fruit stage more likely to be available for the spring populations of both G. molesta and G. dimorpha. Thus, we evaluated immature fruits of peach, plum, and apple as food sources by assessing their effects on biological and behavioral attributes of these moths in the laboratory. Immature fruits were collected in May and June of 2016 and again in 2017. The first-instar larvae of G. molesta preferred either peach or plum, which showed exit rates of mature larvae of 81.0 and 100.0% for the two fruits, respectively. On peach, development time was shorter, and fecundity was lower than plum. However, G. dimorpha preferred plum and apple, showing the lowest fruit-boring rate and lowest mature larval exit rate on peach, from which only one female moth emerged but produced no eggs. In conclusion, it seems that at the immature fruit stage, plum and apple are better food sources for both G. molesta and G. dimorpha than is peach.
Among the microlepidopterans, the Tortricoidea is one of the most diverse superfamilies . Tortricoidea contains a single family (Tortricidae), comprising over 9,800 species in 1,050 genera (http://www.tortricidae.com). Grapholita molesta (Busck) and Grapholita dimorpha Komai belong to the subfamily of Olethreutinae and are among the most destructive of fruit pests [1–8]. Grapholita molesta (Oriental fruit moth) is an invasive oligophagous insect of Asian origin that reproduces on Rosaceous plants, having 3–6 generations per year . The main hosts of Oriental fruit moth are species of Prunus (Rosaceace, subfamily Drupaceae) including peaches, nectarines, plums, and apricots . This moth is widely distributed throughout the temperate and subtropical regions of the world [8, 10, 11, 12, 13, 14]. Another closely related species, G. dimorpha (the plum fruit moth) was first reported by Komai  and is now found in many northeast Asia regions, including Japan, Korea, China, and Russia [2, 7, 15, 16]. Grapholita dimorpha is reported as a pest of plum, pear, and apple [17–19]. The female G. dimorpha lays one or two eggs on the fruit surface, and the larva makes a pinhole in the fruit skin after hatching and then bores into the fruit . As the pinhole is small, it is very difficult to distinguish damaged from undamaged fruits at harvest .
Host plant availability is a major factor determining the population dynamics of herbivorous insects [8, 28, 29]. Larval development rate, development time, survival rate, and fecundity are affected by the physical characteristics as well as chemical components of the host plants [25, 28, 30, 31, 32, 33, 34]. Population dynamics of phytophagous insects is significantly influenced by the diversity of plant species and the nutritional levels of plant tissues . The ability of feeding on a wide variety of hosts is a common feature among various invasive herbivores [14, 36, 37].