Bionomics of Codling Moth- Introduction

Bionomics of Codling Moth

Introduction

The Codling Moth, Cydia pomonella L. is a cosmopolitan insect pest of deciduous fruits. It has a remarkable ability to adapt to a wide range of climatic conditions. This pest is able to synchronize its life cycle with the fruiting period of its host. Codling moth and its preferred host, apple, have similar ecological requirements. It occurs where apples are grown throughout the world except in parts of Asia including Japan and Korea. The Codling Moth is a mutivoltine species with facultative diapause (Riedl, 1983). Depending on the latitude or elevation, codling moth may complete one (e.g. Canada, some parts of Russia and UK), two [Northwestern USA (Setyobudi, 1989), South Africa (Nel, 1985), Pakistan (Bajwa, 1985), etc.], three/four [California (Benthall, 1978)] or five [Israel (Janjua, 1958)] generations a year. The number of generations gradually increases toward the southern latitude in the Northern Hemisphere and towards the north in the Southern Hemisphere. In, general, the larva of codling moth have five instars (Dickson 1949, Smotavac 1957, Petterson and Hammer, 1968). Weitzner and Whalon (1987) describes that the codling moth overwinters as either a fourth or fifth instar diapausing larvae. However, a major portion (above 95%) of the hibernating larvae are found in the fifth instar. Figure 1 shows the life system of the codling moth.

Codling moth overwinters as a mature larva beneath tree bark scales or at the base of the tree. Adults appear in the spring and eggs are laid singly on or near the fruit. Eggs hatch in 5 to 12 days, depending upon temperature, and the young larvae move to developing fruit within a few hours, chew through the skin, and burrow into the flesh. Subsequently, the larva burrows to the fruit core and feeds on seeds. After 25 to 40 days, the larva is mature, exits the fruit, spins a cocoon, and pupates. Moths of the second generation emerge two to three weeks later. The potential for crop loss to the codling moth makes it the most important pest of pome fruits. When uncontrolled, the codling moth is capable of annually destroying 80% or more of an apple crop and 40-60% of a pear crop. Environmentally benign biological controls operating alone can not provide sufficient suppression of codling moth to protect fruit. Even chemical control is difficult because of the short time young larvae are exposed and the small amount of feeding done before entering the fruit. This behavior makes codling moth control with many alternative insecticides which act as stomach poisons, such as Bacillus thuringiensis (Bt) products or viruses very difficult. Replacing conventional control tactics (use of neuroactive insecticides, primarily organophosphates) with safer and less disruptive controls requires a combination of tactics. The most promising tactics include mating disruption, insect growth regulators, a granulosis virus, biological controls, sterile insect release, and cultural practices, most likely used in various combinations.

A few codling moth larvae are capable of diapausing more than one year (Hammar, 1912, Yothers and Carlson 1941, Setyobudi 1989). It has been observed that a few larvae of each generation enter diapause as shown in the Figure 2. Thus spring moths, not only come from the last generation of preceding year, but also from the hibernating larvae of the earlier generations (Mathew and Kitching 1984, Nel 1985). Besides apples, the codling moth can develop on other pome fruits such as pear and quince, on stone fruits such as apricot, plum and peaches as well as on walnuts (Newcomer and Whitcomb 1925), apricot, almond, pecan nuts and pomegranates (Nel 1985).