A study on number and development of codling moth Laspeyresia pomonella L. generations in apple and walnut orchards in Chahar Mahal Va Bakhtiari province

Biology and population changes of codling moth Laspeyresia pomonella was investigated on apple and walnut orchards in Saman, Overgan and Shahr-E-Kord region in Chahar Mahal Va Bakhtiari province in 2000-2002. Pheromone traps were placed in each orchard and male moth trap was recorded weekly. In order to detection pest damage in each orchard 5 tree were selected and with begin fruitlet drop, number of infected and uninfected fruits were counted until harvest time. At harvest time total fruits of each tree were evaluated individually for infection . Studies showed that codling moth overwinters as a mature larva within a cocoon under bark scale and crevices. Pest emergence in walnut orchards usually was simultaneous in apple orchards and sometimes was delayed. The female moths laid their eggs directly on the fruits or sometimes on leaves. Young larvae bore into nutlets through the blossom end and start to feeding, after maturation inside fruits, under bark tree or in soil were pupated. Most nuts with codling moth damage from the overwintered generation drop to the ground. Newly hatched second generation larvae bore into walnuts anywhere on their surfaces but prefer the spot where two nuts touch and feed upon from nut. The larvae leave the nuts when they are fully grown and move to tree trunks or debris to spin cocoons, enter their diapause until next spring. Nuts attacked by larvae from the last part of the first generation and from the second generation remain on the tree but are unmarketable because of the feeding damage to the kernel. Results showed that the pest has 2 generation in Chahar Mahal Va Bakhtiari province per year and a 3 rd partial generation in some regions and some years. Pest population on apple orchards was usually higher than walnut orchards. The pest prefer paper shell than hard shell except in nuts which have ticker seal that pest simply entered this nuts. Average apple infection in Shahr-E-Kord was 38-93%,Saman 86-96% and Overgan 46-95% respectively. If the pest do not control with chemicals in apple orchards, its damage will reach to near 98%.Average walnut infection in Kord was 7-37%, Saman 1-2% and Overagan 2-6% respectively.