Determination of Generation Numbers and Adult Population Fluctuation of Lobesia botrana (Lep.: Tortricidae) Using Pheromone Trap in Sisakht, Kohgiluyeh and Boyer-Ahmad Province

Introduction; The European grapevine moth, Lobesia botrana (Denis and Schiffermüller, 1776), (Lep.: Tortricidae) is the most serious insect pest of vineyards in Sisakhat. It is a polyvoltine pest and can complete two to four generations in one year depending on environmental conditions. The larvae penetrate berries very quickly after egg hatching and damage the grapes directly by feeding and webbing or indirectly by favoring the gray mold. Its control is necessary to harvest crop in commercial vineyards. In spite of two to four times of chemical control in this region, its population is always high especially in the first generation which is mainly rooted in inappropriate chemical spraying time. In the present study, it was attempted to optimize spraying time by determination of number of generations, population fluctuation and density of adult moths through sex pheromone-baited traps.
Materials and Methods; This research was done in two consecutive years (2012 and 2013) using sex pheromone traps in vineyards of Sisakht, Kohgiluyeh and Boyer-Ahmad province. Three vineyards selected which were 1.5 kilometers away from each other and three traps installed in each vineyard within tree canopy at height of 1.5 meters above the ground. the pheromone trade mark was Scentomos and traps were delta type. Traps in each vineyard were more than 150 meters away from each other. Traps were being replaced once every 15 days and inspected once every 5 days. Trapped moths were being removed with a forceps and recorded in each inspection. This trend continued from late March to late September when no longer moth trapped. Finally mean of trapped adults were calculated and plotted against time to determine generation numbers, flying periods and flight peaks.
Results and Discussion; The results of different vineyards and years coincided and confirmed each other well. Pest population graph had three distinct ups and downs during each season which was indicative of three generations per year. The first moths were trapped at the end of March and the beginning of April. Then, number of trapped moths increased until late April and continued in a steady state up to May 20th when it started to decrease. For a long part of June, number of trapped moths was averagely less than one moth per trap per night. From June 20th, the trapped moths increased again and reached its peak very soon at early July and decreased gradually up to late July. Late July to early August, trapped moths were less than one moth per trap per night. Early August onwards, trapped moths started to increase once again and reached its peak nearly about late August. Then it decreased up to 25th September when no moth was trapped any longer. Flight peaks of generations occurred early May, early July and late August, respectively. Flying periods of second and third generations were equal but was shorter than flying period of first generation which makes the control of first generation more difficult. In spite of chemical controls, population of the moth was high especially in first generation which could be attributed to chemical spraying at inappropriate time and insufficient knowledge of farmers about the pest overwintering stage and places. Spring rainfalls during emergence of the first generation reduced the trapped moth adults severely which have to be considered in the interpretation of the adult population fluctuation. The optimal spraying time could be adjusted based on the adults population fluctuation and type of the insecticide used. As usual, the insect growth regulators should be applied before egg laying or egg hatching. Contact and ingested insecticides (e.g., organophosphates, pyrethroids, and carbamates) should be applied after egg hatching to kill larvae as they emerge from eggs. Since the pesticides which are used in this region are mostly contact organophosphates or pyrethroids, the peak flights could be considered as the optimal spraying time. Since first generation emerge gradually and its population is high, optimizing the first chemical control is more critical and may decrease the necessity of next spraying. Due to spring rainfalls during May, any chemical spraying against the first generation should be done with considering the weather forecasting.
Conclusions; In this region, European grapevine moth adults emerged from early April to late May (60 days), mid-June to late July (45 days) and early August to late September (45 days), respectively. Flight peaks of the moth generations occurred early May, early July and late August, respectively. The moth population was high especially in first generation which implies that control of first generation is necessary. Flying period of the first generation was much longer than that of the other two generations which makes the control of first generation population more difficult. However, the chemical spraying time could be adjusted based on the mentioned peak flights and type of insecticide which have to be applied in this region.