Evaluation of chemical control of Lepidosaphes malicola borchsenius (Hom., Diaspididae) in the apple orchards of Semirom, Isfahan Parvaneh Nazari p.nazari@ag.iut.ac.ir Monday, Jun, 18, 2018 Department of Plant Protection Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc. Language: Farsi Supervisor: Dr. Nafiseh Poorjavad. n. Poorjavad @cc.iut.ac.ir Lepidosaghes malicola is one of the prominent pests for apple trees in Iran. It incurs more appreciable damages on mountainous areas and on the heights. Regarding to damages incurred by Lepidosaghes malicola on Semirom gardens, especially on Gollab variety, the paper started to study some of efficiency aspects of new insecticides in order to control the pests in the area. Also, that how is the pests’ distribution and biology was studied to be used in evaluating the toxin tests. In the paper, the effects of insecticides such as flupyradifurone, thiacloprid, preproxyphene, and two different concentration rates of spirotetramat such as .5/1000 and .75/1000 were evaluated for first and second generations of pests’ mashing and for mature second-generation pest’s aphis. To control pre-spring, the effect of Volck oil with 1%, 1.5% and 2 % was controlled on pest with wintering egg. Cold tolerance and alterations in total sugar, glycogen and protein for wintering egg of the insect were also measured in both autumn and winter. With controls on pests’ distribution, it was determined that the population of Lepidosaghes malicola on upper parts of tree branches was more than lowers. Also, the population was more on 1-year branches than 2- or more-years ones. In mashing, spirotetramat with 75/1000 ratio was the best in reducing Lepidosaghes malicola population. However, due to its shocking effect, flupyradifurone was more effective than the other treatments at 3days after spraying. Preproxyphene and thiacloprid were with lowest efficiency. All toxins caused the pests’ mashing to be reduced for 1 day after spraying, while because of a wax coating on the pest, none of them was effective for the pest on the mature. Therefore, it is very important to observe the proper time to control the pest. To control the pest in pre-spring, 2% of Volck oil has the best efficiency. According to the results, it seems that the reductions in population by pre-spring control allow an easier with less chemical control in spring. Cold tolerance of Lepidosaghes malicola ’s eggs was controlled under temperatures 5, -10, -20 and -25°C for 24, 48 and 72 h, respectively during November to March. For all temperatures, differences of rested eggs percent were significant for 24h exposure during November to March. For all temperatures, the percentage was increased in February and March. This is the case with similar results for cold exposure for 24h and 72h. Total sugar increased as the temperature decreased in both autumn and winter, with March in highest level. It seems that the pest stores the simple sugar to survival. In February, glycogen decreased significantly. Protein increased from November to March. The obtained information may be used in the pest control plans and in combined control of pests for apple trees in Semirom. Keywords: oystershell scale, Population fluctuantions, Insecticide, Cold tolerance, Oil spraying