Binomial Sampling System for Monitoring PopulationLevels of Orange Pulvinaria Scale in Citrus OrchardsUsing Probit and Logit Models

To control the harmful effects of pesicides of environment, properapplication of an integrated pest management system is necessary. Thissystem would not be operational in the absence of population density.Therefore, it is required to develop a simple and practical system to controlthe population levels of Orange Pulvinaria Scale, Pulvinaria aurantii(Cockerel) (Homoptera: Coccidae) in citrus orchards, in which nolaboratory equipment is employed and only is based on presence or absenceof insects on leaves. To this end, an orchard consisted fifteen rows, eachrow planted with 60 to 70 trees was selected. The area of the orchard wastwo hectares. Fifteen rows and on each row twelve trees were chosen (total180), eight leaves randomly taken from the four sides of each tree, and thenumber of different stages of P. aurantii was counted. Binomial samplingusing both probit and logit models, based on expressions relating theproportion of infested units to the log average plus one number of insects per unit was applied, and then an expression for the fiducial limitsintroduced. The results based on Pearson and deviance 2 goodness of fitshowed that there is no statistically significance between these two models,however because of smaller values of the chi squares, probit model waschosen, because of practical preference. Based on this model, percent ofinfested units for 20, 17, 9 and 6 as Economic Injury Level values were 42,38, 26 and 19, respectively. So that, over these percents the citrus producersshould apply spray on their orchards. This system may be a suitable modelto control the excess uses of spray application in citrus orchards.

Keywords:

Probit , Logit , Binomial Sampling , Pulvinaria aurantii , Citrus Orchard , Pesticide Spray