Spatial analysis of lethal chlorosis cucurbits caused by Zucchini lethal chlorosis virus (ZLCV)

The lethal chlorosis of cucurbits, caused by Zucchini lethal chlorosis virus (ZLCV), has been an important viral disease that can occur in high incidence and can cause severe yield damages specially on zucchini squash crops. It is transmitted by the thrips Frankliniella zucchini. Four experiments were conducted between December 2006 and January 2009 in order to study the spatial distribution of the disease. Each experiment was conducted by using 300 plants and which were evaluated every 3 days. Disease incidence was observed by the presence of symptoms and later confirmed by serological test PTA-ELISA. Forty one assessments were carried out over the 4 trials. The parameters of Taylor's power law suggested random distribution of the disease and the values of dispersion index were significantly equal to 1.0. This result indicates the predominance of primary infection on the field, and probably the pathogen migrated from alternative host plants carried by viruliferous thrips.