Spatial distribution of nymphs populations Bactericera cockerelli sulc in tomato crops (Physalis ixocarpa brot)

Abstract

Tomato crops (Physalis ixocarpa Brot.) are produced in almost all Mexico, part of the United States and Central America. Recently the tomato production has suffered economic losses of 70% to 80% due the presence of yellowing and floral abortion, whose causal agent has been attributed to the presence of phytoplasma; an insect vector of these phytoplasma is Bactericera cockerrelli Sulc. Alternative control of this psyllid has lacked effectiveness because their spatial distribution is unknown within tomato plots. This study aimed to determine the spatial distribution of populations of nymphs of B. cockerelli in four tomato plots, the determination of the spatial distribution was performed by means of geostatistics. The experimental semivariogram was determined to adjust to a theoretical model (spherical, exponential or Gaussian) through the program Variowin 2.2, the adjustment was validated with the method of cross-validation and aggregation maps of the pest were obtained through Kriging with Surfer 9.0 program. The short-term time-space stability of the pest was determined through the tests Crámer-von Mises. The results showed that populations of nymphs of B. cockerelli have a distribution of aggregate type, which was corroborated by density maps. Infestations are not present in 100% of the surface of the experimental plots, which helps to direct control measures on specific areas of infestation.