Issue
Related invasive species
- Idioscopus clypealis
Detailed examination of the flower panicles is needed to determine the population size for damage assessment and control studies. Verghese et al. (1985) developed a sequential sampling plan for classifying infestation of I. clypealis into light, moderate and severe on the basis of sample counts. Negative binomial distributions for nymphs and adults were fitted. Operating characteristic values, giving the probability of reaching a correct decision for a range of population means for both adults and nymphs, together with average sample number values, were used to predict the average number of trees to be sampled under different sequential plans. In the case of the closely related I. niveosparsus, studies by Tandon et al. (1989) on the spatial distribution of nymphs on mango trees in Karnataka, India, to determine a sampling plan for the pest showed that nymphs were aggregated on the mango panicles. Their distribution was best explained by Iwao's patchiness regression which showed that mean colony size was fixed and that colonies followed a negative binomial series. The optimum sample size recommended was 59 panicles per tree for damage assessment and control studies, and 98 panicles per tree for ecological studies when greater precision was required. Tandon et al. (1989) found no significant differences in the distribution of nymphs between the north, south, east or west portions of the tree or between the upper and lower canopies, indicating that sampling can be conducted from any point on the tree.