Sequential sampling

1. Sequential sampling How to decide when to ‘take action’ based on a threshold and counts Based on: Robson, J.D., Wright, M.G. & Almeida, R.P.P. 2006. Within-plant spatial distribution and binomial sampling of Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) on banana in Hawai'i. Journal of Economic Entomology 99: 2185-2190. (Funded by PBARC, WSARE, TSTAR)

2. The ‘average’ • The average count always has ‘error’ – counts may range say from 3 to 9, with an average of 6; or 7; or 5. When can you be sure you have the correct average? • Sample size calculations – include error judgments

3. Sequential sampling • Have an economic threshold – number of insect that cause you to take action; • Take a series of small samples • Add up numbers of insects • Make quick decision at low or high pest density

5. Sample 15 plants, count insects

7. Sample 5 more, add number of insect to first 15

9. Sample 5 more, add number of insects to first 25

11. Low numbers?

12. So much counting! Go Binomial • Just say yes; or no (any aphids or none) • Count number of plants with aphids, and plot them on the graph…. • This saves time and effort, and allows a quick and accurate decision.

13. Action Zone!! Count-more Zone No-action Zone