be assessed again in a short period of time. The 

 monitoring program described here meets these 

 goals. 



This monitoring procedure classifies ERM 

 density into one of three categories: 1 ) greater than 

 treatment threshold, indicating application of a 

 miticide is necessary, 2) less than treatment 

 threshold, but requiring assessment again in about 

 7 days, and 3) much less than a treatment 

 threshold and not requiring assessment again for 

 14 days. 



ERM are small and often numerous. This 

 makes counting these pests a tedious and often 

 difficult task. For monitoring purposes, it is only 

 necessary to record the number of leaves infested 

 with one or more motile mites. A mathematical 

 relationship between the proportion of infested 

 leaves and actual density can then be used to 

 classify mite density. Because higher mite numbers 

 can be tolerated as the season progresses, three 

 sampling procedures are used at different times of 

 the growing season; one each for June, July, and 

 August with treatment thresholds of 2.5, 5, and 

 7.5 mites per leaf , respectively. 



The sampling guides are used as follows: 



1. Sampling trees from throughout the orchard 



block, collect five intermediate aged leaves 

 from each of four trees. To make sure the 

 leaves are of an intermediate age, pick them 

 from the middle of the fruit cluster before July 

 and from the middle of fruit clusters or 

 terminals thereafter. 



2. Using a magnifier, examine the top and bottom 

 surface of each leaf for motile mites (anything 

 but eggs), and keep track of the number of 

 leaves with mites on them. 



3. When all 20 leaves have been examined, 

 compare this number with the numbers on the 

 decision guide. When the counts fall into any 

 of the shaded regions, sampling is terminated 

 and a decision to either "Treat", "Sample in 7 

 days," or "Sample in 14 days" is made. If the 

 counts fall in the region labeled "Continue 

 sampling" collect and examine groups of 10 

 leaves until the counts fall into one of the 

 shaded regions. If the number of leaves with 

 mites is equal to the values on the guide, use the 

 decision indicated by the value minus one (e.g., 

 for the June chart, if 18 leaves have ERM after 

 examining 20 leaves, use 17 leaves with mites 

 and make a decision to "Continue sampling"). 













Fruit Notes, Volume 64 (Number 1), Winter, 1999 



