73 



(20 snail hours) which reduced the population by 83.77o. After this point 

 (Figure 24) there was an increase in the mite population. Field ob- 

 servations indicated that areas cleaned by the snail could become rein- 

 fested from immigrating rust mites. The immigration and migration of 

 mites by locomotion, wind dispersal, and rain could account for tlie rein- 

 festation of previously cleared areas. 



This test demonstrated that even in this type of uncontrollable 

 mite infestation a high degree of citrus rust mite population suppres- 

 sion was attained briefly. Greater suppression was displayed by the 

 units containing three mites per cubic foot (X = 3). By day four, as 

 high as 90% reduction in the rust mite population was observed. This 

 again demonstrated the capacity of the snails for rust mite removal. 



Having determined the amount of surface area covered by a snail 

 per snail hour (S), it was possible to determine the number of snails 

 (N) necessary to clean the surface of a tree (A) in any given number of 

 days (T). 



The snail hours per night (h) were calculated by monitoring periods 



of 100% R.H. and its daily occurrence. The value for S, surface area 



2 



cm cleaned by a snail per snail hour, was taken as an average S = 



2 

 131.34 cm /snail hour, as calculated earlier. 



Calculations of the number of snails (N) that would be needed is 



as follows: 



N = 2A X 10,000 

 Txhxs 



N = Number of snails needed 



A = Surface area of tree (meter"^) 



T - Time (days) to completion 



h - Snail hours/night 



s = Area cleaned by snail per hour. 



