-8- 



* A listing of the activity spectrums of apple fungicides is avail 

 able from the Plant Pathology Department, Fernald Hall, University 

 of Massachusetts, Amherst, MA 01003. 



**************** 



SPIDER MITE SUBSTANCES INFLUENCING SEARCHING BEHAVIOR 

 OF THE MITE PREDATOR, A mblyseius fallacis , ON APPLES 



Robert G. Hislop, Nancy Alves, and Ronald J. Prokopy 

 Department of Entomology, Fernald Hall 

 University of Massachusetts 



In the preceding two issues of Fruit Notes , we described our 

 laboratory and field results on effects of various orchard spray 

 materials on the survival and reproduction of Amblyseius fallacis , 

 the most important mite predator in Massachusetts commercial apple 

 orchards. We observed that even in orchards using materials com- 

 paratively safe for /u_ fallacis , this predator's performance was 

 often less effective against red mites than against two-spotted 

 mites. We suggested that factors such as late-season competition 

 from other predators might partially explain this difference. Furthe 

 observations, however, suggested that this reduced effectiveness 

 against red mites might also be due to particular early-season habits 

 of A^ fal lacis which could possibly allow red mites to build up 

 uncheclceH^ in the Spring and early Summer. 



Adult A. f allacis females spend the Winter in orchard surface 

 litter. In'~Spring, warming temperatures bring them out of their 

 Winter shelters up into the ground cover vegetation where they feed 

 on two -spotted mite prey. In early Summer, they invade the apple 

 tree foliage in search of red and two-spotted mites. Because two- 

 spotted mites (but not red mites which were introduced here from 

 Europe) are believed to be the native prey of A_^ fallacis , we theo- 

 rized that perhaps this predator had evolved certain capabilities 

 allowing it to locate two-spotted mites more efficiently than red 

 mites. If this were true, and A^ f allacis could more readily locate 

 two- spotted mite infestations, particularly in the orchard understory 

 then it would seem that A^ f allacis might become preoccupied feeding 

 on this host. Red mites could then escape predator detection while 

 building up in the trees. 



The purpose of this research described here was to examine the 

 possible influence of physical and chemical substances deposited by 

 red and two-spotted mites on the host searching behavior of A. fallaci 

 As we will show, such behavior- influencing substances do in Tact exist 

 At the conclusion of thie article we outline how, in the future, 

 spray applications of the synthetic equivalents of these substances 

 to apple trees might enhance the ability of A_^ fallacis to better con- 

 trol red and two -spotted mites. 



