What Species of Predaceous Mites 

 Exist in IVIassaciiusetts Commercial 

 Apple Orchards? 



Xingping Hu and Ronald Prokopy 



Department of Entomology, University of Massachusetts 



Under favorable orchard pest management 

 conditions, predaceous mites can provide a mod- 

 erate to high level of control of pest mites such 

 as European red mites and two-spotted spider 

 mites. Reports from New York State clearly 

 suggest considerable variation among different 

 species of predaceous mites in ability to control 

 pest mites. For example, the predator 

 Typhlodromus pyri is better able to survive 

 harsh winter temperatures and to provide sea- 

 son-long control of low to moderate pest mite 

 numbers than is the predator Amblyseius 

 fallacis. In turn, the latter is better able thanT. 

 pyri to control rapidly building numbers of pest 

 mites in the summer. A third predator, ZeteeZZta 

 mali, appears rather similar in biology to T. 

 pyri, but rather Uttle is known about its ability 

 to suppress pest mites. 



In 1977, we conducted a survey of 21 com- 

 mercial apple orchards scattered throughout 

 Massachusetts to determine the proportion of 

 sampled orchards that 

 contained each of these 

 three species of preda- 

 ceous mites. We surveyed 

 again in 1993 in 12 dif- 

 ferent commercial or- 

 chards scattered across 

 the state. Samples con- 

 sistedof 100 leaves taken 

 weekly in each orchard 

 from April through June 

 and 50 leaves taken bi- 

 weekly from July through 

 September. Leaves were 

 placed in a cooler imme- 



diately after picking and returned to the labora- 

 tory for predator identification. Identification 

 involved removing the predators fi'om leaves, 

 mounting them on microscope shdes, and using 

 taxonomic keys to distinguish between some 

 species on the basis of the number and location 

 of tiny hairs on the body surface. 



There was remarkably little change over 1 6 

 years in species composition of predators (Table 

 1). In both surveys, A. fallacis was present in 

 81 to 92% of sampled orchards, Z. mali in 30 to 

 33%, and T. pyri in to 8%. The similarity in 

 data patterns across years is even more re- 

 markable given the fact that all orchards 

 sampled in 1977 were different from the ones 

 sampled in 1993. 



We conclude that if we want to achieve 

 biocontrol of pest mites with existing preda- 

 ceous mites in Massachusetts orchards , we ought 

 to pay particular attention to A. fallacis and 

 ways of encouraging its buildup. T. pyri, which 



Table 1. Percentage of Massachusetts commercial apple 

 orchards sampled in 1977 and 1993 containing predaceous 

 mites. 



Year 



Number of 

 orchards 

 sampled 



Species of predator 



Amblyseuis Typhlodromus Zetzellia 

 fallacis pyri mali 



1977 

 1993 



21 



12 



81 

 92 







8 



30 

 33 



10 



Fruit Notes, Spring, 1994 



