Making Integrated Mite Control Work in 

 Northeast Apple Orchards 



Jan P. Nyrop 



Department of Entomology, Cornell University, NYSAES, Geneva, New York 



European red mites (ERM), Panonychus idmi, 

 feed on leaves of apple trees and thereby interfere 

 with photosynthesis and production of carbohy- 

 drates. At high levels, ERM damage to apple 

 leaves reduces fruit yield and quality. As a general 

 rule, keeping ERM numbers below 2.5 per leaf 

 before July, below 5 per leaf during July, and 

 below 7.5 per leaf in August will prevent economic 

 losses from this pest. 



Three strategies can be used to control ERM in 

 apple orchards. First, protectant miticides (e.g., 

 dormant oil or an ovicide) can be applied early in 

 the growing season. Second, pest mite numbers 

 can be monitored and miticides applied if densities 

 exceed threshold levels. Third, natural enemies 

 that feed on ERM can be encouraged and managed 

 to constrain pest mite numbers. Strategies based 

 solely on miticides are relatively expensive and 

 eventually lead to the development of resistance by 

 ERM to the miticides. With the help of natural 

 enemies, the cost of managing ERM in apples can 

 be greatly reduced and resistance delayed. 



Insect and mite predators, including several 

 species of phytoseiid mites, stigmaeid mites such as 

 Zetzellia malt, and ladybird beetles, feed on ERM. 

 Phytoseiid mites are the most effective of these 

 predators in the Northeast. Several species of 

 phytoseiid mites, including Amhlyseius fallaas, 

 Typhlodromus pyri, T. occidentalis, T. vulgaris, 

 and A. cucumeris, can be found in commercial 

 orchards. Species cannot be identified in the field 

 because they are so similar in appearance. They 

 are only distinguishable through microscopic 

 examination of the arrangement of the setae 

 (hairs) on their bodies. T. pyri and A. fallacis are 

 the two most common species in Northeast 

 orchards. Of the two, T. pyri is better able to 

 regulate ERM populations. This is the species that 

 should be established and maintained for 



biological mite control in Northeast orchards. In 

 this article I answer three questions: First, why is 

 it that T. pyri is such an effective predator? 

 Second, is T. pyri an effective predator throughout 

 the northeast? Third, how can you make use of 

 this natural enemy to provide cost-free mite 

 control? 



Why is Typhlodromus pyri such an effective 

 predator? For many years A. fallacis was 



promoted as an effective biological control agent 

 for ERM. In truth, A. fallacis gives sporadic and 

 unreliable ERM control, while T. pyri is highly 

 effective in this capacity. Differences in 

 effectiveness of T. pyri and A. fallacis as biological 

 control agents are rooted in their biologies. 



T. pyri require approximately 32 days to 

 complete a generation, and have three to four 

 generations per year. They overwinter as mated 

 adult females on trees wherever they can find a 

 protective site (e.g., bark crevices, branches, 

 spurs). Adult females emerge from overwintering 

 sites on warm spring days before budbreak. The 

 adults live about 20 days and lay an average of 20 

 eggs starting as early as tight cluster or pink bud 

 growth stages. Eggs are usually laid on the 

 undersides of leaves along the midrib. The eggs 

 hatch in 1-3 days and resulting immatures are 

 nearly transparent and look like smaller versions 

 of the adults. Immatures and adults feed on a wide 

 variety of food sources, including pollen and rust 

 mites, along with ERM and two-spotted spider 

 mites (Tetranychus itrticae). An adult female will 

 consume one to two ERM adults or three to four 

 ERM nymphs per day. These predators do not 

 concentrate on leaves with large numbers of ERM, 

 unlike some other phytoseiids (e.g., A. fallacis). T. 

 pyri are relatively winter hardy and remain in the 

 tree even when ERM are scarce, feeding on 

 alternative food sources. 



A. fallacis require 16 days for each generation, 



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



