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Apples - Chap 19 11/4/03 11:01 am Page 489 19 Ecology and Management of Apple Arthropod Pests Elizabeth H. Beers,1 D. Max Suckling,2 Ronald J. Prokopy3 and Jesús Avilla4 1Washington State University, Tree Fruit Research and Extension Center, Wenatchee, Washington, USA; 2The Horticulture and Food Research Institute of New Zealand Ltd, Canterbury, New Zealand; 3Department of Entomology, University of Massachusetts, Amherst, Massachusetts, USA; 4Centro UdL-IRTA de R+D de Lleida, Universidad de Lleida, Lleida, Spain 19.1 Introduction 489 19.2 Systems of Pest Management 490 19.2.1 Pesticide-based 490 19.2.2 Integrated pest management 499 19.3 Fruit Feeders 501 19.3.1 Direct pests of buds and fruitlets 502 19.3.2 Mature-fruit feeders 503 19.4 Foliage Feeders 509 19.4.1 Mesophyll stylet feeders 510 19.4.2 Bulk leaf feeders 512 19.5 Structural Feeders 512 19.5.1 Superficial woody-tissue and shoot feeders 512 19.5.2 Wood-boring insects 513 19.5.3 Root-system pests 514 19.6 Conclusion 514 19.1 Introduction ered pests at some point in time. This sur- vey referred to one orchard in a temperate Apples present a distinct challenge to inte- production zone in central North America, grated pest management (IPM), due in part and we can only presume the total for the to their perennial growth habit and physical world is far greater. Despite this, only a complexity. The various organs of the tree’s dozen or so arthropods in any given region structure provide multiple habitats suitable are considered serious or chronic pests. A for arthropod colonization. In one study few, such as the codling moth, the European (Oatman et al., 1964), 763 species of arthro- red mite and, to a lesser extent, the two- pods were discovered using apple as a host spotted spider mite are pests virtually plant. While many of these were transitory, wherever apples are grown; others are perhaps 100 or so species have been consid- strictly regional pests. © CAB International 2003. Apples: Botany, Production and Uses (eds D.C. Ferree and I.J. Warrington) 489 Apples - Chap 19 11/4/03 11:01 am Page 490 490 E.H. Beers et al. When the pest complexes are viewed as The classification of pests in this chapter a whole, a pattern of ecological homo- is necessarily an arbitrary choice. We refer logues emerges. These homologues may be to arthropod taxa, but, for pest-manage- closely related species, or unrelated taxa ment purposes, the taxon is not necessarily that have similar feeding habits. The the most useful unit. Our approach has tetranychid mite complex in the Pacific been more crop-centred, in that groupings north-west (Tetranychus urticae Koch, have been made on the basis of damage Panonychus ulmi (Koch) and Tetranychus type (Fig. 19.1), which is in turn usually mcdanieli McGregor) all feed in the same highly related to its potential economic manner and cause a similar type of foliar importance. Within some of the larger damage (Beers et al., 1993). The leaf-roller groups (fruit feeders), we have grouped complex (moths in the family Tortricidae) pests by time of attack or by type of damage all feed on leaves and the surface of apple caused. Overarching the crop and produc- fruits. Weevils (e.g. the plum curculio tivity issues, we have superimposed the Conotrachelus nenuphar (Herbst)) and thrips ecological niche and ecological homologue (the western flower thrips, Frankliniella occi- concepts in an attempt to make the dentalis (Pergande)) are examples of two plant–herbivore relationship clearer. unrelated taxa that cause similar types of damage (surface feeding and oviposition, leaving a superficial scar) and at about the 19.2 Systems of Pest Management same period in fruit development (during or shortly after bloom). 19.2.1 Pesticide-based A number of pest species are strictly monophagous on apple (e.g. Aphis pomi De The discovery and commercialization of Geer), while others are oligophagous or synthetic organic pesticides in the latter half even highly polyphagous (e.g. T. urticae). of the 20th century represented a major The degree of host specialization does not qualitative change in pest management. For appear to be related to pest status. One of the first time since the beginning of agricul- the key pests worldwide (codling moth, ture, producers had a broad range of highly Cydia pomonella (L.)) is moderately effective and relatively inexpensive prod- oligophagous, feeding primarily on a few ucts to use for insect control (Table 19.1). species of Rosaceae and one member (wal- Their ease of use and often long residual nut) of the Juglandaceae. However, many toxicity to pests made them very popular species exhibit a certain degree of plasticity and, to some extent, the applications were in their feeding behaviour and are capable an insurance policy against pest damage. of shifting hosts or expanding their host The euphoria was short-lived, as resistance range over time. An example is the apple problems began developing, sometimes maggot, Rhagoletis pomonella Walsh, in west- within a few seasons’ use. The organochlo- ern North America. A host shift was recently rines, introduced to agriculture after the demonstrated for this species (from apple to Second World War, were largely supplanted cherry) (Jones et al., 1989), even though a by the organophosphates, carbamates and closely related species, Rhagoletis indifferens pyrethroids within a few decades. The Curran, already occupied this niche in this problems associated with the use of these region (Utah). Apple is an introduced crop products became apparent after a relatively in the majority of the areas where it is short time, including environmental persis- grown, so the pest complex of any given tence and damage (especially the region is typically a mixture of pests from organochlorines), mammalian toxicity (e.g. the native region that have been introduced applicator and farm-worker safety, espe- over time (many before strict quarantine cially the organophosphates), possible con- regulations were imposed) and native pests sumer effects from residues on foods that have adapted to using apple as a host (carcinogenicity, teratogenicity, mutagenic- (e.g. apple maggot). ity or chronic neural effects), and destruc- Apples - Chap 19 11/4/03 11:01 am Page 491 Apple Arthropod Pests 491 Fig. 19.1. Examples of arthropod pests attacking various parts of the tree. Clockwise from top: scale (feed on bark); aphids (phloem feeders in shoots and leaves); leafhoppers (pierce mesophyll cells and remove contents); woolly apple aphid galls (on roots); bark beetles (attack trunk and major scaffolds); leaf-rollers (feed on fruit surface and leaves); codling moth (feeds internally in fruit); plum curculio (oviposits and scars young fruitlets). (Illustration by G. Steffan.) tion of pests’ natural enemies and selection tive tactics was minimal, because of the effi- for resistant pest populations. There were cacy of the new pesticides. Non-pesticidal clear economic benefits driving the use of tactics with some degree of promise were these materials: 30–50% damage from dismissed because of their relatively higher codling moth in the latter part of the lead expense, lower efficacy or greater complexity arsenate era (1940s) was common (Driggers, of implementation. The concept of mating 1937), whereas the economic threshold for disruption, well established by the 1970s this pest today is generally set at < 1%. (Roelofs, 1979), was not registered for use on Despite this, the disenchantment with these apples in North America until the early 1990s, materials has been growing steadily since and is still not registered in some European the 1950s. countries. Similarly, the sterile-insect tech- One of the side-effects of the pesticide- nique, although demonstrated as feasible for based era was that the bulk of entomological codling-moth control in the 1960s (Proverbs research was directed at the development et al., 1966), was not implemented in tree and optimum use of the new pesticides, and fruit on a large commercial scale until the basic biology and biological-control research early 1990s, and then only on a limited slowed considerably. The search for alterna- acreage in British Columbia, Canada. Apples -Chap1911/4/0311:01amPage492 Table 19.1. Historical use of insecticides and acaricides in apple. 492 E.H.Beers Type (I = insecticide, Use period Class/pesticidea A = acaricide) (approximate) Comments Inorganic Lead Arsenate I 1890s–1950s Once the sole control measure for codling moth and other pests, this compound was used for > 50 years until resistance occurred and replacement insecticides became available. Soil residues are still present Sulphur I/A Late 1800s–present Often applied with lime as a safener, this material is still widely used for both day arthropod pests and diseases. Used in late winter or early spring, it can be phytotoxic Cryolite I Used briefly during periods of codling-moth resistance; occasional use in organic production Dinitro Compounds Several compounds in this group have been used, but DNOC was the most common Dinitro-o-cresol (DNOC) I/A 1930s–1970s Highly phytotoxic; thus use was confined to dormant sprays. Used with oil to control aphid eggs and overwintering scale. No longer permitted in Europe (2000) DN-111 A 1940s–early 1950s A summer acaricide. Phytotoxic Botanicals As a group, these were once the primary pesticides allowed in organic produc- et al tion; some are being withdrawn (see individual chemicals). Widely variable in . terms of mammalian toxicity Neem I 1980s–present Derived from the seeds of neem (tree) (Azadirachta indica A. Juss); has antifeedant, repellency and/or growth-regulator influence on many orders of insects Ryania extracts (main I 1950s–present Ground bark of a tropical shrub (Ryania spp.); once widely used for codling-moth active ingredient ryanodine) control, it still has a limited place in organic apple production Rotenone I/A 1930s–present A neurotoxin best known for its toxicity to fish; no longer allowed in most organic certification programmes.