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Historic, Archive Document Do not assume content reflects current scientific knowledge, policies, or practices. cy eniptaerdtmSteanttesof Biological Control of the gricujture Animaland Russian Wheat Aphid PlantHealth Inspection Service ProgramAid Number1507 Coverphoto: Parasiticwasps sucli as Diaeretlellarapaekeep Russian wtieataphid populationsfrom reactiing damaging levels on small grains and manyothercrops. (Photo courtesyofJack KellyClark, Universityof CaliforniaStatewide IPM Project.) 2 — Populations of most native insects are Origin of the Problem held in check by parasites, predators, and disease organisms. But exotic The Russian wheat aphid Diuraphis — pests that manage to enterthe United noxia (Mordviiko) originated in south- States, like the Russian wheat aphid, central Russia and is common in adja- do not have locally established natural cent countries in Europe, northern enemies. When the population of such Africa, the Middle East, and Asia. Per- pests builds to the pointwhere they are haps as a result of expanded interna- causing economic damage, farmers tional trade in grains during recent often turn to the use ofchemical insec- decades, this insect has been carried ticides. Since 1962, the U.S. Depart- into othercountries, including South ment ofAgriculture (USDA) has been Africa and Chile. In North America, the wteocrhkniinqguteosdteovseulpopprbeisoslopgeisctasl.coTnthreosle tDhiestrUinbiutteidonStmaatpes,ofaRsuosfsiDaencewmhebaetra1p9h9i2d.in tRhuesseiaralnyw1h9e8a0t'sajpuhsitdnworatshfoifrstMefxoiucnod in techniques can reduce farmers' depen- (Dataarederivedfromthe National Agricul- City. From this initial infestation, it dency on insecticides. tural Pest Information System [NAPIS].) spread northward and reached Texas in In biological control, natural ene- 1986. By 1990, the Russian wheat aphid mies are used to reduce pes—t popula- when the Russian wheat aphid first was found in 16 Western States and 3 tions to subeconomic levels not appeared in the United States in 1986, Canadian Provinces, but it has not sig- eradicate pests altogether. Biological APHIS' biological control program was nificantly expanded its North American control has been successful against already working on a projectto release distribution since then. many insect pests, including aphids, in natural enemies against otheraphid North Americafor over a century. pests. This projectformed the basis for USDA's Animal and Plant Health becoming involved in a more intense, Inspection Service (APHIS) has been cooperative campaign directed specifi- cooperatively involved with biological cally againstthe Russian wheat aphid. control projects for many years. In fact, 3 — Characteristics of tlie Pest Nature and Cost of the Problem — Aphids sometimes called plant lice Like other aphids, the Russian wheat are small, soft-bodied insects thatfeed aphid feeds on plants by inserting its on plants by sucking theirjuices. The mouthparts into vasculartissues to tap Russian wheat aphid is pale green and the flow of nutrient-rich sap. By itself, usually covered with powdery white wax. such interference with a plant's nutrition Most individuals are wingless, but large can reduce yields. Butwhile it feeds, numbers ofwinged forms develop when the Russian wheat aphid also injects a grain plants mature. Although aphids toxin thatcauses leavesto discolor and are weakfliers, the wind carries them roll into strawlike tubes that enclosethe long distances. pests. Heavily infested grain fields may Three characteristics distinguish the have large areas of stunted and dying Russian wheat aphid from otheraphids plants. thatfeed on small grains: • Stubby, hard-to-see cornicles (twin projections nearthetip ofthe abdo- men); • An apparentdouble tail, especially when viewed from the side (no other grain aphids have this); • Short antennae that are less than half the length ofthe body. Russianwheataphidcolonyon damaged wheatleaf. Atlowerleftisabrown parasit- ized aphid ("mummy"). Russianwheataphidadultsand nymphs feeding on agrain leaf. 4 The Russian wheat aphid prefers When afield is initially invaded by coalesce, eventually resulting in large barley and wheat but also attacks oats. Russian wheat aphid, widely spaced areas of dead ordying plants. In some infested fields, grain yields patches of plants with characteristic Since the Russian wheat aphid have dropped by as much as 70 per- symptoms appear. Asthe infestation came to North America, grain farmers cent. The grain from infested plants progresses, these patches expand and may also be of lower nutritional quality. The presence of Russian wheat aphids in afield is usually revealed by damageto host plants. • Infested leaves have whiteto reddish- purple streaks along the veins. • The margins of infested leaves roll up into atube. Rolled leaves may become so disfigured thattheytake on acorkscrew appearance. • Infested plants appearstunted and produce fewertillers, which often become prostrate instead of remain- ing upright. Russian wheat aphid infestations usually originate on basal leaves of tillers, but astillers elongate, aphids move upward to younger leaves. Moder- ately infested plants produce smaller grains and fewergrains per head. When developing grain heads gettrapped inside infested terminal leaves, the heads cannot reach theirfull extension. Heavily infested plants may die. Awheatplantshowing Russianwheat aphiddamage. (Photo courtesyofTexasA& M University.) 5 have controlled it primarily bytlie appli- great concern thatthe initiation of From 1987through the 1988-89 cation of insecticides. However, with the chemical control programs in expansive growing season, crop losses attributable aphids protected inside rolled-up leaves acreages ofsmall grains may aggravate to Russian wheat aphid infestations in ofthe host plant, insecticidal control is existing environmental problems orcre- the Western United States totaled difficult and expensive. Also, there is ate new ones. Thisdrylandwheatfield in New Mexicosufferedsignificantdamage from Russianwheataphid. (APHIS photoby Bob Flanders.) 5 approximately $221 million, and an addi- The goal of biological control efforts tional $55 million was expended for con- againstthe Russian wheat aphid in trol. During the 1989-90 growing North America is to locate, import, and season, infestations were not as wide- establish effective natural enemies. spread as in previous years, but yield When successful, this approach will losses still totaled over $33 million. safely and permanently reduce Russian Control costs amounted tojust over $1 wheat aphid densities below economi- million, and the pest exerted an esti- cally significant levels. mated indirect impact on the community of over $44 million. These monetary losses, as well as possible environmental and social costs, may increase and will continue to accumulate if more effective and environmentally appropri- ate control measures are not developed. In the native home ofthe Russian wheat aphid, several species of parasites, predators, and pathogens attack it. These natural enemies probably are the primary reason why high densities of the pest rarely develop in these regions. In newly invaded regions, where no effective natural enemies exist, the Rus- Wheat leaves in aplantattacked bythe Rus- sian wheat aphid quickly becomes a sdieavnelwohpeiantgagprahiindhteeandd.toWrholel,ntrtahpepignrgaitnhehead major pest. cannot mature properly, yield andqualityare adverselyaffected. 7 Initial Biological Control in the Westthe sevenspotted lady Activities beetle (Coccinella septempunctata L.), a predatorofseveral aphid pests. In When the Russian wheat aphid first Europe and Asia, this lady beetle is a invaded Texas, the APHIS Biological common predatorofthe Russian wheat Control Program was already releasing Parasiticwasp (Aphidiussp. ovipositing in a Russian wheataphid. Adultladybeetle (Cyclonedaancoralissp.] feeding on agrain aphid. (Photocourtesyof The larvaofapredaceousfly (Leucopissp.] Max Badgley.) feeding on Russianwheataphid. 8