Providing practical information to help you protect your farm from biosecurity risks

Cotton pests

 

Cotton | Cotton best management practice | Cotton pests | Cotton product management

 

The following are high priority exotic pest threats for the Australian cotton industry as identified through the development of the cotton industry biosecurity plan (IBP). All of these pests would have serious consequences should they enter and become established in Australia.

Information about other pests of cotton is available from the cotton industry page on the Plant Health Australia website.

To improve biosecurity measures on your farm, include exotic pests when undertaking routine pest surveillance activities. Ensure that all surveillance activities, for both endemic and exotic pests, are recorded. Consultants carrying out the surveillance should be provided with pest fact sheets that show key symptoms for identifying characteristics of the target exotic pests.

Fusarium wilt (exotic races)

fusarium wilt-1436005

  • Fungus – Fusarium oxysporum f. sp. vasinfectum
  • Found in every cotton-growing region in the world
  • Risk is from new strains establishing to which the local cotton varieties have little or no resistance
  • External symptoms: stunted growth, wilted leaves, yellowing, browning, eventual death
  • Internal symptoms: brown discolouration of stem tissue
  • Spread by spores in soil, water and infected plant material
  • Look for Fusarium symptoms on varieties that should be resistant

Fact sheet

 

 Bacterial blight (exotic/hypervirulent races)

Bacterial leaf blight-5439527

Xanthomonas axonopodis pv. malvacearum: Photo by OP Sharma, NCIPM, New Delhi, India, Bugwood.org

  • Bacterium – Xanthomonas citri subsp. malvacearum
  • Hypervirulent strains found in North Africa
  • Risk is from new strains establishing to which the local cotton varieties have little or no resistance
  • Angular water-soaked lesions on leaves, stems and bolls
  • Severe infestations lead to defoliation Stems show ‘black arm’ symptom, bolls unable to open
  • Look for Bacterial blight symptoms on varieties that should be resistant
  • Spread by rain-splash, in seed and plant material

Fact sheet

 

 Cotton aphid (exotic strains)

cotton aphid-4387054

Aphis gossypii Glover: Photo by Mississippi State University Archive, Mississippi State University, Bugwood.org

  • Aphid (Hemiptera) – Aphis gossypii
  • Found in every cotton-growing region in the world
  • Risk is from new strains establishing that may carry exotic pathogens or show greater pesticide resistance
  • Small (less than 1.5 mm), range in colour from pale green to almost black, and have two short projections (‘exhaust pipes’) from the rear end
  • Infestations often associated with honey-dew on leaves
  • Look for aphid infestations that do not respond to current pesticide applications
  • Can walk or fly between plants and spread long distances in wind or on plant material

Fact sheet

 Cotton boll weevil

boll weevil-1949054

Anthonomus grandis: Photo by F Benci, Boll Weevil Research Laboratory, United States, Bugwood.org

  • Weevil (Coleoptera) – Anthonomus grandis
  • Found in North, Central and South America
  • Greyish-brown adults, body 5 mm, conspicuous snout 3 mm
  • White legless larvae, 13 mm, grow within developing squares and bolls
  • Spread in seed or bolls and harvested seed cotton
  • Can fly long distances on wind currents

Fact sheet

 

 Cotton leaf curl disease

cotton leaf curl virus-1572414

Begomovirus CLCuV: Photo by Gerald Holmes, Valent USA Corporation, Bugwood.org

  • Virus complex – including the Cotton leaf curl virus (Begomovirus)
  • Found in Pakistan, India, Egypt, Nigeria, Tanzania, Sudan
  • Swelling, darkening of leaf veins, cupping leaves, leaf-like growths from veins, early stunting
  • Many alternative hosts (e.g. tobacco, tomato, chilli, radish, okra)
  • Spread by whiteflies

Fact sheet

 

 Spider mites (exotic species)

carmine spider mite-5368117

Photo by Merle Shepard, Gerald R Carner, and PAC Ooi, Insects and their Natural Enemies Associated with Vegetables and Soybean in Southeast Asia, United States, Bugwood.org

  • Mites – e.g. Tetranychus turkestani, T. pacificus
  • Spider mites high risk to the Australian cotton industry are present in North and South America, Asia and Africa
  • Small (less than 0.5 mm), red or green in colour and have eight legs
  • Exotic species may not respond to current pesticides or may attack crops not normally affected by spider mites
  • Look for intense crop damage, unusual looking mites or the presence of mites on the upper leaf surface (T. pacificus only)
  • Long distance spread may occur with infested plant material

Fact sheet

 

 Verticillium wilt (defoliating strains)

verticillium wilt-5365934

Verticillium dahliae: Photo by Howard F Schwartz, Colorado State University, United States; Bugwood.org

  • Fungus – Verticillium dahliae
  • Found in China, Iran, Israel, Mexico, Peru, Spain, USA, former USSR
  • Risk is from new, defoliating strains establishing to which the local cotton varieties have little or no resistance (non-defoliating strains present in Australia)
  • Extremely wide host range, including vegetable, fruit and broadacre crops
  • Leaf mottling, vascular peppering, total defoliation, boll shedding
  • When the stem is cut lengthways, vascular discolouration exhibits flecking of the inner tissues
  • Spread by spores in water, soil and infected plant material, clothing and equipment

Fact sheet

 

 Cotton blue disease

cotton blue disease

Photo by Stephen Allen, CSIRO, Australia

  • Virus – Luteovirus (suspected)
  • Found in parts of Africa, Asia and South America
  • Stunted plants with down-rolling leaf edges, intense blue-green leaves, darkening of veins, petioles, stems, zig-zag stems, smaller flowers and bolls
  • Cotton aphid is the only known vector
  • Host plant resistance is available but may be overcome by some variants of the disease

Fact sheet

 

 Indian green jassid

Indian green jassid 10

Amrasca devastans: Photo by James Litsinger, IRRI

  • Sap-sucking insect (Hemiptera) – Amrasca devastans
  • Found in Asia and the Indian subcontinent
  • Yellowish white eggs (1 mm long) and greenish-yellow nymphs (1-2 mm long) with bluish legs
  • Adults yellowish-green in summer, reddish-brown in winter
  • Prominent black spots – two on head and one on each forewing
  • Plant symptoms include leaf yellowing, crinkling, curling, stunted growth and fewer bolls
  • Flying adults spread in wind currents, and eggs and nymphs can be carried on seeds, bolls and harvested seed cotton

Fact sheet

 

 Tarnished plant bug

tarnished plant bug-1318094

Lygus lineolaris: Photo by Scott Bauer, USDA Agricultural Research Service, United States, Bugwood.org

  • Insect (Hemiptera) – Lygus lineolaris
  • Found throughout North America
  • Wide host range
  • Greenish yellow to brown bug (6 mm long) with varied markings
  • Nymphs are yellow-green with dark markings
  • Infest leaves, squares, bolls, flowers, cause seed/shoot damage, lint discolouration and delayed maturity
  • Adults spread in wind, especially in storms
  • Can develop resistance to pesticides

Fact sheet

 

 Texas root rot

Texas root rot 2

Photo by Chris Anderson, Department of Primary Industries, NSW

  • Fungus – Phymatotrichopsis omnivora
  • Found in USA, Mexico, Brazil, Venezuela and reported in Libya
  • Wide host range, including vegetable, fruit and broadacre crops
  • Symptoms include wilting, dead leaves on plant, dead roots covered with white-tan fungus
  • Generally results in circular patches of dead/dying plants in the field
  • Spread via infected root contact, in soil and with infected root material

Fact sheet

 

More information

Pest surveillance

Reporting suspect pests