Dr. Phyto

cotton (upland cotton)

Gossypium hirsutum

Diseases & pests on this plant

• Cotton bollworm (corn earworm)Helicoverpa zea

  Caterpillars bore into squares, flowers and bolls, feeding inside; damaged squares yellow and drop, and holes in bolls let rot in. Eggs are laid singly on upper foliage; larvae vary from pale green to brown with stripes. The American sibling of the Old-World Helicoverpa armigera.

• Reniform nematodeRotylenchulus reniformis

  No specific above-ground symptom — general stunting, patchy poor growth, yellowing and mid-day wilt on lighter soils, with reduced boll set. Roots carry sticky egg masses with adhering soil. Confirmed only by a soil nematode assay.

• Fusarium wilt of cottonFusarium oxysporum f. sp. vasinfectum

  Yellowing and wilting that often starts on one side of the plant or one half of a leaf; brown streaks in the woody stem when split lengthwise; stunting and premature defoliation. Damage is far worse where root-knot or reniform nematodes are also present.

• Bacterial blight (angular leaf spot) of cottonXanthomonas citri pv. malvacearum

  Small, water-soaked angular spots on leaves, bounded by the veins, later turning brown; black, greasy lesions run along stems ('black arm'); sunken dark spots rot the bolls and stain the lint. Spread by rain-splash and worst in warm, wet, windy weather.

• Cotton (Texas) root rotPhymatotrichopsis omnivora

  Sudden, permanent wilt in mid- to late summer, usually in expanding circular patches; the leaves stay attached and turn bronze. Roots are rotted and covered with tan-to-brown fungal strands; plants pull up easily. Confined to alkaline, calcareous soils of the US Southwest.

• olive Verticillium wiltVerticillium dahliae

  Half a tree wilting in summer while the other half stays green, blackish discoloration in cross-section of affected wood, partial recovery in winter then relapse, dieback over 2–4 seasons.