Common plant health problems of maize in Zambia

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1 2 cm 2 cm African maize stalk borer African pink stem borer INSECT Busseola fusca INSECT Sesamia calamistis ( Anne Bruntse, Tanzania Ministry of Agriculture, ICIPE, CIMMYT, Rob Harling) ( Rob Harling) Caterpillars are soft, segmented, 1 to 3.5 cm. They look smooth & shiny; creamy-white, rarely greyish or pinkish-white, no hairs or markings Head is dark brown First, young caterpillars feed holes into leave whorls. When whorls open, see 'windows' in straight lines across leaves Then, they feed in the leaf hearts (leaf funnels), leading to yellowish and dying leaf hearts. Later, they bore into the stems; later into cobs Caterpillars are soft, segmented, 1 to 3.5 cm. They look smooth and shiny; creamy-white with a pink touch; no hairs or markings Head is dark brown Caterpillars do not usually feed on the young terminal leaves (not on leaf whorls). Thus, no `windows' in straight lines Caterpillars feed in stems, eating out frass-filled galleries Later, caterpillars also tunnel into maize cobs Spotted stem (stalk) borer Termites INSECT Chilo partellus INSECT Macrotermes spp.,odontotermes spp. ( ICIPE, Rob Harling) ( J.N.K. Maniania Eigen werk) Caterpillars are soft, segmented, 1 to 2.5 cm. They are creamy whitish-yellowish to grey with 4 thin purple-brown long stripes and many tiny side lines and few dorsal spots Head is first light, later brown Young caterpillars feed holes on leave whorls. Later, see 'windows ' in straight lines on leaves Then, they feed in the leaf hearts (leaf funnels), leading to yellowish and dying leaf hearts. Later, they bore into the stems, then into cobs Termites are mostly wingless ant-like 0.5 to 1cm long insects Termites build galleries packed with soils onto the maize stems, or tunnels made of thin sheets of soil Sheets of soil on the leaf show termite attack. The maize plant may lodge

2 Front Back Fall armyworm African armyworm INSECT Spodoptera frugiperda INSECT Spodoptera (Agrotis) exempta ( R. Ottens, Bugwood.org) ( J ICOSAMP; Rikus Kloppers; Tom Berndt, NRCS) About 1 to 3.5 cm greyish-light brown patterned soft caterpillars that are smooth on touch Caterpillar has a dark head with an upside down pale ^-shaped marking on the front Caterpillar s body segments have 4 raised spots when seen from above (see white circle) Caterpillar s body end has 4 dark spots forming a square (see black square) Feeding similar to other stem borers, except that armyworm caterpillars also enter through side of the ear to feed on developing kernels Young 1 to 2 cm shiny caterpillars eat on fresh maize or grasses and turn green after feeding Older caterpillars (3 to 4 cm) are dark, and have thick whitish and dark strips along the sides and the back They have a black shiny head with an upside down pale ^-shaped mark on the front Caterpillars eat maize leaves and sometimes only midribs remain Phosphate deficiency Nitrogen deficiency ABIOTIC ABIOTIC ( P. Kumar) ( P. Kumar) Symptoms first seen on older leaves Leaves start to get green-reddish from tip and leaf edges onwards. Symptoms are symmetrical on leaves Symptoms appear over larger area of field and not only on few plants The reddening can be mistaken for phytoplasma attack Symptoms first seen on older leaves Leaves start to yellow from tip and leaf edges onwards. Symptoms are symmetrical on leaves Symptoms appear over larger area of a field and not only on few plants The yellowing and death of the lower leaves can be mistaken for natural ageing

3 Maize streak virus MSV Grey leaf spot disease (Angular leaf spot) VIRUS Maize streak virus MSV, syn. cereal African streak virus, maize mottle virus FUNGUS Cercospora zeae-maydis ( Julian Ward/KwaZulu-Natal; B. Das and Kanyanta Musonda) ( Manitoba University, A.A. Seif, ICIPE) Affects sorghum, sugarcane, some wild grasses. Thin parallel yellow chlorosis streaks that follow the leaf veins with whitish-green long spots and thin streaks covering entire leaves No larger yellow patches; no necrotic symptoms. Young plants are dwarfed. Plants will not die. Small poorly filled cobs, or sometimes no cobs. The disease is vectored by plant hoppers First, yellow stripes are thin, short, angular, scattered over the leaf (in contrast MSV has thin and long stripes covering entire leaves) Later larger light-brownish grey sometimes necrotic patches. The spots may join together to cover the whole leaf turning it brown. Plants usually do not die. Underside of leaves may be small black spots Maize lethal necrosis disease MLND Common maize smut FUNGUS Ustilago maydis VIRUS Co-infection with Maize chlorotic mottle virus & Sugarcane mosaic virus or Wheat streak mosaic virus. ( CPC, H. Kaufemann) ( CIMMYT, Rob Reeder) First many long AND some short yellow stripes on leaves often starting along one side Later, stripes become larger Leaf edges become entirely yellow, and dry from the edges moving towards the midrib, thus necrosis Pants dwarf or premature early. Finally, the entire plant dries and dies. Infected plants will have few to no grains. Plant hoppers and thrips spread the disease. First indications are small bumps on leaves. Formation of galls or tumours on the cobs, and sometimes on stems or leaves Galls are one to several centimetres large and covered by a whitish-green membrane. Later galls become grey. Inside the galls are powdery black masses of spores that may burst out. Plants usually do not die.

4 Smooth pigweed WEED - Amaranthus hybridus (syn. A. frumentaceus) ( Phil Westra, Bouba) Amaranthus is eaten as a vegetable but can also be a serious weed in maize and other crops. Has rough, soft, grey-greenish or green-reddish alternate leaves. Leaves are oval or diamond shaped and broader at the base Amaranthus produce large number of seeds Rottboellia itch grass WEED Rottboellia cochinchinensis ( Roed CIRAD; Chris Parker CABI ; EOL) Annual grassy weed of often up to 3 m high Itch grasses emerge within 4 to 6 weeks from maize planting. Itch grass stems are covered in fine stiff hairs that are irritating to the skin hence its name Green thin flowers heads are spike-like cylindrical up to 15 cm long Often rooting at the node Suffering maize Yellow nutsedge WEED Cyperus esculentus ( J. Kelly; Chufa J. M. Di Tomaso, University of California, Bugwood.org, S.Bauer) Stems are erect, triangular shaped, yellow green. Leaves are also yellow- green and about wide. When un-controlled, it grow s quickly and uses most of the nutrients needed by the maize. Such maize plants may have thin stems and are small. Striga witch weed WEED Striga hermonthica ( Hakizamungu Leon, Rob Reeder, CABI, USDA APHIS PPQ, Bugwood.org) In areas with low soil fertility and poor rainfall Grows in contact with maize, sorghum, millet. Attaches itself to the roots of the crop and sucks water and nutrients out of the crop Seen first 2-3 weeks after maize emergence. 5 to 30 cm high with orange-pink flowers. Attacked maize lose colour and leaves dry. Maize may be stunted over entire field areas. Symptoms of phosphorus deficiency such as purplish leaves may be a hint of Striga causing deficiency before it emerges from ground.

5 Aspergillus fungal ear rot Diplodia cob rot (ear rot) FUNGUS - Aspergillus spp. FUNGUS Stenocarpella maydis (Diplodia maydis) ( CIMMYT, Purdue University North Carolina State University, Bugwood.org) ( Iowa State University, Langa Tembo, UNZA; Bradley Flett CPC) Infects flowering developing cobs during hot, dry weather after flowering. Later appears yellowish- green-grey powder on grains on ripening cob In contrast, other ear rot fungi produce whitish powder or dusts. Cob rot fungi can produce poisonous chemicals in the grains. Do not eat, do not feed to livestock Attacks mature maize cobs The fungus turns the grains brown. Whitish threads can be seen. In contrast, other cob rot diseases cause reddish, blackish or greyish grains; and maize smut causes big deformed grains/cobs Cob rot fungi can produce poisonous chemicals in the grains. Do not eat, do not feed to livestock 0.5 cm 0.5 cm Larger grain borer Common maize weevil INSECT Prostephanus (Dinoderus) truncatus INSECT Sitophilus zeamais ( CSIRO) ( Georg Goergen IITA Insect Museum, ARS, US Department of Agriculture) Small dark brown weevil adult with long snout boring into grain Dark-brown wings of adult weevil with 4 light brown areas Feeding holes on maize cob caused by weevil Exit holes may have feeding powder from grains. Adult brown beetle around 0.5 cm only Beetles have a cylindrical body shape, looks square-shaped when viewed from above Adults tunnel through maize husks, cobs and from grain to grain producing maize dust. Larva is less than 0.5 cm, grub-like, whitishfleshy with 3 pairs of tiny legs Larvae develop inside grains