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![Corn Leaf Aphid
Rhopalosiphum maidis
Heavily infested corn leaves may wilt, curl, and show yellow patches of discoloration. When
tassels and silks are covered with honeydew, the pollination process may be disrupted.
The corn leaf aphid is a blue-green or gray, soft-bodied, spherical insect about the size of a
pinhead (1.6 mm) in length].
It has approximately 9 generations per year.
Female corn leaf aphids do not lay eggs, as do most other insects, but give birth to living
young.
These young, called nymphs, resemble the adults except that they are smaller and are sexually
immature.
Adults and nymphs can often be found clustered within the whorls or upper parts of corn
plants over isolated or wide areas of a field.](https://image.slidesharecdn.com/mlndiseaseanditsmanagementteampresentation2015-151128190900-lva1-app6892/85/MLN-disease-and-its-management-2015-34-320.jpg)
Uploaded bySuresh, L.M
‘MLN disease and its management’ 2015
1. Maize lethal necrosis (MLN) is a devastating disease in East Africa caused by the co-infection of maize chlorotic mottle virus (MCMV) and either sugarcane mosaic virus (SCMV) or maize dwarf mosaic virus (MDMV). 2. The disease was first reported in Kenya in 2011 and has since spread to several other East African countries. It causes symptoms ranging from chlorosis and leaf necrosis to dead hearts and poor grain filling. 3. The disease is transmitted by various sucking insects including aphids, thrips, and whiteflies. Its spread in East Africa has been exacerbated by the cultivation of susceptible germplasm and potentially new viral
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Similar to ‘MLN disease and its management’ 2015
‘MLN disease and its management’ 2015
- 1. Dr. Suresh, L.M. MaizePathology Lead – Sub saharan Africa CIMMYT – Kenya Nairobi ‘MLN Disease and its Management’ Global Maize Program
- 2. History of MLN •First report of viral co-infection (MCMV+MDMV) leading to MLN was reported in Kansas and Nebraska (USA) in 1976 (Niblett). Disease was termed Corn Lethal Necrosis (CLN) • In the 1990s, co-infection of MCMV+MMV was reported to cause extensive damage to temperate seed production in Hawai. • First report of MLN in Africa made in 2011 in Kenya (Wangai et al, 2012). Causal agents identified to be MCMV and SCMV by tissue blot immuno- assay and PCR.
- 3. MLN Disease Development Vectors: Presenceof aphids and thrips Environment: Conditions favoring vectors and disease Susceptible Germplasm Virus: Either individual or compound
- 4. MCMVMCMV Potyvirus SCMV MDMV WSMV MLNMLN • Individual infectionwith mixture of viruses can also cause disease • Typically, infection with one virus results in milder symptoms than MLN but reaction depends on germplasm and viral strain. Maize Lethal NecrosisMaize Lethal Necrosis
- 5. Why is theMLN devastating in EA? • MCMV is new to the region • Potentially new strains of SCMV/MDMV • Widespread cultivation of susceptible germplasm that has never been screened for MCMV • Characterization of viral populations will reveal identify of strains in the region.
- 6. Disease Symptoms • Dyingleaves, leading to premature plant death • Failure to tassel and sterility in male plants • Malformed or no ears • Rotting cob
- 7. Symptoms of thedisease • Symptoms observed vary widely depending on; -Germplasm -Time of infection -Prevailing environmental conditions -Ratios of the viruses infecting the plant • The symptoms can easily be confused with drought , micro- nutrient deficiency or stalk borer infestation
- 8. Symptoms in artificiallyinoculated maize plants in screen house MCMV SCMV
- 9. Early Symptoms Mild mosaicand mottling Mild mosaic and mottling
- 10. Chlorosis and MottlingDiffuse mottling and chlorosis Early MLN Symptoms
- 11. Severe chlorosis andleaf necrosis
- 12. Shortened internodes andsevere chlorotic mottle
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- 14. Premature drying ofthe husks
- 15. Poor or nograin filling
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- 17. Recommendation for preventionfor disease spread
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- 19. 19 Initial inoculum source (Weed) Vector– Transmits Virus Rapid spread due to vector movement and Host susceptibility Disease
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- 23. 1.Vehicles or machinerycan introduce pathogens to production area from outside. 2.Vehicles can visit many places and agricultural area so wheels and car body can be contaminated by pathogen Precaution 1. Disinfect all vehicles and machinery before entering to our research /production area 2. If disinfection is not available, prepare parking lots isolated from production area to prevent contamination. Red zone is allowed. Risk: Vehicle or agricultural machinery not disinfected
- 24. 1.All waste materialscame from our GH/field area must be dumped at designated area only and it should not throw away near facility or near walk way. Rain or people can carry pathogen and this mechanism will cause disease again. If facility is poor without fence or less depth, plant sap can overflow in rainy season and its sap can come to the field. Precaution 1.Designate waste area far away from our field. 2.If it is not available, waste area will fenced and covered. Putting chemical or lime will stimulate decomposing 2. Plant materials will bury or burn Risk: No waste designated area
- 25. MLN - infectedMLN - free
- 26. Spread of MaizeLethal Necrosis (MLN) in Eastern Africa Country Year Reference Kenya 2012 Wangai et al. (2012 Tanzania 2012 CIMMYT TF Report to Ministry of Agriculture, Tanzania Uganda 2012 G. Asea, Workshop (Nairobi; Feb 12-13, 2013) Rwanda 2013 C. Ngabiyasonga, MLN Training Workshop (Nairobi; 2013) DRC 2014 Kumar , FAO Regional Meeting, Nairobi, 2014 Ethiopia 2014 CIMMYT T-Force Report to Ministry of Agriculture, Ethiopia Next ????
- 27. MLN Transmission Can betransmitted through: 1.Infected seed: reported transmission rates •MCMV = 17/42,000 plants (0.04%) •SCMV = 21/72,897 plants (0.03%) 2. Insects •Aphids (Aphis gossypii, Myzus persicae ) •Corn Thrips(Frankliniella williamsi) •Corn flea beetle (Chaetocnema pulicaria) •Southern corn rootworm (Diabroticaundecimpunctata) •Northern corn rootworm (D. lonicornis) •Western corn rootworm (D. virgifera) •Flea beetle (Systenafrontalis) •Cereal leaf beetle (Oulemamelanopa) 3. Infected soil and plant debris 4. Mechanically
- 28. Corn thrips(Frankliniella williamsi) DESCRIPTIONOF THE PEST Thrips are small insects, about 0.04 inch long. Immature thrips are wingless, whitish to yellowish in color, and are most commonly found in whorls, tassels, ears, or on the underside of leaves. Adults emerge continuously throughout the warm months. Adults and immatures may be found in corn at any time during the growing season. Eggs are deposited in plant tissue and hatching occurs in about 5 days during the summer months; the immature stages take about 5 to 7 days to complete development. DAMAGE Thrips are most noticeable and of greatest concern at two periods during the corn growing season: on young seedling plants and a2t ear formation. On young seedlings their feeding makes the plants look stunted. A common sign of a heavy thrips infestation is distorted leaves that turn brownish around the edges and cup upward. Usually the plants will grow away from the problem, just as they outgrow severe ragging resulting from wind damage. At ear formation, thrips and thrips injury to developing kernels provides entry for infection by Fusarium spp. The actual thrips injury does little damage; however, the ear rot diseases can be devastating. Foliage-feeding thrips are effective predators on early-season spider mite infestations. Both adult and immature thrips may be found in spider mite colonies feeding on spider mite eggs.
- 29. Corn thrips(Frankliniella williamsi) MANAGEMENT Treatmentis usually not necessary on seedlings because plants recover from thrips injury. Thrips are also beneficial at this time because of their role as mite predators. No threshold has been established for damage from thrips at ear formation. Biological Control Minute pirate bugs (Orius tristicolor) play a major role in controlling thrips populations. Cultural Control Thrips populations tend to build up on weeds. Cultivating nearby weedy areas before corn emerges will reduce the potential of a thrips problem when the weeds begin to dry out. Cultivating weedy areas after corn emergence will increase thrips problems.
- 30. Corn flea beetle(Chaetocnema pulicaria Adult The corn flea beetle is a tiny pinhead-sized [1.6 mm) in length black insect with thickened hind legs that enable it to leap considerable distances when disturbed. Flea beetle eggs are deposited on weeds, corn, other cultivated crops, or in the soil near the host plant. Larvae hatch, feed on the roots of plants, pupate in the soil and emerge as adults Damage Badly damage plants appear frosted. The corn flea beetle feeds on corn leaves by stripping away the top layer of plant tissue. This feeding leaves gray to brown lines or "tracks" etched on the leaf surface. Heavily infested plants may appear gray as their leaves shrivel and die.
- 31. Southern corn rootworm (Diabroticaundecimpunctata) larvaego through three instars, or developmental stages, that each lasts seven to ten days. The first instar is less than 1/8 inch in length. By the third instar larva can measure up to 1/2 inch in length. After the larvae have completed the three developmental stages (instars), they will pupate in the soil. The pupal stage is a dormant stage when no feeding takes place. During this stage the larva is developing into an adult.
- 32. Flea beetle (Systenafrontalis) Adult Shinyblack adults are nearly twice as long as With a hands lens and good light, you can see the reddish head. Antennae are light colored near the head and dark near the tips. The enlarged femur on the hind leg allows adults Eggs Pale yellow eggs are laid singly in the soil. Larvae Creamy white larvae have a brown head capsule, three pairs of jointed legs and can get to just under a ½” at maturity. The last body segment has a fleshy upward projection that has hairs on the tip
- 33. Cereal leaf beetle(Oulemamelanopa Adult cereal leaf beetles are about 5-mm long and have metallic bluish-black heads and elytraEggs are about 1-mm. Eggs darken and turn black as hatching approaches. Larvae are yellowish-orange, but this color is usually obscured by a layer of feces and mucus, giving them a shiny appearance. The larval stage passes in about two weeks. Mature larvae burrow into the ground to pupate. Adults emerge about two weeks later, and will feed in small-grain and corn fields for a short time before remaining inactive for most of the summer. Adult feeding in small grains and corn has not been shown to be economically significant and targeting adults
- 34. Corn Leaf Aphid Rhopalosiphummaidis Heavily infested corn leaves may wilt, curl, and show yellow patches of discoloration. When tassels and silks are covered with honeydew, the pollination process may be disrupted. The corn leaf aphid is a blue-green or gray, soft-bodied, spherical insect about the size of a pinhead (1.6 mm) in length]. It has approximately 9 generations per year. Female corn leaf aphids do not lay eggs, as do most other insects, but give birth to living young. These young, called nymphs, resemble the adults except that they are smaller and are sexually immature. Adults and nymphs can often be found clustered within the whorls or upper parts of corn plants over isolated or wide areas of a field.
- 35. Integrated Management of MLN Awarenesscreation to all stakeholders •Policy makers, researchers, extension staff, seed producers and farmers. Use clean seeds •Use certified MLN- free seeds •Grow nurseries in MLN free regions •Regularly send samples for viral diagnostic verification •Treat seed to provide early stage protection against vectors using: Clothianidin (Poncho), Thiamethoxam (Cruiser), Imidacloprid (Gaucho) Imidacloprid + thiodicarb (Aeris)
- 36. Integrated management ofMLN cont. Reduce inoculum level • Maize- free “Break” seasons • Early planting. Plant at the onset of main rainy season • Crop rotation with non-host crops (legumes) • Crop diversification • Scout daily, record, rogue and destroy symptomatic plants • Farm planning –plant first nurseries as far downwind as possible • Weed fields regularly to control alternate weed hosts (esp. grassy weeds)
- 37. Integrated management ofMLN cont. Control spread of the virus •Visit non- infected fields before visiting infected fields •Use farm implements/ machinery in non- infected fields first and disinfect after use. •Avoid unnecessary people and machines in the field Use MLN-resistant varieties. •Screening of maize germplasm for MLN resistance at CIMMYT Naivasha MLN facility Control Vectors •Scout and monitor daily for presence of potential vectors. •Erect insect sticky traps •Apply insecticides 1-2 weeks to control insect vectors •Alternate insecticides molecules and chemistries to prevent insects from developing resistance. •Use appropriate chemical dosage and ensure proper coverage of the crop when spraying.
- 38. Safety measures whileapplying insecticides Use proper PPE’s when spraying •Gloves •Spraying suits •Closed shoes •Spray early in the morning or in the evening when the wind is less •Observe Re-entry periods (REI) after spraying.
- 39. Managing MLN inthe maize seed increase/ Breeding Nursery at Kiboko Maize free period: At least one-month maize free period within 5km radius Seed treatment •Treat seed before planting using Clothianidin (Poncho)/ Thiamethoxam (Cruiser)/ Imidacloprid (Gaucho)/ Imidacloprid + thiodicarb (Aeris) Monitoring of vectors and viral diseases •Daily monitor, record, rogue out, and destroy plants •with viral symptoms •Weekly monitor for vectors (thrips/aphids) Purpose of seed increase and breeding nursery • The source of seed for the next generation • Beginning of large seed increases • The source of seed to be distributed to large areas
- 40. Managing MLN inthe maize seed increase/ Breeding Nursery at Kiboko Control of vectors •Spray the first spray immediately after germination and continue up to physiological maturity •Spray insecticides 1-2 weeks while changing their chemistries over time. Phytosanitary measures by KEPHIS •Regular field inspections by KEPHIS •Testing of seed for MLN by KEPHIS before distribution (DH facility and nurseries) Farm planning •Planting early nurseries far downwind to avoid spread of vectors by wind from old to younger crop Control alternate hosts •Fields weeded regularly
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