Plantwise Factsheets for Farmers
Control vectors of Maize Lethal Necrotic Disease
Bemisia spp., Aphid spp.
Recognize the problem
Maize Lethal Necrosis Disease (MLND)
is a viral maize disease. Leaves of infected plants become yellow from the tip and margins to the centre. Older leaves (bottom of plant) remain
green. Ears and leaves dry up and sometimes look like a mature plant. The
whole plant dies and maize cobs remain without kernels. MLND symptoms can be
confused with symptoms of nutrient deficiency but plants affected by MLND
appear only in some areas and are scattered or clumped in a field while
nutrient deficiency appears on many plants over large
areas of a field.
causes total crop loss and there are no chemical sprays against the disease. MLND
is transported by insects such as aphids which are roundish, soft, green or
black with or without small transparent wings, and planthoppers which look
like tiny cicadas. These insects, which are known as disease vectors,
transmit MLND when they feed on infected maize and then fly to feed on other
maize fields. The disease is more prevalent in the hot season, when vector
populations are high. The control of vectors using contact or systemic
chemicals can prevent disease transmission. Systemic pesticides are
recommended against aphids and planthoppers. These chemicals penetrate the
plant and are taken up by the insects when they suck sap from the plant.
Start to observe your
field 2 weeks after maize emergence
- When 5 to 10 plants become
infected per acre, or when the disease is detected in neighbouring farms, uproot
diseased plants immediately, and consider chemical sprays against whiteflies
- Apply malathion products such
as Mupathion 50EC, Magic 50EC, Severe 50
- All of these are toxic to
you (toxicity class III = slightly hazardous)
- The dosage depends on the
products. It is usually 20-30ml per 20 litre of water but double-check with
- Do not spray 14 days or
less before harvest, and do not enter the field during the 3 days after spraying.
Spray a maximum of twice/season.
- Use thiamethoxam products such
as Actara 25WG, Tromethoxam 25WG. They are also toxic (class III = slightly
- Do not spray 3 days or
less before harvest. Do not enter the field for 1 day after spray. Spray
maximum twice/season in 7 day intervals.
- Spray early morning when
insects are inactive and still on the leaves
- Spray under the leaves and
on the growing tips
not re-use chemical containers/ packets. Dispose of them safely.
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.
The recommendations in this factsheet are relevant to:
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