Download South African Maize Leafhopper - Plant Biosecurity Toolbox

Diagnostic Methods
for
South African Maize Leafhopper
Cicadulina mbila
This Diagnostic Protocol can be constantly updated and is only correct at time of printing (Thursday
8th of June 2017 at 03:34:32 PM).
The website http://www.padil.gov.au/pbt should be consulted to ensure you have the most current
version before relying on the information contained.
Introduction
Cicadulina mbila appears to be the most important vector of maize streak virus (MSV) in East Africa
and recent studies show it is the most abundant vector across major ecological zones. Leafhopper
vectors may either move within the crop, migrate from maturing crops, or move from perennial
alternative hosts.
C. mbila can acquire MSV from infected plants within 15 seconds and inoculate it within 5 minutes.
Biology
Stages of Development
Eggs are laid in plant tissue by the female, and the development period is 5 - 6 weeks (in East
Africa). The adult is a tiny leafhopper, 2 - 3 mm in length, with transparent wings bearing a brown
longitudinal stripe. Head, thorax and abdomen are mainly yellow with dark brown markings on the
dorsum. The eyes are dark brown.
Adults may be found at rest on the upper surface of young maize leaves forming the terminal cone of
the plant. Field densities have been recorded as high as one leafhopper per 20 maize plants, but this is
unusually high.
The leafhopper exists in 2 forms (biological races) - an 'active' form capable of virus transmission,
and an 'inactive' form which is incapable of transmission. The active form becomes infective 24 hours
after feeding on a diseased plant, and will remain so for up to several months (Hill, 2008).
Host Range
Maize is the main host. Alternative hosts include sugarcane, wheat, millets and various wild grasses.
Distribution
East and West Africa, Zimbabwe, South Africa, Yemen, Uganda, Kenya, Tanzania, Reunion.
Effect
Sucks the juices from leaves. Its main damage to the plant is to infect it with Maize Streak Virus
which causes yellow streaks to appear on the leaf on either side of the main vein. Damage is
generally to plants younger than 6 weeks.
Attacked plants show no signs of insect damage, but the Streak Virus symptoms are conspicuous
yellow streaking against the normal green of the leaf.
Research into the Maize Streak Virus (MSV) destroying Africa's most important food crop has thrown
light on the strain's emergence and its rapid spread across the continent. According to University of
Cape Town researchers, MSV has descended from relatively harmless wild grass affecting strains by
a process called recombination. In this process, genes are selectively exchanged between the strains
making the offspring more powerful. Two grass adapted MSVs recombined over the years to produce
the present-day "wide-host range" strain that can infect maize severely and survive harsh weather
conditions more effectively than its parents.
Transmitted by leafhoppers (Cicadulina mbila), major symptoms include severely dwarfed cobs and
yellowing. More tests are required to develop resistance strategies, said the study.
Risk Analysis
Entry Potential
Low; most likely to enter via infested plant material. (Plant Health Australia, 2004b)
Establishment Potential
High (Plant Health Australia, 2004b)
Spread Potential
High (Plant Health Australia, 2004b)
Taxonomy
Classification
Kingdom Animalia
Phylum Insecta
Order Homoptera
Family Cicadellidae
Genus Cicadulina
Species mbila
Name and Synonyms
Common Name:
African corn leafhopper
Maize leafhopper
Synonyms:
Balclutha mbila (Naudé)
Detection
Symptom Description
Maize Streak Virus (MSV).
The disease, reported first from East Africa, has now extended to many other African countries. The
virus is transmitted by Cicadulina spp. leafhoppers. Cicadulina mbila (Naude) is the most prevalent
vector, and will transmit the virus for most of its life after feeding on an infected plant. Early disease
symptoms begin within a week after infection and consist of very small, round, scattered spots in the
youngest leaves. The number of spots increases with plant growth; they enlarge parallel to the leaf
veins. Soon spots become more profuse at leaf bases and are particularly conspicuous in the youngest
leaves. Fully elongated leaves develop a chlorosis with broken yellow streaks along the veins,
contrasting with the dark green color of normal foliage (see Figures 1, 2 & 3 below). Severe infection
causes stunting, and plants can die prematurely or are barren. Many cereal crops and wild grasses
serve as reservoirs of the virus and the vectors (The CIMMYT Maize Program, 2003).
Symptom Images
Figure 1. Cicadulina mbila is a vector of maize streak geminivirus. Viral symptoms on maize plant
are shown. Photo: Astri Wayadande, Oklahoma State University.
Figure2. Maize streak virus symptoms. Photo: The CIMMYT Maize Program.
Figure 3. Close-up of maize streak virus symptoms. Photo: The CIMMYT Maize Program.
Identification
Morphological Methods
Figure 4. Adult Cicadulina mbila. Photo: Astri Wayadande, Oklahoma State University.
Figure 5. A. Male pygofer, lateral aspect; B. aedeagus, internal aspect; C, aedeagus ventral aspect;
D, right style, dorsal aspect; E, female seventh sternum, ventral aspect. From: Nielson, 1968.
Further Information
Contacts
If you have further information about this pest and would like to post it on this site, or would like to
amend or correct any information currently displayed, please contact:
Gary Kong
Principal Plant Pathologist
Plant Science, Delivery
PO Box 102 Toowoomba
Qld 4350
Ph: 61+7 4688 1319
mob: 61+ 428103521
Email: [email protected]
References
Distribution Map: CAB International, Nosworthy Way, Wallingford, Oxfordshire, OX10 8DE, UK.
www.cabi.org/datapage.asp?iDocID=778
Hill, D.S. (2008). Pests of Crops in Warmer Climates and their Control.
http://books.google.com.au/books?id=U5dezH9_eEMC&pg=PA172&lpg=PA172&dq=cicadulina+
mbila&source=web&ots=wNWkerqqDT&sig=wb0QC1be2lc4rd0jGKEdsPEednM&hl=en&sa=X&
oi=book_result&resnum=1&ct=result
Nielson, M.W., (1968). The leafhopper vectors of phytopathogenic virises (Homoptera, Cicadell).
Taxonomy, biology and virus transmission. Tech. Bull. U.S. Dept. Agrric. No.1382, 386 pp.
Wavadande, Astri. Leafhopper vectors of plant pathogens - powerpoint presentation.
http://diagnostics.montana.edu/GPDN/IVDW/Leafhopper%20Vectors%20of%20Plant%20Pathogen
s.pdf
Other useful websites:
Plant Health Australia. National Sugar Industry Biosecurity Plan, Version 1, June 2004a
http://www.bses.org.au/pdf/sugar_biosecurity_plan.pdf
Plant Health Australia. National Sugar Industry Biosecurity Plan, Version 1 June 2004b Threat
Identification, Pest Risk Analysis, and Incursion Management Funding Arrangements.
http://www.planthealthaustralia.com.au/sugar/threat_id/threat_id_pdfs/threat_id.pdf
The CIMMYT Maize Program (2003). Maize Diseases: A Guide for Field Identification. 4th edition
http://www.cimmyt.org/english/docs/field_guides/maize/pdf/Maizediseases.pdf