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Trans-boundary Plant Pests
and Diseases
in the SADC region
Tomato leafminer:
ScientificName: Tuta absoluta (Meyrick)
Taxonomic Tree
•Domain: Eukaryota
• Kingdom: Metazoa
•
Phylum: Arthropoda
•
Subphylum: Uniramia
•
Class: Insecta
•
Order: Lepidoptera
•
Family: Gelechiidae
•
Genus: Tuta
•
Species: Tuta absoluta
Scouting Guide: Description
Egg:
The eggs are elliptical, and their colour varies from oysterwhite to bright yellow, darkening in the embryonic phase and
becoming almost black near eclosion.
Larva:
The first-instar larvae are whitish soon after eclosion,
becoming greenish or light pink in the second to fourth
instars according to food (leaflet or ripe fruit, respectively).
There are usually four instars.
Pre-pupa
• The pre-pupae are lighter than the feeding larvae (first to
fourth instars) and develop a distinguishing pink colouration
on the dorsal surface.
• They leave the mines and build silk cocoons on the leaflets
or in the soil, according to habitat.
• When pupation occurs inside mines or fruit the pre-pupae
do not build cocoons.
Pupa
• Pupae are obtecta with greenish coloration at first, turning
chestnut brown and dark brown near adult emergence.
Adult
• Adult moths are about 10 mm long, with silverish-grey
scales, filiformantenae, alternating light or dark segments and
recurved labial palps which are well developed.
Hosts/Species Affected
•T. absoluta feeds almost exclusively on tomato (Solanum
lycopersicum) and there is also some reports that it feeds on
potato (Solanum tuberosum).
•Other Solanaceae reported as hosts for T. absoluta, besides
tomato, include the wild species Solanum nigrum, S.
elaeagnifolium, Lycopersi conpuberulum, Datura stramonium,
D. ferox and Nicotia naglauca
Growth Stages
•Flowering stage, Fruiting stage, Post-harvest, Seedling
stage, Vegetative growing stage
Detection and Inspection
•T. absoluta is easily found on tomato apical buds,
flowers or new fruits.
•When there is a severe attack it colonizes the leaves
on the other parts of the plant.
•Mines are evident on attacked leaves.
Symptoms
 Fruit: abnormal shape, visible frass,
internal feeding, exit hole premature drop
nd reduced size
 Growing point: dead heart, distortion,
visible frass, internal feeding,and lesions
 Inflorescence: external feeding, fall of
shedding, visible frass and internal
feeding
 Leaves: abnormal forms, external
feeding, visible frass, internal feeding and
rolled od folded leaves
 Stems: dead heart, die back, witches
broom, distortion, internal feeding, visible
frass and wilting
 Whole plant: dead heart, distortion,
visible frass, internal feeding, dieback
and dead plant
Prevention and Control
Cultural Control
•Ploughing, manuring, irrigation, crop rotation, solarisation,
and the elimination of symptomatic leaves and destruction of
infested tomato plants have all been used to control this pest.
•The removal of alternative reservoir hosts is strongly
recommended before and during the cropping cycle.
• In greenhouses, one of the management tactics used to
reduce the initial level of populations is to keep infested
greenhouses closed after harvest to prevent the migration of
adults to open-field crops.
Semiochemicals
•Pheromone traps are considered as the first line of
defence against this moth both in open fields and in
greenhouses as they are used for monitoring and male
annihilation, mating disruption.
Inherited sterility (sterile males)
•Inherited sterility programs which involve releasing
irradiated sterile males was recently proposed as a
possible method for control of this moth..
Chemical Control
• The most common method of controlling T. absoluta is the
application of insecticides, usually pyrethroids and
carbamates and organophosphates.
• However, these insecticides are of low to moderate
effectiveness.
• In addition, several cases of insecticide resistance have
been reported including resistance to organophosphates,
pyrethroids, abamectin.
Biological Control
•Several bio-control agents are used to control the tomato
leaf miner in open field and greenhouse tomato cultivation.
•The most common predators are the mirid bugs
Nesidiocoris tenuis and Macrolophus pygmaeus.
•Bacillus thuringiensis(Bt)-based insecticide formulations
have been used to control T. absoluta.
•Entomopathogenic nematodes Steinerne mafeltiae have
been tested for the management of T. absoluta.
•Several fungal species including Metarhizium
anisopliae and Beauveria bassiana are reported to attack the
eggs, larvae and adults of the pest.
Host-Plant Resistance
•Host-plant resistance is being explored by developing
tomato accessions with high zingiberene and/or acylsugar
contents that result in low ovipostion rates and larval feeding
of T. absoluta.