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Factsheet on American leafminer
Adult moths on a leaf Enlarged size of adult moth Adult moth with eggs Caterpillar on a leaf
Fully damaged tomato leaf Caterpillar burrowing
on tomato fruit
Green fruits, no
foliage leading to
immature fruits
No fruit harvest
in the long run

The pest adult is a moth, meaning that it is active at night. It will thus lay eggs mainly at night. The moth is almost same size and posture as diamondback moth when looked at a distance. The larva (caterpillar) is the damaging stage.

Pest Category 
This is a new pest in Kenya. It was first reported in Isiolo in 2014 but now has spread to most parts of Kenya. It has been confirmed present in counties: Nairobi, Meru, Kirinyaga, Kakamega, Lamu, Kajiando, Kitui, Machakos, Nakuru, Narok, Elgeyo Marakwet, Laikipia and Embu. Likelihood of presence in neighbor counties is high and shall be confirmed.

The caterpillar burrows (mines) in the middle of leaf tissue. However, it does not feed like the other leafminers, which are flies. It feeds indiscriminately, from a distance you see leaves are ‘burning’.

It bores on fruits, leaving symptomatic tiny holes. These are very small compared to those caused by the African bollworm (Helicoverpa armigera). It also burrows on stems, causing breakages.

Conditions prevailing that contribute to success 
High use of synthetic pesticides will result to resistance build up; leaving plant debris in the field; continuous cropping of tomato and other solanaceous crops such as potatoes

Control Strategy 
1. Pheromone traps: These will trap males, reducing males available for mating with females. This will result to females laying unfertilized eggs resulting to no caterpillars. Some contacts for pheromones in Kenya (Kenya Biologics, 0710724629)

2. Sticky traps: there are black sticky traps that are effective on both male and female adults. Some contacts in Kenya (Koppert Kenya, 0723-144-690)

3. Chemicals: Pesticides registered for leaf miners such as Corragen, proclaim, radiant may be effective but these have not been tested on this pest, therefore use with care. There are on going trials to test efficiency of pesticides against the pest. This pest is known to develop quick resistance against pesticides. Avoid using same active ingredient (a.i.) more than 3 times in a season.

4. Cultural practices: remove damaged leaves and burn them. Dead plant tissues should be burned to break the pest life cycle, hence reduce its population

5. Crop rotation: avoid relay cropping and rotate with other crops of different families, e.g. French beans, cabbages etc. Also farmers in an area can agree to grow tomatoes on given season only to break the cycle of the pest.

Mode of spread 
1. Flying: the pest is a flyer and may infest many farms by flying to new farms
2. Fruits: the movement of tomato fruits in different parts of the country could be the number 1 cause for the pest spread in Kenya. The pest may move as eggs or caterpillar
3. Leaves and stems: infested plant material especially for fodder

Mandate Centres Kabete, Thika

Reference Links – book, journal paper, magazine, brochure, bulletin, fact sheet, web etc 

 Geographic Coverage
The pest has been reported in the yellow highlighted counties but this will expand after a full country survey. The border counties are likely to have the pest

Tomato Leafminer (Tuta absoluta)

Expert (s) Name  Dr. Muo Kasina, Miriam Otipa and Dr. Lusike Wasilwa

Expert Contact Details

Date last modified: 13th November 2014