The Plant Health Directorate has told tomato growers about the importance to continue following preventive steps for an effective control strategy against the tomato leafminer moth, Tuta absoluta, a harmful leafmining moth with a strong preference for tomato but which can also attack other solanaceous plants.

Tuta absoluta can reproduce very rapidly. One female may lay up to 260 eggs during her life which are deposited on the aboveground parts of the plant. The caterpillar lives as a miner in the leaf, stem or fruit but usually exits the mine to pupate. Larger caterpillars can sometimes be found outside the mine or fruit. Pupation may take place in the soil as well as on the surface of a leaf, in a curled-up leaf or in a mine. The moths are active during the night and hide between the leaves at daytime.

For an effective control strategy against the pest, the following should be kept in mind.

The areas where tomatoes are grown in fields and greenhouses devoid of netting in Malta and Gozo, should have properly installed and maintained pheromone traps for the mass trap monitoring of Tuta absoluta. In the case of such greenhouses, these should have installed pheromone traps or other mass trap device on the inside and should also have installed pheromone traps around the greenhouse, on the outside as instructed in Government Notice No. 232 of 2010, Guidelines/instructions for growers for the control and containment of Tuta absoluta.

Greenhouses equipped with adequate netting should have pheromone traps installed around the greenhouse, on the outside. Although not obliged, such persons are still encouraged to install pheromone traps inside greenhouses equipped with adequate netting, as well.

For mass trap monitoring, traps should be placed according to the label instructions of pheromones and should be positioned not more than one metre above ground level, and should be distributed uniformly in the greenhouse or field. Any means of mass trap monitoring, should keep on being used for at least 15 days after harvesting.

Pheromone traps should be monitored regularly, and the approximate number of adult moths captured should be recorded and removed once a week and recorded as per Schedule 1 of Government Notice No. 232. Pheromone lures should be replaced periodically as per label instructions.

Tomato plants infected with Tuta absoluta should be treated with the appropriate insecticides which are registered by the national competent authority for use on tomatoes against the pest. Appropriate records of pesticide used should be kept as per Schedule 2 of Government Notice No. 232.

When the level of infested tomato plants exceeds the 50% damage level of the interested cultivated area the grower shall communicate the findings either with his PO/PG/COOP or directly to the Plant Health Directorate if he is not associated with any organisation representing him.

Any post-harvest tomato plant material, whether infected or not, should be destroyed. No tomato plant material should be left in fields or opened greenhouses, but should be destroyed as soon as possible, and not later than 72 hours from harvesting of the plant material. Tomato growers should keep a record of the control measures carried out on tomato cultivated areas, against Tuta absoluta.

Other control methods include cultural practices such as rotation with non-solanaceous crops, ploughing, adequate fertilisation and irrigation.

For further information, one can contact the Plant Health Directorate on 2292-7106, or freephone 8007-2310. One can also visit the website www.planthealth.gov.mt