Nematodes against
BIOLOGICAL CONTROL OF TOMATO LEAFMINER
The tomato leaf miner (Tuta absoluta) is a highly specialised pest that threatens tomato crops worldwide. Originally native to South America, the moth has spread through international trade to many regions of the world, including Europe, Africa and Asia. Due to its rapid multiplication and ability to cause damage to tomato plants at every stage of growth, it poses a major challenge to tomato producers.
LIFE CYCLE OF THE TOMATO LEAF MINER
The tomato leaf miner goes through four stages of development, which differ greatly in appearance and behaviour: Egg, larva, pupa and adult stage. The entire life cycle takes 24 to 38 days, depending on the temperature, which can lead to several generations per year.
1. egg laying
The females lay their tiny, creamy white eggs individually or in small groups on the leaves, stems or fruit of tomato plants. A female can lay up to 150-250 eggs in her short life.
2. larval stage
After 4 to 6 days, the larvae hatch, initially cream-coloured and later greenish-yellow. The larvae feed on the leaves, stems or fruit of the tomato plants and leave behind characteristic miner's tunnels or feeding sites. They cause the most damage in this phase.
3. pupation
After 12 to 15 days, the larvae pupate either in the soil or on the surface of the plant. The pupae are greenish at first and turn brownish in colour.
4. adult stage
The adult moths are small (approx. 6-7 mm) and have silver-grey wings with black spots. They are nocturnal and mate shortly after hatching, starting the life cycle all over again.
Tuta absoluta larva on the leaf of a tomato plant
DAMAGES CAUSED BY TUTA ABSOLUTA
The tomato leaf miner mainly attacks tomato plants (Solanum lycopersicum), but can also damage other nightshade plants such as potatoes, aubergines and peppers. The larvae cause considerable damage by nesting in leaves, stems and fruits. Typical symptoms are
- Mining tunnels in the leaves, which greatly reduce photosynthetic performance.
- Feeding spots in fruits that make them impossible to market.
- Secondary infections caused by invading pathogens.
An untreated infestation can destroy up to 100% of the harvest, especially in protected cultivation systems such as greenhouses, where the conditions for the moths are optimal.
Typical feeding marks of the larvae on the leaves
CONTROL TOMATO LEAFMINER WITH BENEFICIAL NEMATODES
Nematodes of the species Steinernema carpocapsae and Steinernema feltiae can be used effectively against the larvae of the tomato leaf miner. The application rate is 1 million nematodes per litre of spray liquid with 1,600 litres of water per hectare.
Trials at the Julius Kühn Institute have shown that additives can increase the effect
by up to 15 %. Xanthan and chitosan were the most effective.
The nematodes are stored in a natural carrier material and are simply mixed with water and applied. They can be mixed with many other active ingredients. A detailed overview of the miscibility of nematodes can be found here.
Miscibility of nematodes
Nematodes of the species Steinernema carpocapsae