Spotted tentiform leafminer
(Lithocolletis blancardella)
Generally occurring in Europe, generally multivoltine species. Its fourth generation may also evolve upon favourable weather conditions.
Food plant:
Apple, pome, occasionally other fruit trees
Detriment:
The caterpillar consumes the inner leaf tissues by moving in from the underside of the leaf. Its mine has a longish shape, mostly bordered by thicker veins, blistered and wrinkled on the underside. The mine is cambered on the upper side of the leaf, its surface is mosaic spotted. Individual leaves may have more than ten mines.
Lifestyle:
It winters as a pupa, staying in the mines, on the fallen leaves. Depending on the weather, the swarming of the first generation is expected in April-May, the second generation is from the first half of June, peaks from the end of July until the end of August, and it can last until the beginning of September. The times of peak swarming converge and recur in approximately every five weeks. The moths lay their eggs one by one on to the underside of the leaves. The caterpillar hatching out of the egg immediately starts chewing itself in to the leaf.
Recommended protection:
Pheromone traps can collect moths in large numbers, and can thin the population, however, it is common that a strong swarm causes negligible harm, or no harm at all. Therefore it is practical to wait for the hatching of the caterpillars before protecting with pesticides, and decide on the protection accordingly. Mass hatching of the caterpillars is expected usually 10-12 days of peak swarming. Ichneumon wasps significantly thin the population of this pest. Their swarming peaks 1-2 weeks of the time of peak swarming of the spotted tentiform leafminer, therefore spraying is not recommended in this period.
Pheromone trap placement:
The placement is due in the beginning of April. Replace the dispenser and the sticky boards in every week 6-8 weeks.
Check the traps twice a week. Count the number of moths captured in the particular period and note the number. The swarming dynamics are visible from the data and the time of intervention is definable. Should the trap capture too few moths, even at peak swarming time, it refers to low infection. In this case the moths can be captured by placing some further traps in smaller areas and the population can be controlled without spraying, so that we can preserve our environment.
Empirical swarming curve of the spotted tentiform leafminer in Central-Europe:
The introduced empirical swarming curve was prepared by using data of many years, however the swarming may be different depending on the weather and the microclimate of the arable land, therefore the thorough observation of swarming is also important.