Observation and restriction of Aculops lycopersici dispersal in tomato layer cultivation

The tomato russet mite Aculops lycopersici has become a challenging pest in tomato production in the EU. The number of
available acaricides is low, and the efficacy of biological control is limited. With this study, we aim to understand better the
unhindered dispersal dynamics and develop a method to reduce dispersal on plants.
To better understand the dynamics of A. lycopersici dispersal in layered tomato cultivation under practical conditions, a
first trial was carried out. The trial confirmed that first A. lycopersici symptoms in practical cultivation usually occur in the
lower or the middle third of tomato plants and then move upwards on plants. It was observed that plants, for a limited period
of time often are able to grow new healthy leaves in the same pace as existing leaves, mostly in the lower and middle part
of the plant are damaged by A. lycopersici. This is possible due to the fast growth rate of hybrid tomato varieties in layer
cultivation. To test if the observed effect can be supported by further slowing down the upwards movement of the pest, a
second trial was conducted. Here, the stems of inoculated tomato plants were blocked weekly for A. lycopersici by applying
a ring of insect glue 15 cm below the tip of the plants. This stem blockage severely impaired the only active dispersal mode
of A. lycopersici: walking. The growth of new plant material, when the method is applied, is able to exceed the speed with
which A. lycopersici destroys plant material in layered tomato cultivation. This resulted in significantly less plant damage
and prevented fruit damage on all treated plants. The approach of manipulating the plant stem and thereby restricting the
movement of the mite on tomato plants could potentially be exploited for plant protection purposes under practical conditions.