Glue barriers reduced the density of tomato russet mites on plant stems in a commercial interplanted tomato crop, but did not prevent leaf damage

Abstract: Upward movement of the tomato russet mite (Aculops lycopersici Tryon) along
tomato stems can be reduced by stem barriers. We tested the effect of weekly/biweekly applied insect glue barriers on mite numbers and leaf damage in a 0.5 ha commercial tomato greenhouse with layered cropping method and interplanting that effectively ensures infestation of new seedlings before old plants are removed. The experimental design was a split-plot-with-repeated-measures structure. Mites were sampled and leaves with symptoms assessed from four plants in the middle of the experimental plot. Glue rings were applied at the level of the newest flowering cluster, and tape imprints (1 × 2 cm) were taken from above the uppermost glue ring and the ring at the level of the 5th cluster every 2-4 weeks for 3 months. The glue barriers reduced mite numbers per tape on all sampling times with an efficacy of over 90 % at both heights, but with no effects on the proportion of plants with browned leaves, number of browned leaves per plant, in the lower parts of the plants (height measured as the number of fruit cluster internodes with one or more russeted leaves) nor distribution of leaves among three severity classes of damage. Whether the reduction of mite numbers on the stems is reflected in the yield must be studied to understand the feasibility of the method due to practical challenges of its application. Interplanting creates very heavy infestation pressure for the new crop which likely explains that no reduction in leaf damage took place in the study. Placing the barriers below leaves should be investigated to see if mite movement from stems to leaves can be reduced.