[Barrier effect against Bemisia tabaci and the control of tomato yellow leaf curl virus in a tomato-maize...

We examined the barrier effects against Bemisia tabaci and the potential to control the tomato yellow leaf curl virus (TYLCV) of different tomato-maize intercropping modes. Tomatoes (variety Jinshan 511) were planted at a fixed row distance either as a monoculture or together with maize (variety Xianyu 335) at the distances of 10, 20, and 30 cm. We investigated the viral index for TYLCV and the population density of B. tabaci. Compared with tomato monoculture, the natural barrier established by the maize stabilized the growth environment for tomato. When the maize spacing was 10, 20, and 30 cm, the average temperature of tomato plants from 6:00 to 20:00 decreased by 3.01, 2.26, and 1.45 ℃, the average relative humidity increased by 13.0%, 8.8%, and 6.0%, and the mean light intensity reduced by 26.1%, 20.4%, and 14.5%, respectively. The changes of those factors alleviated the adverse environmental conditions (i.e., intense light, high temperature, and lack of moisture) that promote the spread of virus-related diseases during the high-temperature period of the day, with the most effective planting distance for the maize being 10 cm. Our results suggested that the intercropping of tomato and maize had a barrier effect against B. tabaci and was able to control the TYLCV in tomato. When the planting distance for the maize was 10, 20, and 30 cm, the number of B. tabaci was 88.7%, 82.0%, and 73.9% lower than tomato monoculture, respectively. The TYLCV was inhibited, with the viral disease index being decreased by 67.3%, 59.4%, and 44.5%, respectively. Tomato-maize intercropping was also beneficial for tomato plant growth and fruit set, which could enhance tomato yield. Such effect was strengthened under higher maize density.