Covering the soil between rows: Aphid ecology, canopy reflectance and crop growth in broccoli/legume living mulches

A living mulch is an intercropping system in which annual crops are planted directly into established cover crops. Living mulches have been studied as to their effect on main crop aphid populations, yet no studies have field tested the possible mechanisms responsible for differential alate aphid colonization nor looked closely at how living mulches affect aphid population dynamics.;Results show that abundance of both aphid species is lower on broccoli in living mulches compared to broccoli with no cover crop. Myzus persicae had higher population growth rates in the living mulches, which was attributed to lowered parasitization of M. persicae by Diaretiella rapae in the living mulches. Levels of B. brassicae infestation in harvested broccoli heads were lower in the living mulches, and was lower in the synthetic fertilizer (high nitrogen) treatment. There is some indication that water stress may contribute to higher levels of infestation.;Intensity of light reflectance from the crop canopy was reduced by the presence of cover crop for all spectral wavebands except the blue. Broccoli crop growth (increased main crop cover) decreased light intensity from the blue-green, yellow and orange wavebands in the absence of cover crop. Alate aphid abundance was lower in the living mulches and this appeared to be associated with canopy spectral reflectance properties. Myzus persicae alate abundance was positively correlated with energy reflected from the yellow waveband and negatively correlated with broccoli crop cover.;Crop performance was not negatively affected by the presence of cover crop, although fertilizing with compost severely reduced broccoli growth and yields. Comparison of living mulches in the two fertilizer treatments indicate that nitrogen is not the limiting factor in the competition between main crop and cover crop. Adequate water, light and subsoil aeration may be more important factors in maintaining yields in living mulches comparable to conventional cropping.;Living mulches were established by transplanting broccoli into different leguminous cover crops and were compared to broccoli grown without interrow cover under two fertilizer treatments. The aphids Myzus persicae and Brevicoryne brassicae were sampled, light reflectance above the crop canopy was measured and broccoli growth parameters and yields were recorded.