The microclimate of corn and bean cropping systems: Its relationship with Dalbulus maidis, some aphids, and the diseases they transmit

Different vegetated surfaces create their very own microclimates. Mixed cropping systems rather than monocultures constitute a traditional planting technique in the tropics, and it has been observed that mixed crops are usually less prone to damage from pathogens carried by insects than monocultures. Microclimatic differences between crops are thought to be partly responsible.; The microclimate of corn and bean crops, planted at different combinations and densities, was studied in this research and related to the activity of some insects: aphids and a leafhopper, Dalbulus maidis; and to the diseases transmitted by these insects: bean common mosaic virus, corn stunt spiroplasma, maize bushy stunt mycoplasma and maize rayado fino virus. The location for the experiments was Costa Rica, in the tropics.; Some microclimatic characteristics differed among cropping systems, particularly wind and temperature profiles above the canopy, but differences were not always significant. It is suspected that the small size of the plots was responsible for the lack of differentiation among cropping systems. Under such circumstances, wind speed and the rainfall annual cycle were the only environmental parameters that appeared to influence the number of aphids landing over the crops. Microclimatic conditions inappropriate for aphid flight are most likely to occur in high density foliage mixed crops, landings over these crops were always among the lowest. The numbers of Dalbulus maidis were usually largest in the traps over corn in monocultures, but this preference could not be attributed to microclimate.; There seems to be a relationship between D. maidis directional flight displacement and wind direction, but it could not be clearly defined because the measurement schedule of insects and wind direction were not appropriately coordinated.