Leaf colour has been proposed to signal levels of host defence to insect herbivores, but we lack data on herbivory, leaf colour and levels of defence for wild host populations necessary to test this hypothesis. Such a test requires measurements of leaf spectra as they would be sensed by herbivore visual systems, as well as simultaneous measurements of chemical defences and herbivore responses t...

The cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae), is a perennial pest that specializes on plants of the Brassicaceae family, attacking winter canola (Brassica napus L.) mainly during and after flowering. Under field conditions, cabbage aphid colonizes the upper flowering canopy. Population dynamics of aphids in the flowering canopy could be regulated by differences in either p...

cabbage aphid (brevicoryne brassicae l.) is a important pest of canola (brassica napus l.) throughout the world, and as the host plant resistance is considered as a useful method to control the pest, therefore twenty one genotypes of canola were evaluated from the view point of their resistance to cabbage aphid infestation in a randomized complete block design with three replications and under ...

Resistance of four brassica leafy vegetables: kale, Chinese cabbage, rape and Ethiopian mustard to cabbage aphid, Brevicoryne brassicae (L.) was studied in cage experiments at the Botswana College of Agriculture, Gaborone, Botswana. A completely randomised design with cultivars as treatments and four replicates per treatment was used. One newly laid nymph was placed on each of the four potted p...

Outbreaks of clubroot disease caused by the soil-borne obligate parasite Plasmodiophora brassicae are common in oilseed rape (OSR) in Sweden. A DNA-based soil testing service that identifies fields where P. brassicae poses a significant risk of clubroot infection is now commercially available. It was applied here in field surveys to monitor the prevalence of P. brassicae DNA in field soils inte...