Rutherglen bugs are sap suckers that can kill perennial seedlings. Tagasaste and other tree / shrub seedlings are particularly vunerable.
Rutherglen bugs are worst in early summer (eg during harvest). There numbers can also build up in autumn if there has been summer rain to promote summer weeds.
Rutherglen bugs are hard to kill and the higher rates of insecticide will be needed. To find Rutherglen bugs you need to get on your hands and knees and look underneath the leaves of radish and cape weed.

Cut worms live between the soil surface during the day and only come to the surface on dusk. Cut worm prefer sandy soils and usually occur in patches. Heavy infestations can kill all plants in areas covering several hectares. Farmers often mistakenly thing that they have a germination / seeding failure as the cut worm wipe out seedlings just as they are emerging. This photo is of the 'pink' cutworm, but they can also be brown or grey. Cutworm are fairly easy to kill. Spray late in the afternoon, just before they come to the surface.