Gaucho

Grass grub (Costelytra zealandica) is the larval stage of the bronze beetle and is found throughout New Zealand from Southland as far north as Waikato. Grass grubs feed on the roots of pasture and autumn planted cereals and can cause extensive plant death if not controlled. Grass grubs have three larval instars and each one is capable of causing damage but the third instar, which is usually between February and spring, is the most damaging. Not all the larvae at their largest but this also coincides with plant establishment. The treatment threshold for grass grub is two grubs per spade square. Well before sowing, take a garden spade and dig ten sample squares to the depth of the spade blade in a diagonal across the paddock. Sift through the soil and if an average of more than two grubs per sample is found treat with an effective seed treatment.

Argentine Stem Weevil (Listronotus bonariensis), often referred to as ASW, is a small weevil from South America that is now found throughout New Zealand. Adult stem weevils are hard to detect by eye being only 3.5mm long. Larvae feed in the developing shoots of many important crops including pasture, maize, sweetcorn, cereals and brassicas and it is the larvae that are responsible for the tremendous economic losses attributable to ASW in New Zealand each year. Depending upon the weather experience ASW can complete multiple life cycles each year with egg laying taking place between July and March.

The brassica or common springtail is one of several springtails that feed on brassicas causing economic damage by reducing plant establishment. Brassica springtails are tiny at around 1.00 mm and are difficult to find. They live on the soil surface, laying eggs in the soil and as each lifecycle is rapid several generations can occur each year.