Cereals such as wheat, oats and barley are important grain crops in Canterbury. Arable crops are often grown as a feed supplement for pasture-fed stock and include maize, winter oats and a range of brassicas such as kale, rape and turnips. Brassicas are affected by the same pests that affect horticulture crops.
Maize is widely grown in the northern North Island, where pests that attack ryegrass, such as African black beetles and Argentine stem weevils, can also do considerable damage to young maize plants.
The greasy cutworm (Agrotis ipsilon) severs young maize shoots at their base. These pests are generally controlled by an insecticide coating around seeds to protect plants as they get established.
Several aphid species are common pests of cereal crops. By sucking sap, aphids can stunt and distort plant growth. But they cause most damage as transmitters of barley yellow dwarf virus and cereal yellow dwarf virus. Associated crop losses have been estimated to cost Canterbury growers $3.7 million annually.
The wheat bug (Nysius huttoni) is a common insect that infests a range of crops. In wheat, it pierces the grain and sucks out the nutrients. In the process it injects an enzyme, which causes dough made from the wheat to become sticky and of poor quality.