Damage from corn pests and diseases is on the rise in China
In recent years, China's corn planting area has steadily increased. In 2014, China's corn planting area reached 553 million mu, making it the grain crop with the largest planting area in China. With the adjustment of planting structure, changes in cultivation techniques, and the replacement of new varieties, obvious changes have taken place in corn pests in China, mainly showing the following characteristics.
Many species and a large area
In China, there are more than 50 species of corn pests that cause economic losses, and more than 20 species of frequently occurring pests. The area damaged by corn pests has been on the rise. In 2014, the area affected by corn pests in China was 837 million mu, the control area was 782 million mu, and 12.51 million tons of losses were recovered, but 3.98 million tons were still lost.
Damage from frequently occurring pests has worsened
⟦NL> Damage from the Asian corn borer, soil pests and others has worsened. The Asian corn borer is the most important pest in corn production, and in recent years the damage from the Asian corn borer has shown an upward trend. In 2014, the affected area of the Asian corn borer in China was 353 million mu-times, mainly concentrated in Northeast China, North China and the Huang-Huai-Hai region, among which some areas in Liaoning, Heilongjiang, Hebei and other provinces reached severe to outbreak levels.
The main soil pests in corn fields in China include white grubs, mole crickets, wireworms, cutworms, stem borers and the two-spotted maize armyworm. Since 2008, damage from soil pests such as white grubs, mole crickets, wireworms and cutworms in corn fields has increased. In 2014, the affected area of soil pests in corn in China was 112 million mu-times, including 44.78 million mu-times of white grubs, 27.68 million mu-times of cutworms and 24.15 million mu-times of wireworms. The affected areas are mainly in eight provinces (regions) in Northeast China, North China and Northwest China, among which Liaoning, Shanxi and other provinces had severe occurrence.
Some secondary pests and newly emerging pests cause severe damage
Peach fruit borer: it originally occurred only sporadically, but in recent years it has occurred commonly, especially with relatively severe occurrence in Anhui, Shandong and Shaanxi provinces.
Two-spotted leaf beetle: in recent years, the occurrence of the two-spotted leaf beetle has become noticeably more severe. Originally the two-spotted leaf beetle was a pest of vegetables and oil crops and rarely damaged corn. In recent years it has occurred relatively severely in the northern spring corn region of China, the Huang-Huai-Hai summer corn region and some areas of Shaanxi.
Two-spotted maize armyworm: with the promotion of no-till and stubble-seeding cultivation techniques after wheat harvest, the damage from the two-spotted maize armyworm has expanded year by year. In 2014, the affected area of the two-spotted maize armyworm in China reached 15.16 million mu-times.
Because spring corn in Northeast China has been continuously cropped over large areas for many years, the main production areas in the Huang-Huai-Hai region adopt planting patterns such as wheat—corn rotation, relay cropping and mixed cropping of spring and summer corn. In addition, measures such as dense planting, no-till, straw return and cross-regional mechanical operations are commonly adopted in various places, providing a favorable living environment for pest outbreaks and favoring the accumulation, spread and diffusion of corn pest sources. At the same time, corn varieties in most areas have poor pest resistance, and if suitable climate conditions occur, the Asian corn borer, soil pests and others will occur severely.
As the corn planting area continues to increase, the Asian corn borer will continue to occur severely to outbreak levels in the northern spring corn region, and the situation of moderate to moderately severe occurrence of the Asian corn borer in the Southwest region will continue. In the Huang-Huai-Hai summer corn region, the large-scale implementation of straw return has reduced the overwintering population of the Asian corn borer and reduced the area of spring-sown hosts, so the population of the first generation of the Asian corn borer will decrease. However, the summer corn area is large, damage from the generation during the summer corn whorl stage is light, and control is seldom adopted, so the Asian corn borer of the generation during the ear stage will still maintain a moderate occurrence situation.
Changes in tillage methods and the promotion of no-till and shallow tillage techniques have protected the habitats of soil pests, increasing soil pest populations. Damage from white grubs, cutworms, wireworms, mole crickets, stem borers, corn ground mealybugs and others will show a worsening trend. The future damage range of the two-spotted maize armyworm will continue to expand, becoming a frequently occurring seedling-stage pest of summer corn. Apart from relatively severe occurrence in some areas of Hebei, Shandong, Henan and other provinces, a large-scale outbreak is unlikely in the near future.