Short Communication |
Corresponding author: David Hunter ( davidmhunter100@gmail.com ) Academic editor: Corinna S. Bazelet
© 2017 Long Zhang, David Hunter.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Zhang L, Hunter DM (2017) Management of locusts and grasshoppers in China. Journal of Orthoptera Research 26(2): 155-159. https://doi.org/10.3897/jor.26.20119
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Locusts and grasshoppers are major economic pests in China and are controlled by a strategy of preventive management where about 1.5 million ha are treated each year. The preventive management system aims to keep locusts and grasshoppers at lower densities, so that the dense swarms seen in the past are no longer common and crop and pasture damage minimized. There is substantial cultural control, including conservation of natural enemies and reducing the area of favorable habitats through habitat modification. Even with substantial cultural control, locust and grasshopper infestations are still widespread, with 127 field stations having more than 2000 technicians involved in monitoring and control. These officers monitor and treat locust and grasshopper infestations and the data collected are integrated into a national computer-based platform. These data are analyzed and news bulletins are issued on where and when the densest infestations are likely to be so that extra resources can be provided when needed as part of coordinating an effective locust and grasshopper management program. In the past, treatments were by chemical pesticides, but in recent years there has been an increasing use of bio pesticides: namely, the naturally occurring fungus Metarhizium acridum and the microsporidian Paranosema locustae. While such products were used in only 5% of treatments during 2004, their use has increased to over 30% in recent years, which amounts to over 100,000 ha per year sprayed. These applications of bio pesticides against locusts and grasshoppers are more than all of the rest of the world combined.
biological control, habitat modification, history, information platform
Locusts and grasshoppers are serious pests to crops in many areas of the world and can cause serious economic loss (
There were many ancient poems describing locust outbreaks and their control such as one by Juyi Bai during the Tang dynasty:
“Locust outbreaks distributed widely in the center,
Eating like silkworms and flying like rain.
Green crop shoots disappear,
Only black soil left for thousands of miles,
Governors worried about yield,
Demand that people catch locusts day and night.”
Migratory locusts, Locusta migratoria (Linnaeus, 1758) are serious pests in a number of regions in China (Fig.
Locusts and grasshoppers | Distribution | Range in area infested/year (millions of ha) |
|
Locusts | Locusta migratoria | 17 provinces, ~290 counties |
1.5–3.0 |
Grasshoppers in agricultural lands | 900 species in total, 60 spp. economically important |
18 provinces, ~500 counties |
4.7–7.0 |
Grasshoppers in grasslands | 800 species in total, 50 spp. economically important |
13 provinces, ~300 counties |
12.0–18.0 |
Total | 18.2–28.0 |
At times grasshoppers like Oedaleus asiaticus Bey-Bienko, 1941 migrate into cities where they are attracted to light at night, and during the years 2002-2009 there were many reports of them falling like rain, covering streets and gardens. A number of grasshopper species are a major problem in the north and west of China and, along with the Asian migratory locust, often invade China from neighboring countries, particularly Mongolia and Kazakhstan. The trans-boundary movement of these pests has led to an international cooperative treatment program between the Chinese and Kazakh governments. Locusts and grasshoppers in these northern areas have one generation per year, though some species have two generations per year further south and migratory locusts have three or even four generations per year on Hainan Island in the far south.
Monitoring for locust and grasshopper populations is quite labor intensive and involves digging up egg beds to monitor egg development as well as regular surveys to determine locust densities and distribution. Treatment programs often involve spraying using ground equipment, and aircraft are used to treat larger infestations, requiring staff to mark the boundaries of spray targets. Efforts are being made to identify inefficiencies in all of the processes involved in the monitoring and treatment of locusts and grasshoppers as part of an improved management program and such improvements require updated training such that technicians are well-trained in the latest techniques.
The current management strategy for locust and grasshopper control is preventive in that the aim is to keep locusts and grasshoppers at lower densities, so that migration is much reduced and crop and pasture damage minimized. The dense swarms of the migratory locust are much less common than in the past and when such swarms do form, they are quickly treated so that there have not been swarms in plague proportions for many years. There has been a great deal of recent research on this locust and this has led to substantial modernizing of management programs (
In the past, almost all treatments were by chemical pesticides but in recent years, non-chemical control forms an increasingly important part of locust and grasshopper management in China (
With Paranosema,
Data collected on locusts and grasshoppers are integrated into a computer-based platform that analyses data and issues news bulletins on where and when the densest locust and grasshopper infestations are likely to be. Within the platform, areas favored by locusts and grasshoppers have been digitally mapped. To these maps are added the survey data collected by field officers: the GPS coordinates of locations having locusts or grasshoppers are recorded by mobile devices and the data are then transferred to the computer-based platform. The location of areas treated are recorded either by GPS for ground treatments or DGPS (Differential Global Positioning System) for treatments by aircraft and these are also sent. The management platform analyses these data as part of providing an effective organization for locust and grasshopper control at both national and local levels (
The preventive management platform is part of a well-organized system for locust and grasshopper management. There are now 127 field stations with more than 2000 technicians involved in locust and grasshopper monitoring and control. The central and provincial governments coordinate the efforts of these technicians and ensure that they are well trained and that the field stations are well equipped with pesticides, application equipment and staff. But a critical part of the management system is the central authority’s use of the preventive management platform to allow recognition of areas with the densest infestations. Extra resources can then be provided when needed as part of ensuring the successful implementation of the locust and grasshopper management program.
Research areas that show promise in locust and grasshopper management include investigations of other bio control alternatives including the fungus Aspergillus, which has been shown to have high virulence against locusts, causing 80% mortality in 13 days (