Short Communication

Journal of Orthoptera Research 2017, 26(2): 155-159

Management of locusts and grasshoppers in China

LONG ZHANG!, David M. HUNTER?

1 Department of Entomology, China Agricultural University, Beijing 100193, China.

2 Locust and Grasshopper Control, 125 William Webb Drive, Canberra, Australia.

Corresponding author: David M. Hunter (davidmhunter100 @gmail.com)

Academic editor: Corinna S. Bazelet | Received 27 May 2017 | Accepted 9 August 2017 | Published 24 November 2017

http://zoobank.org/AA781 806-E863-4505-87F4-237D3B44B2E3

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

Abstract

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 en-
emies and reducing the area of favorable habitats through habitat modifica-
tion. Even with substantial cultural control, locust and grasshopper infesta-
tions 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 integrat-
ed 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 occur-
ring fungus Metarhizium acridum and the microsporidian Paranosema locus-
tae. 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 lo-
custs and grasshoppers are more than all of the rest of the world combined.

Key words

biological control, habitat modification, history, information platform

The long history of the locust and grasshopper problem in
China

Locusts and grasshoppers are serious pests to crops in many
areas of the world and can cause serious economic loss (Wright
1986, Brader et al. 2006, Millist and Abdalla 2011, Latchininsky
2013). In China, locust plagues have had a 3000-year history
(Fig. 1) (Zhou 1990), with more than 800 plagues recorded since
707 BC. Since ancient times, locust plagues, along with floods and
droughts, have been considered one of the three biggest natural
disasters. According to Ma et al. (1965), who studied detailed

data from the 11 to 19" centuries, plagues occurred about every
9-11 years and were present in nearly half of years in most cen-
turies. The frequency of damaging plagues led ancient Emperors
and their governments to mandate treatment programs: full time
locust control officers were appointed during the Tang Dynasty in
the eighth century (Wang et al. 2003). Laws were also passed dur-
ing the 11", 12" and 15" centuries that required local governors
to conduct locust control, which included paying people to catch
locusts and then bury them in pits.

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.”

The current locust and grasshopper problem

Migratory locusts, Locusta migratoria (Linnaeus, 1758) are seri-
ous pests in a number of regions in China (Fig. 2). The taxonomic
relationships between migratory locusts have recently been re-
vised such that those in the north are Locusta migratoria migratoria
(Linneaus, 1758) and those in the south are L. m. migratorioides
(Fairmaire & LJ. Reiche, 1849) (Ma et al. 2012). The northern in-
festations consist of those in the northwest, which are contigu-
ous with those of neighboring countries and their management at
times requires cooperative efforts with those countries, and those
in eastern China, which are often the most important. In the past
the northern infestations sometimes were continuous but in re-
cent years preventive management programs have limited the size
of these infestations such that the northwest and east infestations
are now managed quite separately. In the south are also two sepa-
rate infestations: on and near Hainan Island and near the Tibetan
plateau. Overall, migratory locusts commonly infest about 290
counties in 17 provinces, covering between 1.5 to 3 million ha

JOURNAL OF ORTHOPTERA RESEARCH 2017, 26(2)

156 L. ZHANG AND D.M. HUNTER

Table 1. Area infested by economically important locusts and

grasshoppers.
Range in area
ee as Distribution infested/year
8 PP (millions of ha)
) . 17 provinces,
Locusts Locusta migratoria OO colinties 1.5-3.0
Grasshoppers in gO epeces te total, 18 provinces,
: 60 spp. economically ; 4.7-7.0
agricultural lands : ~500 counties
important
; 800 species in total, .
Grasshoppetsm 50 spp. economically 5 De haere 12.0-18.0
grasslands : ~300 counties
important
Total 18.2-28.0

each year (Table 1). There are also economically important grass-
hoppers in many areas of China (Fig. 3), and each year they infest
up to 7 million ha of crops (which is about 10% of the total crop
area) and 18 million ha of grasslands (which is about 5% of the
total area of grassland) (Table 1). Clearly, locust and grasshopper
infestations are widespread and significant treatment programs
are conducted to limit the damage these pests can cause to grass-
Fig. 1. Chinese character representing locusts on an Oracle bone lands and crops. During major outbreaks between 1999-2004, 2-3
inscription in a 3000-year-old Shang Dynasty tomb. The character million ha were treated each year, though in recent years treat-
within the red circle means locust in ancient Chinese. ments have averaged about 1.5 million ha.

Inner Mongolia

Fig. 2. Regions where migratory locusts are common in China.

JOURNAL OF ORTHOPTERA RESEARCH 2017, 26(2)

L. ZHANG AND D.M. HUNTER

157

Fig. 3. Regions where pest grasshoppers are common in China.

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 fall-
ing like rain, covering streets and gardens. A number of grasshop-
per 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 Kazakh-
stan. The trans-boundary movement of these pests has led to an
international cooperative treatment program between the Chi-
nese 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 densi-
ties and distribution. Treatment programs often involve spraying
using ground equipment, and aircraft are used to treat larger in-
festations, requiring staff to mark the boundaries of spray targets.
Efforts are being made to identify inefficiencies in all of the pro-
cesses 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 preventive management strategy for locust and grass-
hopper control

The current management strategy for locust and grasshopper
control is preventive in that the aim is to keep locusts and grass-
hoppers at lower densities, so that migration is much reduced and
crop and pasture damage minimized. The dense swarms of the mi-
gratory 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 (Zhang
2011). Migratory locust breeding has been shown to be common
in the large flood prone areas near rivers and lakes with locust
numbers higher when precipitation is less (Tian et al. 2011) which,
in China, is often associated with El Nifo events (Zhang and Li
1999). Stige et al. (2007) showed that during dry periods follow-
ing floods, large areas of green vegetation are exposed providing
substantial areas suitable for locust breeding. The association of
migratory locusts with the reeds in flood prone areas led Ma et al.
(1965) to suggest that flood mitigation and habitat modification
could reduce these favored areas substantially. Many of the rivers
have been dammed to control floods, reducing the size of flooded
areas (Chen 1979, Zhu 2004). In many areas, the reeds favored
by locusts have been replaced with non-host plants such as Rob-

JOURNAL OF ORTHOPTERA RESEARCH 2017, 26(2)

158

inia pseudoacacia L. (false acacia) or Ziziphus jujuba Miller (Chinese
date) or non-host crops like alfalfa or cotton. Studies have shown
that in areas where non-host trees have been planted, locust densi-
ties have declined by more than 90%. The areas favorable for lo-
cust breeding are now much reduced and have been mapped (Zhu
1999) so that they can be extensively monitored for locust activity.
For grasshoppers in pastures, conservation of natural enemies is
important: in northwest of China, rosy starlings (Pastor roseus L.)
are not only conserved, but bird nests are also constructed, to pro-
vide nesting places for the birds on farms.

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
(Zhu et al. 2013). There has been substantial use of the naturally
occurring fungus Metarhizium acridum (Driver and Milner) and the
microsporidian Paranosema locustae (Canning) (formerly, Nosema
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 more than 100,000 ha per year sprayed with
these products. These applications of bio pesticides against locusts
and grasshoppers are more than all of the rest of the world com-
bined. The aim is to have 60% of treatments with non-chemical
control by 2020. Local production of these bio pesticides has
meant their price is almost the same as that of chemical pesticides
and while mortality is slower than with chemicals, a high level
of mortality can be obtained both with Metarhizium (Zhang and
Hunter 2005, Ding and Zhang 2009, Zhang 2011) and with Para-
nosema (Zhang et al. 1995, Gong et al. 2003, Fu et al. 2010).

With Paranosema, Zhou and Zhang (2009) conducted labora-
tory experiments to increase the virulence of local and introduced
strains by choosing spores from locusts that died most quickly and
infecting the subsequent generation of locusts. The LD,,’s of three
different strains declined by 26%, 56% and 76% respectively after
three generations of selection. And the two bio pesticides com-
monly used complement each other: M. acridum causes a high
(>80%) mortality more quickly (in 10-14 days), while P. locustae
generally leads to a lower initial mortality (60-70%) but horizon-
tal transmission between individuals and vertical transmission be-
tween generations means the latter continues to cause mortality
for many weeks and months and even in subsequent years (Zhang
et al. 1995, Gong et al. 2003, Zhang and Yan 2008). The major
advantages of using bio pesticides, which include specificity to lo-
custs and grasshoppers, preservation of natural enemies (Zhang
and Hunter 2005), as well as avoiding chemical residues both in
agricultural products and in environmentally sensitive areas such
as near water, mean that the credibility of having bio pesticides as
part of management programs is being recognized (Hunter 2010).

Integration of data into a preventive management platform

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 re-
corded either by GPS for ground treatments or DGPS (Differential
Global Positioning System) for treatments by aircraft and these are

L. ZHANG AND D.M. HUNTER

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 (Li et al. 2014).

The preventive management platform is part of a well-organ-
ized 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 author-
ity’s use of the preventive management platform to allow recogni-
tion of areas with the densest infestations. Extra resources can then
be provided when needed as part of ensuring the successful imple-
mentation of the locust and grasshopper management program.

Future prospects

Research areas that show promise in locust and grasshopper
management include investigations of other bio control alterna-
tives including the fungus Aspergillus, which has been shown to
have high virulence against locusts, causing 80% mortality in 13
days (Zhang et al. 2015). In addition, the Cotton bollworm Nu-
clear Polyhedrosis Virus (NPV) causes high mortality of locusts
when viral DNA is mixed with nano-particles (Liu et al. 2016).
Recent research has shown that heavy grazing promotes outbreaks
of the Asiatic grasshopper Oedaleus asiaticus (Cease et al. 2012),
which means that better management of grasslands could reduce
outbreaks. In recent years, there has been the development and
testing of new more precise monitoring and spraying methods,
which are being incorporated into the preventive management
program. A number of these advances have been in cooperation
with international scientists and such cooperation will continue
as part of ensuring China uses the most up to date techniques in
locust and grasshopper management.

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