The brown planthopper (BPH), ''Nilaparvata lugens'' (Stål) (Hemiptera: Delphacidae) is a
planthopper
A planthopper is any insect in the infraorder Fulgoromorpha, in the suborder Auchenorrhyncha, a group exceeding 12,500 described species worldwide. The name comes from their remarkable resemblance to leaves and other plants of their environment ...
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
that feeds on
rice
Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...
plants (''Oryza sativa'' L.). These insects are among the most important pests of rice, which is the major staple crop for about half the world's population. They damage rice directly through feeding and also by transmitting two viruses,
rice ragged stunt virus
Rice ragged stunt virus (RRSV) is a plant pathogenic virus of the family '' Spinareoviridae''.
RRSV, vectored by the brown planthopper (BPH) (Delphacidae: ''Nilaparvata lugens''), causes ragged stunt disease of rice (''Oryza'' spp., especially ' ...
and
rice grassy stunt virus. Up to 60% yield loss is common in susceptible rice cultivars attacked by the insect.
The BPH is distributed throughout Australia, Bangladesh, Bhutan, Burma (Myanmar), Cambodia, China, Fiji, India, Indonesia, Japan, North and South Korea, Laos, Malaysia, India, Nepal, Pakistan, Papua New Guinea, Philippines, Sri Lanka, Taiwan, Thailand, and Vietnam.
Their alternative host plant other than rice is ''
Leersia hexandra
''Leersia hexandra'' is a species of grass known by the common names southern cutgrass, clubhead cutgrass, and swamp rice grass. ''.
Biology
The brown planthopper is dimorphic, with fully winged 'macropterous' and truncate-winged 'brachypterous' forms. The macropterous forms are potentially migrants and are responsible for colonizing new fields. They migrate on the wind, with East Asian populations undergoing closed circuit journeys between
Indochina
Mainland Southeast Asia (historically known as Indochina and the Indochinese Peninsula) is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to th ...
and the Far East. Malay Archipelago and South Asia populations, on the other hand, make one-way migrations to Indochina. After settling on rice plants, they produce the next generation, where most of the female insects develop as brachypters and males as macropters. Adults usually mate on the day of emergence, and the females start laying eggs from the day following mating. Brachypterous females lay 300 to 350 eggs, whereas macropterous females lay fewer eggs. The eggs are thrust in a straight line generally along the mid-region of the leaf sheath. Eggs hatch in about six to nine days. The newly hatched nymphs are cottony white, and turn purple brown within an hour. They feed on plant sap. They pass through five instars before becoming adults.
Damage
BPH infest the rice crop at all stages of plant growth. Due to feeding by both the nymphs and adults at the base of the tillers, plants turn yellow and dry up rapidly. During the early infestation stage, round yellow patches appear, which soon become brownish due to the drying up of the plants. This condition is called 'hopper burn'.
Temperature is a critical factor that affects the life activities of this insect. The hatchability and survival rate are the highest around 25 °C. The eggs are highly sensitive to desiccation and soon shrivel when the host plant starts wilting. BPH population growth is maximal in a temperature range from 28 to 30 °C.
Predators
Predators of this insect include the
spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s ''
Pardosa pseudoannulata'' and ''
Araneus
''Araneus'' is a genus of common orb-weaving spiders. It includes about 650 species, among which are the European garden spider and the barn spider. The genus was erected by Carl Alexander Clerck in 1757.
Description
Spiders of this genus prese ...
inustus''. In some cases, BPHs lay eggs in the rice seed beds (also known as rice nurseries) shortly before transplanting, so enter the field in this manner.
Differential mortality of predators and hoppers does not appear to be the only factor for insecticide-induced
resurgence. Some insecticides evidently increase the protein content of BPH male accessory glands, and thereby increase planthopper fecundity. Some insecticides increase the amount of amino acids and sucrose available in the phloem of rice plants, and thereby increase BPH survival.
Management and control
Excessive use of
urea
Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...
as
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
ous
fertilizer
A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...
and
insecticide
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...
s can lead to outbreaks by increasing the
fecundity
Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the capability to produc ...
of the brown planthopper, and by reducing populations of natural enemies. It follows that the primary
integrated pest management
Integrated pest management (IPM), also known as integrated pest control (IPC) integrates both chemical and non-chemical practices for economic control of pests. The UN's Food and Agriculture Organization defines IPM as "the careful consideratio ...
(IPM) approach includes restricting the inappropriate and excessive use of these inputs. For example in 2011, the Thai government announced an initiative to respond to a major brown planthoppers outbreak by restricting outbreak-causing insecticides including
abamectin and
cypermethrin
Cypermethrin (CP) is a synthetic pyrethroid used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. It behaves as a fast-acting neurotoxin in insects. It is easily degrad ...
; the decision was supported by the
International Rice Research Institute
The International Rice Research Institute (IRRI) is an international agricultural research and training organization with its headquarters in Los Baños, Laguna, in the Philippines, and offices in seventeen countries. IRRI is known for its w ...
(IRRI).
[ IRRI media release: IRRI supports Thai move to stop insecticide use in rice.] IRRI also outlined recommendations foe an
Integrated Pest Management
Integrated pest management (IPM), also known as integrated pest control (IPC) integrates both chemical and non-chemical practices for economic control of pests. The UN's Food and Agriculture Organization defines IPM as "the careful consideratio ...
(IPM) action plan to limit planthopper outbreaks. In December 2011, the IRRI held a conference in Vietnam to address the threats of insecticide misuse and explore options for mitigation.
Rice varieties with resistance to BPH, e.g. IR64, are important for preventing outbreaks. However, in areas with low insecticide use, high levels of BPH resistance are not usually necessary. Chemical mutagenesis can significantly increase or decrease BPH resistance levels of rice. Some chemical insecticides, e.g.
imidacloprid
Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. ...
, can affect the gene expression of rice and thereby increase susceptibility to BPH.
In an attempt to make BPH control more species-specific, researchers are trying to develop methods of turning off specific BPH genes for digestion-, defense- and xenobiotic metabolism. Many novel genes for these functions have been detected in tissue from BPH intestines.
Some plant lectins are antifeedants to BPH and if properly formulated may have the potential to protect rice from BPH.
Impact of climate change
Research indicates that BPH nymphs are already living at the upper limits of tolerable temperatures. This suggests that climate warming in tropical regions with occasional extremely high temperatures would limit the survival and distribution of BPH.
References
लाल mohamad
External links
Ricehoppers – a blog on the latest information and issues relevant to managing rice planthopper problems
{{DEFAULTSORT:Brown Planthopper
Delphacinae
Insect pests of rice
Insects described in 1854
Hemiptera of Asia
Insect pests of millets
Taxa named by Carl Stål
Insect vectors of plant pathogens