Insect Pests of Rice
Rice Water Weevil – Lissorhoptrus oryzophilus
rice water weevil adult The rice water weevil is the most
serious pest of rice in the US. It is native to
Texas, but was accidentally introduced into
California, as well as China, North and South
Korea, Taiwan, Japan and Europe. Thus, it is
now a global pest of rice. Adults feed on rice
leaves and lay their eggs underwater in rice
stems. Eggs hatch
and larvae move to
the roots upon
which they feed. As larvae
the larvae grow, they shed their skins periodically and increase in
size. The larvae complete four instars (stages between molts) before
pupating in a mud cocoon attached to rice roots. Research shows
that an average of 1 larva per plant reduces yield about 80 lb/acre.
This is a linear relationship; thus, 3 larvae per plant reduce yield
about 240 lb/acre. Thus, 3 larvae per plant is the economic injury
level (EIL) for the rice water weevil. The EIL is the population
density that causes damage equal to the cost of control.
This insect is controlled by 3 seed treatments (Dermacor X- pupa
100, NipSIt INSIDE and CruiserMaxx Rice) and various foliar-
applied insecticides. Currently, the United States Environmental Protection Agency (USEPA) is
concerned about the use of pesticides because of possible toxicity to honey bees. USEPA and the
Texas Department of Agriculture (TDA) regulate and label pesticides for use in our country and
state.
Rice Stink Bug – Oebalus pugnax
rice stink bug adult The rice stink bug is another serious
pest of rice. It is native to Texas and the other
southeastern rice-producing states---Arkansas,
Louisiana, Mississippi and Missouri. It does
not occur in California---the other rice-
producing state. This insect has piercing-
sucking mouthparts which the insect inserts in
rice grains and extracts the contents.
Generally, no yield losses are associated with
this feeding but rice quality can be affected.
Damage results in ‘pecky’ rice which is
discolored rice caused by rice stink bug feeding. In addition, upon milling, ‘pecky’ rice tends to
break so head rice (% whole grain rice after milling) is reduced. Farmers receive less money for
lower quality rice. The rice stink bug lays its eggs in masses (two rows per mass) on rice foliage.
After egg hatch, nymphs (immature rice stink bugs without
wings) complete five instars before becoming adults. Each instar rice stink bug nymph
is a little bigger than the previous instar. The later instars (4th
and 5th) and adults cause the most severe damage. The rice stink
bug is controlled by various insecticides including Tenchu 20SG
which is systemic (absorbed by the plant), pyrethroids and
carbaryl. The most susceptible stages of rice to rice stink bug are
heading (flowering) and milk. Thus, the EILs for rice stink bug
are lower for these stages than later stages---soft dough and hard
dough.
Fields with abundant weeds (particularly barnyardgrass)
generally harbor high rice stink bug populations. Also,
populations of rice stink bug are generally higher near the margins of fields.
Fall Armyworm – Spodoptera frugiperda
The fall armyworm is a sporadic
pest of rice. The larvae have chewing
mouthparts and defoliate (consume foliage)
of rice. The adult is a moth which lays its
eggs in masses on rice leaves. Eggs hatch
and the larvae complete four to six instars
(stages of growth) before pupating in a
cocoon in the soil. Generally, fall
fall armyworm adult moth
fall armyworm larva
armyworm are more severe on rice before the
permanent flood. Usually, fall armyworm can be
controlled by applying a flush (temporary flood) or
permanent flood which drowns the larvae. A wasp
parasite (Cotesia sp.) and egrets also can help
control populations. Dermacor X-100 seed
treatment controls fall armyworms. Some farmers
apply pyrethroid insecticides (not systemic) when defoliation reaches 20% which is the EIL for
this insect.
Chinch Bug – Blissus leucopterus leucopterus
The chinch bug is another sporadic pest of rice. This insect has piercing-sucking
mouthparts like the rice stink bug. Adults are winged and are black and white. Adult female
chinch bugs lay their orange eggs singly in soil cracks or on rice stems. Eggs hatch and nymphs
begin feeding on rice stems usually near the soil surface. The insect completes five nymphal
instars before becoming an adult. Seedling rice is very susceptible to attack. At this stage, an
average of only one adult per two seedlings can kill rice. Frequently, an effective method of
control is to flush rice or apply a permanent flood which drowns
insects or forces them to move up the plants where feeding adults
results in less damage compared to feeding on stems near the
soil surface. However, rice growing on levees can still be
damaged. NipsIt INSIDE and CruiserMaxx Rice seed treatments
control this pest. Foliar applied insecticides, such as pyrethroids,
also provide control.
nymphs
Stalk Borers – Mexican rice borer (Eoreuma loftini), rice stalk borer (Chilo plejadellus) and
sugarcane borer (Diatraea saccharalis)
The most abundant and damaging stem borer is
the Mexican rice borer which was introduced from
Mexico into the Texas Rice Belt in 1988. The Mexican
Mexican rice borer
rice borer lays eggs on dead or dying rice foliage. Eggs
hatch and larvae move to the inside of leaf sheaths where
they are partially protected from natural enemies and
pesticide residues. These small larvae feed in the sheaths
and eventually bore into the culm. Inside the culm, they
sugarcane borer
feed
between
nodes to
cause
rice stalk borer
“deadhearts” (dead leaves) and “whiteheads”
(panicles with unfilled grains). After
completing five larval instars, the insect pupates
stalk borer within the culm and emerges as an adult moth.
damage to culm whitehead Stem borers are controlled with the seed
treatment insecticide Dermacor X-100. They
can also be controlled with pyrethroids applied late in the season shortly before and after panicle
emergence. Late planted rice is more susceptible to stem borers than earlier planted rice. Hybrid
rice varieties tend to be more resistant to stem borers than other varieties.
Grasshoppers – Orthoptera
Grasshoppers are seldom pests of rice. Usually
populations are highest near the margins of fields. long-horned
Grasshoppers feed on foliage and sometimes panicles. grasshopper
The most common
short-horned grasshoppers in rice
grasshopper are long-horned
grasshoppers which
can also be beneficial
since they feed on pest
insects as well as rice.
Long-horned grasshoppers are easily identified by their very
long antennae.
Blister Beetles – Epicauta texana
Blister beetles are sporadic pests of rice.
The adults usually move in mass from weedy
field margins. They typically defoliate rice and
broadleaf weeds late in the season. Occasionally,
blister beetles will also feed on the reproductive
organs of rice flowers. Insecticides registered for
rice stink bug also control blister beetles. Usually
‘spot’ treatments of insecticides effectively
control blister beetle populations.
Leafhoppers – Cicadellidae (Graminella nigrifrons)
Leafhoppers are sporadic pests of rice. The
most common leafhopper in Texas rice fields is the
blackfaced leafhopper. Leafhoppers have piercing-
sucking mouthparts and remove fluids from the plant
causing yield and quality losses. Sooty mold fungus is
black and grows on leafhopper exudates called
honeydew. A good indication of high populations of
leafhoppers is abundant sooty mold fungus on rice
foliage. In addition, foliage takes on a bronze
appearance.
Rice Delphacid – Tagosodes orizicolus
A new pest of rice is the rice delphacid which is related to a adults
leafhopper. These insects are native to Latin America and have
piercing-sucking mouthparts like
nymph leafhoppers. They were found for the
first time attacking maturing ratoon
rice in 2015 in several counties in the
western part of the Texas Rice Belt.
High densities can kill rice plants.
Honeydew and black sooty mold fungus are associated with high
numbers of this exotic insect which also has the ability to transmit a
virus to the rice plant which causes “hoja blanca” disease. Hoja
blanca means white leaf in Spanish; thus, symptoms of the disease
are bleaching of foliage and stunting of the affected rice plant. In addition, in severe cases,
panicles do not develop resulting in 100% yield loss.
