Friday, October 4, 2013

Insect Pest Of Rice: Rice Bug

Rice Bug is one of the most economically important insect pests of the world. In rice producing countries is one of the major problems. That means rice bug is very common pest of rice. Scientific name of the rice bug is Leptocorisa acuta. This insect belongs to the family named Coreidae of Hemiptera order.

This harmful stage or destructive stage of this insect is not only the adult stage but also nymphs stage. Most of the damages are done by this insect when rice grains are at milky stage. Rice bug  sucks milk of the grains and for this reason rice grains remain unfilled.

Nature Of damage:
Nymphs and the adult bus feed on endosperm of the developing grains of rice.  Growing nymphs are active feeders than adult insect but adult rice bugs do more damage than nymphs of this insects. Because adult rice bugs remain more times on the grains and feed there for a long times than nymphs. They attack grains when grains are at milking stages. But they remain on the grains from milking stage to ripening stage. Nymphs and adults insert their proboscises at the point of lemma and palea ( where lemma and palea meet ).  So characteristic symptoms that brown spots are seen on the grains. As adult bugs suck the milk of grains, the grains remains unfilled and at later panicles are shriveled. Infested straw has an off-flavor that why cattle do not want to eat that straw.  Grains that are partially damaged by bugs, has also as off flavor and these grains are not cooked.
A Rice bug on grains
Damaged Grains

Control Measures:
When we are going for rice cultivation, at first we must consider preventive measure to control the insects and diseases. We must give priority to cultural control and biological control than chemical control. Because chemicals do harm to our environment where biological control is eco friendly. We can practice chemical control to save our crops when severe attack has done by rice bugs.
1. Cultural control
  Rice bugs feed on different grasses near the crop fields and they also breed on these grasses during  the off-season. So or first target is to uproot these unnecessary grasses.
2. Mechanical control
  We can use light traps, sticky traps and other traps to capture adult insects.
3. Use of resistant variety is effective.
4. Biological control
  Gryon nixoni ( small scelionid wasps) is an egg parasitoids of the rice bug. So we can apply this egg parasitoids in our rice field to control rice bugs.
  Meadow grasshoppers ( Conocephalus longipennis ) are feed on rice bug’s egg. So it is a good idea that if we increase the population of Meadow grasshoppers in our rice fields, Meadow grasshopper will feed eggs of bugs and the population of rice bugs will decrease rapidly.
   Many spiders such as Tetragnatha javana, Neoscona theisi prey on nymphs. So we may introduce these type spiders to our rice fields to control rice bugs.
5. Chemical control is  our last option to control rice bug.
  Carbaryl 5% and Malathion 5% are very effective against rice bugs. We may apply this insecticides @ 25 kg per ha as dust to control insects. We must not use chemicals indiscriminately because chemicals are very harmful for human life, wild life as well as our beautiful environment .

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