Yellow stem borer (YSB), Scirpophaga incertulas (Walker) is the most dominant species among stem borers on rice in India. It is a pest which feeds and survives only on the rice plant. Yellow stem borer is a regular pest affecting all the growth stages of the plant from nursery to harvest. In India there may be 4-5 generations in a year. The YSB larvae emerge out from the egg masses laid on the leaf laminae, slide down to the base of the tillers with the help of silky strings, invade the stem by making tiny hole just above the water level and feed on the growing stem primordia. Once the larva gains entry into the tillers, invariably the damage is reflected either as dead heart or white ear head or the grain filling in the panicle is affected depending on the stage of the crop. The yield loss has been estimated to range from 38 to 80 %. In spite of the timely chemical application, the damage can only be minimized, but cannot be totally averted. Sex pheromones were found to be effective in monitoring and mass trapping of the yellow stem borer moths, thus minimizing the damage but non-availability of the pheromone lures is the major constraint in this technology. Therefore a look for alternatives, lead to the concept of adopting an age old practice of planting inter crop as trap crops for yellow stem borer management.
Concept of trap crop
Trap crops have been defined as “plant stands grown to attract insects or other organisms like nematodes to protect target crops from pest attack, preventing pests from reaching the crop or concentrating them in a certain part of the field where they can be economically destroyed”. Therefore, trap crops are plant stands that are; per se or via manipulation, deployed to attract, divert, intercept, and/or retain targeted insects or the pathogens they vector in order to reduce damage to the main crop. This broader definition encompasses the inherent characteristics of the trap crops themselves as well as their deployment. Insects and their host plants interact and become influenced by size, fragmentation and connectivity of host patches.
Enhancing the effectiveness of the trap crop is vital to minimize the land sacrificed to production when using trap cropping as pest management strategy. General guidelines for trap cropping recommend that about 10% of the total crop area be planted with the trap crop, although the percentage of trap crop needed for each particular system has to be determined for each case. Ultimately, the combination of insect and trap crop characteristics and practical considerations determines the success of a trap cropping system.
Based on the basic principles of trap cropping a strategy was developed at Directorate of Rice Research to trap the YSB insects on a susceptible rice variety (Pusa Basmati1) and minimize the damage on the main crop. A proper understanding of the insect biology, behaviour and dynamics is very important in successful adoption of this strategy.
Which crop to use as a trap crop?
As YSB larvae feed only on rice plants we can use only a rice plant as trap crop. It was found that Pusa Basmati 1 attracts more of yellow stem borer as compared to other varieties and can be used as a trap crop. One tenth area of the main field is sufficient to plant a trap crop.
How do you raise the nursery?
To facilitate easy adoption by the farmers the technology was modified to reap the optimum benefits. The duration of Pusa basmati 1 is 135 days. For a trap crop to be effective, the trap crop should reach booting stage 6-7 days before the main crop. The duration of the main crop and the trap crop are considered based on which the date of sowing is adjusted so that the trap crop would come to booting a week earlier than the main crop. Thus date of sowings differ (Table 1) but both the varieties are transplanted at the same time in the field.
This technology was tested in farmer’s fields in RangaReddy and Mahaboobnagar districts of Andhra Pradesh and at few locations in the All India Rice coordinated programme where stem borer is a regular pest. Pusa Basmati 1 was tested with Krishnahamsa, Swarna, MTU1010, BPT 5204, JalPriya (a deep water rice variety), HMT Sona, hybrids (6444) as main crops and was found successful.
How do you plant it?
Planting of main crop and trap crop is done at the same time. For every 2.5- 3m of main crop one row of trap crop (Pusa Basmati-1) should be planted preferably in east – west direction. In brown planthopper endemic areas when alley ways are advocated it was proved that trap crop can be planted along the alley way. This method is more convenient when we are advocating line planting. When planting is given on contract basis, it is advisable to plant rows of Pusa Basmati 1 by employing one or two labourers before the planting of main field by the contractual labourers.
Precautions
- The nursery should be free from any stem borer infestation. We should ensure that there is no carry over from nursery to the main field.
- Once planting is done ensure that the trap crop seedlings are well established in the field.
- In case of use of combines for harvesting, the trap crop rows may be harvested manually a day earlier to the normal harvest.
- This trap crop is useful only for the management of yellow stem borer.
Advantages of using a trap crop in rice cultivation are:
- It is an eco- friendly pest management strategy to control YSB.
- The damage observed in the main crop was half of the damage that was recorded in the trap crop. It can protect the main crop without much economic loss (up to 25% dead heart damage in the trap crop). Hence by adopting this methodology in a stem borer endemic area, one impulsive spraying of chemical pesticides can be avoided at the vegetative stage. This would help in conserving the natural enemies.
- The yield in both the main crops would be almost same or at times higher in the main crop where trap crop is grown, but yield from the trap crop would be of an added advantage. The yield in the main crop depends on the main crop variety grown.
- Pusa Basmati 1 being a premier scented variety, fetches more price in the market. Hence the cost benefit ratio has always been favourable and is e” 1: 1.5 for the combination of varieties tested.
Extracted from AgriGold SwarnaSedyam
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