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Effects of Rice Hispa Damage on Grain Yield

Dr. Sheikh Shamiul Haque
Principal Scientific Officer
Entomology Division, BRRI, Gazipur

Dr. Zahirul Islam
Ex Principal Scientific Officer
Entomology Division, BRRI, Gazipur

Abstract/ Executive Summary:

Impact of rice hispa (RH), Dicladispa armigera (Oliv.) damage and grain yields was investigated through a series of field experiments under controlled conditions in the experimental farm of the Bangladesh Rice Research Institute at Gazipur in Bangladesh. Seven field experiments were conducted in the aus (summer) and aman (monsoon) seasons. Rice plants were exposed to different densities of RH at different ages. Leaf damage increased with the increase of beetle population. In the aus season, at a given RH population density younger plants (var. BR3) suffered more damage than older ones indicating plant resistance increased with the age. However, such trends were not distinct in the aman season (var. BRRI dhan32). Leaf damage potential of RH appeared to vary between crop seasons and varieties, with more in the aus than in the aman season. RH feeding affected new leaf production, which was influenced by plant age and damage intensity. At the early to mid- tillering stages rice plants that suffered 20% or less leaf damage produced a similar number of new leaves to that of undamaged plants. However, severe damage, particularly to older plants, affected leaf production more than the younger ones. Season and varietal differences were observed in plant response to damage and in grain yield. Severe leaf damage affected some yield component viz. filled grain number, grain filling (weight); and grain yield in the aman but did not affect in the aus season. In the aman season, negative relationships between the level of leaf damage and grain yield were observed, irrespective of the time of damage. Photoperiod sensitive rice varieties grown in the aman season appeared to be prone to RH damage, while photoperiod insensitive varieties grown in the aus season appeared to have the ability to tolerate, or compensate for, RH damage. Further in depth studies could resolve the dilemma of varietal and seasonal variations in crop response and yield loss.

Keywords: Rice hispa, Dicladispa armigera, Yield loss, Compensation, Relationship.

Location: BRRI, Gazipur

Start Date: 00-00-1999

End Date: 00-00-1999

Program Area: Pest Management

Commodity: Insects

Objectives:

To determine the relationship between rice hispa (RH) beetle density and leaf damage.
To understand plant's response to rice hispa damage.
To determine the effect of leaf damage on grain yield, and to fine out the relationship between leaf damage levels and grain yield.

Methodology:

The study was conducted at the experimental farm of the Bangladesh Rice Research Institute (BRRI) in Gazipur, Bangladesh in 1999. In total, three experiments were conducted in the aus and four in the aman seasons. In order to achieve gradients of leaf damage, adult RH beetles were confined on rice plants at the rate of 0, 0.2, 0.5, 1.0, 2.0 and 4.0 per tiller for 2-weeks. All the experiments were conducted in randomized complete block design with four replications. Unit plots were 2 m x 2 m and a 100 em wide footpath separated the plots and blocks. In the aus season, RH was confined at 20, 40 and 60 days after transplanting (DAT), and at 20, 30, 50 and 70 DAT in the aman season. A mass culture of RH was maintained in the net-house.Modern rice variety BR3 was planted in the aus season and BRRI dhan32 in the aman season. Four to five week old seedlings were transplanted at 20 cm x 20 cm hill spacing. Blanket applications of fertilizers viz. urea, triple superphosphate, murate of potash, zinc sulphate and gypsum were applied at recommended rates. Standard water management practices were adopted for all the experiments. Weeds were controlled manually at 15 and 35 DAT. In order to control infestations of other insect pests granular insecticide (Basudin lOG) was applied at the rate of 16.80 kg/ha (formulated), once during the season. Depending on the treatment, Basudin was either applied one-month before or after hispa infestation schedule.Four rice hills in a 2 x 2 hill grid were selected (excluding border hills) in each plot. Tiller numbers of selected hills were counted. Then, the number of RH beetles needed for infestation was estimated and recently emerged adult RH beetles (from the mass culture) were confined on selected hills by the help of a 50 x 50 x 150 em white nylon mesh cage supported by four bamboo sticks. Rice hills in the control plots were also covered by nylon mesh cages. Two weeks after confinement beetles and the cages were removed and the severity of leaf damage was estimated using two methods. Firstly, the leaf damage was estimated visually using a 0 to 9 scale with zero as no damage and 9 as 100% damage (INGER 1996). Then the number of leaves with degree of damages viz., 0-25%, 26-50%, 51-75% and 76-100%; and new leaves produced after damage were counted at 3, 7, 15 and 21 days after damage (DAD). All the panicles of one random hill from the four hill were harvested separately and the numbers of filled and empty grains were counted. Panicles of the remaining three hills were harvested, threshed and cleaned. Two samples of each plot were then bulked and three readings on grain moisture taken and weighed. Grain weights were adjusted to 14% level. One thousand grains were separated, dried at 600 C for 48 hours and then weighed. To compare leaf damage between different plant growth stages, the leaf damage index (S₁L₁ + S₂L₂ + S₃L₃ + S₄L₄ + ... where S_I = 1, S₂ = 2, S₃ = 3, S₄ = 4 ... score for damage rates; and L₁, L₂, L₃ and L₄ were number of leaves under that damage category) was calculated.

Source of Information: IRRN 26:2, December 2001,page:44-45.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The ability of the rice hispa beetle for leaf damage varies between seasons and variety. In the summer when environmental conditions are favorable, the photoperiod insensitive varieties suffered more leaf damage than the photoperiod sensitive varieties grown in the monsoon. Young plants are more susceptible and plant resistance to leaf damage increases with the age. Although summer (aus) crop suffers more leaf damage than monsoon (aman) crops, plants appear to compensate fully resulting in very little or no effect on yield components and grain yield in the aus season. Photoperiod insensitivity of the variety for panicle initiation and favourable environmental conditions appear to playa significant role in such a high level of compensation. hereas, photoperiod sensitive rice variety in the monsoon (aman) season appeared to be sensitive to hispa damage. A high level of damage at any growth stages can affect most yield components and grain yield. Effects on yield increases with the increase in leaf damage intensity but plant age has little influence. Photoperiod sensitivity and unfavourable environment (low solar radiation) in the monsoon may be responsible for low compensation. Therefore, the impression that "leaf damage in the vegetative stage does not affect rice grain yield" is not true for every situation. Yield loss may occur depending on the nature of the variety and/or environment/-growing season in addition to intensity of damage.

Knowledge Management: Journal