C.W. Chan, Senior Principal Scientist, Mechanization and Automation Research Center (MA), Malaysian Agricultural Research and Development Institute (MARDI), Serdang, Malayia and
K.L. Heong, International Rice Research Institute, Los Baños, Philippines
Outbreaks of the rice brown planthopper (BPH) are quite rare in Malaysia. But when they occur fields are often completely destroyed. In 2008 outbreaks occurred in Sekinchan area when fields of hybrid rice were heavily sprayed with fipronil and thiametoxam ( a neonicotinoid) that are typically destructive to natural biological control. This was followed with outbreaks in the Muda irrigation scheme, Malaysia’s rice bowl. The hopperburn occurred in parallel rows where the spray booms passed. Blast outbreaks are also rare although incidences are more common in the last 5 years. BPH and blast are the two most important threats to rice production in Malaysia. Ecological engineering was first experimented in a large rice estate and found to reduce pest control cost from 40% to 13% of production costs.
MARDI initiated a project to automate pest and disease monitoring to provide data for vulnerability assessments. As BPH and blast outbreaks generally occur in specific areas where conditions are conducive, vulnerability assessments may be used to trigger management operations to reduce vulnerability and prevent the impending outbreaks.
BPH outbreaks occur when the environment is conducive and are triggered by high immigration. Each year between May and October is the SW monsoon with winds that can potentially displace BPH immigrants from Sumatra. Thus monitoring of immigrant BPH, especially on the western coasts of Peninsular Malaysia, is an important activity to provide early warnings. In the project MARDI is working on an automatic BPH monitoring device. For blast on the other hand, high spore counts of virulent strains and conducive environments make fields highly vulnerable.
The two consultative workshops on modeling of rice pests and diseases focusing on populations, forecasting and vulnerability in Malaysia was sponsored by MARDI in collaboration with IRRI and CABI SE Asia. Drs K L Heong and Adam Sparks were invited resource persons to lead the discussions on the use of models, use of R in modeling, forecasting techniques and vulnerability assessment approaches.
A number of factors contribute to pest outbreaks. These include fertilizer use, pesticide frequency, timing and types used, rice varieties planted and how widely adopted are they, seed rates, temperature, humidity, leaf wetness, etc. These factors are often quantified using either parametric or non parametric variables. The workshop is working on a rule-based modeling method to integrate these factors into a vulnerability index ranging from zero (least vulnerable) to 1.0 (most vulnerable). Regional distributions of the different degrees of vulnerability may be mapped to guide management decisions. The vulnerability index can also be used to assess individual rice fields.