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A Non-Destructive Method of Estimating Red Tip Disease in Pineapple

F. Abu Kassim, G. Vadamalai, A. Mohd Hanif, S. K. Balasundram

Universiti Putra Malaysia

Red Tip disease typically reduces pineapple yields by up to 50%. At present, the causal agent of Red Tip disease is still unconfirmed. Based on disease symptoms and transmission mode within the field, however, Red Tip disease seems to be strongly associated with viral infection. In this work, we assessed the feasibility of using Greenseeker®, an optical sensor, to estimate Red Tip disease severity. This work was performed in a commercial pineapple plantation located in Simpang Renggam, Johor, Peninsular Malaysia. Four 1-ha plots bearing pineapple variety SR36 were demarcated based on crop growth stage. Two plots were used for Disease Severity (DS) and Normalized Difference Vegetation Index (NDVI) recording followed by model calibration, and the other two were used for model validation. A total of eighty corresponding measurements of % DS and NDVI were taken from each observation plot. Results showed a strong correlation between % DS and NDVI. The 7- and 11-month plantings had an r value of -0.83 and -0.88, respectively. The negative correlation infers that NDVI increases when disease severity is low. This is expected since healthy leaves reflect more near-infrared light and less visible light which results in a higher NDVI. The regression of NDVI on % DS for the 7-month planting was explained by: % DS = 181.6 - 185.6*NDVI. Meanwhile, the regression of NDVI on % DS for the 11-month planting was explained by: % DS = 213.2 - 219.8*NDVI. The linear fit between measured % DS and estimated % DS from the 7-month and 11-month plantings was relatively strong (r value of 0.84 and 0.91, respectively). This infers that NDVI is a reliable predictor of % DS in pineapple. This work suggests that the Greenseeker® is a feasible tool for non-destructive estimation of Red Tip disease in pineapple.

Keyword: Pineapple, Red Tip disease, Greenseeker®

F. Abu kassim G. Vadamalai A. Mohd hanif S. K. Balasundram Precision Crop Protection Poster 2012

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