|Meagher, Robert - Rob|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/1998
Publication Date: N/A
Citation: Legaspi, J.C., Legaspi, B.C., Irvine, J.E., Johnson, J., Meagher Jr, R.L., Rozeff, N. 1999. EFFECTS OF STALKBORER DAMAGE ON YIELD AND QUALITY OF SUGARCANE IN THE LOWER RIO GRANDE VALLEY OF TEXAS. Journal of Economic Entomology. 92(1):228-234. Interpretive Summary: All sugarcane grown in Texas is planted in the Lower Rio Grande Valley. The industry has an annual economic value of about $65 million. In the Valley, the Mexican rice borer damages about 20% of sugarcane annually. Farmers do not spray against the pest because they believe it is not economical to do so. The rice borer tunnels inside the cane stalk, thereby protecting itsel from the insecticide. We wanted to calculate the dollar value of the crop loss to help farmers decide whether or not it is best not to attempt to control the rice borer. We found that several measures of sugar yield and quality all declined with greater insect damage. Based on scientific analysis, we estimate that current levels of damage result in a loss of $477.96 per acre. For the entire Valley, this amounts to a total of $21.5 million. Farmers share $12.9 million of the total, while the sugar mill loses about $8.6 million. Because one third of the value of the industry i lost to this pest, we believe that the sugarcane industry cannot afford to ignore the Mexican rice borer and that it must actively seek biological or other control agents to lessen the loss.
Technical Abstract: In the Lower Rio Grande Valley of Texas, the pyralid stalkborer Eoreuma loftini saccharalis damages -20% of sugarcane internodes annually. Because insecticides have been abandoned as a control measure, it is important to quantify the relationships between stalkborer damage with sugar yield and quality. We also compared damage and sugar quality between the 2 major varieties grown in the region, 'NCo 310' and 'CP 70-321'. NCo 310 suffered a significantly greater mean percentage of bored internodes (19.4%) than CP 70-321 (10.9%). Sugar per ton also was greater in CP 70-321 (108 g/kg) than in NCo 310 (95.5 g/kg); as were juice purity and sucrose content. Sugar per acre, juice purity, stalk weight, cane per acre, sucrose per ton of sugarcane, and sucrose content all. were inversely related to damage. Regression slopes for CP 70-321 were steeper than for NCo 310, suggesting that it may be affected more severely by borer damage due to its higher sugar content. In Texas, the share agreements between farmers and the suga mill. mandate that the mill retains 40% of proceeds as compensation for milling. Losses are also shared in the same ratio. Assuming the value of raw sugar is $420 / t, 20% damage results in a loss of $1,181.04 / ha. For average Texas sugarcane acreage of 18,200 ha, total losses would be $21.5M ($12.9M to the producers and $8.6M to the mill). In the absence of effective chemical controls alternatives such as resistant varieties and biological agents, must be evaluated to lessen the economic losses.