What ails your sugarcane crop?

Outbreaks of sugarcane diseases and pests wreak havoc on sugar production. In the last 14 years, reduction in tonnage due to mosaic disease averaged 23.03 percent. Yellow spot disease’s first outbreak in Negros resulted in a yield loss of 16.30 percent. Catastrophes like these have prompted the Philippine Sugar Research Institute Foundation Inc. to create efficient disease and pest management programs.

Collaborating with scientists, resear-chers, crop physiologists and plant breeders, Philsurin utilizes biotechnology to determine the nature of each sugarcane disease and pest.

"Knowledge is our best weapon against sugarcane diseases and pests, enabling us to initiate effective control measures and produce highly-resistant sugarcane varieties," Philsurin director general Leon Arceo said.

Thorough quarantining and indexing of imported sugarcane varieties is one disease control measure that Philsurin has implemented. A method used to determine the presence of disease-causing organisms in plants, called pathogens, disease indexing forms part of Philsurin’s activities in the regional variety improvement program. Techniques such as the enzyme-linked immunosorbent assay (ELISA) and the polymerase chain reaction (PCR) are used to accurately detect sugarcane diseases.

Varieties brought in from other countries are close-quarantined and indexed for diseases at the University of the Philippines Los Baños Institutue of Plant Breeding’s post-entry quarantine greenhouse for two years. Then, the sugarcane varieties are transferred to an open quarantine area in Guimaras, Iloilo and monitored for other diseases over another one-year period.

Among the prevalent sugarcane diseases indexed by Philsurin are leaf scald, yellow leaf syndrome, mosaic and ratoon stunting disease.

At UPLB-IPB post-entry quarantine greenhouse, cane leaves are visually examined to spot symptoms of leaf scald and mosaic. Four months after planting, the varieties are indexed for mosaic using the ELISA method. Ten months after planting, pathologists used ELISA to index sugarcane varieties for RSD. Leaf scald is identified via isolation and PCR, while yellow leaf syndrome is detected by applying both the PCR and ELISA methods.

A bacterial disease, leaf scald is characterized by white streaks on the leaf’s blade. Yellow leaf syndrome is transmitted by aphids and causes the plant’s midrib to yellow. Mosaic disease is distinguished by irregular stripes or streaks on the leaves. Caused by the bacteria Clavibacter xyli, RSD on the other hand, is identified by the shortening of sugarcane internodes resulting in stunted plant growth.

Funding a study on "Molecular Marker-Assisted Selection in Identifying Downy Mildew and Smut Resistance Genes in Sugarcane," Philsurin is exploring the application of molecular techniques to identify sugarcane varieties that are resistant to the disease. The use of molecular markers or genetic markers enable the breeders to eliminate susceptible varieties and plant only the resistant types.

A fungal disease which attacks sugarcane during warm and wet conditions, downy mildew causes leaf discoloration and thinning of the stalks. Smut, on the other hand, infects sugarcane buds, producing a long, whip-like structure with a black, powdery mass of spores.

Other sugarcane diseases being monitored and studied by Philsurin includes leaf scorch, sugarcane rust, pokkah boeng, yellow spot, banded sclerotial, and pineapple diseases.

Characterized by reddish-brown spots on the leaves that spread gradually, leaf scorch attacks the leaves and disrupts the plant’s photosynthetic activity. Also infecting the plant’s leaves, sugarcane rust is determined by yellow-orange spots that eventually turn reddish-brown.

Pokkah boeng disease causes the wrinkling and shortening of cane leaves, while yellow spot disease is characterized by yellow dots on the leaves which gradually turn red. Banded sclerotial disease is recognizable by the yellow patches on the leaves. Pineapple disease got its name from the pineapple-like odor given off by decaying sugarcane.

Striving to eradicate sugarcane pests, Philsurin awarded a three-year research grant to the National Crop Protection Center of UPLB that previously conducted studies on rats, sugarcane borers and nematodes. Their study of white grubs is ongoing.

Rat population is hard to contain. One female rat can produce 2,046 offsprings in 13 months. Philsurin recommends the use of a need-based technique to bait rats, and a monthly application of first and second generation anticoagulants such as Ratoxin and Racumin. For two years, the Victorias Mill District Coordinating Council has conducted the monthly application of anticoagulants, costing them P2 million. The experiment yielded promising results with sugar losses reduced by P59 million over the two-year period.

Sugarcane borers are most destructive during the dry season with infestation ranging from 50 to 70 percent. Plants attacked by the pest do not mature, resulting in low sucrose content and a low yield. With borers becoming resistant to costly insecticides, Philsurin has resorted to utilizing the biological control agent, Trichogramma chilonis, a parasite that feeds on the sugarcane borer’s eggs. Philsurin has constructed seven laboratories that mass-produce Trichogramma, with satisfactory results.

Nematodes and white grubs are pests that feed on sugarcane roots, causing growth stunting in cane plants. Nematodes are worm-like organisms that are barely seen by the naked eye, while white grubs are beetles in their larval stage. Philsurin has studied the pests’ life cycle and is searching for ways to develop biological control agents that will be effective in eradicating nematodes and white grubs.

Helping planters combat sugarcane diseases and pests is a continuing exercise for Philsurin.