NEGROS OCCIDENTAL, PHILIPPINES – Sugarcane farmers should strengthen natural and biological methods to combat the red-striped soft scale insect (RSSI), with early detection, field sanitation, and protection of natural enemies forming the first line of defense against the pest, according to entomologist and CPSU Visiting Professor Dr. Ravindra C. Joshi.
Joshi discussed the approach during a training and forum on combating RSSI at Central Philippines State University (CPSU)-Main Campus on Saturday, August 8, 2026, as the pest continues to threaten sugarcane production in Negros Island and other parts of the country.
RSSI, scientifically known as Pulvinaria tenuivalvata, is a soft scale insect that feeds on sugarcane by sucking phloem sap from the underside of leaves.
Joshi explained that the pest is particularly difficult to manage because all adult RSSI are female and reproduce through parthenogenesis, meaning they do not need males to reproduce.
A single female can produce roughly 197 to 200 eggs, protected beneath a cottony wax covering. The pest can complete its life cycle in about 63 days, passing through the egg, nymph or crawler, and adult female stages, he said.
Joshi added that the crawler stage is particularly important in controlling the pest because the newly hatched insects can be carried by wind, rain, vehicles, tools and clothing into previously clean fields.
Heat accelerates growth
Joshi also pointed to temperature as an important factor in the pest’s multiplication.
He said that, based on research, one generation may take about 60 days under cooler conditions of around 20°C, but only about 30 days at 32°C.
“Heat cuts the breeding cycle time in half,” Joshi said.
This means warmer conditions can allow RSSI populations to build up much faster, making regular field monitoring even more important during hot periods, he explained.
So far, 20,693.7 hectares of sugarcane were confirmed infested nationwide based on Sugar Regulatory Administration (SRA)-validated data as of July 2-3, 2026.
The Visayas accounted for the largest portion, with 18,572.14 hectares affected across the Negros Island Region and Regions VI, VII and VIII.
The Negros Island Region (NIR) alone accounted for 17,506.16 hectares of the validated Visayas total.
RSSI was confirmed in Negros Occidental on March 21, 2025, and has since been reported in sugarcane-growing areas including La Carlota City, Victorias City, Murcia and La Castellana.
Joshi said RSSI’s damage goes beyond the visible presence of insects on leaves. Tens of thousands of insects can cluster on the lower leaf surface and drain the plant’s sap, causing yellowing, wilting, and stunted stalk development.
“The pest also produces honeydew, a sugar-rich substance that encourages the growth of black sooty mold,” he said. “The mold can turn the sugarcane canopy black and interfere with photosynthesis.”
Severe RSSI outbreaks can reduce sugar content by up to 50%, while also affecting millable cane height, stalk weight, internode count and juice purity, Joshi said.
Cropping gives RSSI food
The researcher identified continuous ratooning and monoculture as factors that can help sustain RSSI populations.
Repeated ratoon cropping and year-round sugarcane production provide an uninterrupted food source, allowing overlapping generations of the pest to survive from one crop cycle to the next.
RSSI can also survive on weeds outside sugarcane fields.
Joshi identified several potential bridging hosts, including cogon grass, deccan grass, guinea grass and sida or broomweed, which can keep scale populations alive between sugarcane crops.
Joshi urged farmers to make early detection a routine practice.
During the first 120 days after planting, farmers should conduct weekly inspections, particularly along field perimeters and roadside margins where wind-blown crawlers are likely to settle first.
His recommendation is to “walk the zig-zag” across field edges instead of merely following a straight border line. Farmers should inspect the underside of leaves for pinkish-white scales, reddish stripes, honeydew and black sooty mold.
Nature’s own pest controllers
A major component of Joshi’s approach is biological control.
Field surveys have documented natural enemies already working against RSSI, including parasitoid wasps, ladybird beetles, lacewings and other beneficial organisms.
Joshi identified Coccophagus species as parasitoid wasps that attack RSSI from inside. Parasitized scales turn dark brown or black and develop a small round exit hole, indicating that the wasps are working.
Several ladybird beetle and lacewing species have likewise been documented feeding on RSSI nymphs and adults in Negros Occidental.
He said farmers should give these natural enemies time to establish.
A zero-chemical spray window during crop months 5 to 8 can allow beneficial wasps, beetles and lacewings to build up their populations and suppress RSSI naturally, the expert said.
Joshi also discussed the use of neem tree, or nimtree, and citronella as plant-based options in a more natural RSSI management strategy.
“The use of such plant-based preparations can complement biological and cultural controls and help reduce reliance on synthetic pesticides,” he said. “The broader objective is to create farm conditions where natural enemies, sanitation and other biological controls can work together.”
This includes microbial biological controls such as Beauveria bassiana and Metarhizium, which can be applied during the appropriate crop stage, Joshi said.
Protect beneficial organisms
Joshi stressed that biological sprays must be properly timed.
Beauveria bassiana and Metarhizium should be applied during the early morning or late afternoon, when intense sunlight is less likely to damage the fungal spores.
Farmers should also maintain a 10- to 15-day buffer between synthetic chemical sprays and biological treatments, research shows.
The purpose is to prevent chemical applications from destroying the beneficial organisms farmers are trying to establish, Joshi said.
He also warned that ants can undermine natural biological control.
Certain ant species “farm” scale insects for their honeydew, protecting RSSI from predators and parasitoids in exchange for the sugary secretion.
Joshi identified Camponotus, Solenopsis invicta, Crematogaster, and Monomorium among ants associated with this relationship.
Managing ant colonies around infested blocks can therefore break what the training describes as the “ant-scale alliance,” exposing RSSI once again to its natural enemies, he said.
Cultural sanitation is another key part of the strategy.
Joshi recommended scheduled de-trashing at Day 150 and Day 210 after planting, when lower infested leaves should be removed to eliminate nymph colonies before population peaks.
Infested leaf material should be moved out of the production zone and destroyed to eliminate unhatched eggs and crawlers.
Tools, trucks and other equipment should also be cleaned, while workers should change clothing after clearing infested fields to prevent crawlers from hitchhiking into clean areas, he said.
What if all fails?
Joshi emphasized that scouting, sanitation and biocontrol should come first, with additional intervention considered only when these measures fail to control a confirmed hotspot.
Farmers are advised to seek assessment and recommendations from their local SRA Extension Office, municipal or provincial agriculturist, or La Granja Agricultural Research and Extension Center (LGAREC) before applying interventions beyond cultural and biological controls.
Young RSSI nymphs are considered particularly vulnerable because they lack the stronger protective wax shield of mature adult females, Joshi said.
He stressed that farmers cannot afford to wait until RSSI populations become severe. Because adult females can reproduce without mating and produce nearly 200 eggs, even a small population can rapidly expand, particularly under favorable temperatures.*
Reymund Titong is a Filipino journalist steadily building his voice in the field of news reporting, driven by a commitment to tell meaningful and relevant stories.
He serves as a correspondent for Rappler, contributes to Negros Daily Bulletin, and maintains a blog on Medium.