Busseola fusca / Chilo partellus / Sesamia calamistis
6
Damage Signs
4
Organic Methods
3
Chemical Options
5
ID Tips
2
FAQs
5
Crops Affected
Updated February 2026
Ubona Cereal Stem Borer Complex ku bimera byawe?
Ohereza ifoto kugira ngo umenye ako kanya hamwe n'uburyo bw'ibinyabuzima n'imiti bwo kurwanya.
Overview
Stem borers are the most important insect pest group of cereal crops (maize, sorghum, millet, rice, sugarcane) in Africa and Asia. Multiple species attack cereals: Busseola fusca (African maize stalk borer, highland), Chilo partellus (spotted stemborer, lowland, invasive from Asia), and Sesamia calamistis (pink stemborer). Larvae bore into stems, disrupting nutrient transport and causing 'dead hearts' in young plants and stem breakage in older plants.
Field Guide
B. fusca: grayish-brown larvae (30-40 mm) with dark head and spots along body. C. partellus: creamy-white larvae with dark spots, smaller (25 mm). Sesamia: pink-tinged smooth larvae. All bore into stems and produce frass-filled tunnels. Adults are medium-sized brown moths.
Dead heart symptom — pull the central whorl of a young maize plant; if it comes out easily and smells rotten, stemborer is the cause
Split stems lengthwise to find larvae and tunnels — the definitive diagnostic method
Look for frass pushed out of small round holes in the stem
Check leaf sheaths for egg masses (B. fusca lays behind the sheath)
Window-paned leaves (young larvae feeding) precede stem boring by 5-7 days — the intervention window
Scouting Guide
Dead heart — central leaf whorl dies and can be pulled out easily in young plants
Small round holes in stems with frass (sawdust-like droppings) pushed out
Stem tunneling visible when stalks are split open
Lodging (stem breakage) at the tunnel site in older plants
Peduncle damage causing partial or complete ear/panicle failure
Leaf window-paning from young larvae feeding before boring into stem
Biology
Complete metamorphosis: egg mass on leaf surface or sheath (7-10 days) → 5-8 larval instars boring in stem (25-40 days) → pupa inside stem (10-14 days) → adult moth (7-14 days). 2-4 generations per year. B. fusca diapauses in dry season inside stems.
Pest Management
Push-pull technology
Intercrop maize with Desmodium (repels moths) and border with Napier/Brachiaria grass (attracts moths to lay eggs on grass instead). Reduces stemborer damage by 80%+.
Crop residue destruction
Destroy maize and sorghum stubble after harvest by chopping, burning, or composting. This kills diapausing B. fusca larvae inside stems — the primary carryover mechanism.
Early planting
Plant early at the onset of rains to establish plants before moth emergence from diapausing pupae in old stalks.
Bt maize
Where available and registered (South Africa), Bt maize expressing Cry1Ab protein provides effective stemborer control without insecticide.
Use as last resort. Follow label instructions. Wear protective equipment.
Carbofuran granules in whorl
Apply carbofuran (Furadan 5G) granules into the maize whorl at first signs of leaf damage. Effective but toxic — handle with extreme care.
Chlorantraniliprole (Coragen 20SC)
Apply at 0.4 ml/L into the whorl targeting young larvae before they bore into the stem. Safer alternative to carbofuran.
Trichlorfon (Dipterex 95SP)
Apply at 1.5 g/L as whorl drench when young larvae are feeding on leaves. Timing is critical — once inside the stem, larvae are protected from sprays.
Host Range
Cereal Stem Borer Complex can attack 5 crop species.
Common Questions
Once larvae have bored into the stem (typically 7-10 days after egg hatch), insecticide sprays cannot reach them. The window for chemical control is the brief period when young larvae are feeding on the leaf surface and whorl before boring in — usually just 5-7 days after egg hatch. This is why early detection and push-pull prevention are more reliable than reactive spraying.
Push-pull reduces stemborer damage by 80%+ consistently across multiple research sites in East Africa (ICIPE research since 1997). It also controls striga weed (95% reduction) and fall armyworm. Over 250,000 farming families in East Africa have adopted the technology.
CuraPlant
Scan your crop and get an instant AI pest identification, damage assessment, and action plan — even offline.
