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Class |
Insecta |
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Order |
Lepidoptera |
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Family |
Pyralidae |
The stemborer is one of the most destructive pests of sweetpotato in
tropical and subtropical Asia and the Pacific.
Infestation during the establishment phase of the crop can result in yield
losses of 30-50% or more.
Generally widespread in the Philippines, Indonesia, India, Sri Lanka,
Malaysia, Taiwan, Hawaii and Vietnam. It also occurs in China, Japan, Cambodia,
Laos, Burma (Myanmar), and Thailand.
The larva bores into the main stem and sometimes penetrates the storage
roots. Larval feeding produces large tunnels causing hollow cavities in the stem
resulting in wilting and eventual death of infested plants. Attack at early
stages of plant growth prevents storage root formation since translocation of
food and its storage in the roots become severely affected. Further damage
occurs when the larva tunnels into the storage roots making them non-marketable.
Infestation during the establishment phase of the crop can result in yield
losses of 30-50% or more.
Infested plants usually have a pile of frass
that can be found close to the attacked stem.
Egg.The flattened yellow, oval eggs are laid in groups of 2 or 3 in crevices on the stem,
or on the lower leaf surface around the margin or in single
row of 6 or more eggs along the midrib of the leaf.
Larva. The newly-hatched larva has a
reddish tinge on its body and black head. After few days, it turns yellowish
with blackish markings on both the dorsal and lateral sides of the body. Setae
(bristles)
are brown and sparse becoming more noticeable as the larva matures. The
full grown larva reaches 33 mm in length.
Pupa. The
obtect pupa is brown.
Adult. The adult moth is 15 mm long,
has a wingspan of 33 mm, with a reddish-brown body and reddish brown markings on
the white wings.
The larva emerges after an incubation period of 3-8 days. There are five
larval instars with a total developmental
period of 12-50 days. Before pupating the larva makes an exit hole that is
covered with the epidermis of the stem. Pupation last about two weeks and takes
place in a web-covered cocoon within the tunnel. The adults emerge by breaking
through the dry papery covering of the exit hole. They live for 5 -10 days. The
total life cycle ranges from 22-30 days.
The females lay an average of 150-300 eggs.
Sweetpotato stemborer also lives on another Convolvulaceae - Ipomea
pescaprae (L.).
Cultural control
Using planting materials infested with stemborer eggs or planting a new field
next to an infested one are often the main means of disseminating this pest.
Treatment of planting materials and crop rotation are good means of controlling
the pest. Hilling-up is effective when the holes that provide the adults with an
exit from the stem are covered with soil.
Biological control
Earwigs and ants may attack the larvae developing within sweetpotato vines.
Undetermined hymenopteran species (family Encyrtidae) have been observed
attacking this pest.
Host resistance
Sources of resistance have been identified by the Asian Vegetable Research
and Development Center, Taiwan.
Amalin, D.M. and Vasquez, E. A. 1993. A handbook on Philippine sweet potato
pests and their natural enemies. International Potato Center (CIP), Los Baños,
Philipppines. 82 p.
Ames, T., Smit, N.E.J.M., Braun, A.R., O’Sullivan, J.N., and Skoglund, L.G.
1996. Sweetpotato: Major pests diseases, and nutritional disorders.
International Potato Center (CIP). Lima, Perú. 152 p.
PANS. 1978. Pest Control in Tropical Root Crop. Manual No. 4. Center for
Overseas Pest Research. London. 235 p.
Vasquez, E.A. and
Sajise, C.E. 1990. Pests of sweetpotato: Insects, mites and diseases. Philippine
Root Crop Information Service, Philippine Root Crop Research & Training
Center. 65 p.
Contributed by: Erlinda
Vasquez and
Vilma Amante |
