Chilo Partellus

''Chilo partellus'', the spotted stalk borer or spotted stem borer, is a moth in the family Crambidae. It was described by Charles Swinhoe in 1885. It is found in India, Pakistan, Iran, Ethiopia, Lesotho, Madagascar, Malawi, South Africa, Sudan, Tanzania, Uganda and on Mayotte.

''C. partellus'' is a pest that was introduced to Africa most likely from India in the early 20th century. After arriving in Africa, it has spread to nearly all countries in eastern and southern Africa, and it is assumed that it is spreading to western Africa. ''C. partellus'' is indigenous to Asia and became established in eastern Africa in the early 1930s.

''C. partellus'' is one of the most economically damaging pests in Asia and Africa, attacking all parts of the plant except the roots.

Habitat

''C. partellus'' has rapidly spread over a wide geographical range and has proven to be a very efficient colonizer and devastating pest wherever it may occur. In general, ''C. partellus'' occurs in low to mid-elevations (less than 1500 m) and warmer areas. However, they can now be found in higher elevations such as Ethiopia at 2088 m.

''C. partellus'' is highly invasive and can fully or partially displace other indigenous stemborer species such as '' Busseola fusca'' and '' Chilo orichalcociliellus''. Temperature and humidity can have a significant impact on the survival and establishment of adult ''C. partellus'' in new ecological niches.

Food

''C. partellus'' is a generalist herbivore that feeds on several species of cultivated and wild plants.

Appearance

Eggs are flat and oval and look creamy white and are about 0.8 mm in length.

Larvae of ''C. partellus'' resemble caterpillars and can be creamy white to yellowish brown. These larvae also have four purple-brown longitudinal stripes and are usually found with characteristically dark brown spots along the back, therefore giving off a spotted appearance. When the larvae of the spotted stalk borer are fully grown, they produce a conspicuous reddish-brown head. It has a plate on the dorsal surface of the thorax which is known as a prothoracic shield and is reddish brown to dark brown and shiny.

Pupae can be up to 15 mm in length, slender and shiny. The pupae of ''C. partellus'' are light yellow brown to dark red brown.

Adults are small moths with wing lengths ranging from 7–17 mm and a wingspan of 20–25 mm. The forewings of adults are brown yellowish with darker scale patterns forming longitudinal stripes. The hindwings of males are a pale straw colour and in females the hindwings are white.

Similar species such as ''Chilo orichalcociliellus'' located in East Africa may be confused with ''Chilo partellus''.

Reproduction and life cycle

Eggs are laid in batches of 10–80 on the upperside and underside of leaf surfaces, usually close to the midrib. They hatch after 4–10 days.

Younger larvae (caterpillars) feed on the leaf whorl. Older larvae tunnel into the stems, and it is within these tunnels that they feed and grow for about 2–3 weeks. When these larvae grow completely, they pupate and remain in the stem of the maize. After 1–2 weeks, the adults evolve from the pupae stage and emerge from the stem. They mate and lay eggs on other maize plants and continue to cause damage to the crop.

During dry seasons, larvae may enter a state of diapause or a period suspended development for several months and will pupate once it the dry season is over and there is rain. Adults can emerge from pupae in the late afternoon or early evenings and are active at night. Adults will rest on plants during the day. The whole life cycle takes about 3–4 weeks, however it can vary due to temperature, humidity and other factors. Five or more successive generations may develop in favourable conditions and in regions where there is warm temperatures, high relative humidity, sufficient water and an abundance of host plants. ''C. partellus'' can reproduce and develop all year-round.

Host relationship

This pest causes US$334 million annual loss to sorghum alone in the semiarid tropics.

''C. partellus'' attacks several grass species which can be both cultivated and wild. Cultivated crop hosts include but are not limited to maize, sorghum, pearl millet, rice, and sugarcane. Wild hosts include elephant grass (''Pennisetum purpureum''), reeds (''Phragmites'') and vossia (''Vossia cuspidata">Phragmites">arrell, G., Simons, S. A., & Hillock ...