Pumpkin stem borer (Coleoptera: Cerambycidae

Pumpkin stem borer

(Coleoptera: Cerambycidae)

Pumpkin stem borer occurs throughout South Africa, it has also been recorded in other parts of Africa including Sudan, Tanzania, Uganda, Nigeria, Kenya and Mozambique.

Nozibusiso Maphumulo

IPM-PROGRAM, NORTH-WEST UNIVERSITY

Pumpkin stem borer classification: Class: Insecta (insects) Order: Coleoptera (beetles) Family: Cerambycidae Genus: Apomecyna Species: binubila

Pumpkin stem borer, which is also known as melon stem borer, is a pest of cucurbits. Plants from the Cucurbitaceae family such as pumpkin, cucumber, watermelon, squash and muskmelon are hosts of this pest.

Females lay eggs on young stems of plants. Eggs hatch within four days after which the legless larvae start feeding on the stem. Larvae pupate inside the stem after 3-4 weeks. Adult beetles emerge from pupae within 4-8 days. The life cycle is therefore completed inside the stems of host plants. There are only two generations per season in South Africa, one in spring and one in autumn.

The eggs of the pumpkin stem borer are white in colour, elongated and have circular ends. The size of the egg is 1,7 mm x 0,5 mm. First-instar larvae are white in colour with a brown head. The size of first-instars is 1,5 mm x 0,5 mm after hatching. The mature larvae have a cylindrical shape that is slightly tapered on the anterior and posterior ends. The body of the mature larvae is soft and white to whitish-yellow in colour. The size of the mature larvae varies depending on food consumption rate, with the average length being 17 mm. Both neonate and mature larvae does not have legs.

The pupa, which is 13 mm long, has a soft body that is yellow to yellowish-brown and becomes darker as it develops. The adults are elongate in shape with a shining dark brown body colour covered with dense white and yellow-brown short hairs that gives it a greyish and dark yellow-brown appearance. Adults are 10 mm to 12,5 mm in length. Larval feeding inside stems and leaf stalks cause these to split or crack and become swollen. Infested stems eventually die and fail to produce any fruits. Crop failure due to pumpkin stem borer has been reported on different crops, such as cucumbers, muskmelon and watermelon in South Africa. However, pumpkin stem borer is not considered a pest of economic importance of cucurbits although it occasionally inflicts losses. A parasitic wasp, Iphiaulax sp. has been reported as a natural enemy that provides some level of biocontrol.

Enquiries: mashimanenozi03@gmail.com

Figure 1: Dorsal and ventral view of pumpkin stem borer adult.

https://commons.wikimedia.org/wiki/File:Apomecyna_binubila.jpg

Figure 2: Lateral view of pumpkin stem borer adult. https://www.insectimages.org/browse/ taxthumb.cfm?fam= 102&genus =Apomecyna

Figure 3: Different types of pumpkins that are hosts plants of pumpkin stem borer. https://www.gardeningknowhow.com/edible/vegetables/vgen/cucurbit-plantinformation.htm

Figure 4: Different types of melons that are hosts plants of pumpkin stem borer. https://www.homestratosphere.com/wp-content/uploads/2020/08/types-ofmelons-aug192020-min.jpg