Aspidimorpha spp.

Sweet potato cassides
 

General

• Phytophagous beetle insects of the family Chrysomelidae and of the subfamily Cassidinae .
• The genus Aspidimorpha (sometimes incorrectly spelled Aspidomorpha ) includes some 200 species. Among them, some attack the Convolvulaceae.
• Species encountered: Aspidimorpha quinqefasciata  (Fabricius, 1801) which is most frequent on sweet potato, A. aurata (Montrouzier, 1855), A. convolvuli (Boheman, 1862) endemic to New Caledonia. A. quinquefasciata shows a colored crest on the top of its shell which is bordered by translucent patches, and brown-brown to black in color (sexual polymorphism). Native to equatorial Africa, we find this species in Réunion, Madagascar and New Caledonia where it was introduced in 2008. It  only moves during the day and remains on the upper surface of the leaves, while the larvae s' observe under the leaves.
• These insects are observed in the open field.

• Sensitive botanical family (s)

• Affected production areas :

• Organs attacked

 Symptoms, damage

• Symptoms :
  • Larvae and adults parasitize sweet potato (Figure 1).
  • Parenchyma nibbled under the imbe, without damaging the upper epidermis (young larval stages).
  • Rather large irregular leaf perforations (last larval stages, and adults)
  • Detrimental damage during an attack at the start of a crop, less on an installed crop.

• Signs : Presence of adult insects and larvae on plants and in the crop (Figures 3 to 7).
• Possible confusion :

 Biology

•  Development cycle : it is essentially aerial. After the eggs hatch, the life cycle includes 3 developmental phases in the foliage of the attacked plants: 5 larval stages, a pupal, and an adult.
  
  • the eggs are deposited in clusters within a structure formed of layers. These clusters are attached to the lower surface of the leaves (Figure 2).
  • Mobile but wingless larval stages (Figures 3 and 4). The larvae are about 1cm long and show a characteristic "feather duster" consisting of the accumulation of their molts at the end of the abdomen. They use it to protect themselves by placing it between her and the predator.
  • Pupae are attached under the leaf by the end of the abdomen (Figure 5).
  • The adults are winged (figures 6 and 7), they evolve mainly outside the foliage. They are ovoid or round in shape, with a flattened rim all around their body, including above the head (in front of the prothorax). They have very variable colors, Some have colors similar to those of ladybugs, others are solid in color, ranging from black to gold.

 Protection

• Produce the cuttings in an nursery insect-proof .
• Check the sanitary quality of the plants before and during their introduction into the crop or shelter.
• Remove the leaves from the cuttings so as not to introduce eggs on the new plots and destroy the plant waste generated.
• Plant the new crops in locations far enough from old plots, in order to delay the arrival of these pests.
• Destroy crop residues (tops) after harvest.
• Note the existence of natural predators in Africa, they are Aprostocetus aspidomorphae and A. cassidocida, two micro-hymenoptera of the Chalcidoid family.