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Delphastus pusillus

Predator of Whitefly

Delphastus pusillus is a small ladybird beetle which feeds on all stages of whitefly, but prefers whitefly eggs and larvae. Adult beetles are small, shiny, dark brown to black and 1.3 to 1.4 mm long. Females have a reddish yellow head and are lighter coloured than males.

Adult beetles are active flyers that are attracted to the smell secreted by young whiteflies. In this way the beetles can detect whitefly hot spots. Larvae of D. pusillus slowly move from plant to plant on leaves.

Male beetles live on average 1.5 months; female beetles live for about 2 months, to a maximum of 80 days. During this time they can lay 3 to 4 eggs per day. Females prefer to deposit their eggs in whitefly clusters, so that the young larvae can easily find prey. The eggs of D. pusillus are about 0.2 mm long and transparent. When the eggs hatch the larvae are pale to light yellow. The larval stage takes 1.5 to 3 days. The larvae pupate in the lower part of the crop, preferably in groups. The pupal stage takes about 6 days. Young adults are light brown to almost white but gradually turn black with a brown head. The development time of D. pusillus is strongly influenced by temperature and light. The complete life cycle takes 21 to 25 days at 25 to 30°C. The optimal temperature for D. pusillus is situated between 16 and 35°C; at temperatures below 13°C Delphastus does not fly. It does not go in diapause under short-day circumstances and is therefore active during the entire season. It can stand light frost, but does not survive longer periods of cold.

Both larvae and adults are excellent predators that can consume numerous eggs and larvae each day. An adult beetle devours daily up to 160 eggs or 12 whitefly larvae. A larva eats about 1,000 whitefly eggs during its entire development (or less if it also eats whitefly larvae). A single Delphastus can consume 10,000 whitefly eggs or 700 larvae during its lifetime! Females feed more on eggs and first instars than on later stages. Adult female beetles must feed on more than 200 eggs per day in order to reproduce. D. pusillus avoids whitefly larvae parasitized by parasitic wasps (Encarsia formosa / Eretmocerus eremicus) when the wasps are in later stages of development. If food is scarce, D. pusillus also feeds on spider mites, aphids and its own sort!

Advantages:

  • Enormous gluttony
  • Immediate action
  • Eats all stages of whitefly
  • Avoids whitefly pupae parasitised by Encarsia
  • Controls both greenhouse and tobacco whitefly