Storage pests of Sweet Sorghum:

Rice Weevil/Black Weevil (Sitophilus oryzae)

There are three types of rice weevil

1. Rice or black weevil

2. Maize weevil

3. Granary weevil

Grains attacked:

Rice weevil mainly affects stored food grains such as wheat, rice, maize and sorghum

Nature of damage:

The damage to the grains is mainly caused by two stages of this insect

(1) Larvae

(2) Adults

Due to infestation by the above stages of the insect, the grains are hollowed out and in some cases the kernels are reduced to mere powder. Rice weevil and maize weevil are also known to cause infestation right from the field. Adult insects cut circular holes in the grains . When the intensity of infestation increases it results in heating, referred to as dry heating.

Identification:

The insect can be identified easily by the following criteria:

• Size is around 3 mm

• It possesses characteristic beak or snout

• Antennae are elbowed and slightly clubbed

• Hind wings are present except in granary weevil

• The color ranges from reddish brown, chocolate to almost black

• The maize weevil is the largest amongst the three species.

Other information:

Grains with less than 10% moisture are not attacked by the insect. The life cycle of the insect is completed in about 26 days at 30°C and 75% relative humidity (RH). The optimum climatic conditions, especially the temperature for development, ranges from 26°C to 30°C.

Fig. 1 : Damage of Rice Weevil on Sweet Sorghum