APICULTURE

Pests and Diseases

Pests

Brood mite (Tropilaelaps clareae): Infests the brood and the infestation is severe during the major brood rearing season (October-January). These ectoparasites feed on the haemolymph of developing broods slowly killing them. Dusting sulphur on the topbars of the frames at the rate of 200 mg / frame at 7-14 days interval during brood rearing season is very effective in checking the infestation.

Yellow-banded wasp (Vespa cincta): These predatory wasps catch the bees from both the hive entrance and inside the hives. Locating and destroying their nests by burning or insecticidal usage is an effective control measure.

Wax moth (Galleria mellonella): Infests weak and unattended colonies. Proper cleaning of the hives periodically and keeping the hives without cracks and crevices can avoid infestation.

Black ants: Various species of black ants intrude beehives and take away honey and pollen and kill the brood and bees, which may lead to absconding of colony. The apiary should be kept clean and the ant nests destroyed by insecticidal applications. Ant wells should be provided for the beehive stands.

Red tree-ant (Oecophyla smaragdina): If not protected properly, the red tree-ants can cause considerable damage to the bees and the brood. The bees that come in contact with the ground are attacked and killed by the ants and dragged to their nests by a number of ants. In the apiary, if the branch of a tree with these ants happens to come in contact with the hive, the entire colony is attacked and destroyed. Providing ant wells will keep away the ants. Care should be taken not to keep the colonies near or under the trees having ant nests.

Bee-eater bird (Merops orientalis): These predatory birds do much harm in certain localities. They pick the bees on wings and 30-43 honeybees have been found in the stomach of a bird. Attack by these birds is mostly seen during December-January. These birds are also very useful in keeping down the insect population in a locality and hence no large-scale measures against them can be recommended. Scaring them away from apiaries is suggested.

Diseases

Thai sac brood virus

Symptoms

All the larval instars are susceptible to the disease, earlier instars being more susceptible. Affected larvae appear slightly plumby compared to healthy ones when examined on taking out of the comb cells. The infected larvae see stretched on their back in the cells with the head directed outwards and turned upwards like the prow of a boat. The dead larvae look like a sac filled with milky white fluid when lifted up and it ruptures even with the slight pressure releasing the milky fluid. The cadavers change their colour from white to pale yellow and sunk down to the floor of the cell and dry up in 10-15 days as brownish black boat shaped scales, which is easily removable from the cells.

The sequence of visible symptoms found in the field is:

• Presence of unsealed cells in brood area containing diseased larvae with their head directed outwards like the prow of a boat.
• Dead larvae are seen lying stretched out on their back on the floor of brood cells and look like a sac filled with milky white fluid when lifted up.
• Appearance of dead larvae strewn on the floorboards, hive entrance or on the floor near the hive.
• Mottled appearance of brood combs with uncapped cells interspersed with capped cells or cells with perforated capping.
• Appearance of more and more dead larvae left within the cells without being ejected by the worker bees.
• Appearance of sac like remnants of dead larvae within the cells.
• Lack of cleaning activity within the hive.
• Decrease in egg laying rate and irregular placement of eggs.
• Decrease in foraging activity and presence of idling workers inside the hive.
• Dwindling of bee population of the colony.
• Desertion of infected hives by the bees causing total loss to the apiary.

Control

Being a virus disease there is no known remedy for its cure. However, the following measures may help in minimizing the possibilities of further spread: a) Keeping colonies strong; b) avoid exchange of hive parts, combs etc. from infected colonies to healthy colonies; c) avoid procurement of colonies or swarms from infected areas.

Last updated: 21-3-2007