Agriculture Reference
In-Depth Information
The larvae die in an upright position in the cell, and this is very noticeable (see
Figure 26).
The larva eventually dries to a scale resembling a Chinese slipper or gondola. This
does not adhere tightly to the cell wall and so, unlike AFB scales, the workers can
remove them. By doing this, however, they tend to spread the virus throughout the
hive.
After a few weeks the larval remains are no longer infective.
Treating of sacbrood
Strong colonies and regular re-queening seem to be the best means of combating this
disease - no antibiotic is effective at preventing or controlling it. Colonies suffering
from this virus usually recover spontaneously when the honey flow starts because, at
this time, there are fewer adults in the hive to pass on the disease.
Chalkbrood
Chalkbrood is a disease caused by the fungus,
Ascosphaera apis
, and it affects unsealed
and sealed brood. It can be triggered by a change in brood-nest temperature. When
there are insufficient nurse bees to cope with extreme weather conditions (e.g. for cold
clustering and heat fanning), the brood may be left unattended. The first larvae affected
are usually those around the edges of the brood, where the brood temperature may be
higher or lower.
Stress of any kind can result in chalkbrood: high or low temperatures, wet or dry
conditions, an increase in CO
2
, poor nutrition, a failing queen, poor hive management
and moving hives. In other words, all sorts of environmental factors have been linked
to the disease at one time or another, which means
the trigger is not completely
understood.
Identifying chalkbrood
Chalkbrood is fairly easy to recognize, especially in its later stages, because the hive's
floor and front will be littered with small hexagonal blocks of chalk-like material.
Initially, the larvae are covered by a fluffy white fungal (mycelial) growth, which looks
