Winter 2017 with Ernesto Guzman
UNIT TWELVE – Pest and Pesticides
Pest of Honey Bees
Wax moths are the most damaging invertebrate pests known to affect honey bees. Wax moths can reduce
drawn comb to webbing and debris. A description of the most relevant aspects of these pests follows:
• Types: there are at least two species of moths that cause damage to comb in the hive: the greater
wax moth and the smaller wax moth. The most common is the first one, Galleria melonella. The
moth's larvae feed on wax, honey, and pollen. They more easily attack weak colonies that cannot
defend themselves and cannot protect all the comb in the hive. Stored combs in warehouses are
also affected by wax moths during the warmest months of the year.
• Life cycle: adults mate outside the hive and females return to the hive to lay eggs on combs.
Larvae burrow tunnels in the midrib of combs (protected from worker bees), spinning silken
threads. Galleria pupates on wooden frames and boxes; after pupation, adults emerge. The life
cycle is completed in 1-6 months, depending on the time of the year and location. The life cycle is
short during warm months and long during cold months of the year. Combs are destroyed by the
larvae and wooden parts of the hive are damaged and left with marks by the pupae.
• Control: the best control against this pest is to keep colonies strong so they can defend themselves.
Empty equipment must be stored at freezing temperatures during the winter (freezing
temperatures kill the moths). Carbon dioxide fumigation also kills all stages of the moths.
Biological control against the larvae using Bacillus thuringiensis (Bt) is available in Europe but not
in North America. Chemicals can be used as fumigants of stored equipment in some countries
(acetic acid, PDB, aluminum phosphide and others) but their use may be hazardous and thus are
not registered neither in the USA or Canada.
Small Hive Beetle (SHB)
The SHB, Aethina tumida, is becoming a pest of serious consideration in recent years. Present in
neighbouring states of the USA, it was first reported in Manitoba, Canada in 2002 and in Ontario in 2009.
This beetle is native of Southern Africa and has caused damage to colonies in the warmer states of the
USA. Adults disperse during warm months of the year by flying between apiaries (7 km range). Adults ENVS*2210*DE
Winter 2017 with Ernesto Guzman
mate inside hives and females lay eggs in wooden crevices or combs. Larvae feed on honey and pollen and
eventually crawl out of the hive and pupate in the soil in front of the hive entrance. Adults emerge and
return to hives. The beetle larvae damage comb and the honey of affected colonies ferments and spills in
the hive as a consequence of beetle defecation; its odour causes bees to abscond (leave the hive). Beetle
faeces also spoil stored honey awaiting extraction. Control measures against this pest include the use of
coumaphos strips applied on bottom boards of hives to kill larvae as they exit the hive to pupate. Drenches
on the ground in front of hive entrances are also recommended to kill beetle pupae. Some beekeepers use
traps containing mineral oil inside hives. These traps attract larvae to the trap container where they
drown in the oil. The most effective measures against SHB are keeping strong colonies and clean honey
Other Insect Pests
The most common insect pests other than wax moths and SHB are described below:
• Ants: sometimes ants become pests: stealing honey, pollen and dead bees from hives, especially in
warmer climates. Besides keeping strong colonies, placing hives on stands coated with diesel fuel
or mounted in containers filled with burnt motor oil, will resolve the problem in most cases.
• Wasps: several wasp species such as yellow jackets are scavengers that steal honey from hives and
feed on dead adult bees. Some wasps are carnivorous and may attack and kill bees, like in Japan,
the so-called giant hornet, Vespa mandarinia, or in Europe, Vespa velutina. A strong colony with
entrance reducers is the best defense for the bees against these pests.
• Flies: The bee louse (Braula coeca), a wingless fly that lives on the body of bees is harmless to
them. The bee louse feeds on tiny amounts of nectar from the mouth of bees. Some flies like the
so-called zombie fly (Apocephalus borealis) deposit eggs into the body of an adult honey bee and
their larvae devour the bee from the inside.
Mice can damage combs and wooden parts of hives when nesting inside them during winter. Entrance
reducers and strong colonies are the best defense against them. Skunks scratch on the hive entrance to
attract bees to the outside. They roll the bees with their paws and put them in their mouth. Boards with
nails on the ground in front of the hive entrance deter these occasional pests. Bears, however, can be very
damaging. In their attempt to eat combs containing brood and pollen (not so much the honey), they tear ENVS*2210*DE
Winter 2017 with Ernesto Guzman
apart hives. Electric fences may help in their control. The Ontario provincial government has established a
fund to pay beekeepers for losses caused by bears.
Pesticides and Honey Bees
Pesticides are chemicals or biological agents used to control pests. Most pesticides are used as plant
protection products in agriculture and are useful tools for food production. However, pesticides have
drawbacks such as toxicity to non-target organisms like bees. For the beekeeper and honey bee students,
some of the critical issues to know regarding pesticides and bees include the following:
Types of Pesticides
Pesticides can be classified in different ways. Generally, they are classified based on the type of pests they
control: insecticides (kill insects), herbicides (kill weeds), fungicides (kill fungi), miticides (kill mites),
rodenticides (kill mice), etc. Pesticides are also classified according to their chemical structure (eg.
organophosphates), or source of origin (eg. pyrethroids). Most pesticides are considered safe for honey
bees, but a small proportion of them (about 20-25%) may cause some degree of damage to them; mostly
insecticides. Insecticides are nerve toxins that interfere with the transmission of electrical nerve impulses,
paralyzing and killing insects. Other insecticides disrupt normal growth, development, or other biological
functions of insects.