**5. Classification of toxicants**

*Modern Beekeeping - Bases for Sustainable Production*

*Source: Data extracted from Mackensen [22].*

*Pollen gathering by bees after anesthetic treatments.*

This is the major mode of intake of toxicants by the bees since they are exposed to direct contact of pesticides in the fields while foraging on the crops. Honey bee foragers come in direct contact with several pesticides while foraging and such chemicals can be lethal even in small quantities. Dermal toxicity through topical spray has been reported for various insecticides and thorax has widely been regarded as a major route of dermal exposure of pesticides to the honey bees [16, 17]. Other than thorax, insect wings have been reported as a more lethal route of exposure to the bees [18]. Some of the majorly important and frequent ways of dermal intakes are following:

With pollen 0 0 0 15 Without pollen 16 33 25 25

**N2O CO2 Ammonium nitrate Control**

• Majority of bee poisoning is due to application of insecticides to crops during

• Bees coming in contact with insecticides residues on plants and collect insecti-

• Bees drinking or touching contaminated water or honeydew on the ground or

• Contamination through treated nectar sources. Dimethaote is the only systemic insecticide known to be excreted in hazardous amount in nectar under

• One of the obvious signs of pesticide poisoning is the presence of a large

have been exposed to pesticides sprayed in the fields.

number of dead or dying bees at the hive entrance. These bees are foragers who

• Another common symptom includes the presence of a moist and sticky mass of dead bees at the hive entrance. This results from poisoning by some fast-acting pesticides, e.g., organophosphorus pesticides. Dying bees extend their tongues through which nectar is regurgitated resulting in sticky and moist dead bees. Bees that have been exposed to a pesticide may regurgitate a thick and dark fluid.

• Swiftly-acting insecticides kill foraging bees in the field itself, while only some of them manage to return to the hive. Sometimes, while spraying is done in the nearby fields to the apiaries, if such chemicals come in direct contact with colony, the whole colony may also die instantly. Stronger colonies suffer greater

**3.3 Dermal intake**

**Table 1.**

blooming period.

cide dust with pollen.

field conditions.

**4. Symptoms of bee poisoning**

• Bees coming in contact of treated areas.

foliage or from nearby water bodies.

**16**

Classification of different toxicants to honey bees can be done either on the basis of levels of toxicity or on the basis of sources in the nature. Different toxicants have variable toxicity levels, according to their mode of action on bees and this toxicity level is measured as LD50, which is the dose at which 50% of the bee population dies due to the intoxication. On the basis of their LD50 levels, toxicants have been classified into four different categories [19].


Second type of classification is based on the type of toxicants which are originated from different sources, due to human interventions. These toxicants include:
