*5.3.2 Fungicides*

"A fungicide is a specific type of pesticide that controls fungal disease by specifically inhibiting or killing the fungus causing the disease."

It is believed to be nontoxic to bees by farmers and hence it is mostly applied during the flowering of plant coinciding with maximum bee activity. Thus, fungicides often account for most of the pesticide content of pollen [9]. An alarming concentration of fungicide chlorothalonil (99 ppm) has been reported from the honey bee pollen [76]. Other than chlorothalonil, in other studies, fungicides like vinclozolin (32 ppm) and iprodione (5.5 ppm) captan (contact) and difenoconazole [77] have also been reported from beebread. While fungicides are considered to be fairly safe for use around adult honey bees, beekeepers have reported losses of brood in larval and pupal stages coinciding with fungicide use during bloom. Fungicide applications also have been determined to trigger hypothermia in adult honey bees [78]. Fungicide was causing toxic effects to honey bee brood based on finding malformed, and frequently wingless, pupae and recently emerged adult bees. The affected bees accumulated on the bottom boards and at the entrance so hives about 2 week after applications. The toxicity levels for different fungicides lies in the range of LD50 > 200 to as small as 0.2 μg/ bee (**Table 6**).


**25**

*Detailed Review on Pesticidal Toxicity to Honey Bees and Its Management*

**Herbicide LD50 (μg/bee)** 2,4-DB acid 14.5 2,4-DP-P, dimethylamines 25 Trifloxysulfuron-sodium 25 Pendimethalin 49.5 Triclopyr, butoxyethyl ester 62.5 Alachlor 68.1 Simazine 96.7 Atrazine 97 Picloram, potassium salt 100 Glyphosate, isopropylamine 100 2,4-D, 2-ethylhexyl ester 100

Even though the main purpose of using different herbicides is to control the unwanted weed populations in the fields and there is no such objective to kill insects through them. The toxicity level of herbicides is known to be very less to most of the insects and due to this these pesticides are applied without any restrictions regarding insects. Bees usually come across these chemicals in higher concentrations [79] and toxic effects of these have also been reported on honey bees. Toxicity levels in LD50 values differ from one chemical to another with a range of 14.5–100 μg/bee (**Table 7**). A widely used herbicide, paraquat has been reported to be toxic to the bees in laboratory conditions, causing median life of worker ten times reduced than the normal, on injecting at the rate of 15 μg per worker and death within a span of 3 days' time, when sprayed at the rate of 4.5 kg AI/ha [79]. These pesticides may harm the bees in other way around as well as they reduce the number of plants offering

• **Use pesticides only when needed**: insect pests, pathogen or any environmental factor infest or infect the particular crops during specific growth stages of the plant and pesticide application should be done only after surveying the crop fields for the presence of weeds, pest population or disease incidence for threshold levels. This helps in safeguarding the population of insect pollina-

• **Do not apply pesticides while crops are in bloom**: use of different pesticides should only be performed only when the crop concerned is not in

• **Apply pesticide when bees are not flying**: the most pollinators are active during 8 a.m. to 5 p.m. and in such favorable conditions pesticides should not be sprayed to help in protecting the forager bees from coming in the direct contact

**6. Management of pesticidal toxicity to the honey bees**

*DOI: http://dx.doi.org/10.5772/intechopen.91196*

*Source: Data compiled from ECOTOX database [54].*

*5.3.3 Herbicides*

*List of herbicide toxic to bees.*

**Table 7.**

floral resources to the bees.

tors, beneficial insects.

flowering stages.

#### **Table 6.** *List of fungicides toxic to bees.*

*Detailed Review on Pesticidal Toxicity to Honey Bees and Its Management DOI: http://dx.doi.org/10.5772/intechopen.91196*


#### **Table 7.**

*Modern Beekeeping - Bases for Sustainable Production*

*5.3.1.3.1 Toxic symptoms of synthetic pyrethroids*

• Regurgitation of ingested food

• Erratic movement of the bees

• Paralysis

*5.3.2 Fungicides*

bee (**Table 6**).

*Source: Data compiled from ECOTOX database [54].*

appears to be less toxic or safer to the honey bees but in higher concentrations this chemical has been reported to affect the health of different castes of honey bee colony. Colonies exposed to high doses of tau-fluvalinate had smaller queen bees [75]. Drones exposed to tau-fluvalinate during development were also reported to

"A fungicide is a specific type of pesticide that controls fungal disease by specifi-

It is believed to be nontoxic to bees by farmers and hence it is mostly applied

during the flowering of plant coinciding with maximum bee activity. Thus, fungicides often account for most of the pesticide content of pollen [9]. An alarming concentration of fungicide chlorothalonil (99 ppm) has been reported from the honey bee pollen [76]. Other than chlorothalonil, in other studies, fungicides like vinclozolin (32 ppm) and iprodione (5.5 ppm) captan (contact) and difenoconazole [77] have also been reported from beebread. While fungicides are considered to be fairly safe for use around adult honey bees, beekeepers have reported losses of brood in larval and pupal stages coinciding with fungicide use during bloom. Fungicide applications also have been determined to trigger hypothermia in adult honey bees [78]. Fungicide was causing toxic effects to honey bee brood based on finding malformed, and frequently wingless, pupae and recently emerged adult bees. The affected bees accumulated on the bottom boards and at the entrance so hives about 2 week after applications. The toxicity levels for different fungicides lies in the range of LD50 > 200 to as small as 0.2 μg/

**Active ingredient Trade name LD50 (μg/bee)** Dicloran Botran 0.2 Captan Captan 10 Dodine Syllit FL 12.5 Propiconazole Bumper 25 Ziram Ziram 46.6 Thiram Thiram 74 Sulfur Disperss >100 Mancozeb Dithane 178.9 Trifloxystrobin Flint >200

be affected with lesser chances of attaining sexual maturity [14].

• Many bees die between foraging area and colony

cally inhibiting or killing the fungus causing the disease."

**24**

**Table 6.**

*List of fungicides toxic to bees.*

*List of herbicide toxic to bees.*
