Characteristics of pesticide retailers and farmers
More than half (58.8%, n = 10) of the agrovet stores were in Kilombero district, while the remaining 41.2% (n = 7) were in Ulanga district. Two-thirds of participants (65.2%, n = 11.3) were females with age ranging between18 and 43 years.
Table 1 summarises the demographic characteristics of the farmers who participated in the survey. Of the farmers who participated in the survey, males comprised of 51.5% (n = 220) and females 48.4% (n = 207). Most farmers practiced both small scale subsistence farmers (51.3%, n = 219) and large scale cultivation (48.5%, n = 2017) for food and business, and had worked on their farms for at least five years (89.2%, n = 381). The main farm crops farmed were rice, maize, vegetable and fruit.
Table 1
Socio-demographic characteristics of farmers involved in the survey
Variable | Category | Percentage (n) |
Gender | Males Females | 51.5% (220) 48.4% (207) |
Age (years) | 18–30 31–40 41–50 51–60 > 60 | 16.9% (72) 31.1% (133) 28.3% (121) 17.6% (75) 6.1% (26) |
Education attainment | Primary school Secondary school College/university Professional training No formal training | 85.2% (364) 9.6% (41) 0.7% (3) 0.5% (2) 4.0% (17) |
Main economic activities¥ | Small-scale subsistence farming activities Large-scale farming for food and business Livestock keeping Small-scale business Large-scale business Private employment Others | 51.3% (219) 48.5% (207) 9.8% (12) 41.7% (178) 2.8% (3) 0.7% (2) 0.5% (42) |
¥ (farmers with more than one sources of income, multiple responses) |
Types and classes of agricultural pesticides
All the agricultural pesticides (supplementary file), chemical class, and their active ingredients (Table 2) observed in the agrovet stores. Most of these (87.5%, n = 91) were approved plant protection substances under full registration category, (6.7%, n = 7) and (2.9%, n = 3) had restricted registration or provisional registration according to Tanzania regulations[40, 41]. A small proportion (2.9%, n = 3) were unregistered. Insecticides accounted for (59.6%, n = 62) of the pesticides, followed by herbicides (27.9%, n = 29) and fungicides (10.6%, n = 11). The highest proportion of agricultural insecticides surveyed were organophosphates (34%), followed by pyrethroids (30%). Herbicides from the amino-phosphonates class were the most popular (59%). The two main fungicide classes were dithiocarbamate (54.5%) and acylalanine organochlorine (27.3%), widely used by most vegetable growers (Table 2). The insecticide formulations were EC (63%), while 66% herbicides and 64% fungicides were formulated as soluble (liquid) concentrate (SL) and wettable powders (WP), respectively.
Most insecticides had a single active ingredient (72.6%, n = 45), while (27.4%, n = 17) were mixed products with two different active ingredients at different doses (Table 2 and Table 3). The commonest pyrethroid was lambda-cyhalothrin, while chlorpyrifos and profenofos were the commonest organophosphates (Table 2). Most of the insecticides are non-systemic broad-spectrum insecticides with contact and stomach actions against crop pests. Over half of the herbicides (59%) were glyphosates based and were frequently used by the majority of rice farmers (76.8%). The principle active ingredients in most fungicide were metalaxyl and mancozeb (45%) and chlorothalonil (27%) (Table 2). Table 3 summarises some of the commonly used pesticide products with more than one active ingredients. A wide range of insecticide classes and active ingredients used in crop protection had similar target sites and mode of action with the limited public health insecticide (Table 4).
Table 2
Common active ingredients found in the agricultural pesticides in the study locality
Pesticide type | Active ingredient (s) | N | % | Chemical class |
Insecticides (N = 62) | Abamectin | 4 | 6.5 | Macrocyclic lactones |
Alphacypermethrin | 3 | 4.8 | Pyrethroids |
Carbaryl and permethrin | 1 | 1.6 | Carbamates and pyrethroids |
Carbofuran | 1 | 1.6 | N-methyl carbamate Ib |
Carbryl and lambda-cyhalothrin | 2 | 3.2 | Carbamates and pyrethroids |
Chlorpyrifos | 5 | 8.1 | Organophosphates |
Cypermethrin | 1 | 1.6 | Pyrethroids |
Cypermethrin and chlorpyrifos | 1 | 1.6 | Pyrethroids and organophosphates |
Cypermethrin and imidacloprid | 3 | 4.8 | Pyrethroids and neonicotinoids |
Deltamethrin | 1 | 1.6 | Pyrethroids |
Diazinon | 2 | 3.2 | Organophosphates |
Dichlorvos | 3 | 4.8 | Organophosphates |
Dimethoate | 1 | 1.6 | Organophosphates |
Fenitrothion and deltamethrin | 3 | 4.8 | Organophosphates and pyrethroids |
Fipronil | 1 | 1.6 | Phenylpyrazole |
Imidacloprid | 3 | 4.8 | Neonicotinoids |
Imidacloprid and beta-cyfluthrin | 2 | 3.2 | Neonicotinoids and pyrethroids |
Lambda-cyhalothrin | 11 | 17.7 | Pyrethroids |
Lambda-cyhalothrin and acetamiprid | 1 | 1.6 | Neonicotinoids and pyrethroids |
Malathion | 1 | 1.6 | Organophosphates |
Permethrin | 1 | 1.6 | Pyrethroids |
Pirimiphos-methyl | 2 | 3.2 | Organophosphates |
Pirimiphos-methyl and permethrin | 3 | 4.8 | Organophosphates and pyrethroids |
Pirimiphos-methyl and thiamethoxam | 1 | 1.6 | Organophosphates and neonicotinoids |
Profenofos | 5 | 8.1 | Organophosphates |
Herbicide (N = 29) | Bispyribac sodium | 1 | 3.5 | Bispyribac sodium |
S-metolachlor and atrazine | 1 | 3.5 | Triazines |
Amine salt | 4 | 13.8 | Aryloxyacides |
Atrazine | 1 | 3.5 | Dinitroanilines |
Glyphosate | 17 | 58.6 | Amino-phosphonates |
Paraquat | 4 | 13.8 | Pyridines |
Triclopyr | 1 | 3.5 | Pyridines |
Fungicide (N = 11) | Monopotassium and dipotassium phosphonates | 1 | 9.1 | Phosphonic acid |
Chlorothalonil | 3 | 27.3 | Organochlorine |
Mancozeb | 1 | 9.1 | Dithiocarbamate |
Mancozeb and cymoxanil | 1 | 9.1 | Acylalanine and dithiocarbamate |
Metalaxyl and mancozeb | 5 | 45.5 | Dithiocarbamate and acylalanine |
Insecticide + fungicide (N = 2) | Imidacloprid, metalaxyl and carbendazim | 2 | 100 | Neonicotinoids, acylalanine and benzimidazole |
Table 3
Example of pesticide products with more than one active ingredient (as obtained from the factory)
WHO class/family | Brand name | Active ingredient(s) |
Organophosphates and pyrethroids | Simba powder 113DP | 10 g/kg of fenitrothion and 1.3 g/kg of deltamethrin |
Duduba 450EC | 350 g/l of chlorpyrifos and 100 g/l of cypermethrin |
Mupa dust | 1.0% of fenitrothion and 0.13% of deltamethrin |
Stocal super dust | 16 g/kg of pirimiphos-methyl and 3 g/kg of permethrin |
Shumba super dust | 1% of fenitrothion and 0.13% of deltamethrin |
Actellic Gold Dust | 16 g/kg of pirimiphos-methyl and 3.6 g/kg of thiamethoxam |
Haigram 90 dusting powder (DP) | 6 g/kg of pirimiphos-methyl and 3 g/kg of permethrin |
Actellic super dust | 16 g/kg of pirimiphos-methyl and 3 g/kg of permethrin |
Pyrethroids and neonicotinoids | Amekan C344 SE | 144 g/l of cypermethrin and 200 g/l of imidacloprid |
Rapid-attack 344SE | 144 g/l of cypermethrin and 200 g/l of imidacloprid |
Blast 60 EC | 3% g/l lambda-cyhalothrin and 3% g/l of aceptamiprid |
Buffalo 450OD | 2.5% of betacyfluthrin and 7.5% of imidacloprid |
Thunder Oil Dispersion (OD) 145 | 45 g/l of beta-cyfluthrin and 100 g/l of imidacloprid |
Farmguard 344SE | 144 g/l of cypermethrin and 200 g/l of imidacloprid |
Carbamates and pyrethroids | Bakiller | 5% w/w of carbaryl and 0.1% w/w of lambda cyhalothrin |
Akheri Powder | 5% w/w carbryl and 0.1% w/w lambda-cyhalothrin |
Ultravin® Dudu dust | 5% w/w of carbaryl, 1% w/w of permethrin and 94% w/w of inert carriers |
Neonicotinoids, acylalanine and benzimidazole | Seed plus 20 wettable soluble (WS) | 10% imidacloprid, 5% metalaxyl and 5% carbendazim WS |
Table 4
Similarities between agricultural and public health insecticide classes and reported resistance mechanisms in disease vectors
Class of insecticide | Trade name (active ingredient (s) | Primary site/mode of action in an insect/vector | Agricultural use | Public health use | Known resistance and resistance mechanism in disease vectors |
Pyrethroids | Karate 5 EC (lambda-cyhalothrinin) | Voltage-gated sodium channels/neurotoxic | Control of bollworms and aphids in vegetables and cotton [42] | Disease and vector control (IRS and LLINs) [43, 44] | Knock-down mutation [45] Metabolic resistance [46] Cuticle thickening [47] |
Organophosphates | Dasba 40 EC (chloropyrifos) | Acetylcholinesterase (AChE) inhibitors | Insecticide against insect pests in fruits, beans, tomatoes, cotton, coffee and green vegetables [48] | Disease and vector control (IRS and LLINs) [49] | Metabolic resistance [50] |
Neonicotinoids | Amekan C344 SE (200 g/l of imidacloprid and 144 g/l of cypermethrin) | Nicotinic acetylcholine receptors (n AChRs) | Systemic insecticides with contact and stomach action against sucking and chewing pests on cotton, vegetables and flowers [51]. | Prequalified vector and disease control products [52, 53] | Metabolic resistance and target-sites [54, 55] |
Carbamates | Farmerzeb 80 WP (80% WP of mancozeb) | Acetylcholinesterase (AChE) inhibitors | A broad spectrum protectant and preventive fungicide for the control of fungal diseases on vegetables | Disease and vector control (IRS and LLINs) [56] | Metabolic resistance [57, 58] |
Awareness and perceptions of pesticides use among agrovet store retailers
Most retailers stated that their customers were mostly rice farmers or horticulture farmers, particularly those relying on the irrigation system. The frequency of purchasing particular pesticides depended on the season. A majority of retailers reported to have no formal training on the pesticides they were selling, and poor knowledge on the type of crop pests, disease and relevant pesticides to be used for each. They were only able to recommend the use (dilution and frequency of application) based on experiences, or based on recommendations from the store owners and pesticide suppliers:
“I have been selling pesticides for a long time. I started to work in Ifakara town shops. Also, the owner of the shop understands pesticides, and she does assist with information whenever needed” (male retailer).
A majority of the retailers also reported giving instructions to their customers on pesticides usage, dosage and application time. However, upon examining the pesticides labels, the dosage suggested by the retailers was sometimes higher or lower than those recommended by the manufacturers on the product label. The handling of pesticides was commonly practised without protective measures. However, the retailers also occasionally provided information on use of protective measures such as wearing long-sleeve shirts and boots during preparation and spraying of pesticides:
“Most of my customers do not know the dosage of chemicals to use. I tell them that quantity of chemicals depends on the size of the farm, amount and type weeds, and particular for insecticides it depends on the pest problem…if they ask me I always ask them how big their problem is, then I tell them too add 250mls of Agroround (480 g/l of glyphosate) to a 15Liter bucket” (female retailer).
A total of 18 (17.5%) pesticides were commercially found repacked into small quantities in small unlabelled bottles. Decanted pesticide products were mainly targeting average income farmers who were able to afford small amounts.
Crop calendar and pesticide usage practices
Most of the farmers reported cultivating more than one type of crop. Overall, 421 of the farmers (64.8%) grew cereal crops, predominantly rice and maize, 168 (25.8%) cultivated vegetables and fruits such as spinach, cabbages and watermelon, 34 (5.2%) cultivated legumes such as beans and 27 (3.2%) grew other crops such as cashew nuts and peanuts. Most farmers owned 1 to 20 ha of land. In the wet season, rice farmers prepared their land in November and December, planted in January and harvested in May or June. For the dry season (assisted by irrigation) they prepared farms starting in May, planted in June and harvested in October, [29]. The irrigated farming practices used short-duration rice seeds, maturing in 4 months, while the non-irrigation farming method that depends on rainfall during wet season used long-duration rice seeds that mature in 5–6 months. The irrigated rice agro-ecosystem was reported to be prone to pests’ infestations, and hence, required regular insecticide applications. The farming methods also corresponded to the application patterns of various pesticides:
“Normally in the rain season there are few pests and can easily be destroyed by rainwater. From my experience, the rice seed cultivated in rainy season is not vulnerable to pests, thus different from the swamp rice farming that relies on irrigation, without pesticides application you will not have good produces” (female farmer).
Knowledge and practices of farmers regarding pesticides and pesticide application
Majority of farmers (89.3%, n = 381.3) had no awareness of pesticides. Most farmers (n = 316, 54.4%) sprayed doses of pesticides based on instructions received from the pesticides dealers, while 106 (18.2%) relied on personal experiences or direct observations based on the estimation of farm sizes and incidence of pests and weeds. Only 90 (15.5%) farmers reported that they read product labels, and only if written in the local language, Kiswahili. The rest of farmers (n = 67, 11.5%) relied on experts, such as agricultural officers or other sources on information knowledgeable about pesticide usage:
“I always get instructions from the seller of the pesticides at the agrovet shop, but sometimes I read from the leaflet on the pesticide bottle only those written in Swahili” (female farmer).
Only 27% of farmers believed it was necessary to use recommended pesticide dose as stipulated by the manufacturer for each pesticide, though there is no evidence that they followed those instructions. On the other hand, 62.1% perceived the right pesticide dosage as any amount enough to kill all the pests in the farm. Mixing of the pesticides was mostly done in a Knapsack® Sprayer tank, traditionally recognised as “Solo”. Overall, 400 farmers (93.7%) performed pesticides dilution and mixing at the farms, nearby water sources such as the irrigation canals or rivers (Fig. 2). Most of the pesticides come with the measuring equipment, but farmers typically used empty soda bottles/syringe pipe to measure liquid pesticides. Pesticides dose rates also varied among farmers (Table 5).
Table 5
Example of pesticides spray dosage as reported by farmers compared to the recommended dosage on the product label
Pesticide class | Trade name | Active ingredient (s) | Class of the pesticide | Knapsack spray dilution by farmers ml/l, g/l of water | Recommended knapsack dilution rate ml/l, g/l of water | Recommended dose (ml/ha) | Target crop |
Insecticide | Karate 5EC | 50 gm/l of lambda-cyhalothrin | Pyrethroids | 15–40 ml/20 l | 12 ml/20 l | 300–400 ml/ha | Rice, maize, vegetables, fruits, green pepper, watermelon, beans green peas and tomatoes |
Amekan C344 SE | 144 g/l of cypermethrin and 200 g/l of imidacloprid | Pyrethroids and Neonicotinoids | 30 ml/20 l | 8–10 ml/15 l | 500 ml/ha | Tomatoes, watermelon, okra, potatoes, rice, spinach, maize, green pepper and cabbages |
Duduba 450EC | 100 g/l of cypermethrin and 350 g/l of chlorpyrifos | Pyrethroids and organophosphates | 30–50 ml/20 l | 10 ml/20 l | 400 ml/ha | Rice, cucumber, tomatoes, green pepper, cereals crops and fruits |
Buffalo 100OD | 75 g/l of imidacloprid and 25 g/l of beta-cyfluthrin | Neonicotinoids and pyrethroids | 35–60 ml/20 l | 10 ml/20 l | 500 ml/ha | Tomatoes, maize, green peas potatoes, green pepper, beans and onions |
Ninja 5EC | 50 g/l of lambda-cyhalothrin | Pyrethroids | 25 ml/15 l | 40–60 ml/20 l | 150–400 ml/ha | Rice, fruits, green peas vegetables and maize |
KungFu 5EC | 50 gm/l of lambda-cyhalothrin | Pyrethroids | 15–40 ml/20 l | 12 ml/20 l | 300–400 ml/ha | Tomatoes, watermelon, cucumber, rice, onions, vegetables, fruits and green pepper |
Suracron 720 EC/720/ Profecron 720 EC | 720 g/l of profenofos | Organophosphates | 200–350 ml/20 l | 20–40 ml/15 l | 500–800 ml/ha | Cabbage and tomatoes, okra, eggplant, cucumber and watermelon |
Nogozone 60 EC | 600 g/l diazinon | Organophosphates | 20–40 ml/20 l | 5–30 ml/15 l | 150–700 ml/ha | Watermelon and cucumber |
Herbicide | 2,4 D Amine | 720 g/l of 2, 4 D- dimethyl amine salt | Aryloxyacides | 150–300 ml/16 l | 200 ml/20 l | 2,000 ml/ha | Rice and maize |
Roundup | 360 g/l of glyphosate | Amino-phosphonates | 300–350 ml/15 l | 200–300 ml/20 l | 2,000-3000 ml/ha | Rice and maize |
Parapaz 200 SL | 200 g/l of paraquat dichloride | Pyridines | 300–350 ml/15 l | 100–200 ml/20 l | 800-1,600 ml/ha | Maize, rice, sugarcane and tomatoes |
Fungicide | Farmerzeb 800 WP | 800 g/kg of mancozeb | Dithiocarbamate | 60 g/15 l | 40–60 g/20 l | 1,000–3,000 g/ha | Tomatoes, African eggplant, green pepper and potatoes |
Linkonil 500 SC | 500 g/l of chlorothalonil | Organochlorine fungicide | 20–50 ml/20 l | 46 ml/20 l | 1,000–3,500 ml/ha | Tomatoes, okra, eggplant, watermelon and cucumber |
Victory 72 WP | 640 g/kg of mancozeb and 80 g/kg of metalaxyl | Dithiocarbamate and acylalanine | 60–80 g/20 l | 50 g/20 l | 2000–2500 g/ha | Tomatoes, okra, and potatoes, cucumber, watermelon and cabbage |
Frequency and spraying patterns of pesticides
Most rice farmers reported re-applying insecticides at least twice every week, or anytime there were pests to achieve maximum control (Table 6). Other farmers reported pre-emptively re-spraying their farms to prevent pests coming from unsprayed neighbouring farms. Farmers also frequently sprayed herbicides to prevent or delay weeds:
“Since most of the insecticides are not as effective as they used to be, for instance, I have to reapply Karate (lambda-cyhalothrin) two times after every week. I think it is time the effectiveness of the insecticide has depleted and cannot kill or repel pests anymore. Sometimes, I reapply more often because there are a lot of insect-pests coming from neighbouring farms, especially those who haven’t /delayed sprayed” (male farmer).
Table 6
Farmer’s responses about insecticide spray frequency
Application frequency | No. of farmers | Percentage (%) |
Twice every week | 120 | 28.1 |
Once every two weeks | 61 | 14.3 |
2–4 times per growing season | 71 | 16.6 |
Any time I find pests in the farm | 111 | 26.0 |
I do not remember | 64 | 15.0 |
Insecticides and fungicides were mostly used during the dry season for irrigated rice cultivation and vegetable farming. Most of the non-selective, systemic, post-emergence herbicides such as Roundup (glyphosate) were, however, sprayed before farming and planting of rice seeds, shortly before rains start during farms preparation. The selective herbicides such as 2,4-D Amine (2,4-D amine salt) were commonly used during weeding to control soft weeds in rice farms:
“I spray Kung-fu (lambda-cyhalothrin) in the dry and wet season but mostly in the dry season because this is the period there are a lot of pests. In the wet season, there are few or no pests because of rainfall. Pest does not survive when there is a lot of water, unlike in dry season” (female farmer, Lupiro ward).
Challenges faced by the farmers regarding the usage of pesticides
Farmers reported multiple challenges when using pesticides. Half of the farmers (51.3%) claimed to have experienced adverse health events, such as skin irritation or coughing after spraying pesticides. The most common challenge and concern reported by about two-third of the farmers (64.6%) was that pesticides lost their killing efficiency against weeds and pests as they have had pests rebound after pesticides application. About 7.7% of the farmers suspected some pesticides are counterfeit, and 3.3% had experienced some pesticides, being more diluted than expected. Switching to different classes of insecticide or mixing pesticides was a common practice (75.6% of the farmers):
“You will find in few days sometimes even the following day after spraying there are still some pests in the farms. I surveyed and tried to spray different pesticides other than the ones I’m used to. I realised rapid attack (a mixture of cypermethrin and imidacloprid) and Amekan (a mixture of cypermethrin and imidacloprid) are far better and effective insecticides than Duduba alone (a mixture of cypermethrin and chlorpyrifos) against most of the pests affecting vegetables, watermelons and rice” (male farmer, 44 years, Mavimba ward).
Use of pesticide mixtures
Tank mixing of more than one pesticide with the same or different active ingredients before spraying was commonly practiced (Table 7), which was also observed at the farms, despite being against label instructions. Sometimes pesticides were combined with fertilizers before application following retailers’ recommendations (Table 7). The popular pesticide mixtures were: (i) two herbicides (38.7%); (ii) two insecticides (16.1%); (iii) one fertilizer and one insecticide (16.1%); (iv) one insecticide and one fungicide (12.9%); and (v) one herbicide and one insecticide (9.7%), and other mixtures (6.5%). Most farmers (86.4%) perceived cocktail sprays are more efficient than when sprayed as a single product. They also perceived that mixing two or more pesticides into a single spray solution simplified work and saved time. For example, a cocktail of KungFu (lambda-cyhalothrin) and Duduba (cypermethrin, chlorpyrifos) was used on fruits and vegetables such as watermelon, tomatoes, cabbages, okra and spinach.
Table 7
Pesticides combination practices by farmers at the study sites
Pesticides cocktail | Type of pesticides | Pesticide class |
KungFu and Duduba | Two insecticides | Two pyrethroids and one organophosphate |
2,4-D and Roundup | Two herbicides | One aryloxyacide and one amino-phosphonates |
Booster + Supercron | One fertilizer and One insecticide | Nitrogen, phosphorous, potassium and trace elements and one organophosphate |
Karate and KungFu | Two insecticides | Two pyrethroids |
Rapid attack and Amekan | Two insecticides | Two (pyrethroids and neonicotinoids) |
Echlonil and Karate | One fungicide and one insecticide | One organochlorine fungicide and one pyrethroid |
Rapid attack and Farmerzeb | One insecticide and one fungicide | One (pyrethroids and neonicotinoids) and one dithiocarbamate |
Handling and disposal practices of left-over pesticides and pesticide containers
Most farmers practised unsafe handling and disposal of pesticides. About half of the farmers (n = 221, 51.8%) reported storing pesticide leftovers in their homes for either re-spraying rebounding pests or use in the next farming season. One third (n = 128) dumped out leftover pesticides into either river or nearby bushes. A small minority reported burying the left-over pesticides underground (6/427) or using the pesticides to kill domestic insects such as cockroaches and houseflies in their houses (2/427). Regarding disposal of containers, the majority of farmers (238, 55.7%) reported that they discarded empty pesticide containers into either running water in the river or bush on the farms, while approximately one fifth (22.0%) considered burning the empty pesticides bottles. Some 18.5% of the farmers, however, buried the containers in the ground, and a small minority (3.7%) reported to wash and re-use the empty bottles for either repacking pesticides or other domestic activities.