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    Kelvin Kigen, a sales representative at Favor Machinery Ltd demonstrating how to use a Knapsack Power Sprayer at the Central Kenya National Show, Nyeri on 16th Sept 2017. (PIC: Japhet Ruto, FarmBiz Africa)

    Pesticides are chemicals used to control pests, weeds or diseases in crops and livestock. These chemicals play a crucial role in agricultural production, a key sector for smallholder farmers in Kenya who produce about 70% of the food in the country. It is therefore important for farmers to understand that pesticides are poisons with varying degrees of toxicity to man, animals and other non-targets in the environment.

    In developing countries, frequent exposure to pesticides by farmers and farm workers is very common. The World Health Organization (WHO) and the United Nations Environment Program (UNEP) estimate pesticide poisoning rates at 2-3 people per minute. It has been argued that pesticide-related health issues constitute a serious threat to development and can easily reverse or undermine the gains made in agricultural growth.

    READ ALSO: Nandi farmers receive Ksh. 2.5 million pesticides to fight army worms

    READ ALSO: Tithonia flowers used to make home-made pesticides in Kitale

    READ ALSO: Kenya goes after fake pesticides with new law

    The correct usage of pesticides according to the Pest Control Products Board (PCPB) includes proper sourcing, preparing, applying, storage and disposal. The main aim of using pesticides is to maximize their benefits while minimizing risks to the operators, the public and the environment.

    Before using pesticides, the following MUST be considered:

    • Only use registered products – those bearing a PCPB registration number PCPB (CR) #### on the label and use PCPs for their registered use only.
    • Only procure right quantities of pesticide with intact packaging (not leaking) and from licensed dealers.
    • Always store pesticides under lock and key, out of reach of children and other non-targets, foods and feeds.
    • Some pesticides are flammable and can ignite easily and should NOT therefore be stored near fire sources such as stoves, lamps or direct sunlight.
    • Always read the product labels carefully and entirely before use and stick to the label instructions accordingly.
    • Wear appropriate protective gear as indicated on the label when mixing and applying pesticides, such as rubber gloves, gumboots, overalls and respirators.
    • Keep non targets including children from areas where pesticides have been applied.
    • Do not eat, drink or smoke while mixing or spraying pesticides.
    • Triple rinse the containers and puncture them to render them un-usable, dispose as per the PCPB disposal guidelines. (Never use empty pesticide containers for any other purpose)
    • Wash hands thoroughly with soap and water after handling pesticides. Do the same for the protective gear.
    • Always observe pre-harvest intervals (PHI) for crops and re-entry intervals in the greenhouses.

    Pesticides users should note that:

    • Under dosing may lead to pest/disease resistance to the product(s) and poor control of intended pests/diseases.
    • Over dosing may lead to high level(s) of pesticide residue in the produce and environment which may compromise on safety of food and human health in general.
    • Wrong timing of application may affect efficacy of the product(s) or food safety with respect to residues or non- targets such as bees that be actively foraging at the time of application.
    • Using pesticides for purpose not intended and for which they are not registered or using wrong application techniques/areas. This may not only affect performance of the product but may expose people and the environment to unacceptable levels of residue.


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    The Fall Armyworm (FAW) (scientific name Spodoptera frugiperda) is a moth, native to tropical and subtropical regions of the Americas, but it is the caterpillar that causes damage. It has a voracious appetite, it can reproduce rapidly in favourable conditions, and can spread very quickly using the wind. Whilst much of its biological and ecological adaptation to the African continent is still unknown, it has spread rapidly across Africa.

    After mating, female moths lay hundreds of eggs in groups on the underside of leaves and within a few days, young caterpillars emerge and start feeding. In the Americas almost 100 different crops and other plants are attacked, but there is a preference for maize, rice, sorghum, and sugarcane.

    The developing larvae eat many parts of the host plant, depending on the stage of crop development and the age of the larvae. Young larvae usually feed on leaves, creating a characteristic “windowing” effect and moist sawdust-like frass near the funnel and upper leaves. 

    ALSO READ: Plant extracts show positive results in containing fall armyworm

    Early in the season, this feeding can kill the growing point, a symptom called 'dead heart' in maize, which prevents any cobs forming. Young larvae hide in the funnel during the day but emerge at night to feed on the leaves. In young plants, the stem may be cut. Older larvae stay inside the funnel and so are protected from spray applications and predators. In older plants the larger larvae can bore into the developing reproductive structures, such as maize cobs, reducing yield quantity and quality.

    Fully developed caterpillars usually burrow into the soil to pupate inside a loose cocoon, but sometimes do so between leaves on the plant. Adult moths emerge at night and can travel great distances by flying up into the low-level jet stream. In the Amercias this can enable them to fly from Mississippi to Canada in 30 hours.

    The rate at which caterpillars develop is affected by diet and temperature (optimum range between 11°C and 30°C). In cooler climates development slows down to one or a few generations a year. Frost kills the insect, providing some mitigation in cooler climates.


    • Distribution in Africa

    In the first evidence note (Fall Armyworm Status: Impacts and control options in Africa, Preliminary Evidence Note) written by CABI in April 2017, 17 countries confirmed FAW  presence through official and unofficial sources. Nine more were suspected of having the pest. As this report shows however, the situation is constantly evolving.

    At the time of publication of this document in September 2017, FAW has been reported from 28 countries. These include a variety of sources including IPPC reports, ministerial declarations, peer reviewed journals, and UN affiliated organisation reports.  A further nine countries have conducted or are presently conducting surveys, and either strongly suspect its presence or are awaiting official confirmation, at the time of publication. Two countries have stated that FAW is absent from the country.

    The FAW is now well distributed across the African continent and national reports on the status in many countries have been published. However, the content of information in the reports is very variable, which makes wider estimates of FAW impacts on maize yield and economics at a national level based on these sources difficult.
    Economic impact

    Thus, to estimate the potential impacts on yield and economics on the major maize producing countries that is likely to happen over the next few maize producing seasons assuming that the FAW will spread throughout all areas where it is predicted to survive, CABI has estimated impacts of FAW for 10 substantial maize producing countries by extrapolating estimates of proportion of yield loss derived from a survey from Ghana and Zambia and combining this with published data on national maize production and other information for the 10 countries. 



    The total estimated yield and economic losses for each of the 10 countries are given in Table 1, below.


    Table 1. The estimated lower and upper yield and economic losses in the 10 countries included in the study



    Yield loss (lower) (tonnes)

    Yield loss (upper) (tonnes)

    Economic loss (lower) (US$)

    Economic loss (upper) (US$)




































































    On this basis it can be seen that currently Benin, Malawi and Zimbabwe are most affected.

     ALSO READ: Africa faces permanent $2bn+ maize deficit if Fall Armyworm poorly managed

    The estimates indicate that for these 10 countries taken together, the potential impact of FAW on maize yield lies between 7.2 and 17.9m tonnes per year and with losses lying between $2,218m and $5,518m per year. The economic losses have also been expressed as (lower and upper) percentage loss to agricultural GDP (averaged over the last three years) in Table 2, below.


    Table 2. The estimated lower and upper economic losses for the 10 countries  expressed as percentages of their agricultural GDP




    % agricultural GDP loss (lower)


    % agricultural GDP loss (upper)










































    • Control options

    In the Americas pesticides and genetically modified (GM) crops are the main methods of control, although FAW has developed some resistance to both. Most countries in Africa do not yet plant GM crops. 

    Pesticides including Bacillus thuringiensis are an option in Africa, though are not always affordable to many small-scale farmers; subsidy or government-funded implementation is therefore being used in some countries.

    Lower-cost mechanical and cultural control methods have yet to be proven in Africa, but could be adopted in the meantime.

    Mass rearing and release of parasitoids and predators is used as an alternative in the Americas but currently costs may be prohibitive without subsidy in Africa.

    Classical (introduction) biological control should be pursued immediately. Virus-based biopesticides available in the Americas may offer a low-risk option, but are not yet registered in Africa, and again may be expensive for many farmers. 

    In all cases a widespread communications programme is necessary to inform farmers how to monitor and identify the pest, and what management methods are available which can be selected according to local context.

    In this, any direct control methods target the larvae, but two aspects of the biology pose constraints:

    • Larvae are relatively inactive during the day, so treatment (e.g. spraying) is best done in the early or late part of the day
    • Older larvae tend to bore into the whorl or cob (of maize), so contact pesticides are not effective unless applied when the larvae are young. Monitoring is required to detect the young larvae, and to determine whether treatment is justified.


    Monitoring for treatment decision making

    Two approaches to monitoring are used, both of which need further investigation in Africa:


    Trapping adults: Pheromone traps attract the male moths with a synthetic sex pheromone, and give an indication of the adult population in an area.


    Scouting: Plants are inspected in detail, and different aspects of the damage and/or the presence or number of eggs and different sizes of larvae recorded. Different scouting protocols may be used for different crops, and times of the season. Based on the results of monitoring, a decision whether to treat can be made.


    Pesticide registrations and recommendations

    To be legally used for FAW control, a pesticide must be registered, requiring efficacy and toxicity data. Large numbers of pesticides are registered in the Americas; Brazil has around 40 products registered for Fall Armyworm. In the USA each state makes its own recommendations, usually by crop. However, in the Americas, resistance has developed to some types of pesticide; the risk of this can be reduced by rotating pesticides with different types of action.


    In Africa registration processes exist, but can be lengthy. No pesticides are fully registered for FAW yet; in some cases emergency registration is possible. Much un-registered (and therefore technically illegal) pesticide use is occurring.


    • Immediate actions

    Farmers need advice on what actions they can take immediately. The following are suggested, though not all are supported by evidence, and they should be adjusted when more evidence is available on alternatives to pesticides and how agronomic practices can reduce risk/damage.

     READ ALSO: OPINION: African governments move into race to halt armyworm catastrophe

    • Monitor susceptible crops at least weekly, with the aim of detecting egg masses and/or young larvae. Large scale farms could consider using pheromone traps for monitoring but visual inspection is also advised.
    • On detecting FAW or early damage (windowing of leaves) consider treatment:
      • Small farms, depending on resource availability: Handpicking; placing sand/soil mixed with ash/lime into the whorl; pesticide application. Give priority to damaged plants but treat whole field if possible.
      • Large farms: Pesticide application to affected fields
      • Pesticides: Use WHO Class 3 or U if possible (though lower risk products tend to be more expensive), from a nationally recommended list. Use personal protective equipment and follow manufacturer’s instructions.
    • After treatment, continue monitoring, and consider further treatment if more young larvae appear. Continue until plants become too large to monitor/treat.


    It is suggested that national authorities undertake the following steps as far as possible:


    • Promote awareness of FAW, its identification, damage and control
    • In consultation with agro-input suppliers, prepare and communicate a list of recommended pesticides. The pesticides should be available, and preferably already registered for the crop in which they are to be used, and/or for use on other caterpillars. Pesticides registered/recommended for FAW control in the Americas could be selected, but WHO class 1a or 1b pesticides should never be recommended (recommendations in US are for very specific uses).
    • Provide emergency/temporary registration for the recommended pesticides. Registrants should provide supporting data from the Americas within a specified period.
    • Arrange for laboratory efficacy tests of recommended pesticides to be conducted by authorised national laboratories.
    • Regularly review recommendations and publicise changes promptly and widely.
    • Consider short term subsidies for small scale farmers, for example to reduce prices for lower risk product.

    A comprehensive range of actions for the short, medium and long term was identified at an international meeting organised by AGRA, FAO and CIMMYT in Nairobi in April 2017.  This has subsequently been developed by FAO and partners into a framework containing 4 components:

    1. FAW Management, including early warning and control methods
    2. Assessment of the impact of the pest
    3. Communication, information sharing and awareness raising
    4. Coordination. The Nairobi meeting agreed that FAO should be responsible for overall coordination.


    FAO will be publishing the final version of the framework in September, which will provide a guide for development of projects and programmes by the various stakeholders in the areas of their mandates.

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                  irish potato.jpg

    Potato cyst nematode (Globodera rostochiensis or G. rostochiensis) which is resistant to pesticides and persist in soil threatens the production of potatoes in Kenya.

    The pest was last year first identified in Nyandarua County after potato and soil samples taken from the county were tested in Kenya and Germany confirmed the presence of the pest. The region produces more than 40 per cent of the potatoes produced in Kenya.

    “There is no pesticide chemical or biological that is known to control the pest. The only control measure is to stop potato production in infested farms for up to 7 years,” said Mary Mwangi, a crop breeder at KALRO Embu.

    The pest, however, can remain in the soil for more than 30 years. The potato pest may spread fast to other parts of the country because more than 90 per cent of potato growers in the country buy seed from neighbours.

    READ ALSO: KEPHIS introduces 52 new disease resistant potato varieties

    READ ALSO: Stick harvesting cuts potato losses

    READ ALSO: Canola extracts curb potato nematodes

    Many farmers in Nyandarua county also sell potato seeds to farmers in other parts of the country, increasing the possibility of rapid spread of the pest to other potato growing areas.

    Agricultural scientists and researchers blame importation of potato seeds as the root cause of the pest saying the imported seeds have the potential to introduce new diseases and pests.

    Kenya can only produce 2 per cent of the required certified potato seed, limited to this following the grabbing of land meant for research and potato seed multiplication, among other challenges.

              Irish potatoes in the market, Coast Weekly.JPG

    Scientists at the Kenya Agricultural and Livestock Research Organisation (KALRO) have noted with concern that some varieties of potato seed had been imported into the country without stringent checks by the Kenya Plant Health Inspection Service (KEPHIS).

    These have the potential to introduce new diseases and pests into the country.

    Any seed variety imported into Kenya has to undergo screening and quarantine protocols. This is meant to ensure the seeds do not introduce diseases and pests that could affect potato production.

    In Africa, potato cyst nematodes have been reported in Northern African countries including Algeria, Egypt, Libya, Tunisia and Morocco (under quarantines). Other countries where the pest has been reported are Sierra Leone and South Africa where they are also controlled.

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