Exploiting the modes of action of insecticides and acaricides to manage the development of resistance in arthropod pests in Ghana

The importation and use of insecticides and acaricides in agriculture and public health are on the increase in Ghana, while populations of arthropod pests have developed resistance to some active ingredients. However, effective strategies for managing arthropod pest resistance in Ghana are lacking due to the absence of appropriate research for developing effective resistance management strategies. For instance, laboratory studies to evaluate cross-resistance patterns and stability of resistance are not conducted in Ghana. Laboratory studies to determine the mechanisms of resistance to specific active ingredients are also not conducted. In Ghana, resistance research is focused on the detection of esterases in field populations of pests, complemented by resistance ratio which is computed in a wrong manner as the susceptibility of test population divided by the recommended field concentration of active ingredient. Until the right research for developing effective strategies to manage resistance are conducted, the modes of action (MoAs) of active ingredients could be used to help manage resistance development. However, in Ghana, insecticide and acaricide recommendation and their use indicate that the knowledge on exploiting MoAs for resistance management is also lacking. For instance, it is recommended that any of the approved insecticides, imidacloprid, thiamethoxam and bifenthrin, for cocoa mirid control could be used when it is time to spray against mirids. The report that the acaricidal products Cypertop® (contains mixture of cypermethrin and chlorpyrifos), Vetancid® Max (contains mixture of cypermethrin and trichlorfon) and Ectocyp® (contains cypermethrin) were alternated to control ticks also shows the lack of knowledge on exploiting MoAs to manage resistance. This review paper discusses how the MoAs of active ingredients of insecticides and acaricides can be exploited to manage resistance development in arthropod pests in Ghana and the scientific basis of the strategy. Resources for determining the MoAs of active ingredients of insecticides and acaricides are also shared

Susceptibility of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) to acetamiprid and selected insecticides by foliar treatment and strategy for resistance management

AbstractThe dependence on pyrethroids and organophosphates to control the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae) on cabbage and cauliflower in Ghana since the 1990’s, and the absence of effective resistance management strategies has led to reported cases of widespread development of DBM resistance to these insecticides since 2002.  The study was undertaken to identify alternative insecticides to the pyrethroids and organophosphates, and recommend a strategy that would effectively manage DBM resistance to insecticides in Ghana.  The susceptibility of the DBM to acetamiprid (neonicotinoid), chlorfluazuron (benzoylphenyl urea) and Bacillus thuringiensis subsp. kurstaki Berliner (Btk) (microbial) was compared with susceptibility to esfenvalerate and phenthoate, which were selected as reference pyrethroid and organophosphate compounds, respectively.  The Osaka susceptible strain of DBM and the leaf-dipping method were used.  The results showed that esfenvalerate was most toxic after 72-h treatment.  However, when the end-points for the insecticides were considered, chlorfluazuron was the most toxic after 168-h treatment and Btk the next most toxic after 96-h treatment.  Acetamiprid was the least toxic to the DBM by foliar treatment.  The low toxicity of acetamiprid would subject the DBM to a low selection pressure, and as a result delay the development of resistance in the pest.  Acetamiprid should, therefore, be a preferred alternative for DBM control in Ghana.  Chlorfluazuron and Btk by virtue of their toxicity against the DBM and favourable safety levels should also be a preferred alternatives for DBM control in Ghana.  An effective resistance management strategy against the DBM in Ghana would be the rotational use of acetamiprid, chlorfluazuron and Btk for DBM control since these insecticides show no cross-resistance to each other.Original scientific paper. Received 31 Jul 14; revised 04 Mar 15

The Ghana Cocoa Board (COCOBOD) approved insecticides, imidacloprid, thiamethoxam and bifenthrin, for the control of cocoa mirids (Hemiptera: Miridae): Implications for insecticide-resistance development in Distantiella theobroma (Dist.) and Sahlbergella

The Ghana Cocoa Board (COCOBOD) in 2001 initiated a national Cocoa Diseases and Pest Control (CODAPEC) programme (popularly known as mass-spraying programme) against the cocoa mirids (Hemiptera: Miridae), which are predominantly Distantiella theobroma (Dist.) and Sahlbergella singularis Hagl. The insecticides approved by COCOBOD for controlling the cocoa mirids under CODAPEC and for individual farmer applications are Confidor® (imidacloprid 200 g/l), Actara® (thiamethoxam 240 g/l) and Akate Master® (bifenthrin 27 g/l). Imidacloprid and thiamethoxam are both neonicotinoid insecticides with cross-resistance between them, while cross-resistance has been established between the neonicotinoids and bifenthrin, a pyrethroid insecticide. Using imidacloprid, thiamethoxam and bifenthrin singly or rotationally selects for genes that confer resistance to the approved insecticides. The detection of ɣ-BHC-resistant D. theobroma in Ghana after widespread use of the insecticide against mirids from the mid 1950s through early 1960s indicated the genetic ability of mirids to develop resistance to insecticides. The mass-spraying of imidacloprid, thiamethoxam or bifenthrin to control mirids is, therefore, increasing selection pressure on field populations of mirids, and escalating the risk of the mirids developing resistance to all three insecticides. Preventing resistance development in the cocoa mirids to the COCOBOD approved insecticides is crucial to avert resistance associated yield losses, reduce the risk of insecticide residues in cocoa beans and safeguards Ghana's foreign exchange earnings from cocoa. Measures for protecting imidacloprid, thiamethoxam and bifenthrin from mirid resistance development are recommended

Development of a resistance management strategy for ixodid ticks (Acari: Ixodidae) infesting livestock from market available acaricides in southern Ghana

The ixodid ticks (Acari: Ixodidae) are the most important ectoparasites infesting livestock in Ghana, causing direct damage to the animals and spreading diseases. The use of acaricides remains the main method for controlling ticks in Ghana. A recent study in Ghana concluded that using a wide variety of acaricides to control ticks on livestock was dangerous as it could lead to resistance in ticks. While it was observed that acaricides of same chemistry were alternated for tick control. These events indicated that in Ghana there is a lack of knowledge on the importance of and how to exploit variety of acaricides to manage tick resistance when cross-resistance patterns have not yet been established. This paper investigated the variety of acaricides on the market for tick conrtol in Accra, Tema and Kasoa in southern Ghana. The acaricides on the market were then used to develop a strategy for managing acaricide-resistance in ticks on livestock. The variety of market acaricides were determined by surveying veterinary pharmacies. Twenty (20) acaricidal products with 8 active ingredients of 4 chemistries were encountered in the study. The chemical groups were amidines, macrocyclic lactones, organophosphates and pyrethroids. The strategy developed for managing resistance in ticks with the acaricidal products on the market was based on mode of action of the active ingredients. The strategy requires the rotaional use of the acaricidal products in ways that reduces the selection pressure of active ingredients of same chemistry on the target-site in tick populations and as a result retard resistance development

Incipient bifenthrin-resistance in field populations of cocoa mirids, Distantiella theobroma (Dist.) and Sahlbergella singularis Hagl. (Hemiptera: Miridae)

Bifenthrin is one of the insecticides approved by the Ghana Cocoa Board (COCOBOD) for the control of cocoa mirids. Bifenthrin-resistance levels of D. theobroma and S. singularis collected from different locations in the Eastern Region (ER), Volta Region (VR) and Central Region (CR) were determined by calculating their resistance ratios (RRs). The highest RRs for S. singularis were recorded from New Tafo in the ER and Logba Alikpati in the VR, which displayed 6-fold and 6.2- fold bifenthrin-resistance, respectively. Populations of S. singularis from Pankese in the ER and Likpe in the VR also displayed 3.6-fold and 3.9-fold bifenthrin-resistance, respectively. The D. theobroma population that displayed the highest bifenthrin-resistance of 3.7-fold was from New Tafo. The results show incipient bifenthrin-resistance in field populations of D. theobroma and S. singularis, which requires the implementation of effective resistance management strategies to prevent full-blown resistance in the cocoa mirids

INSECTICIDE HANDLING IN COCOA PRODUCTION IN FOUR REGIONS IN GHANA

Management of insect pests of cocoa (Theobroma cacao L.) using insecticides began in 1950 and has since gone through various programmes with concomitant challenges and successes. Presently Imidacloprid (Confidor®), Bifenthrin (Akatemaster®) and Thiamethoxam (Actara®)are recommended by Ghana Cocoa Board (COCOBOD) for the management of insect pests. A survey was conducted in the Ashanti, Eastern, Volta and Western Regions of Ghana using questionnaires and farm visits of 147 cocoa farmers’ fields to gather information on the characteristics of the farmers and insecticide handling and use by respondents. The survey showed that males dominated cocoa farming (72.7%) and most of them aged between 50 and 60 years. About 44% have had basic education whilst 37.5% of them belonged to farmer based organizations. About 52.8% of the farmers own motorized mistblower but 47.2% of the farmers use knapsack in the absence of a mistblower. About 44.8% do their own spray application whereas 55.2% hire labour. About 60.9% of the population across the regions read the label on the insecticides before application. A few (31.6 %) of the respondents put on the full personal protective costume during insecticide application and 21.9% do not use any protection. There was a positive correlation between farmers’ membership of farmer-based organisation and the costume-wearing farmers in the Ashanti, Eastern and Volta Regions and it was significant in the Ashanti region. It isrecommended that training and monitoring programmes be organized for farmers on the need to handle pesticides properly for personal and environmental safety and consumer benefit.Keywords: Insecticides; pest management; cocoa farmers; safet