Insects and Cocoa

Entwistle, P. F.

doi:10.1002/9780470698983.ch12

Cited by 12 publications

(14 citation statements)

References 23 publications

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“…They are reported to function as antifungal agents and because of their bitter taste are considered as potential feeding deterrents to insect herbivores (Berenbaum, 1995; Bernays, Cooper Driver, & Bilgener, 1989; Haukioja, Ossipov, & Lempa, 2002; Matern & Kneusel, 1988). On the other hand, nutrients such as nitrogen and carbohydrates have been reported to enhance insect growth and development (Entwistle, 1985; van Emden, 1966; Waring & Cobb, 1992). This study sought to clarify the effect of light and temperature on plant nutrients and phenolic compounds in cocoa, thereby potentially providing some understanding as to why mirids prefer unshaded to shaded cocoa.…”

Section: Discussionmentioning

confidence: 99%

“…Mirids are known to prefer unshaded areas of cocoa farms, where they create extensive damage referred to as pockets (Awudzi, Ackonor, Cudjoe, Dwomoh, & Sarfo, 2009; Babin et al, 2010; Bigger, 1981; Entwistle, 1985; Padi & Owusu, 1998). High solar radiation in unshaded areas of cocoa farms or portions with a break in the shade canopy enhances photosynthetic rate and vegetative growth of the cocoa trees (Babin et al, 2010; Bos, Steffan‐Dewenter, & Tscharntke, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Mirid feeding preference as influenced by light and temperature‐mediated changes in plant nutrient concentration in cocoa

Awudzi

Hadley

Hatcher

et al. 2020

Annals of Applied Biology

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Cocoa mirids are the most important insect pests of cocoa in West Africa. This study investigated the effect of environmental parameters that are modulated by overhead shade, that is, light intensity and temperature, on nutrient and phenolic concentrations in cocoa and their subsequent effect on mirid feeding. Eight‐month‐old cocoa seedlings were maintained for 50 days in two growth chambers set to day temperatures of 25 or 30°C. Each chamber had sections with different light intensities (541, 365 and 181 μmol m−2 s−1 photosynthetically active radiation [PAR]). For the field studies at Akim Tafo in Ghana, 8‐month‐old plants of three cocoa clones were subjected to shaded (PAR = 180 μmol m−2 s−1, between 11:00 a.m. and 12:00 p.m.) and unshaded (PAR = 1,767 μmol m−2 s−1, between 11:00 a.m. and 12:00 p.m.) treatments for 50 days after which nutrient measurements and mirid choice tests were carried out. No significant effect of environment was observed on the phenolic concentration of stems under controlled environment chamber conditions. However, in the field, the phenolic concentration of stems was significantly greater for unshaded compared with shaded plants (p = .04). Under controlled conditions, the leaf nitrogen concentration increased slightly with light intensity (p = .003). The same trend was seen in stems but only at 30°C. In the field, the impact of overhead shade on nitrogen varied between cocoa clones. The concentration of carbohydrates in both leaves and stems in the field was higher under unshaded conditions. When subjected to feeding tests, stems from unshaded cocoa had significantly more mirid feeding lesions (p = .003) after 24 hr exposure to mirids compared to shaded cocoa. Mirid feeding therefore appears not to be deterred by the higher phenolic levels but rather there was a preference for cocoa tissue grown under unshaded conditions. These findings highlight the need to consider the growing environment of cocoa clones when screening for varieties with resistance to mirids.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mirid feeding preference as influenced by light and temperature‐mediated changes in plant nutrient concentration in cocoa

Awudzi

Hadley

Hatcher

et al. 2020

Annals of Applied Biology

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“…Mirid damage is caused by both adults and nymphs, which pierce their feeding mouth parts into pods, chupons and soft portions of branches. This creates a characteristic vivid circular lesion which turns brown and later black after a couple of hours on pods and elliptical dark lesions on chupons and young stems (Entwistle, 1975). In Ghana, mirid damage is a contributory factor to low yields (Dormon et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Knowledge and perception of Ghanaian cocoa farmers on mirid control and their willingness to use forecasting systems

Awudzi

Asamoah

Owusu-Ansah

et al. 2016

Int. J. Trop. Insect Sci.

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Annual losses of cocoa in Ghana from mirids are significant; therefore, accurate timing of insecticide application is critical to enhance yields. However, cocoa farmers often lack information on the expected mirid population for each season to enable them to optimize pesticide use. This study assessed farmers' knowledge and perceptions of mirid control and their willingness to use forecasting systems informing them of the expected mirid peaks and the time of pesticide application. A total of 280 farmers were interviewed in the Eastern and Ashanti regions of Ghana with a structured open- and closed-ended questionnaire. Most farmers (87%) considered mirids the most important insect pest on cocoa, with 47% of them attributing 30–40% of annual crop losses to mirid damage. There was a wide variation in the timing of insecticide application as a result of farmers using different sources of information to guide the start of application. The majority of farmers (56%) did not have access to information about the type, frequency and timing of insecticide use. However, respondents who were members of farmer groups had better access to such information. Extension officers were the preferred channel for information transfer to farmers, with 72% of farmers preferring them to other available methods of communication. Almost all the respondents (99%) saw the need for a comprehensive forecasting system to help farmers manage cocoa mirids. The importance of the accurate timing of mirid control based on forecasted information to farmer groups and extension officers is discussed.

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“…The life cycle of S. singularis is composed of 3 stages: egg stage, nymph stage, and adult stage that develop mainly on pods either on shoots. The eggs are individually inserted into the host plant tissues principally in the cortex of pods and sometimes under the bark of young shoots . The incubation period of eggs is on average 15 days with a minimum of 9 days and a maximum of 21 days before reaching nymph stage.…”

Section: Mirids Odes Modelsmentioning

confidence: 99%

Models for Miridae, a cocoa insect pest. Application in control strategies

Tapi

Beilhe

Bowong

et al. 2018

Math Methods in App Sciences

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Communicated by: R. AnguelovFunding information DP-PCP Agroforesterie Cameroon; CIRAD; IRD; INRIA-LIRIMA MSC Classification: 34A12; 34C12; 34K28; 92D25 Cocoa mirid, Sahlbergella singularis, is one of the major pests of cocoa in West Africa. It is responsible of several damages in plots. In this paper, we study the dynamics of this pest. Based on biological and ecological partial knowledge, we develop 2 cooperative mathematical models that aim to describe the time dynamics of the cocoa mirids. We first develop a cooperative stage-structured model, derived some qualitative results, and a sensitivity analysis study in order to determine the most important parameters. Assuming that all parameters are or not periodic, we obtain conditions that allow the persistence or not of the population. We highlight the influence of cocoa pods variation along the year on the time evolution of the population. Then, we derive a 2-stage cooperative time-delay model, with 2 delays, that takes into account the eggs' development time and the females' maturation time. We illustrate our theoretical results with some simulations and show that the delayed system provides the best results compared with real observations. Finally, we focus on chemical control that is commonly used in Cameroon and compare it to a new biological control, mixing mating disrupting and trapping. We discuss the results and provide future perspectives based on this work.

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Insects and Cocoa

Cited by 12 publications

References 23 publications

Mirid feeding preference as influenced by light and temperature‐mediated changes in plant nutrient concentration in cocoa

Mirid feeding preference as influenced by light and temperature‐mediated changes in plant nutrient concentration in cocoa

Knowledge and perception of Ghanaian cocoa farmers on mirid control and their willingness to use forecasting systems

Models for Miridae, a cocoa insect pest. Application in control strategies

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