Enumerative sampling plans for grasshopper egg pods in northern Benin

Shah, P. A.; Godonou, I.; Gbongboui, C.; Hossou, A.; Lomer, C. J.

doi:10.1046/j.1439-0418.2000.00413.x

Cited by 8 publications

(7 citation statements)

References 7 publications

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“…DeÞning an acceptable level of precision is necessarily subjective. We chose the rather liberal standard of D Յ 0.3, which has been used previously in cropping scenarios where a reasonably coarse characterization of the pest population density was acceptable (Barney and Legg 1988, Hutchinson et al 1988, Garat et al 1999, Shah et al 2000, Dawson et al 2006. To place this in context, a value of 0.25 enables detection of a halving or doubling of the sample mean (Southwood and Henderson 2000).…”

Section: Methodsmentioning

confidence: 99%

Validation of Fixed Sample Size Plans for Monitoring Lepidopteran Pests of <I>Brassica oleracea</I> Crops in North Korea

Hamilton¹,

Waters²,

Kim³

et al. 2009

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The combined action of two lepidoteran pests, Plutella xylostella L. (Plutellidae) and Pieris rapae L. (Pieridae),causes significant yield losses in cabbage (Brassica oleracea variety capitata) crops in the Democratic People's Republic of Korea. Integrated pest management (IPM) strategies for these cropping systems are in their infancy, and sampling plans have not yet been developed. We used statistical resampling to assess the performance of fixed sample size plans (ranging from 10 to 50 plants). First, the precision (D = SE/mean) of the plans in estimating the population mean was assessed. There was substantial variation in achieved D for all sample sizes, and sample sizes of at least 20 and 45 plants were required to achieve the acceptable precision level of D < or = 0.3 at least 50 and 75% of the time, respectively. Second, the performance of the plans in classifying the population density relative to an economic threshold (ET) was assessed. To account for the different damage potentials of the two species the ETs were defined in terms of standard insects (SIs), where 1 SI = 1 P. rapae = 5 P. xylostella larvae. The plans were implemented using different economic thresholds (ETs) for the three growth stages of the crop: precupping (1 SI/plant), cupping (0.5 SI/plant), and heading (4 SI/plant). Improvement in the classification certainty with increasing sample sizes could be seen through the increasing steepness of operating characteristic curves. Rather than prescribe a particular plan, we suggest that the results of these analyses be used to inform practitioners of the relative merits of the different sample sizes.

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Section: Methodsmentioning

confidence: 99%

Validation of Fixed Sample Size Plans for Monitoring Lepidopteran Pests of <I>Brassica oleracea</I> Crops in North Korea

Hamilton¹,

Waters²,

Kim³

et al. 2009

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“…where SD is the standard deviation in sample estimate of m x ðÞand n is the number (n) of sampling units collected (Kuno 1969;Waters et al 2009). Normally, D ¼ 0:3i s used as a standard for the fixed level of precision (Barney and Legg 1988;Hutchison et al 1988;Garat et al 1999;Shah et al 2000;Waters et al 2009). The minimum sample size required to estimate density is given by the formula (Kuno 1969):…”

Section: Application Of Regression Through the Origin In Sequential Smentioning

confidence: 99%

Iwao's patchiness regression through the origin: biological importance and efficiency of sampling applications

Waters

Furlong

Benke³

et al. 2013

Population Ecology

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Iwao's mean crowding-mean density relation can be treated both as a linear function describing the biological characteristics of a species at a population level, or a regression model fitted to empirical data (Iwao's patchiness regression). In this latter form its parameters are commonly used to construct sampling plans for insect pests, which are characteristically patchily distributed or overdispersed. It is shown in this paper that modifying both the linear function and statistical model to force the intercept or lower functional limit through the origin results in more intuitive biological interpretation of parameters and better sampling economy. Firstly, forcing the function through the origin has the effect of ensuring that zero crowding occurs when zero individuals occupy a patch. Secondly, it ensures that negative values of the intercept, which do not yield an intuitive biological interpretation, will not arise. It is shown analytically that sequential sampling plans based on regression through the origin should be more efficient compared to plans based on conventional regression. For two overdispersed data sets, through-origin based plans collected a significantly lower sample size during validation than plans based on conventional regression, but the improvement in sampling efficiency was not large enough to be of practical benefit. No difference in sample size was observed when throughorigin and conventional regression based plans were validated using underdispersed data. A field researcher wishing to adopt a through-origin form of Iwao's regression for the biological reasons outlined above can therefore be confident that their sampling strategies will not be affected by doing so.

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“…Dry season surveys carried out by crop protection services can detect areas where there are high egg-pod concentrations. Shah et al (2000) proposed a sampling method to assess eggpod densities with a relatively high degree of accuracy. Monitoring between March and June would be diffi cult since this is the period when farmers are involved in preparing their fi elds for the next cropping season.…”

Section: Monitoring and Control Strategiesmentioning

confidence: 99%

“…Th e only period possible for such assessments would be from December to February. Modder (1986) and Shah et al (2000) suggested fi nancially compensating farmers in order to get enough people involved in these survey operations. Rapidly locating areas with suitable rainfall conditions at the onset of the monsoon season on the basis of fi eld and remote-sensing data could enhance control of just-hatched nymphs (Burt et al 1995(Burt et al , 1997.…”

Section: Monitoring and Control Strategiesmentioning

confidence: 99%

Ecology and management of the Senegalese grasshopperOedaleus senegalensis(Krauss 1877) (Orthoptera: Acrididae) in West Africa: review and prospects

Maïga¹,

Lecoq²,

Kooyman³

2008

Annales de la Société entomologique de France (N.S.)

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Following the droughts that occurred in the Sahel during the 1970s, the Senegalese grasshopper Oedaleus senegalensis (Krauss 1877) suddenly became the main pest grasshopper species in this region, where it regularly causes serious damage to crops, especially millet. The lifecycle of O. senegalensis refl ects the precariousness of the Sahelian environment. The lifecycle and survival strategies of O. senegalensis have evolved to include migration following shifts in the intertropical convergence zone (ITCZ) and embryonic diapause in the dry season. It is thus able to cope with its natural hostile environment and remain in the most suitable ecological conditions for as long as possible. The alternation between outbreaks and recession periods seems to be related to the high spatiotemporal rainfall variability in the Sahel. Senegalese grasshopper outbreaks depend on the rainy season chronological pattern and on the initial quantity of diapaused eggs in the soil. Since the 1970s, many studies have been conducted on this species in the Sahel. Various models designed to monitor the population dynamics of this species have been published. However, some key factors that could explain the variability in outbreaks have not been seriously investigated. The present bibliographical review provides an overview on current knowledge while proposing some avenues for future research to enhance the sustainable management of this major Sahelian pest. Résumé. Ecologie et contrôle du criquet sénégalais Oedalus senegalensis (Krauss 1877) (Orthoptera : Acrididae) en Afrique Occidentale : revue et perspectives. Depuis les années 1970, le criquet sénégalais-Oedaleus senegalensis (Krauss 1877)-est devenu l'un des principaux criquets ravageurs des cultures vivrières du Sahel africain. Il cause régulièrement des dégâts considérables, en particulier sur le mil. Le cycle biologique de ce criquet refl ète la précarité de l'environnement sahélien. Cette espèce a développé un cycle biologique et une stratégie de survie incluant à la fois des migrations saisonnières suivant le déplacement du Front Intertropical (FIT) et une diapause embryonnaire pendant la saison sèche. Cela lui permet de faire face à un environnement souvent hostile et, pendant la saison des pluies, de se maintenir dans les conditions écologiques les plus favorables possibles. La succession de périodes de pullulations et d'accalmie est liée à la forte variabilité spatiale et temporelle de la pluviométrie et à l'abondance du stock d'oeufs en diapause dans le sol en fi n de saison sèche. Les nombreux travaux conduits au Sahel depuis les années 1970 ont permis une meilleure compréhension de l'écologie de cette espèce. Divers modèles ont été proposés pour suivre la dynamique de ses populations. Cependant, certains facteurs clés pouvant permettre d'expliquer les pullulations demeurent peu ou pas étudiés. La présente revue bibliographique fait le point sur les connaissances actuelles et propose des voies de recherche pour une gestion durable de ce ravageur.

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Enumerative sampling plans for grasshopper egg pods in northern Benin

Cited by 8 publications

References 7 publications

Validation of Fixed Sample Size Plans for Monitoring Lepidopteran Pests of <I>Brassica oleracea</I> Crops in North Korea

Validation of Fixed Sample Size Plans for Monitoring Lepidopteran Pests of <I>Brassica oleracea</I> Crops in North Korea

Iwao's patchiness regression through the origin: biological importance and efficiency of sampling applications

Ecology and management of the Senegalese grasshopperOedaleus senegalensis(Krauss 1877) (Orthoptera: Acrididae) in West Africa: review and prospects

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