Observers' bias in the assessment of pest and disease symptoms in leek

Theunissen, J.; Legutowska, H.

doi:10.1111/j.1570-7458.1992.tb01599.x

Cited by 7 publications

(3 citation statements)

References 2 publications

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“…Theunissen and Legutowska (1992) compared the accuracy of detailed observation of pest and disease symptoms in leek with a superficial observation, i.e. scanning the plants from above, and found a very low accuracy of the superficial observation for leek rust.…”

Section: Discussionmentioning

confidence: 99%

Sampling for detection: Leek rust as an example

Jong¹

1995

International Journal of Pest Management

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Computer simulation was used to compare four sampling patterns in their efficiency of detecting diseased plants under a variety of spatial distributions of infected plants. The sampling patterns compared were: diagonal sampling, double diagonal sampling, row sampling over two rows and row sampling over four rows. Row sampling over four rows was the most effective sampling pattern. The detection level, the lowest disease level at which the probability to detect the disease is sufficiently large, was studied in relation to temporal and spatial characteristics of the disease, as found in two epidemics in 1992 and 1993. For both epidemics, a weekly sample of 50 plants resulted in detection levels that were low enough to ensure adequate chemical control, indicating the feasibility of sampling for detection of leek rust. Weekly sampling is more efficient than fortnightly sampling.

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Section: Discussionmentioning

confidence: 99%

Sampling for detection: Leek rust as an example

Jong¹

1995

International Journal of Pest Management

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“…Little correlation between feeding symptoms and thrips counts was found in the commercial farms (Tables 3 and 4); this could be because we estimated thrips population densities based mostly on adults rather than larvae, which are considered responsible for most actual crop damage (Theunissen & Legutowska, 1991a; Theunissen & Schelling, 1997). Variability could also be due to observation error, or the ‘human factor’ (Theunissen & Legutowska, 1992). Observers are unlikely to vary in their counts of individual insects, but early thrips feeding symptoms are often vague and measurements can vary considerably in accuracy, even when assessing infestation in different rows of the same field (Theunissen & Legutowska, 1992).…”

Section: Discussionmentioning

confidence: 99%

“…Variability could also be due to observation error, or the ‘human factor’ (Theunissen & Legutowska, 1992). Observers are unlikely to vary in their counts of individual insects, but early thrips feeding symptoms are often vague and measurements can vary considerably in accuracy, even when assessing infestation in different rows of the same field (Theunissen & Legutowska, 1992). Consequently, variation could be great over multiple years, even if visual inspection was done by the same observer.…”

Section: Discussionmentioning

confidence: 99%

Population dynamics and integrated pest management of Thrips tabaci on leek under field conditions in northwest Italy

Bosco

Tavella

2010

Entomologia Exp Applicata

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Thrips tabaci Lindeman (Thysanoptera: Thripidae) is a major pest of leek, Allium porrum L. (Alliaceae), in Piedmont, northwest Italy, and to control its infestation the leek crop is sprayed intensively with insecticides during the summer period. In order to find the most efficient and environment‐friendly method of thrips control, research was conducted on six commercial farms during 2005–2006 to assess thrips population composition and infestation levels, and in an experimental field during 2005–2007. Biological and chemical control were compared during 2005–2006, whereas integrated pest management was adopted during 2007. During the growing season, thrips and natural enemy populations were monitored at 14‐day intervals by beating plants; new leaves of plants were also visually inspected for thrips‐feeding symptoms. Furthermore, in the experimental field at harvest‐time, the level of thrips injury to plants was assigned to one of five classes, depending on the percentage of leaf area damaged. Over 99% of phytophagous adult thrips found were male and female T. tabaci. Infestations were very variable in the crops surveyed, partly due to broad‐spectrum chemical treatments against the leek pests, which often failed to control thrips. In general, populations peaked in September, when they reached the maximum mean values ranging between 1.7 and 33.1 thrips per plant. At harvest, none of the surveyed farms experienced quality losses due to thrips injuries. In the experimental field during 2005–2006, the mean number of thrips per plant was greater in the chemical than in the biological control treatment, even though damage indices showed no significant differences between the two treatments. Predatory thrips of the genus Aeolothrips (Thysanoptera: Thripidae) and predatory bugs of the genus Orius (Heteroptera: Anthocoridae), mostly Orius majusculus Reuter, were particularly abundant during 2007, supporting the importance of management with selective insecticides to encourage natural colonization by predators.

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Order Thysanoptera—Thrips

Capinera¹

2020

Handbook of Vegetable Pests

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Observers' bias in the assessment of pest and disease symptoms in leek

Cited by 7 publications

References 2 publications

Sampling for detection: Leek rust as an example

Sampling for detection: Leek rust as an example

Population dynamics and integrated pest management of Thrips tabaci on leek under field conditions in northwest Italy

Order Thysanoptera—Thrips

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