MONITORING TUBER FLEA BEETLE, EPITRIX TUBERIS GENTNER (COLEOPTERA: CHRYSOMELIDAE) ON POTATO: PARAMETERS AFFECTING THE ACCURACY OF VISUAL SAMPLING

Abstract

The accuracy of visual observations in estimating numbers of tuber flea beetles, Epitrix tuberis Gentner, on young potatoes was determined. Potential sources of observational error examined were as follows: (a) observer competence and experience; (b) time spent observing each plant; (c) time of day; (d) plant height; and (e) weather. Observational accuracy versus tuber flea beetle density on plants followed a linear relationship for both experienced and inexperienced observers. Marked differences between experienced and inexperienced observers generally were reduced after 2 h of sampling experience, but some observers were consistently less accurate at sighting beetles than others. When observing small plants, 5-s observations generally were more accurate at sighting beetles per second of observation than 2-, 8-, or 10-s observations. Under uniform weather conditions, accuracy was the same in the morning as in the afternoon. Observer accuracy was significantly reduced under the combined influences of observer fatigue and wind. The relationship of 5-s-per-plant sampling accuracy to plants between 14 and 56 cm in height was linear; however, a quadratic relationship is suspected for plants over the full range of plant heights (i.e. >1 cm). From these data, total tuber flea beetles per plant estimated by 5-s visual observations per plant would be: TFB = TFB0/EhE0n where TFB0 is the total number of flea beetles observed, n is the total number of plants sampled, Eh is a sampling accuracy constant for the mean plant height sampled, and E0 is the observer accuracy constant calculated as a proportion of the most proficient observer(s).

Population development of the green peach aphid and beneficial insects in potato fields in British Columbia

“…In the lower Fraser Valley of British Columbia (BC), M. persicae was once considered the main pest of potatoes, and production guides from the 1970s suggest that growers apply insecticidal sprays every 7-10 days from mid-July through to harvest each year (Anonymous 1978). Growers following the suggested spray routines for aphids and applying additional early-season sprays for the tuber flea beetle, Epitrix tuberis Gentner, 1944 (Coleoptera: Chrysomelidae), in May and June (Finlayson 1950;Vernon et al 1990) could apply as many as 10 insecticidal sprays per season (R.S. Vernon, personal observation).…”

Epitrix flea beetles: new threats to potato production in Europe

“…The economic injury level (EIL) for E. tuberis has been calculated as ten beetles per 50 sweeps with an insect net in Oregon 11 and one beetle per 60 plants in British Columbia. 19 The economic injury level for E. cucumeris is much higher. In Manitoba the EIL is 65 beetles per plant for the variety Norland, and 190 per plant for Russet Burbank.…”

“…The economic injury level (EIL) for E. tuberis has been calculated as ten beetles per 50 sweeps with an insect net in Oregon and one beetle per 60 plants in British Columbia . The economic injury level for E. cucumeris is much higher.…”

“…14 In British Columbia, E. tuberis has two complete generations a year. 19 It overwinters in the adult stage in the soil, in and around fields in which potatoes were grown in the previous season. They move back into potato or tomato crops in mid-May, feeding and egg laying.…”

Les insectes ravageurs importants de la pomme de terre au Canada

“…En Colombie-Britannique, les consultants en lutte intégrée échantillonnent généralement des rangs périphériques de même que les rangs plus à l'intérieur des champs pour dépister les altises et autres insectes ravageurs. Afin de prévenir les pontes et le développement de générations ultérieures, Vernon et al, (1990) utilisent un seuil de 1 altise-adulte par 60 plants observés. Cette pratique a permis une réduction du nombre de traitements insecticides de huit traitements, sur toute la superficie du champ par an, à un seul traitement partiel (en périphérie des champs).…”