Influence of crop background on aphids and other phytophagous insects on Brussels sprouts

Abstract

S U M M A R YMore Brevicoryne brassicae and other alate aphids were caught in yellow water-traps in a weed-free crop of Brussels sprouts than in a crop with a weedy background. More B. brassicae colonized Brussels sprout plants in Present address: Departamento de Zoologia, Universidade Federal do Parand, Caixa postal 756, Curitiba 80.000, Parand, Brazil. 1-2 2 JUDITH G. SMITH Brevicoryne brassicae L., although other species of aphids and some other brassica pests (Aley~odes brassicae (Wlk.) and certain Lepidoptera) were also counted. Effects of background on natural enemies of aphids are described separately (Smith, 1969(Smith, ,1976.The work was part of a programme aimed at integrated control of insect pests on Brussels sprout plants, the manipulation of crop background being considered as a possible component of an integrated control practice. MATERIALS A N D M E T H O D S Field experimentsExperiments. Field experiments were done in a I-acre (0.4 ha) crop of Brussels sprouts (B~assic~ oleracea gemmifera L. cv. Irish Elegance) in Silwood Bottom at Imperial College Field Station, Silwood Park, Berkshire, between 1965 and 1967. Young plants were planted out during early June at spacings of 36 x 30 in (91 x 76 cm) (1965) or 36 x 36 in (1967); in 1966, plants were initially spaced at 36 x 18 in and thinned out in early August to 36 x 36 in. The 1965 experiment consisted of eight plots, each 210 yd2 (176 m2), of Brussels sprout plants, four kept weed-free by regular hoeing and four where the indigenous weeds were allowed to grow but were cut back regularly to about 6 in (IS cm) high;weeds growing immediately beneath sprout plants were removed. The experiment was laid out with two adjacent blocks of alternating weedy and weed-free plots. In a similar experiment in 1967, there were two weed-free and two weedy plots, each 120 yd2 ( IOO m2); in 1966 a 4 x 4 latin square was set up with weedy and weed-free plots, each 75 yd2 (63 m2), and with plots with artificially coloured green and brown backgrounds, formed by placing 3 ft (91 cm) wide strips of painted hessian between the rows of plants. A layer of straw beneath the hessian prevented it from being soiled in wet weather.In the years 1966 and 1967, dry weather delayed the germination of weeds and hence delayed establishment of the contrasting weedy or weed-free backgrounds. In early July, 0.02 yo (v/v) mevinphos in water was therefore applied to eliminate aphid colonies established before the backgrounds differentiated. Yellow and suction traps. Numbers of flying insects were assessed from July to November from catches in yellow water-traps 3-7 in (9-4 cm) in diameter, positioned at the centre of each plot and kept level with the heart and young leaves of the sprout plants; the traps were emptied three times a week.Catches of aphids and syrphids in four 9 in (23 cm) diameter suction traps (Johnson, 1950) which were operated in fine weather between July and September 1966, were compared in plots with different backgrounds.Plant samples. The outer row of each plot was di...

Abundance, growth rate and parasitism of Brevicoryne brassicae and Myzus persicae (Homoptera: Aphididae) on broccoli grown in living mulches

“…Densities of Brevicoryne brassi cae in living mulches were very low in 1990, when parasitism was lower compared with clean culti vation. However, tht:; higher rates of parasitism found by Smith (1976b) in a Brussels sprouts monoculture were at equivalent aphid densities as the weedy Brussels sprouts (Smith, 1976a), and Helenius ( 1990) found a higher rate of par asitism in an oat monoculture despite finding a higher aphid density in mixtures ofoats and fava beans. Thus, further studies on parasitism with control of aphid density would be helpful in sep arating the effects of host density from crop diversity.…”

Multiple cropping systems as drivers for providing multiple ecosystem services: from concepts to design

“…Resource dilution of a host plant in the plant mixture potentially makes the pest less efficient in locating and colonizing its host (Trenbath 1993;Ratnadass et al 2012). Resource dilution has been shown to be an appropriate means of managing many pests, such as aphids (A'Brook 1968;Smith 1976) and other phytophageous insects (Altieri 1999). Multiple cropping systems can also reduce dispersal by creating physical barriers (groups A and C) through the structure and layout of the planting scheme or by modifying the microclimates in plant associations.…”

Visual ecology of aphids—a critical review on the role of colours in host finding

“…Green living plants as background of targets for landing, such as used in intercropping systems, are also efficient in reducing aphid catches (e.g. Moericke 1957;Mü ller 1964;Gonzá lez and Rawlins 1968;Heathcote 1968;Smith 1976;Bigler et al 1995;Lehmhus 2001). For green mulches, colour contrast effects are conceivable but have not been separated experimentally from other effects.…”