Varietal differences in the susceptibility of Brussels sprouts to lepidopterous pests

The attack by cabbage caterpillars on open-pollinated cultivars of Brussels sprouts at Wellesbourne was recorded approximately weekly from July to October in 1973 and 1974. The red-foliaged cv. Rubine was much less attacked by Pieris rapae than any of the twenty-five green-foliaged cultivars tested, the least attacked of which were The Aristocrat, Continuity, Evergreen and Pride of the Market. Rubine also showed some resistance to attack by Mamestra brassicae and Evergestis forficialis, as did The Aristocrat. Continuity, though as resistant as any of the cultivars to E. forficialis, was not resistant to M. brassicae. No evidence of antibiosis was found and resistance, based on non-preference, is considered to result from ovipositing P. rapae adults discriminating against the red colour of Rubine and against the leaf composition (relative volatile content) of the green-foliaged resistants. This could also apply with M. brassicae and E. forficialis.     

Control of tomato grey mould on unheated crops using non- systemic fungicide sprays

High volume sprays of dichlofluanid (0.1 % a.i.) reduced total fruit numbers but gave better control of Botrytis cinerea infections of tomato stems, leaves and fruit than sprays at 0.05 or 0.025% a.i. Surface residues from the sprays at 0–1, 0.05 or 0.025% a.i. were respectively 5.4, 1.6, 0.7 μg/g fresh weight of ripe fruit at harvest. Tank-mixed zineb (0.12% a.i.) and captan (0.2% a.i.) were less effective and increasing the spray intervals from 1 wk to 2 and 3 wk reduced the fungitoxicity of captan and zineb more than that of dichlofluanid. Harvest residues on ripe fruit were 7.1, 2.8 or 2.4 μg/g when dichlofluanid (0.1 % a.i.) sprays were applied at 1, 2 and 3 wk intervals respectively. Good control of B. cinerea was achieved if the whole plant was sprayed initially with dichlofluanid as soon as the second truss was flowering and subsequent sprays were restricted to the upper section of stem including the four or five youngest trusses of buds, flowers and fruit. When used as a post-infection spray there was a period of c. 8 wk before dichlofluanid markedly reduced the incidence of grey mould. Tank-mixed zineb (0.12% a.i.) controlled Botrytis fruit spotting but not leaf and stem infections. Botrytis stem lesions extended more rapidly on zineb-sprayed plants than on unsprayed plants or on plants treated with captan or dichlofluanid.     

Seasonal changes in aphid populations on Brussels sprouts

Populations of Brevicoryne brassicae (L.) and Myzus persicae (Sulz.) were assessed weekly on Brussels sprouts at Wellesbourne, from July onwards in each of 3 years. A peak of B. brassicae numbers occurred every year about the end of July, and in 1968 and 1970 this was larger than the September peak. Some alates were produced in the generation born to the June immigrants and the dispersal of those produced at the end of July consistently brought a decline in B. brassicae populations in early August. In 1968 and 1970, however, outbreaks of entomogenous fungi which followed rain, added considerably to this decline. Records of predators and parasites indicated that these natural enemies had only a minor effect on aphid numbers. M. persicae colonized sprouts slightly earlier than B. brassicae; in 1969 and 1970 its numbers in July were low and some persisted after the first week of August in 1968 only. In each year the first eggs of B. brassicae were laid at the beginning of October, but viviparae were still numerous for a further 7 to 10 weeks.     

A Note on the Occurrence of Bacillus cereus and Other Species of Bacillus in Indian Spices of Export Quality

Four unprocessed Indian spices sampled at the point of export were shown to be highly contaminated with bacteria. Bacillus cereus was detected in more samples of these spices than any other spore-forming aerobe.     

Effect of the timing of insecticide applications on infestation by Cavariella aegopodii Scop,on carrots*

The residual effectiveness of demeton-methyl and menazon sprays applied to carrot plants was compared in the laboratory using Cavariella aegopodii Scop, and more observations were made in the field, where applications of both insecticides were timed in relation to the observed immigration period of the aphid. The relative field performances confirmed those found in the laboratory and, as the aphid population control exercised was inversely proportional to the amount of alate immigration occurring after the sprays had become ineffective, the more persistent menazon was progressively superior to demeton-methyl the nearer they were applied to the beginning of immigration. A single spray application of either material towards the end of immigration gave a similar overall control of aphid numbers to that given by disulfoton granules applied at sowing time. To minimize colonization, two spray applications spanning the immigration peak were required and, with 2 weeks between the demeton-methyl sprays and 3 between those of menazon, the highest degree of control was obtained when the first application was made 7–10 days after the beginning of immigration.     

Soil fumigation with methyl bromide: the uptake and distribution of inorganic bromide in tomato plants

Tomato plants grown in soil previously fumigated with methyl bromide accumulated inorganic bromide in the foliage. The concentration present depended on the rate of application of methyl bromide to the soil and on the interval between, soil fumigation and planting, two factors determining the concentration in the soil of inorganic bromide arising from the breakdown of the fumigant. The concentration of bromide in the leaves decreased from the base to the tip of the plant, and increased with the age of the tissue. Bromide was accumulated in the fruit, but to a lesser extent than in the leaves. Mature fruit from plants grown in soil fumigated at the commercially applied rate of 1.5 lb/100 ft² (73 g/m²) contained at the most 45 μg/g of fresh tissue, and generally not more than half this value. The concentration of bromide in fruit was related to the concentration of inorganic bromide present in the soil, but not to the state of ripeness or the position of the fruit on the plant. Similar results were obtained for leaves and fruit from plants grown in soil supplemented with inorganic bromide.