Delia radicum. [Distribution map].

A new distribution map is provided for Delia radicum (L.) (Hylemya brassicae(Bch.)) (Dipt., Anthomyiidae) (Cabbage root fly). Host Plants: Brassica spp. Information is given on the geographical distribution in EUROPE (excl. USSR), Austria, Azores, Belgium, Britain, Bulgaria, Czechoslovakia, Denmark, Finland, France, Germany, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Poland, Romania, Spain, Sweden, Switzerland, Yugoslavia, ASIA (excl. USSR), Israel, Turkey, USSR, AFRICA, Madeira, Morocco, NORTH AMERICA, Canada, USA.

BIOASSAY OF TOXICITY OF INSECTICIDES IN SOIL USING EGGS AND LARVAE OF THE CABBAGE MAGGOT, HYLEMYA BRASSICAE (DIPTERA: ANTHOMYIIDAE)

A bioassay method was developed for estimating persistence and rate of vertical movement of toxic residues of insecticides in soil Laboratory or field microplots of soil 15 to 45 cm deep were enclosed within a metal or plastic framework comprised of 1 or 5 cm sections which could be readily separated for bioassay. Using eggs and larvae of the cabbage maggot, toxic residues of carbofuran could be estimated at concentrations ranging from ca. 0.2 to 30 μg AI/g of dry soil. Higher concentrations were estimated from bioassays on treated soil serially diluted with untreated soil.

TOXICITY OF PROPOXUR IN WET AND DRY MINERAL SOIL TO ADULTS AND LARVAE OF THE CABBAGE MAGGOT, HYLEMYA BRASSICAE (DIPTERA: ANTHOMYIIDAE)

In greenhouse tests conducted in moist acid mineral soils, propoxur was highly toxic and fast acting as an adulticide against flies of the cabbage maggot, Hylemya brassicae (Bouché), and many other types of adult insects. Some flies in contact with the surface of treated soil were killed in 30 sec or less. When banded at depths of 1, 3.5, and 7 cm, propoxur moved upward and reached peak toxicity to flies standing on the surface in ca. 5, 20, and 35 days, respectively. Deeper placement of the insecticide resulted in lower levels of peak toxicity. Toxicant from 5 to 10 cm depth treatments was still detectable 6 months after soil treatment. Adulticide tests demonstrated that propoxur could be leached downward by addition of excess water to the soil surface. Under the conditions of tests where flies in cages landed at random on treated soils in miniplots, no toxicity was detected when the surface of the treated soil became air dry.A single preplanting subsurface application of propoxur banded below the soil surface in field experiments provided all season protection against cabbage maggot infestations during normal to relatively dry growing seasons but was ineffective during abnormally wet seasons.

COMBINED EFFECTS OF SOIL-INCORPORATED AND FOLIAR-APPLIED INSECTICIDES IN BED-SYSTEM PRODUCTION OF BRASSICA CROPS

In a 4-yr study (1974–1977), combinations of selected soil-incorporated insecticides (carbofuran, chlorfenvinphos, disulfoton, fensulfothion, terbufos and isofenphos) and foliar-applied insecticides (Dipel®, methomyl, ethiofencarb/Thuricide®, methamidophos and permethrin) were studied to determine their effects on occurrence of cabbage maggot (Hylemya brassicae [Bouché]) and its parasites, and of various leaf-feeding lepidopterous larvae and aphids during bed-system production of broccoli (Brassica oleracea var. italica Plenck), Brussels sprouts (Brassica oleracea var. gemmifera Zenker), cabbage (Brassica oleracea var. capitata L.) and cauliflower (Brassica oleracea var. botrytis L.). Several soil-incorporated insecticides reduced the numbers of emergent seedlings. Plants treated with carbofuran and chlorfenvinphos had least maggot damage in their roots. Disulfoton was ineffective. The best aphicide was ethiofencarb closely followed by methamidophos. Permethrin was ineffective as an aphicide but very effective against lepidopterous larvae. Numbers of overwintering puparia of H. brassicae were greatest from untreated plants and least from plants treated with chlorfenvinphos. Percentage parasitism by the staphylinid beetle Aleochara bilineata Gyll. averaged 32% in puparia from untreated plots, but only 5.5% in those from treated plots.

INTERACTIONS OF SEVERAL INSECTICIDES AND A CARABID PREDATOR (BEMBIDION LAMPROS (HRBST.)) AND THEIR EFFECTS ON HYLEMYA BRASSICAE (BOUCHÉ)

Bembidion lampros (Hrbst.) is an important egg predator of the cabbage maggot, Hylemya brassicae (Bouché), but populations may be seriously reduced by application of broad spectrum insecticides for the control of other pests. The efficiency of B. lampros as a predator of H. brassicae eggs and the effects of three insecticides on the beetle were determined in experimental plots of Brussels sprouts. In untreated plots, B. lampros ate 45% of the H. brassicae eggs. In plots treated with methomyl, Bacillus thuringiensis (Dipel), and chlorfenvinphos, egg numbers were reduced 35, 44 and 66%, respectively. One subsurface application of chlorfenvinphos granules, early in the season, prevented damage by the cabbage maggot and was not toxic to the beetle. Foliar applications of methomyl significantly reduced the number of B. lampros. In laboratory tests with methomyl at 0.1, 0.05, 0.025 and 0.0125%, the mortality of B. lampros was 100, 70, 40 and 0%, respectively. Dipel sprays at 0.1 or 0.5% and chlorfenvinphos in the soil at 10 or 40 ppm caused only slight mortality.

HOST SELECTION BY THE ADULT CABBAGE MAGGOT, HYLEMYA BRASSICAE (DIPTERA: ANTHOMYIIDAE): EFFECT OF GLUCOSINOLATES AND COMMON NUTRIENTS ON OVIPOSITION

In Hylemya brassicae (Bouché) little oviposition occurred when access to host plant material was denied. The mustard oil, allyl isothiocyanate (AITC), stimulated the flies into greater activity and attracted them to its source. Sinigrin and four other glucosinolates (mustard oil glucosides) tested induced oviposition. AITC by itself did not induce, oviposition, but in the presence of a glucosinolate, small concentrations of AITC caused an increase in the number of eggs laid. Glucose, sucrose, casein, wheat germ oil, and a mixture of B-vitamins did not influence oviposition at the concentrations tested, but casein hydrolysate inhibited it. The role of glucosinolates and common nutrients in host selection by H. brassicae is discussed.

THE RELATIONSHIP BETWEEN GLUCOSINOLATE CONTENT OF CRUCIFEROUS PLANTS AND OVIPOSITION PREFERENCES OF HYLEMYA BRASSICAE (DIPTERA: ANTHOMYIIDAE)

Leaves of each of six cruciferous plant species investigated contained glucosinolates. There was no correlation between the total glucosinolate concentration of the species (identity of the glucosinolates unknown) and the oviposition response of the adult cabbage maggot, Hylemya brassicae (Bouché). Tests with chemical fractions isolated from rutabaga root tissue indicated that glucosinolates are the major, and perhaps the only, oviposition-inducing substances present in cruciferous plants. It is suggested that oviposition preferences are governed by the presence of some ’key’ glucosinolates and the absence of inhibitory chemicals.