Fungus gnats (Bradysia impatiens) can be a serious pest especially to plants grown in confined areas, and although various methods of control are available, safer and more effective control measures are desirable. Mustard seed meal, a by-product remaining after oil removal for use as a biodiesel feedstock, contains compounds called glucosinolates that hydrolyse to insecticidal 2-propenyl isothiocyanate. Our objective was to produce a dose-response curve for making recommendations of Brassica juncea seed meal applications that will result in fungus gnat larvae control. Twenty colony-raised fungus gnat larvae were added to 20g (226 per cm(3)) of potting media, and adult emergence monitored during 2weeks using yellow sticky cards. Treatments included without meal, detoxified meal and 19 doses ranging from 0.05 to 3.0g seed meal. A logistic model was used to predict an LC50 of 0.18 and an LC90 of 0.38g seed meal for the 20-g pot. The amounts of seed meal required to produce the observed LC50 and LC90 were predicted to produce 0.08 and 0.17mol 2-propenyl isothiocyanate per cm(3) potting medium, respectively. B.juncea seed meal has potential utility for the control of B.impatiens, thus warranting additional studies to determine the seed meal's chronic impact on fungus gnats, phytotoxicity and plant fertility benefits.

Classical biological control of insect pests and weeds may lead to potential conflicts, where insect pests are closely related to weed biological control agents. Such a conflict may occur in the classical biological control of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) in North America, which belongs to the same subfamily, Ceutorhynchinae, as a number of agents introduced or proposed for introduction against non-indigenous invasive weed species. We propose a step-by-step procedure to select non-target species and thereby to develop a non-target species test list for screening candidate entomophagous biological control agents of a herbivore pest insect in a way that would simultaneously evaluate non-target potential on weed biological control agents and other non-target species. Using these recommendations, we developed a non-target test list for host specificity evaluations in the area of origin (Europe) and the area of introduction (North America) for cabbage seedpod weevil parasitoids. Scientifically based predictions on expected host-parasitoid interactions and ecological information about the ecological host range in the area of origin can help avoid conflicts, while still allowing the introduction of safe and effective agents against both insect pests and weeds.

Our objective is to develop a pesticidal product from mustard meals that can be used to control insect pests. We have focused our efforts on fungus gnats. This report details our current progress in developing a pesticidal product that can be used to control this plant pest.

Phyllotreta cruciferae is an important insect pest of spring-planted Brassica crops, especially during the seedling stage. To determine the effect of early season P. cruciferae infestation on seed yield, 10 genotypes from each of two canola species (Brassica napus L. and Brassica rapa L.) and two mustard species (Brassica juncea L. and Sinapis alba L.) were grown in 2 yr under three different P. cruciferae treatments: (1) no insecticide control; (2) foliar applications of endosulfan; and (3) carbofuran with seed at planting plus foliar application of carbaryl. Averaged over 10 genotypes, B. rapa showed most visible P. cruciferae injury and showed greatest yield reduction without insecticide application. Mustard species (S. alba and B. juncea) showed least visible injury and higher yield without insecticide compared with canola species (B. napus and B. rapa). Indeed, average seed yield of S. alba without insecticide was higher than either B. napus or B. rapa with most effective P. cruciferae control. Significant variation occurred within each species. A number of lines from B. napus, B. juncea, anid S. alba showed less feeding injury and yield reduction as a result of P. cruciferae infestation compared with other lines from the same species examined, thus having potential genetic background for developing resistant cultivars.

The phenological synchrony of Eustenopus villosus (Boheman) with its host, yellow starthistle, Centaurea solstitialis L. (Asteraceae: Cardueae), was studied in Idaho in 1995 and 1996. Field plots were observed for adult weevil activity periodically throughout the growing season, and yellow starthistle capitula were examined for adult feeding damage, oviposition damage, and larval development. At the study site, weevil phenology was well synchronized with C. solstitialis. Im mature capitula, fed upon by adults, were abundant when E. villosus began to emerge in late May. During both years, the number of weevils and capitula increased throughout June. Adult females fed on capitula for about 2 wk. Weevil ovary dissections revealed that ovaries were mature after a 2-wk period of feeding. The development of mature capitula during late July corresponded to the initiation of oviposition. Eustenopus villosus, unique among the phytophages introduced for C. solstitialis biological control, attacks four plant stages resulting in observable impact to buds. Damaged buds either died or became distorted. Weevil feeding damage on young and mature capitula may make this insect a highly effective control agent.

A population of yellow starthistle (Centaurea solstitialis L.) near Dayton, Washington developed herbicide resistance in response to repeated applications of picloram and other auxin-type herbicides. Laboratory and field experiments were conducted in 1998 to determine host acceptability and suitability of this herbicide-resistant yellow starthistle population to the biological control weevil Eustenopus villosus (Boheman) (Coleoptera: Curculionidae). In choice and no-choice feeding and oviposition experiments using excised buds, the weevil did not demonstrate a consistent preference for either herbicide-resistant (R) or -susceptible (S) yellow starthistle. When caged on buds of intact plants, the E. villosus feeding rate of 97% did not differ between R and S types. Host plant suitability, measured as larval damage and development to adult weevils, was equivalent in R and S types, with weevils maturing in 46% of the R and in 32% of the S capitula bearing oviposition scars. The number of viable achenes per capitulum was reduced by 87% due to larval feeding, with no difference between R and S types. Observations at the field site where resistance was found revealed oviposition scars on 78% of the late-bud-stage capitula on 23 June 1998 and 73% of the flowering and postflowering capitula on 15 August 1998. Selection for herbicide resistance has not created host incompatibility for E. villosus nor reduced the effectiveness of E. villosus as a biological control agent.

Canola (Brassica napus L.), yellow mustard (Sinapis alba L.) and intergeneric crosses of S. alba×B. napus were assessed for resistance (antixenosis) to the cabbage seedpod weevil (Ceutorhynchus assimilis Paykull). Pod trichomes did not appear to be a major factor in the resistance of S. alba to weevils. The number of feeding punctures and eggs per pod in S. alba was not significantly different in pods with trichomes than in those where the trichomes had been removed. Choice and no-choice laboratory tests examining feeding punctures and eggs laid per pod suggested that resistance in S. alba is not conferred in the intergeneric cross, S. alba×B. napus. Similar data on feeding and weevil oviposition were found in field test plots. However, despite many eggs being laid in S. alba×B. napus hybrid plants, fewer cabbage seedpod weevil larvae developed to exit the intergeneric hybrid pods. Glucosinolate analyses of leaves, pods and seeds showed that S. alba plants have a high concentration of p-hydroxybenzyl glucosinolate in all three plant parts, but B. napus has no p-hydroxybenzyl. Interestingly the intergeneric hybrid examined in this study had 62% and 60% of p-hydroxybenzyl concentration in the leaves and seeds, respectively, than was found in the S. alba parent. However, pod tissues contained very little (3%) compared with the S. alba parent. It is possible, therefore, that the adult cabbage seedpod weevil feeds on the pods of the intergeneric hybrid and lays eggs in the pod, because of the low concentration of p-hydroxybenzyl glucosinolate, but the larvae then fail to develop as they feed on the seeds containing high concentrations of p-hydroxybenzyl glucosinolate. It should be noted also that this hybrid produced pods that were more similar in physical shape to canola pods and that this may also be a factor determining cabbage seedpod weevil feeding and subsequent egg laying. In addition, both B. napus and the intergeneric hybrid produced 3-butenyl and 4-pentenyl glucosinolates in their pods, and degradation products (3-butenyl, and 4-pentenyl isothiocyanates) from these glucosinolate types, are known to be stimulatory kairomones that attract cabbage seedpod weevil. Further studies are being conducted to examine these factors in more detail.

The effect of late season insect infestation on seed yield, yield components, oil content and oil quality of two canola species (Brassica napus L. and B. rapa L.) and two mustard species (B. juncea L. and Sinapis alba L.) was examined over 2 years. In each year, ten genotypes from each species were evaluated with late season insects controlled with either methyl parathion or endosulfan insecticides, and without insecticides. Major late season insect damage in 1992 was caused by cabbage seedpod weevil (Ceutorhynchus assimilis Paykull), while diamondback moth (Plutella xylostella L.) and aphids (primarily cabbage aphids, Brevicoryne brassicae L.) were major insect pests in 1993. Insecticide application was very effective in controlling diamondback moth larvae and adult cabbage seedpod weevils, but only partially effective in controlling aphids. Higher numbers of diamondback moth larvae were observed on mustard species compared to canola species. S. alba was completely resistant to cabbage seedpod weevil and there was no damage due to this pest observed. Aphid colonization was observed on plants from all species, but infestation on S. alba and B. rapa occurred too late to have a major effect on seed yield. Seed oil content of canola species was significantly reduced by insect damage although oil quality (indicated by fatty acid profile) was not affected by insect attack. Uncontrolled insect infestation reduced seed yield of canola species by 37 and 32% in B. napus and B. rapa, respectively. Least yield reduction occurred in S. alba, where average yield reduction from plants in untreated control plots was <10% of insecticide treated plants. S. alba, therefore, has good potential as an alternative crop suitable for northern Idaho because it can be grown with reduced late season insecticide application.

Abstract Plots, 3.5 X 12 ft, arranged in a split-plot design with each chem-ical treatment replicated 3 times, and each of 4 genotypes replicated twice within each treatment strip, were planted at Moscow, ID on 20 Aug, 1995 at 9.5 lb/acre using a small-plot, cone seeder. Capture 2 EC and methyl parathion 4 E were applied 5 Jun with a CO2-pressurized tractor-mounted sprayer equipped with 80° fan nozzles on an 8.3-ft boom that delivered 20 gpa at 30 psi. At the time of treatment, wind conditions were calm (<5 mph), and ambient air tem-perature was above 60°F. Plots were sampled for adult CSW 2 before treatment and 2 d after treatment by dislodging them into a 5-gal plastic bucket with a beat of a hand at each end of a plot. To determine the number of exit holes, 10 pods were removed from 10 racemes from each side of each plot on 17 and 18 Jul. Plots were harvested 15 Aug with a small-plot combine (4.6 ft header). All data were subjected to analysis of variance.

This datasheet on Microctonus melanopus covers Identity, Distribution, Further Information.

A laboratory ovipositional bioassay was developed to assess Brassica (Brassicaceae) germplasm for resistance, specifically antixenosis, to the cabbage seedpod weevil, Ceutorhynchus assimilis (Paykull). The effects of seedpod excision, cage size, seedpod length, weevil collection dates, male presence, seedpod to weevil ratios, and weevil preconditioning on C. assimilis ovipositional performance were evaluated. Standardized protocols were then used to assess the acceptability of Brassica napus L. and B. rapa L. germplasm to the weevil. Paired choice tests using B. napus as a standard ('Bridger') identified 1 resistant line, PI 176876 (B. rapa), and 2 susceptible lines, PI 469918 and PI 469849 (B. napus). These tests also confirmed that adult feeding punctures are not correlated with oviposition. In all cases, ovipositional preference was less pronounced in no-choice tests than in the paired choice tests. Results of 6 x 6 choice tests were consistent with the paired choice tests in assessing ovipositional preference.

Soil amendments of Brassica spp. tissues display toxic effects to a number of soil organisms, including insects. However, application rates necessary to obtain effective insect suppression have not been determined. We tested the toxicity of soil amended with rapeseed, Brassica napus L., seed meal or methyl isothiocyanate to black vine weevil, Otiorhynchus sulcatus (F.), larvae. Control treatments included untreated soil and soil treated with detoxified rapeseed meal. Larvae were exposed to treated soil for 24 h; those remaining motionless 30 min after their extraction from soil were recorded as dead. Mortality data were analyzed assuming the probit model. We estimated LC(50s), to be 19 g of rapeseed meal or 6 mg of methyl isothiocyanate per kilogram of soil. Total conversion of rapeseed meal glucosinolates (123 mu mol/g) could produce up to 44.3 mu mol/g of isothiocyanates; however, the actual production was approximate to 15% of the expected value. Lethal concentrations of rapeseed meal necessary for effective control in a nursery or field application may be too high for practical use because of low glucosinolate content in commercially grown rapeseed and canola cultivars. Consequently, Brassica spp. tissues containing higher concentrations of isothiocyanate-generating glucosinolates would have greater insecticidal potential.

Abstract Plots were established at the University of Idaho Plant Science Farm, Moscow, ID. ‘IMC-144’ Canola seed, supplied by Intermoutain Canola, was planted at 6 lb/acre using a 6-row (7 in spacing), small-plot, cone seeder on 19 May. Plots were 8 X 16 ft arranged in a RCBD with each treatment replicated 4 times. The plots were cultivated, harrowed and fertilized (200 lb/acre 40-0-0-6 and 150 lb/acre 16-20-0) prior to planting. Treatments were applied 31 May using a CO2-pressurized backpack sprayer equipped with 80° fan nozzles on a 6-ft boom that delivered 20 gpa at 30 psi. Flea beetle damage ratings, beetle densities, and counts of all plants in 3.3 ft of rows 3 and 10 (of 12) were made 3 and 8 d following the foliar applications. Damage to cotyledons was scored using a 0-6 rating system. Plots were harvested 22 Sep with a small-plot combine (4.6 ft header). All data were subjected to analysis of variance. To control late season aphid infestations, Capture 2EC (0.04 lb[AI]/acre) and Thiodan 3EC (1.0 lb.[AI]/acre) were applied 6 and 24 Jul, respectively.

Myrosinase (beta-thioglucoside glucohydrolase; EC 3.2.3.1) catalyzes the hydrolysis of glucosinolates to form a variety of potential allelochemicals. Although these allelochemicals may exert an influence on soil-borne organisms, the extracellular preservation of plant-derived myrosinase in soil has not been determined. Soil samples from a held of rapeseed (Brassica napus L.) and from a pasture were extracted with a 0.1 M mixture of K2HPO4 and disodium ethylenedinitrilotetraacetate (pH 7.9). Crude extracts were purified with dialysis and assayed for enzymatic activity using sinigrin (allyl glucosinolate) as a substrate. Myrosinase activity was evaluated by monitoring the hydrolysis product, allyl isothiocyanate, using gas chromatography. Reliability and limitations of the assay were verified with autoclaved samples amended with known amounts of enzyme or allyl isothiocyanate. Extracts of soil samples from a rapeseed field showed myrosinase activity, whereas extracts from a pasture soil showed no detectable activity. Highest myrosinase activity was detected in soil sampled directly from rapeseed rows, an activity equivalent to a myrosinase concentration of approximately 20 mu g kg(-1) soil. Soil sampled between rapeseed rows had a lower myrosinase activity equivalent to a myrosinase concentration of approximately 5 mu g kg(-1) of soil. The presence of extracellular myrosinase in soil indicates that glucosinolate hydrolysis in the rhizosphere of Brassica spp. and allelochemical impacts on organisms within the rhizosphere are possible.

The acute toxicity of soil amended with rapeseed (Brassica napus L.) seed meal to wireworms, Limonius californicus (Mannerheim) (Coleoptera: Elateridae), was determined in laboratory bioassays. Wireworms were exposed to rapeseed seed meal at concentrations from 41.7-500 g/kg soil for 24 h. Probit analysis estimated a LC(50) value of 124.8 g/kg soil 7 d after treatment. The LC(50) value decreased to 114.4 g/kg soil 21 d after treatment with no further change in mortality up to 35 d. Brassica napus tissues show potential for reducing populations of L. californicus. However, applications to soil for insect pest management would require plant material with even higher levels of isothiocyanate-producing glucosinolate to provide useful biological fumigation activity.

Abstract Plots were established at the University of Idaho Plant Science, Moscow, ID. ‘IMC 144’ Canola treated by Rhone-Poulenc and untreated seed from the same lot was planted at 6 lb/acre using a 6-row (7 inch spacing), small-plot, cone seeder on 19 May. Some untreated seed plots also received granular Furadan treatments at planting. Control plots were planted with untreated seed and no Furadan. Plots were 3.5 X 16 ft arranged in a RCBD with each treatment replicated 4 times. The plots were cultivated, harrowed and fertilized (200 lb/acre 40-0-0-6 and 150 lb/acre 16-20-0) prior to planting. FB damage ratings and counts of all plants in 3.3 ft of rows 3 and 4 were made on 30 May, 2 and 7 Jun. Damage to cotyledons was scored using a 0-6 rating system. Capture 2EC (0.04 lb [AI]/acre) and Thiodan 3EC (1.0 lb [AI]/acre) were applied 6 and 24 Jul, respectively to control late season aphid infestations. Plots were havested 22 Sep with a small-plot combine (4.6 ft header). All data were subjected to analysis of variance.

Hydrolysis of glucosinolates in Brassica tissues results in formation of allelochemicals potentially useful in controlling soil-borne plant pests. Major degradation products of glucosinolates in soil are organic isothiocyanates and nitriles; however, a clear understanding of allelochemical persistence in soil is lacking. Half-lives of allyl isothiocyanate (AI) and allylnitrile (AN) in six soils were determined using gas chromatographic analysis of ethyl acetate extracts. The half-lives for AI ranged from 20 to 60 h, whereas AN had longer half-lives of 80-120 h. AI transformation increased with reduced soil moisture and higher temperatures and occurred more rapidly in soils containing greater concentrations of organic carbon. AN transformation increased under wetter conditions and lower temperatures and occurred more rapidly in soils having higher inorganic carbon concentrations. Although different mechanisms contribute to substrate disappearance, the relatively rapid dissipation of AI and AN in soil has important implications in the control of soil-borne plant pests with Brassica tissues.

Plant-derived isothiocyanates are rode to a number of soil organisms; however, the differential toxicity of various isothiocyanates to many soil-borne plant pests has not been determined. We tested the contact toxicity of methyl, propyl, allyl, phenyl, benzyl, and 2-phenylethyl isothiocyanates to eggs of the black vine weevil, Otiorhynchus sulcatus(F.). Eggs were collected every 2 d from a colony of field-collected weevils and preconditioned over a 5-d period. To reduce the variability of responses, only eggs with melanized chorions were used for all bioassays. Eggs were clipped into acetone solutions of isothiocyanates for 2 min. Controls were treated with acetone alone. Treated eggs were incubated for 14 d at 24 +/- 2 degrees C and 100% RH. Mortality response curves of black vine weevil eggs were analyzed using probit analysis. AU isothiocyanates tested were toxic to weevil eggs; however, isothiocyanates containing an aromatic moiety (phenyl, benzyl, and e-phenylethyl) were considerably more toxic than aliphatic (methyl, propyl, and allyl) isothiocyanates. Average mortality in acetone-treated controls was <6%. These results suggest that soil amendments of Brassica aromatic isothiocyanates may have greater insecticidal potential than those producing aliphatic isothiocyanates.