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Several types of trap crops have been recommended for managing the diamondback moth, Plutella xylostella , including collards ( Brassica oleracea var. acephala ) and Indian mustard ( Brassica juncea L.). However, results have been variable perhaps because populations of P. xylostella develop on these trap crops and spill over to the cash crop. To overcome this problem, we sought to develop “dead-end” trap crops that were more attractive for oviposition than the cash crop but on which P. xylostella larvae cannot survive. We have produced Bacillus thuringiensis (Bt)-transgenic collard and Indian mustard lines with a cry1C gene that have the potential to be used as a “dead-end” trap crop for P. xylostella . Greenhouse and small cage studies confirmed the control of P. xylostella larvae on the Bt crops. Furthermore, Indian mustard was significantly preferred over cabbage and collards for oviposition, regardless of whether the Indian mustard was Bt or non-Bt. The use of Bt Indian mustard as a trap crop significantly reduced the number of larvae that appeared on a cabbage cash crop, compared with using a non-Bt Indian mustard trap crop. However, this reduction also occurred when using Bt collards as a trap crop, despite collards being less preferred for oviposition. In fact, despite the overall increase in oviposition caused by the presence of Indian mustard compared with collards, the use of either Bt Indian mustard or Bt collards provided the same level of protection to the cash crop. Both plants also resulted in significant suppression of a P. xylostella population over 3 generations in the greenhouse test and 2 generations in the small cage experiment, suggesting that in places where immigration may be limited some long-term population suppression may occur. We suggest that Bt trap crops may be useful tools in situations where the cash crop may not be suitable or desirable for genetic engineering.

A major mechanism of resistance to Bacillus thuringiensis (Bt) toxins in Lepidoptera is a reduction of toxin binding to sites in the midgut membrane. Genetic studies of three different species have shown that mutations in a candidate Bt receptor, a 12-cadherin-domain protein, confer Cry1A toxin resistance. Despite a similar resistance profile in a fourth lepidopteran species, Plutella xylostella, we have previously shown that the cadherin orthologue maps to a different linkage group (LG8) than Cry1Ac resistance (LG22). Here we tested the hypothesis that mutations in other genes encoding candidate Bt-binding targets could be responsible for Bt resistance, by mapping eight aminopeptidases, an alkaline phosphatase (ALP), an intestinal mucin, and a P252 glycoprotein with respect to the 29 AFLP marked linkage groups in a P. xylostella cross segregating for Cry1Ac resistance. A homologue of the Caenorhabditis elegans Bt resistance gene bre-2 was also mapped. None of the genes analysed were on the same chromosome containing the Cry1Ac resistance locus, eliminating them as candidate resistance genes in the parental resistant strain SC1. Although this finding excludes cis-acting mutations in these genes as causing resistance in this strain, one or more of the expressed proteins may still bind Cry1Ac toxin, and post-translational modifications could affect this binding and thereby exert a trans-acting effect on resistance.

Swede midge (Contarinia nasturtii Keiffer) is a serious gall-forming insect pest of cruciferous plants in Europe and southwestern Asia. In North America, it was first identified in Ontario, Canada, in 2000 and in Niagara County, New York, US, in 2004. The insect is now rapidly spreading in Canada and the US. To date, infestation of C. nasturtii has been confirmed in 46 counties in Canada. The US Department of Agriculture has confirmed the presence of C. nasturtii in 6 counties in the US, although our surveys using pheromone traps have identified 19 counties in New York and one county in Massachusetts and New Jersey. Currently, hundreds of farms in the northeastern US that grow cruciferous vegetables are at risk for infestation of C. nasturtii through movement of vegetable seedlings and harvested produce from infested areas. To prevent the spread of C. nasturtii, the efficacy of acetamiprid, the first labeled insecticide in the US for C. nasturtii control, was evaluated by using foliar sprays on cauliflower seedlings. Results indicated the efficacy of acetamiprid on C. nasturtii was 99.52% 100% and 99.83% when cauliflower seedlings were sprayed before inoculation with C. nasturtii, 0 and 4 d after inoculation, respectively. The efficacy of acetamiprid was reduced to 69.89% when seedlings were sprayed 8 d after inoculation, and C. nasturtii larvae could successfully pupate and emerge after the spray. These results indicate that acetamiprid can effectively control C. nasturtii on cauliflower seedlings, especially in the early stage of insect occurrence. Based on these results, we suggest that seedlings be treated with acetamiprid as a foliar spray before shipment of seedlings from C. nasturtii infested areas.

The thermoelasticity of rocksalt (RS) structure MgO is investigated by ab initio plane-wave pseudopotential density functional theory method and the quasi-harmonic Debye model. The obtained lattice constant, aggregate elastic moduli, pressure derivative of isothermal bulk modulus and elastic constants are well consistent with the experimental data and other theoretical results. Moreover, the pressure dependences of individual elastic modulus at 300 and 800 K are also discussed. It is shown that, at 300 K, the Debye temperatures from our obtained elastic constants are well consistent with other theoretical results. The Debye temperature increases nonlinearly with increasing pressure.

Microplitis mediator (Haliday) is an important endoparasitoid of the cotton bollworm, Helicoverpa armigera (Hubner) in northern China. Interactions among H. armigera, its larval parasitoid M. mediator, and insect–resistant transgenic cotton lines were evaluated under laboratory conditions. Two major transgenic cotton cultivars used in Hebei province of northern China, DP99B (Bollgard), carrying the cry1Ac gene, and SGK321, carrying both cry1A and CpTI (Cowpea trypsin inhibitor) genes, were used in the experiments. The results indicated that there was significant growth inhibition of the H. armigera larvae when they were fed a diet containing Bt transgenic cotton powder. The parasitoid offspring developed more slowly and pupal and adult weight was reduced significantly when the parasitized host larvae fed on the Bt cotton powder leaf diet compared with non-Bt treatment. With an increase of Bt cotton leaf powder concentration in the host larvae diet, the parasitism rate and adult emergence of the parasitoid decreased and the abnormal pupal rate increased. There was no evident difference in the effects on M. mediator between the transgenic single- and two-gene cotton cultivars; however, the parasitized host larval mortality was higher than that of unparasitized larvae in most treatments. The observed effects on M. mediator were probably host-quality mediated rather than direct effects of transgenic cotton because the H. armigera larvae which fed on diet with leaf powder of both transgenic cotton cultivars also experienced a significant decrease in weight, particularly when the host larvae were parasitized.

The transition phase of GaN from zincblende (ZB) structure to rocksalt structure (RS) is investigated by ab initio plane-wave pseudopotential density functional theory method, and the thermodynamic properties of the ZB and RS structures are obtained through the quasi-harmonic Debye model. We find that the transition phase from the ZB structure to the RS structure occurs at the pressure of 42.2 GPa, which is in good agreement with other calculated values. Moreover, the dependences of the relative volume V/V-0 on the pressure P, the Debye temperature Theta and heat capacity C-V on the pressure P, as well as the heat capacity C-V on the temperature T are also successfully obtained. (C) 2005 Elsevier Ltd. All rights reserved.

A resistant strain of Helicoverpa armigera selected by cyhalothrin was used to investigate the relative importance of knockdown resistance ( kdr ) for different levels of resistance to cyhalothrin and fenvalerate and the inheritance of kdr to fenvalerate. Pretreatment of piperonyl butoxide (PBO) decreased the resistance ratios from 30.6- to 5.0-fold for cyhalothrin and from 337.0- to 38.0-fold for fenvalerate. Electrophysiological studies showed that kdr ratios were 10.7- and 95.8-fold to cyhalothrin and fenvalerate, repectively, at EC 50 of burst discharge of neuromuscle preparation, and were 15.0- and 507.2-fold to cyhalothrin and fenvalerate, respectively, at EC 50 of blocked neuromuscular transmission. It was indicated that the difference in kdr to fenvalerate and cyhalothrin is the main reason for the difference in resistance level between the two pyrethroids in the resistant strain of H. armigera. Analysis of probit lines from F 1 reciprocal crosses indicated that kdr to fenvalerate was inherited autosomaly as an incompletely recessive factor. The degrees of dominance were −0.74 and −0.78, based on burst discharge and blocked transmission, respectively, with pooled F 1 generations. χ 2 analysis of knockdown responses of backcrossed offspring indicated that the resistance might be controlled by one major gene. Cross-resistance to aconitine was detected in resistant strain after applying PBO, indicating that sodium channels are different in the resistant and susceptible strains of H. armigera.