Manipulating the attractiveness and suitability of hosts for diamondback moth (Lepidoptera: Plutellidae)

Ovipositional preference and larval survival of the diamondback moth, Plutella xylostella (L.), were compared among cabbage, Brassica oleracea L. variety capitata; glossy collards, Brassica oleracea L. variety acephala; and yellow rocket, Barbarea vulgaris (R. Br.) variety arcuata in different treatments of planting density, host plant age, intercropping, and water stress in 2003 and 2004. P. xylostella laid nearly twice as many eggs per plant in the high planting densities of glossy collards and yellow rocket than in the standard planting densities. Ovipositional preference was positively correlated with plant age in cabbage, glossy collards, and yellow rocket. Larval survival on cabbage was 1.9 times higher on 6-wk than on 12-wk-old plants, whereas larval survival on collards was 12.1 times higher on the younger plants. No larvae survived on either 6- or 12-wk-old yellow rocket plants. Intercropping cabbage with either tomato, Lycopersicon esculentum Mill., or fava bean, Vicia fava L., did not reduce the number of eggs laid on cabbage. No significant differences in oviposition were found between water-stressed and well-irrigated host plants treatments. Yet, P. xylostella larval survival on water-stressed cabbage was 2.1 times lower than on well-irrigated cabbage plants. Based on our findings, the effectiveness of trap crops of glossy collards and yellow rocket could be enhanced by integrating the use of higher planting densities in the trap crop than in the main crop and seeding of the trap crop earlier than the main crop.     

Using yellow rocket as a trap crop for diamondback moth (Lepidoptera: Plutellidae)

Yellow rocket, Barbarea vulgaris (R. Br.) variety arcuata, was evaluated as a trap crop for diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), in cabbage, Brassica oleracea L. variety capitata, in 2003 and 2004. In 2003, the numbers of P. xylostella larvae found in field plots of cabbage alone were 5.2-11.3 times higher than those on cabbage plants in plots that included cabbage and several rows of yellow rocket. In an outdoor experiment in screenhouses, P. xylostella oviposition on cabbage was compared among six treatments that varied in the percentage of yellow rocket in relation to cabbage (0, 4, 8, 16, 24, and 32% of the plants were yellow rocket). Results indicated that the percentage of eggs laid on cabbage decreased as the percentage of yellow rocket in the treatment increased, but this decrease was not significant beyond 20% of the plants being yellow rocket. In 2004, the numbers of P. xylostella larvae in field plots of cabbage alone were 1.6-2.4 and 1.7-2.8 times higher than numbers in treatments with 10 and 20% trap crop, respectively. Sticky trap and sweep net captures of P. xylostella adults indicated that within-field dispersal was reduced by the presence of yellow rocket and aggregation occurred around yellow rocket plants. Our study suggests that using yellow rocket as a trap crop may reduce P. xylostella infestations in cabbage fields, and this possibility is discussed in the context of general crop and insect pest management practices in crucifers.     

Cytotoxic and antitumoral properties in a series of new, ring D modified, olivacine analogues

The present study describes the synthesis and pharmacological profiles of new olivacine related compounds, possessing a modified D ring. The impact of this modification has been evaluated with respect to the cytotoxic and in vivo antitumoral effects of these molecules and in comparison with parent S 16020-2 previously prepared and investigated in our laboratory. The D ring size and number of nitrogen atoms as well as the position of the aminoalkyl substituent have a profound impact on the cytotoxic and antitumoral profiles. Thus out of the prepared pyrazinocarbazole compounds, 2 is devoid of any substantial cytotoxic and antitumoral activities while the pyrimidocarbazole 3 has a similar profile compared to 1 (S 16020-2). L1210 and P388 in vivo antitumoral effects are lost for both imidazocarbazoles 4 and 5, but the former conserves an in vivo antitumoral effect on B16 melanoma, this effect being the largest in the series. Structural similarities and differences amongst the studied compounds could be evidenced by calculation of global properties such as molecular electrostatic potentials (MEP maps) and partition coefficients (logP), thus adding information on the impact of chemical changes on these two parameters known to influence biological behavior.     

Leafhoppers on leaves: An analysis of feeding behavior using conditional probabilities

Feeding behavior of four deltocephaline leafhoppers,Graminella nigrifrons, G. oquaka, Amblysellus grex, andDalbulus maidis on maize and johnsongrass was analyzed using an electronic monitoring device. Five distinct waveform patterns were identified: secretion of sheath saliva (salivation), nonvascular probing, nonsieve element ingestion, x-waveform, and phloem ingestion. Waveforms were associated with feeding activities by correlation with light microscopic examination of salivary sheath termination points in leaf tissue and analysis of honeydew excreted by monitored leafhoppers. In previous studies x-waveforms have been reported to occur only when the stylets of homopterans are in contact with the phloem; the function of x-waveforms is poorly understood. There were no differences in time spent salivating or ingesting from nonsieve elements amongG. nigrifrons, G. oquaka andA. grex on either plant.D. maidis differed from other species in phloem probing and feeding behavior; only a small proportion produced x-waveforms, although those that did spent significantly more time in this behavior than other species. Also,D. maidis spent more time than other leafhoppers ingesting from tissues other than sieve elements. Kinetic diagrams of transition probabilities show that probing activities of all species were not random regarding the sequence of behaviors culminating in phloem ingestion. Thirty-five percent ofG. nigrifrons x-waveforms were followed by nonsieve element ingestion. This was consistent with observations showing that salivary sheaths of leafhoppers producing x-waveforms sometimes do not terminate in the phloem, but rather in nearby cells. Phloem ingestion was always preceeded by x-waveforms. The quantitative differences in probing behavior are discussed in relation to ability of these leafhoppers to transmit the phloem-associated maize chlorotic dwarf waikavirus.     

Expression of porcine pro-opiomelanocortin cDNA in heterologous monkey kidney cells. Biosynthesis and secretion of the prohormone without processing

Pro-opiomelanocortin is the common precursor to several pituitary hormones. These include alpha-melanotropic hormone, adrenocorticotropic hormone, beta-lipotropic hormone, and beta-endorphin. The porcine pro-opiomelanocortin cDNA was inserted downstream from the early promoter of a SV40-derived expression vector and transfected into the monkey kidney COS-1 cells. Transient expression of the pro-opiomelanocortin cDNA was observed between 48 and 70 h after transfection. Analysis of pro-opiomelanocortin-related material in COS-1 cell extracts and culture medium revealed that these cells synthesize and secrete constitutively pro-opiomelanocortin without further processing into its mature hormones. Our results suggest that COS-1 cells do not contain the necessary enzymatic machinery to process complex precursors such as pro-opiomelanocortin.     

Relationships between insect predator populations and their prey,Thrips tabaci,in onion fields grown in large-scale and small-scale cropping systems

Onion thrips, Thrips tabaci Lindeman, is the primary pest of onion, which is grown in either large-scale, monoculture systems surrounded by other onion fields, or in small-scale systems surrounded by multiple vegetable crops. In 2011 and 2012, populations of insect predators and their prey, T. tabaci, were assessed weekly in onion fields in both cropping systems. Insect predator taxa (eight species representing five families) were similar in onions grown in both systems and the most commonly occurring predators were from the family Aeolothripidae. Seasonal population dynamics of predators and T. tabaci followed similar trends within both cropping systems and tended to peak in late July and early August. Predator abundance was low in both systems, but predator abundance was nearly 2.5 to 13 times greater in onion fields in the small-scale system. T. tabaci abundance often positively predicted predator abundance in both cropping systems.     

Characterization of resistance, evaluation of the attractiveness of plant odors, and effect of leaf color on different onion cultivars to onion thrips (Thysanoptera: Thripidae)

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a worldwide pest of onion, Allium cepa L. In field studies on onion resistance conducted in 2007 and 2008 using 49 cultivars, 11 showed low leaf damage by T. tabaci. In laboratory studies, the 11 cultivars, along with two susceptible checks and four additional cultivars, were evaluated to characterize resistance to T. tabaci and to determine if color and/or light reflectance were associated with resistance to T tabaci. No-choice tests were performed with adults and the numbers of eggs and larvae were counted on each cultivar after three and 10 d, respectively. In choice tests in which all cultivars were planted together in a circle in a single pot, 100 adults were released and the number of adults on each plant was evaluated 24 h later. The behavioral response of walking T. tabaci adults to plant odors was studied in a glass Y-tube olfactometer. The reflectance spectrum of leaves was measured using a UV-VIS spectrophotometer. Results indicate that resistant cultivars showed an intermediate-high antibiotic effect to T. tabaci and all of them showed a very strong antixenotic effect. There were no significant preferences in the response of walking T. tabaci adults to plant odors. The two susceptible cultivars had the highest values of leaf reflectance for the first (275-375 nm) and second (310-410 nm) theoretical photopigment-system of T. tabaci, and these values were significantly different from most resistant cultivars. These results suggest a strong response of T. tabaci to onion cultivars with higher reflectance in the ultraviolet range (270-400 nm). Overall, these results appear promising in helping to identify categories of resistance to T. tabaci in onions that can be used in breeding programs.     

Albumin-conjugated C34 peptide HIV-1 fusion inhibitor: equipotent to C34 and T-20 in vitro with sustained activity in SCID-hu Thy/Liv mice

Entry inhibitors of human immunodeficiency virus, type 1 (HIV-1) have been the focus of much recent research. C34, a potent fusion inhibitor derived from the HR2 region of gp41, was engineered into a 1:1 human serum albumin conjugate through stable covalent attachment of a maleimido-C34 analog onto cysteine 34 of albumin. This bioconjugate, PC-1505, was designed to require less frequent dosing and less peptide than T-20 and was assessed for its antifusogenic activity both in vitro and in vivo in the SCID-hu Thy/Liv mouse model. PC-1505 was essentially equipotent to the original C34 peptide and to T-20 in vitro. In HIV-1-infected SCID-hu Thy/Liv mice, T-20 lost activity with infrequent dosing, whereas the antiviral potency of PC-1505 was sustained, and PC-1505 was active against T-20-resistant ("DIV") virus with a G36D substitution in gp41. The in vivo results are the direct result of a significantly improved pharmacokinetic profile for the C34 peptide following albumin conjugation. Contrary to previous reports that the gp41 NHR trimer is poorly accessible to C34 fused to protein cargoes of increasing size (Hamburger, A. E., Kim, S., Welch, B. D., and Kay, M. S. (2005) J. Biol. Chem. 280, 12567-12572), these results are the first demonstration of the capacity for a large, endogenous serum protein to gain unobstructed access to the transient gp41 intermediates that exist during the HIV fusion process, and it supports further development of albumin conjugation as a promising approach to inhibit HIV-1 entry.     

Impact of straw mulch on populations of onion thrips (Thysanoptera: Thripidae) in onion

Development of insecticide resistance in onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), populations in onion (Allium spp.) fields and the incidence of the T. tabaci transmitted Iris yellow spot virus have stimulated interest in evaluating alternative management tactics. Effects of straw mulch applied in commercial onion fields in muck areas of western New York were assessed in 2006 and 2007 as a possible onion thrips management strategy. In trials in which no insecticides were applied for thrips control, straw mulch-treated plots supported significantly lower T. tabaci populations compared with control plots. In both years, the action thresholds of one or three larvae per leaf were reached in straw mulch treatments between 7 and 14 d later than in the control. Ground predatory fauna, as evaluated by pitfall trapping, was not increased by straw mulch in 2006; however, populations of the common predatory thrips Aeolothrips fasciatus (L.) (Thysanoptera: Aeolothripidae) were significantly lower in straw mulch plots in both years. Interference of straw mulch in the pupation and emergence of T. tabaci was investigated in the lab and their emergence was reduced by 54% compared with bare soil. In the field the overall yield of onions was not affected by the straw mulch treatment; however, the presence of jumbo grade onions (>77 mm) was increased in 2006, but not in 2007. These results indicate that populations of T. tabaci adults and larvae can be significantly reduced by the use of straw mulch without compromising overall onion yield. The use of this cultural practice in an onion integrated pest management program seems promising.