Microbial control of black cutworm (Lepidoptera: Noctuidae) in turfgrass using Agrotis ipsilon multiple nucleopolyhedrovirus

Agrotis ipsilon multiple nucleopolyhedrovirus (family Baculoviridae, genus Nucleopolyhedrovirus, AgipMNPV), a naturally occurring baculovirus, was found infecting black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), on central Kentucky golf courses. Laboratory, greenhouse, and field studies investigated the potential of AgipMNPV for managing black cutworms in turfgrass. The virus was highly active against first instars (LC50 = 73 occlusion bodies [OBs] per microl with 2-microl dose; 95% confidence intervals, 55-98). First instars that ingested a high lethal dose stopped feeding and died in 3-6 d as early second instars, whereas lethally infected fourth instars continued to feed and grow for 4-9 d until death. Sublethal doses consumed by third or fifth instars had little or no effect on subsequent developmental rate or pupal weight. Horizontal transmission of AgipMNPV in turfgrass plots was shown. Sprayed suspensions of AgipMNPV (5 x 10(8) - 6 x 10(9) OBs/m2) resulted in 75 to > 93% lethal infection of third or fourth instars in field plots of fairway-height creeping bentgrass, Agrostis stolonifera (Huds.), and on a golf course putting green collar. Virus spray residues (7 x 10(9) OBs/m2) allowed to weather on mowed and irrigated creeping bentgrass field plots significantly increased lethal infection of implanted larvae for at least 4 wk. This study, the first to evaluate a virus against a pest in turfgrass, suggests that AgipMNPV has potential as a preventive bioinsecticide targeting early instar black cutworms. Establishing a virus reservoir in the thatch and soil could suppress successive generations of that key pest on golf courses and sport fields.     

Potential of Agrotis ipsilon nucleopolyhedrovirus for suppression of the black cutworm (Lepidoptera: Noctuidae) and effect of an optical brightener on virus efficacy.

Studies were performed in the laboratory, greenhouse and field to assess the potential of Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV) and a viral enhancing agent, M2R, for suppression of Agrotis ipsilon (Hufnagel). In laboratory droplet feeding bioassays, AgipMNPV was shown to be highly active against third-instar A. ipsilon. The optical brightener M2R significantly reduced LD50 estimates by approximately 160-fold, but had no direct effect on survival time estimates. In greenhouse trials, spray and bait formulations of AgipMNPV significantly reduced feeding damage to corn seedlings caused by third-instar A. ipsilon. In two sets of replicated field trials, bait formulations of AgipMNPV significantly reduced feeding damage to corn seedlings by third-instar A. ipsilon. However, there were no beneficial effects attributable to the inclusion of M2R in AgipMNPV formulations under greenhouse or field conditions. It seems likely that in an appropriately designed pest management program AgipMNPV could be used to suppress field populations of early and mid-instar A. ipsilon.     

Residual effects of imidacloprid on Japanese beetle (Coleoptera: Scarabaeidae) oviposition, egg hatch, and larval viability in turfgrass

Preventive control of turf-infesting scarabaeid grubs by neonicotinoid insecticides is presumed to mainly result from residues killing first instars in the soil. The extent to which sublethal behavioral effects or intoxication of other life stages contribute to such control is poorly known. We tested whether Japanese beetle, Popillia japonica Newman, females lay fewer eggs in turf treated with imidacloprid (Merit 75 WP) or an imidacloprid-bifenthrin combination (Allectus GC SC), and whether exposure to those residues in thatch and soil reduces their survival and subsequent ability to feed or take flight. Effects of imidacloprid residues on egg hatch and viability of successive larval instars also were studied. In two sets of choice tests, 68 and 82% fewer eggs were laid in Kentucky bluegrass with Allectus residues than in controls. When females were confined in treated turf, however, neither insecticide consistently reduced their fecundity or affected depth at which eggs were laid, although exposure to fresh Allectus residues reduced the beetles' subsequent viability. Imidacloprid residues up to 2 ppm in soil did not affect egg viability or days to hatch, but they killed neonates soon after eclosion. Imidacloprid curatively applied at label rate (0.34 kg active ingredient/ha) reduced weight gain, burrowing capability, frass production, and survival of second and third instars in turfgrass cores, with high mortality within 30 d. Intoxication and behavioral impairment of third instars also occurred in autumn field trials. Our data suggest that imidacloprid has greater activity against late instars than is generally appreciated.     

A PCR-based linkage map of Agrostis stolonifera and identification of QTL markers for dollar spot resistance

Creeping bentgrass (Agrostis stolonifera L.) is the most widely utilized cool-season turf species for intensively managed sports playing surfaces, including bowling greens and golf course putting greens, tees, and fairways. One of the biggest disease problems affecting creeping bentgrass is dollar spot disease caused by Sclerotinia homoeocarpa F.T. Bennett. Relative to traditional food crops, little attention has been paid to applying molecular technology to traditional creeping bentgrass breeding programs. The objective of this study was to develop a PCR-based linkage map of creeping bentgrass and identify quantitative trait loci (QTLs) associated with dollar spot resistance. Mapping populations segregating for dollar spot resistance were created, phenotyped for disease resistance, and genotyped for simple sequence repeat, conserved intron scanning primer, intron length polymorphism, and amplified fragment length polymorphism markers. As expected, 14 linkage groups (LGs) were detected for each parental map, covering a total of 1,424 and 1,374 cM for the 7418-3 and the L93-10 parental maps, respectively. A total of eight QTL regions (23 markers) for dollar spot resistance were observed for three isolates (Crenshaw, PRG, and UMass1) in our creeping bentgrass mapping populations. LGs 1, 4, and 5 contained at least two overlapping QTL regions to different isolates, indicating that these regions may play a significant role in dollar spot resistance. Identification of QTLs associated with disease resistance will help to facilitate marker-assisted selection in traditional creeping bentgrass breeding programs.     

Age-related decrease in 15-lipoxygenase contributes to reduced vasorelaxation in rabbit aorta

Rabbit 15-lipoxygenase-1 (15-LO-1) oxygenates arachidonic acid (AA) into 15-hydroperoxyeicosatetraenoic acid, which is then converted to the vasodilatory 15-hydroxy-11,12-epoxyeicosatrienoic acid (HEETA) and 11,12,15-trihydroxyeicosatrienoic acid (THETA). We studied the age-dependent expression of the 15-LO-1 in rabbit aorta and its effects on the synthesis of THETA, HEETA, and vasoactivity. Aortas of 1-wk-old rabbits express greater amounts of 15-LO-1 mRNA and protein compared with aortas of 4-, 8-, or 16-wk-old rabbits. The synthesis of THETA and HEETA in the rabbit aorta was also reduced with age. THETA synthesis was maximal in 1-wk-old aortas but decreased in aortas of 4- (42%), 8- (4%), and 16-wk-old (1%) rabbits. Similarly, THETA and HEETA synthesis decreased with age in mesenteric arteries from 1-, 4-, 8-, and 16-wk-old rabbits. The maximum vasorelaxation response to acetylcholine (10(-6) M) in the presence of indomethacin and nitro-l-arginine decreased in the order of 1 wk (64.5 +/- 6.9%), 4 wk (52.6 +/- 8.9%), 8 wk (53.0 +/- 9.4%), and 16 wk (33.3 +/- 6.6%). Similarly, the maximum relaxation to AA (3 x 10(-4) M) decreased with age in the order of 1 wk (60.4 +/- 8.9%), 4 wk (56.3 +/- 5.8%), 8 wk (41.8 +/- 12.3%), and 16 wk (28.9 +/- 1.6%). In contrast, the vasorelaxation to sodium nitroprusside was not significantly altered by age. These data indicate that aortic 15-LO-1 expression and activity are downregulated with aging in rabbits. This decrease is paralleled by the reduced synthesis of vasoactive THETA and HEETA and aortic relaxations to acetylcholine and AA.     

Juvenile hormone analogs greatly increase the production of a nucleopolyhedrovirus

The commercial production of baculovirus insecticides is limited by the need to produce the virus in living insects. The influence of juvenile hormone analogs (JHA) on the growth and survival of Spodoptera exigua larvae placed on treated diet in the fifth instar was examined. Weight increases observed in methoprene- and fenoxycarb-treated larvae were over three-fold greater than that of control insects, whereas other compounds resulted in lower weight gains (pyriproxyfen) or highly variable responses (hydroprene). Approximately 90% and 70% of fenoxycarb and methoprene-treated larvae, respectively, molted to a supernumerary sixth instar and attained a final weight at 8–10 days post-treatment that was approximately double the maximum weight observed in control larvae. Inoculation of fenoxycarb and methoprene-treated sixth instars with a nucleopolyhedrovirus (SeMNPV) resulted in 2.4- or 2.9-fold increases in final weights, compared to control larvae inoculated in the fifth instar. The total yield of SeMNPV occlusion bodies (OBs) per larva was 2.7- and 2.9-fold greater in fenoxycarb- and methoprene-treated larvae, respectively, compared to fifth instar controls. A significant but small increase in the yield of OBs/mg larval weight was observed in fenoxycarb-treated insects but not in the methoprene treatment. The LC₅₀ value of OBs harvested from fenoxycarb-treated insects was slightly higher than that of OBs from control insects, whereas no such difference was observed in OBs from methoprene-treated insects. We conclude that appropriate use of JHA technology is likely to provide considerable benefits for the mass production of baculoviruses.     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

Enhanced toxicity of Bacillus thuringiensis subspecies kurstaki and aizawai to black cutworm larvae (Lepidoptera: Noctuidae) with Bacillus sp. NFD2 and Pseudomonas sp. FNFD1

Bacillus thuringiensis subspecies kurstaki and aizawai are important control agents for lepidopteran pests. Bioassays were designed to test B. t. kurstaki and aizawai against second- and-fourth instar black cutworm larvae with and without Bacillus sp. NFD2 and Pseudomonas sp. FNFD1 bacteria. B. thuringiensis subsp. aizawai (XenTari) was more toxic to both second- and fourth-instar black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), larvae than B. t. kurstaki (DiPel) at 7 d after treatment (DAT). When DiPel was combined with NFD2 or FNFD1 versus second instars, the LC50s were 5.0X and 4.7X lower, respectively, than with DiPel alone. DiPel combined with both NFD2 and FNFD1 versus second instars resulted in an LC50 value 7.7X lower than with DiPel alone. When XenTari was combined with NFD2 or FNFD1 versus second instars, the LC50s were 5.2X and 3.8X lower, respectively, than with XenTari alone. XenTari combined with both NFD2 and FNFD1 versus second instars resulted in an LC50 9.7X lower than with XenTari alone. When DiPel was combined with NFD2 or FNFD1 versus fourth instars, the LC50s were 4.4X and 3.4X lower, respectively, than with DiPel alone. DiPel combined with both NFD2 and FNFD1 versus fourth instars resulted in an LC50 5.0X lower than with DiPel alone. When XenTari was combined with NFD2 or FNFD1 versus fourth instars, the LC50s were 5.7X and 3.3X lower, respectively, than with XenTari alone. XenTari combined with both NFD2 and FNFD1 versus fourth instars resulted in an LC50 6.7X lower than with XenTari alone.     

Comparative study on the susceptibility of cutworms (Lepidoptera: Noctuidae) to Agrotis segetum nucleopolyhedrovirus and Agrotis ipsilon nucleopolyhedrovirus

The common cutworm (Agrotis segetum) and the black cutworm (Agrotis ipsilon) are serious soil pests of many vegetable and field crops all over the world. We have demonstrated the cross-infectivity of two baculoviruses, A. segetum nucleopolyhedrovirus (AgseNPV) and A. ipsilon nucleopolyhedrovirus (AgipNPV) for these two insect pests. The susceptibility of A. segetum to AgipNPV was confirmed by DNA restriction endonuclease analyses of DNA isolated from virus harvested from infected A. segetum larvae. For an initial comparison of both viruses, partial polyhedrin sequences were amplified by PCR, cloned, and sequenced. Both viruses shared a very similar polyhedrin gene sequence resulting in only three amino acid substitutions. Phylogenetic analyses clearly demonstrated that both viruses belong to NPV group II and are most closely related to a clade consisting of Spodoptera exigua NPV, Spodoptera frugiperda NPV, and Spodoptera littoralis NPV. Since AgipNPV shows high virulence for both cutworm species, it appears to be a suitable candidate as a single biological control agent of A. segetum and A. ipsilon.     

Orientation Behavior and Regulatory Gene Expression Profiles in Migratory Agrotis ipsilon (Lepidoptera: Noctuidae)

Journal of Insect Behavior - Many insects such as the crop pest Agrotis ipsilon (black cutworm) migrate seasonally to exploit suitable breeding and winter habitats. The migration of a crop pest...     

Evolution of noctuid pheromone binding proteins: identification of PBP in the black cutworm moth,Agrotis ipsilon

Male black cutworm moths (Agrotis ipsilon, Lepidoptera, Noctuoidea, Noctuidae), which are attracted by a three-component pheromone blend ((Z)-7-dodecenyl acetate, Z7-12:Ac; (Z)-9-tetradecenyl acetate, Z9-14:Ac; (Z)-11-hexadecenyl acetate, Z11-16:Ac), express diverse antennal pheromone binding proteins (PBPs). Two PBP isoforms (Aips-1 and Aips-2) that show 46% identity were cloned from antennal cDNA of male A. ipsilon. The protein Aips-1 displays a high degree of identity (70-95%) with PBPs of other noctuiids, but shows only 42-65% identity with the PBPs of more phylogenetically distant species. The other protein, Aips-2, represents a distinct group of PBP that includes proteins from Sphingidae and Yponomeutidae. These differences observed suggest that each of the two PBPs may be tuned to a specific pheromone ligand.     

DEF sensitive esterases in homogenates of larval and adult Helicoverpa zea, Spodoptera frugiperda, and Agrotis ipsilon (Lepidoptera: Noctuidae)

Homogenates of Helicoverpa zea (Boddie), Agrotis ipsilon (Hufnagle), and Spodoptera frugiperda (J. E. Smith) third instars and adults contained S,S,S-tri-n-butyl phosphorotrithioate (DEF)-sensitive enzymes that hydrolyzed trans-cypermethrin and two known esterase substrates, alpha-naphthyl acetate and beta-naphthyl acetate. Except for H. zea with alpha-naphthyl acetate, larval preparations were more active than those of adults, and no marked sex differences were apparent. The hydrolysis of trans-cypermethrin in noctuid preparations were inhibited by DEF, with pI50 values ranging from 4.5 to 6.7. DEF was a potent inhibitor of the degradation of general carboxylesterase substrates alpha-naphthyl acetate and beta-naphthyl acetate in some cases. Electrophoretic studies confirmed the presence in noctuid gut homogenates of one or more DEF-sensitive esterases that hydrolyzed alpha-naphthyl acetate and beta-naphthyl acetate and that were completely inhibited by dichtorvos.     

Effect of tinopal LPW on the insecticidal properties and genetic stability of the nucleopolyhedrovirus of Spodoptera exigua (Lepidoptera: Noctuidae)

The influence of an optical brightener, Tinopal LPW, on the activity of a purified genotype of the nucleopolyhedrovirus (SeMNPV) of the beet armyworm, Spodoptera exigua (Hübner), was determined in second to fifth instar (L2-L5) S. exigua. When mixed with viral occlusion bodies (OB) 1% Tinopal LPW significantly reduced the median lethal dose (LD50) of the virus in all instars compared with insects treated with SeMNPV alone. Levels of enhancement, as determined by LD50 values, ranged from 2.6- to 580-fold, depending on the instar. The greatest enhancement occurred on the two later instars, L4 (70-fold) and L5 (580-fold), which show a much higher resistance to SeMNPV infection than earlier instars. The median time to death (MTD) values were not significantly different in any instar among larvae treated with SeMNPV + Tinopal LPW and those treated with SeMNPV alone. Larval development in SeMNPV + Tinopal LPW treated larvae was retarded, in second and fourth instars, compared with controls or larvae treated with SeMNPV alone. The OB yields from SeMNPV treated larvae were almost 1.6-fold greater in second instars (9.3 x 10(6) OBs/larvae), and 1.9-fold greater in fourth instars (1.9 x 10(8) OBs/larvae), than those obtained in larvae treated with SeMNPV + Tinopal LPW. The addition of 1% Tinopal LPW to the virus suspension did not alter the genotypic composition of viral progeny during four successive passages of the virus.     

Black cutworm (Lepidoptera: Noctuidae) larval emigration and biomass in mixtures of endophytic perennial ryegrass and Kentucky bluegrass.

Studies examined the possibility that mixtures of endophytic perennial ryegrass and Kentucky bluegrass provide resistance against larvae of the black cutworm, Agrotis ipsilon (Hufnagel). We hypothesized that resistance against A. ipsilon in such stands would stem from the influence of Kentucky bluegrass on A. ipsilon growth and behavior rather than the influence of endophytic perennial rvegrass. In replicated greenhouse experiments, black cutworm larvae initially emigrated more quickly from pots containing monocultures of endophytic perennial ryegrass than from Kentucky bluegrass monocultures or polycultures of Kentucky bluegrass and endophytic perennial ryegrass. However, biomass of emigrating larvae decreased linearly as the proportion of Kentucky bluegrass increased. Turfgrass mixtures containing endophytic perennial ryegrass and Kentucky bluegrass may provide resistance against A. ipsilon mainly through the physiological effects of Kentucky bluegrass on A. ipsilon growth and development, but possibly through the influence of endophytic perennial ryegrass on A. ipsilon movement and foraging behavior as well.     

Response of omnivorous leafroller (Lepidoptera: Tortricidae) and onion thrips (Thysanoptera: Thripidae) to low-temperature storage

Eggs and first-fifth instars of omnivorous leafroller, Platynota stultana Walshingham, had a mean percentage survival to the adult stage of 60.7-95.2% for nonexposed immatures and 14.5-54.3% for immatures exposed to 1 wk at 0-1 degree C. Exposures of 2-5 wk resulted in 0-6.7% survival, and a 6-wk exposure resulted in < 1% survival of all stages tested. A significant reduction in survival of all larval stages occurred between exposures of 0 and 1 wk and between 1 wk and 2-6 wk. Survival of eggs after exposures of 0 and 1 wk was significantly different than survival after exposures of 2-6 wk. The second instar was the stage least susceptible to low-temperature storage. Adults that were exposed to low temperature for 1 wk in the third through fifth instars laid a mean of 120-289 eggs per female, and the mean percentage viability of the eggs ranged from 56.2 to 71.4%. Mean percentage survival of adults and nymphs of onion thrips, Thrips tabaci Lindeman, was inversely related to the duration of exposure from 1 through 3-6 wk at 0-1 and 5 degrees C and was lower at 0-1 (0.2-52.5%) than at 5 degrees C (17.6-66.6%). Exposure to 0-1 degree C for 4 wk attained 91.2% control, which increased to 99.8% after 6 wk. Low-temperature storage has potential to control omnivorous leafroller in table grapes, Vitis vinifera L., and onion thrips in onions, Allium cepa L.     

Joint action of nuclear polyhedrosis virus and chemical insecticides against the black cutworm, Agrotis ipsilon (Hufn.)

A polyhedrosis virus disease was isolated from the larvae of Agrotis ipsilon. Isolation of causative agent from the infected larvae again showed to be positive. Microscopic examination of the infected larvae (by means of a light microscope) gave an evidence of the development of the polyhedral inclusion bodies (PIB) in all typical tissues where the virus is known to develop. Examination by an electron microscope showed various irregular shaped polyhedra; their diameter being about 1.5 to 3.5 mu. Most of these polyhedra were hexagonal and they measured about 2.2 mu. Experimental studies were conducted to investigate its pathogenicity alone and when combined with chemical insecticides. The joint action of the nuclear polyhedrosis virus of A. ipsilon (AINPV) combined with four chemical insecticides namely Fenvalerate, Decamethrin, Cypermethrin and Methomyl was assessed against the second instar larvae of A. ipsilon. Results showed that Decamethrin was the most toxic compound followed by Cypermethrin and Fenvalerate while Methomyl was the least toxic, the median lethal concentrations (LC50) were 0.25, 0.77, 14 and 450 ppm, respectively. The LC50 value of AINPV was 12 x 10(6) PIB/ml. Mixtures containing sublethal concentrations (LC25 and less) of both AINPV and any of the tested insecticides showed synergistic effects. On the other hand, an additive effect was observed with combinations containing doses of chemical insecticides over the range between LC25 and LC50 values.     

Transfer of ingested insecticides among cockroaches: effects of active ingredient, bait formulation, and assay procedures.

Foraging cockroaches ingest insecticide baits, translocate them, and can cause mortality in untreated cockroaches that contact the foragers or ingest their excretions. Translocation of eight ingested baits by adult male Blattella germanica (L.) was examined in relation to the type of the active ingredient, formulation, and foraging area. Ingested boric acid, chlorpyrifos, fipronil, and hydramethylnon that were excreted by adults in small dishes killed 100% of first instars within 10 d and >50% of second instars within 14 d. Residues from these ingested baits were also highly effective on nymphs in larger arenas and killed 16-100% of the adults. However, when the baits and dead cockroaches were removed from the large arenas and replaced with new cockroaches, only residues of the slow-acting hydramethylnon killed most of the nymphs and adults, whereas residues of fast acting insecticides (chlorpyrifos and fipronil) killed fewer nymphs and adults. Excretions from cockroaches that ingested abamectin baits failed to cause significant mortality in cockroaches that contacted the residues. These results suggest that hydramethylnon is highly effective in these assays because cockroaches that feed on the bait have ample time to return to their shelter and defecate insecticide-laden feces. The relatively high concentration of hydramethylnon in the bait (2.15%) and its apparent stability in the digestive tract and feces probably contribute to the efficacy of hydramethylnon. To control for differences among baits in inert ingredients and the amount of active ingredient, we compared 1% chlorpyrifos with 1% hydramethylnon in identical baits. Again, hydramethylnon residues provided greater secondary kill, but the results highlighted the importance of the inert ingredients. We conclude that, in the absence of cannibalism and necrophagy, translocation of baits and secondary kill are most effective with slow acting insecticides in palatable baits that can traverse the digestive tract and be deposited within and around the cockroach aggregation.     

Effects of Cytokinin and Nitrogen on Drought Tolerance of Creeping Bentgrass

Cytokinin (CK) is a vital plant hormone that controls many aspects of growth and development in plants. Nitrogen (N) is the indispensable macronutrient needed in plants and also one of the most important limiting factors for plant growth. This study was designed to investigate the simultaneous effects of CK and N on the visual turf quality and antioxidant metabolism of drought-stressed creeping bentgrass (Agrostis stolonifera L.). ‘PennA-4’ creeping bentgrass treated with trans-zeatin riboside at three rates of CK concentrations of 0, 10 and 100 μM (designated by CK0, 10, and 100) and two nitrogen rates with 2.5 and 7.5 kg N·ha^-1 every 15 days (designated by low and high N) in a complete factorial arrangement was grown under two soil moisture regimes: well-watered and drought stress. Exogenous CK improved turf quality and delayed leaf wilting under drought stress, especially under high N. The grasses treated with CK10 and CK100 had lower O₂^- production and H₂O₂ concentration than those without CK treatment. The CK100 treatment enhanced the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and guaiacol peroxidase (POD) by 25%, 22%, 17% and 24%, respectively, relative to CK0. Moreover, the activity changes of the antioxidant enzyme isoforms were more significant under high N condition relative to low N condition. Our results demonstrated the beneficial impacts of CK and N on physiological reactions, especially antioxidant metabolism, and foliar application of CK at 10 or 100 μM plus 7.5 kg ha^-1 N biweekly may improve drought stress resistance of creeping bentgrass.     

Virulence of a nucleopolyhedrovirus to Neodiprion abietis (Hymenoptera: Diprionidae)

Different larval stages of balsam fir sawfly, Neodiprion abietis (Harris) (Hymenoptera: Diprionidae), were challenged by different concentrations of a nucleopolyhedrovirus in the laboratory to determine larval susceptibility to the virus and to test treatment effects of the virus on the sawfly survivors. The results indicated that younger larvae were more susceptible to the virus than older instars. The speed of larval death depended on the larval age and the virus concentration. Generally, the virus killed second or third instars in approximately 5 d and fourth or fifth instars in 10-12 d at concentrations of 10(7) polyhedral inclusion bodies (PIB) /ml. The virus had profound treatment effects on sawfly survivors. Feeding activity of the survivors was reduced by > 40% compared with that of the control group, pupal weight by approximately 25%, and adult emergence by > 30%. There was also a higher percentage of male adults in the virus-treated groups than in the control.     

Echocardiographic assessment of cardiac function in diabetic db/db and transgenic db/db-hGLUT4 mice

Control db/+ and diabetic db/db mice at 6 and 12 wk of age were subjected to echocardiography to determine whether contractile function was reduced in vivo and restored in transgenic db/db-human glucose transporter 4 (hGLUT4) mice (12 wk old) in which cardiac metabolism has been normalized. Systolic function was unchanged in 6-wk-old db/db mice, but fractional shortening and velocity of circumferential fiber shortening were reduced in 12-wk-old db/db mice (43.8 +/- 2.1% and 8.3 +/- 0.5 circs/s, respectively) relative to db/+ control mice (59.5 +/- 2.3% and 11.8 +/- 0.4 circs/s, respectively). Doppler flow measurements were unchanged in 6-wk-old db/db mice. The ratio of E and A transmitral flows was reduced from 3.56 +/- 0.29 in db/+ mice to 2.40 +/- 0.20 in 12-wk-old db/db mice, indicating diastolic dysfunction. Thus a diabetic cardiomyopathy with systolic and diastolic dysfunction was evident in 12-wk-old diabetic db/db mice. Cardiac function was normalized in transgenic db/db-hGLUT4 mice, indicating that altered cardiac metabolism can produce contractile dysfunction in diabetic db/db hearts.