OKLAHOMA STATE UNIVERSITY
Plant Pathology Department, 110 Noble Research Center, Stillwater,
OK 74078-9947, USA.
R.M. Hunger and J.L. Sherwood (Plant Pathology Department),
and M.E. Payton (Department of Statistics).
Barley yellow dwarf virus.
BYDV occurs in Oklahoma every year and has been a
serious problem during each of the past several years. During
1995-96,
Gaucho 480F (Gustafson, Inc., Dallas, TX) seed treatment was evaluated
for control of aphids and BYDV near Stillwater, OK. Plots consisted
of three, 3-ft rows of each HRWW cultivar planted 0.50 to
0.75 in. deep on 6 October, 1995. The experiment was performed
as a split-plot in a randomized complete block design with
six replications. Insecticide seed treatment (Gaucho 480F @ 3
oz/cwt) was the main-plot treatment, and cultivar was the
subplot treatment. Aphid populations were determined three times
during the growing season by counting the number of aphids in
1 ft of row randomly designated in each plot. BYDV incidence
(the percentage of flag leaves exhibiting BYDV symptoms) was assessed
on 15 May, 1996. Presence of BYDV in foliage was confirmed by
ELISA. Aphid counts were transformed with the square root transformation
due to the count nature of the variable, and multiple comparisons
(LSD a =
0.05) were made on the simple effects of insecticide and cultivar
because of the presence of interaction between cultivar and insecticide
treatment. BYDV incidence was transformed using the arcsinesquare
root transformation due to the percentage nature of the variable.
No variety by insecticide interactions were detected for the
variables BYDV incidence, height, 1,000-kernel weight or yield,
so main effects of these factors were examined.
The 1995-96
season was conducive to aphids, and populations in fields surrounding
the trial were extremely high. Aphid populations 70 days after
planting (15 December, 1995) were significantly lower on plants
from seed treated with Gaucho 480F. By 158 days after planting
(12 March, 1996) and 168 days after planting (22 March, 1996),
aphid populations remained significantly greater on plants from
seed not treated with Gaucho. There was no difference between
aphid incidence on the varieties when not treated with Gaucho
(controls) except for Karl, which had significantly more aphids
on all three dates. Cultivars treated with Gaucho had a lower
BYDV incidence, were significantly taller, and yielded significantly
more than untreated controls. There was no significant difference
in 1,000-kernel weight between treated and control plots. The
cultivars 2137, 2163, and Custer exhibited similar BYDV incidence,
with 2137 having the greatest yield and Custer having the highest
1,000-kernel weight. This trial demonstrated that Gaucho 480F
used as a seed treatment at 3 oz/cwt significantly reduced aphid
populations and BYDV incidence on wheat. The cost of this treatment
is approximately $20.00/bu of seed. In years when aphid pressure
and subsequent BYDV incidence are low, use of Gaucho at the 3
oz rate probably would not provide a positive economic return
on the investment.
Table 1. Effect of Gaucho 480F insecticide treatments on winter wheat and its effect on the control of aphid populations and the incidence of barley yellow dwarf virus.
_____________________________________________________________________________________________
Aphids (no/ft of row)
_________________________________________________________________________________
15 December, 1995. 12 March, 1996. 22 March, 1996.
_________________________ _________________________ ________________________
Gaucho Gaucho Gaucho
Cultivar Control 3 oz/cwt Control 3 oz/cwt Control 3 oz/cwt
_____________________________________________________________________________________________
2137 43.2 a1 ***2 0.0 a 117.7 a *** 58.2 a 216.2 a *** 115.2 a
2163 44.3 a *** 0.0 a 125.5 a *** 64.2 ab 222.2 a *** 115.3 a
Custer 46.5 a *** 0.0 a 125.7 a *** 81.3 c 230.5 a *** 144.5 b
Jagger 46.3 a *** 0.0 a 123.8 a *** 71.8 bc 212.0 a *** 129.5 ab
Karl 71.3 b *** 0.3 a 162.5 b *** 72.2 bc 276.7 b *** 122.8 ab
_____________________________________________________________________________________________
Plant 1,000-kernel
BYDV incidence height (cm) Yield (bu/acre) weight (gm)
_____________________________________________________________________________________________
Gaucho 3 oz/cwt 23.1 a1 66.4 a 77.0 a 25.2 a
Control 50.8 b 59.1 b 64.4 b 24.8 a
Cultivar
-------------------------------------------------------------------------------------------------------------------------------------------
2137 27.5 a1 64.9 ab 81.7 a 25.2 b
2163 34.3 a 62.5 bc 70.0 b 22.6 c
Custer 29.7 a 59.8 c 71.0 b 28.3 a
Jagger 42.9 b 65.7 a 66.9 b 23.2 c
Karl 50.4 b 60.8 c 63.6 b 25.6 b
_____________________________________________________________________________________________
1 Means followed by the same letter within a column are not significantly different (LSD, a = 0.05).
2 *** indicates significant
difference between aphid counts within dates (LSD, a = 0.05).
The incidence of all foliar wheat diseases including
wheat leaf rust was nearly zero, because of extremely dry conditions
for most of the spring in Oklahoma during 1995-96.
No leaf rust ratings of breeder lines or cultivars were made
in the field in 1996, because of the low incidence of leaf rust.
Seedling reaction to wheat leaf rust of entries in regional breeder
nurseries (1996 Southern Regional Performance Nursery, 1996 Northern
Regional Performance Nursery, and 1996 Regional Germplasm Observation
Nursery) were conducted and are available in the annual USDA publication
that summarizes testing of regional nurseries (Dr. Jim Peterson,
USDA-ARS,
Lincoln, NE) or by contacting R.M. Hunger (e-mail: rmh@okway.okstate.edu)
at Oklahoma State University.
Table 2. Visual assessment (VA), ELISA values, yield, and 1,000-kernel weight of entries from the
1996 Southern and Northern Regional Performance Nurseries evaluated for reaction to wheat soilborne
mosaic virus.
_____________________________________________________________________________________
VA 1 Yield 1,000-kernel
Entry and selection number 1-4 ELISA +/- sd 2 (gm) weight (gm) 3
_____________________________________________________________________________________
1996 Southern Regional Performance Nursery.
01 CI1442 ('Kharkof') 3.2 1.10 +/- 0.21 1.8 13.0*
02 CI13996 ('Scout 66') 3.5 1.11 +/- 0.22 5.1 13.7
03 PI495594 ('TAM-107') 3.3 1.09 +/- 0.18 10.2 18.3
04 KS93U206 1.8 1.17 +/- 0.12 24.8 21.0
05 OK91P648 1.0 0.72 +/- 0.62 44.4 21.7
06 OK93P735 1.0 1.07 +/- 0.13 36.2 20.0
07 OK93P634 1.6 1.08 +/- 0.09 28.3 23.7
08 OK92403 1.0 0.03 +/- 0.04 36.9 16.7
09 TX91D6913 1.0 0.01 +/- 0.03 67.8 24.3
10 TX91D6991 1.0 0.03 +/- 0.01 84.1 25.3
11 TX92V3108 3.7 1.02 +/- 0.20 19.1 19.3
12 HBI0531-A2 3.8 1.05 +/- 0.23 14.9 19.7
13 TX93V5919 1.0 0.47 +/- 0.57 30.1 19.0
14 TX93V5922 4.0 1.02 +/- 0.21 2.3 14.7
15 TX93V4927 4.0 1.02 +/- 0.27 1.7 11.3
16 TX92V2519 1.6 0.46 +/- 0.61 13.5 19.0
17 TXGH12588-105 3.7 1.10 +/- 0.16 17.3 21.3
18 CO910424 1.0 0.05 +/- 0.02 39.3 24.3
19 CO910748 4.0 1.02 +/- 0.23 2.6 12.5*
20 KS91H153-2 3.3 1.03 +/- 0.22 12.8 20.3
21 KS941064-3 1.0 0.79 +/- 0.50 50.2 21.7
22 KS941064-6 1.0 1.10 +/- 0.18 52.7 22.3
23 KS940935-7-2-1 1.0 0.05 +/- 0.04 69.0 23.7
24 KS940935-125-5-2 1.0 0.46 +/- 0.28 57.1 23.0
25 KS85W663-11-6-MB 1.0 1.10 +/- 0.15 41.0 22.0
26 KS84W963-9-39-3-MBX 1.0 0.06 +/- 0.06 46.1 17.7
27 NE90476 3.8 1.08 +/- 0.20 10.4 18.3
28 NE92458 1.2 0.76 +/- 0.63 40.9 21.7
29 NE92646 1.3 0.67 +/- 0.50 39.6 21.0
30 NE93405 3.2 0.98 +/- 0.03 13.8 23.0
31 NE93427 1.0 0.56 +/- 0.46 35.2 20.3
32 WX92-0408 1.0 0.37 +/- 0.50 21.2 17.7
33 W93-460 1.0 1.03 +/- 0.09 40.2 23.3
34 T702 1.0 0.76 +/- 0.58 46.8 21.3
35 T834 1.0 1.07 +/- 0.02 49.5 24.0
36 T812 3.0 1.04 +/- 0.04 22.3 19.3
37 T861 2.8 0.96 +/- 0.09 22.2 21.7
38 T89 2.0 1.02 +/- 0.08 33.3 22.3
39 G1878 1.0 0.05 +/- 0.05 46.4 20.0
LSD (P = 0.05) 19.1 4.1
_____________________________________________________________________________________
Table 2 (continued). Visual assessment (VA), ELISA values, yield, and 1,000-kernel weight of entries
from the 1996 Southern and Northern Regional Performance Nurseries evaluated for reaction to wheat
soilborne mosaic virus.
_____________________________________________________________________________________
VA 1 Yield 1,000-kernel
Entry and selection number 1-4 ELISA +/- sd 2 (gm) weight (gm) 3
_____________________________________________________________________________________
1996 Northern Regional Performance Nursery.
01 CI1442 ('Kharkof') 3.8 1.06 +/- 0.09 0.9 14.0*
02 CI17439 ('Roughrider') 3.0 1.06 +/- 0.05 0.7 15.0*
03 PI511307 ('Abilene') 1.3 0.54 +/- 0.65 23.7 19.7
04 SD89153 3.0 1.06 +/- 0.08 8.5 11.7
05 SD91192 3.2 1.18 +/- 0.08 4.9 14.7
06 SD92107 2.5 1.16 +/- 0.08 11.0 15.7
07 SD92124 1.2 0.50 +/- 0.61 40.7 20.3
08 SD92174 1.0 0.40 +/- 0.48 19.0 13.0
09 SD92191 3.2 1.11 +/- 0.09 3.1 16.0*
10 SD92227 3.3 1.06 +/- 0.09 7.4 18.0*
11 SD92266 3.7 1.09 +/- 0.11 9.9 14.3
12 ND9257 3.0 1.03 +/- 0.06 11.4 15.7
13 ND9272 4.0 1.10 +/- 0.06 0.8 -.*
14 ND9274 4.0 1.08 +/- 0.10 0.9 12.0*
15 NE92628 2.3 1.10 +/- 0.05 18.4 22.7
16 NE92662 1.0 0.07 +/- 0.09 24.1 21.3
17 NE92652 1.0 0.52 +/- 0.71 34.5 23.7
18 NE93554 3.3 1.31 +/- 0.42 8.4 23.7
19 NE93613 3.7 1.15 +/- 0.07 7.0 13.3
20 XNH1798 3.0 1.21 +/- 0.03 6.7 8.3*
21 XNH1800 3.2 1.17 +/- 0.02 2.5 15.7
22 MT88046 3.3 1.19 +/- 0.03 5.8 15.0
23 MTS92042 3.8 1.00 +/- 0.10 1.5 16.5*
24 ID0467 3.3 1.21 +/- 0.01 4.3 13.0*
25 ID0483 4.0 1.13 +/- 0.08 1.7 15.0*
26 AMP3JP4A7A 1.0 0.41 +/- 0.65 28.9 17.7
27 AMQ3KC4C7B 1.0 0.79 +/- 0.67 9.3 13.3
28 AMQ3NQ4A7D 3.2 1.16 +/- 0.06 4.3 14.5*
29 AMQ3KF4B7A 3.3 1.15 +/-
0.07 0.2 -.*
LSD (P = 0.05) 10.3 3.9
_____________________________________________________________________________________
1 VA = visual assessment index.
2 ELISA +/- sd = absorbance value from the enzyme-linked immunosorbent assay +/- standard deviation.
3 1,000-kernel weights followed by an asterisk (*) are the average of < 3 reps. The LSD should not be
used to compare these values.
The reaction to WSBMV was determined in the field
for wheat entries in the 1996 Southern Regional Performance Nursery
(SRPN) and the 1996 Northern Regional Performance Nursery (NRPN)
(Table 2, p. 330-331). The trial was conducted near Stillwater,
OK. The experimental design for each nursery was a randomized
complete block with three replications. Plots consisted of three,
2-ft rows per entry. Seed was planted about 0.75 in. deep
at a rate of 24 seeds/2-ft row on 9 October, 1996. Rows
of the wheat cultivars Vona (WSBMV-susceptible, wheat spindle
streak mosaic (WSSMV)-susceptible), Sierra (WSBMV-resistant,
WSSMV-susceptible), and Hawk (WSBMV-resistant, WSSMV-resistant)
were planted between reps to monitor the presence and distribution
of WSBMV and WSSMV. Entries were assessed for stunting and mosaic
symptoms on 5 March and 2 April, 1996, using a visual assessment
(VA) index of 1-4,
where 1 = no stunting, no mosaic, 2 = slight stunting and/or slight
mosaic, 3 = moderate stunting and/or slight mosaic, and 4 = severe
stunting and/or severe mosaic. Young foliage was collected from
each row of each entry on 5 March, for evaluation by the ELISA
(Hunger et al. 1991, Crop Sci 31:900-905), and the
trial was harvested on 7 June (SRPN) and the 11 June (NRPN).
No foliar diseases occurred, but symptoms indicative
of root rot were scattered throughout the trial. Wheat spindle
streak mosaic virus was detected by ELISA (absorbance values >
0.80) in seven of 16 Vona and Sierra samples and may have contributed
to stunting and mosaic symptoms. WSBMV was uniformly distributed
throughout the trial area. Vona plants (n = 28) randomly selected
from the trial had VA indices of 3 or 4 and values from ELISA
for WSBMV from 0.73 to 1.47 (mean = 1.22). Sierra and Hawk plants
(n = 15) randomly assessed from the trial had VA indices of 1
or 2, and values from ELISA for WSBMV from 0.01 to 0.18 (mean
= 0.04) with two exceptions (0.97 and 1.13). Based on VA, 24
SRPN entries and seven NRPN entries were resistant to WSBMV (VA
< 2.0). Most of these entries had ELISA values indicative
of no detectable virus or virus concentrations less than those
of the susceptible check cultivar Vona. Higher yield and greater
1,000-kernel weight also were associated with the resistant entries.
Upon completing the serological analysis of several
isolates of WSMV (Montana et al. 1996), the coat protein region
of many of these isolates has been cloned and sequenced, and the
sequence analysis is being completed. In addition, the coat protein
open reading frame is being placed in a vector for transformation
of wheat in cooperation with Dr. Arron Guenzi, Department of Agronomy,
Oklahoma State University.
Breeding for disease resistance.
Backcrossing of germplasm lines to adapted HRWW cultivars
was continued. These germplasm lines were obtained from crossing
emmers (T. dicoccoides) resistant to leaf rust, WSBMV,
and/or powdery mildew with adapted HRWW cultivars. Other germplasm
lines obtained from crossing Eastern European cultivars with HRWW
cultivars were evaluated in the field. However, the low incidence
of leaf rust in the field in 1996 resulted in evaluations of limited
value. These lines are being evaluated again in the field during
1996-97.
Personnel.
After serving for nearly 11 years as the Department Head of Plant Pathology, Dr. Larry J. Littlefield has stepped down to a faculty position. Larry will be expanding his research on documenting the life cycle of Polymyxa graminis, and initiate other research involving electron microscopy. Dr. John L. Sherwood currently is serving as the interim head.
Publications.
Chenault K, Hunger R, and Sherwood J. 1996. Comparison
of the nucleotide sequence of the coat protein open reading frame
of nine isolates of wheat streak mosaic rymovirus. Virus Genes
13:187-188.
Evans CK, Hunger RM, and Siegerist WC. 1996. Inoculum
density and infection efficiency of conidia and conidiophores
of isolates of Pyrenophora tritici-repentis. Plant
Dis 80:505-512.
Hunger RM, Siegerist WC, Smith EL, Morgan G, and
Payton ME. 1996. Reaction of the Southern Regional Performance
Nursery (SRPN) to wheat leaf rust, 1995. Biol Cul Tests for Control
of Plant Dis 11:86.
Montana JR, Hunger RM, and Sherwood JL. 1996. Serological
characterization of wheat streak mosaic virus isolates. Plant
Dis 80:1239-1244.
PLANT SCIENCE RESEARCH LABORATORY, USDA-ARS
1301 N. Western St., Stillwater, OK 74075, USA.
C.A. Baker, J.D. Burd, N.C. Elliott, M.H. Greenstone,
D.B. Hays, S.D. Kindler, D.W. Mornhinweg, D.R. Porter, K.A. Shufran,
and J.A. Webster.
Host plant resistance/germplasm enhancement.
Topcrossing of RWA-resistant wheat lines to
high-performance recurrent parents continued. Efforts are ongoing
to develop RWA-resistant wheat lines for all market classes
that are grown in areas where RWA is a problem. Over 55 advanced
lines derived from eight different RWA resistance sources were
planted for seed increase and evaluation in preparation for germplasm
release; these lines include hard red and hard white winter, hard
and soft white spring, and hard red spring wheats. Over 400 winter
wheat lines derived from crosses with seven different sources
of RWA resistance were evaluated in the field in Stillwater.
Approximately one quarter of these lines performed well enough
in this stressful environment to warrant further field evaluations.
These field-selected lines plus additional greenhouse selections
made up the approximately 500 lines being planted in the field
in Stillwater this fall. Genetic diversity studies continued.
Results of genetic studies of topcross populations helped explain
most of the conflicting reports in the literature concerning inheritance
of RWA resistance. The 1997 Regional Germplasm Observation Nursery
was tested for greenbug and RWA resistance. Resistance mechanisms
were characterized for greenbug multibiotype-resistant GRS-1201.
Bioassay experiments were developed to identify bird cherry-oat
aphid resistance in seedling wheat and barley.
Modeling. Progress towards development of a computer model for simulation of the landscape and regional population dynamics of the RWA during 1996 included: 1) landcover classification and ground-truthing of Landsat MSS imagery covering eastern Colorado, the Oklahoma Panhandle, the Texas Panhandle, and western Kansas; 2) field studies of RWA population dynamics in Canada wild rye were conducted in southeastern Colorado; 3) acquisition and processing of USGS digital elevation data, NRCS Statsgo soils data, and USGS digital line graphs for the entire region of the Great Plains in which RWA populations typically occur; and 4) acquisition and processing of long-term NOAA meteorological data for over 500 sites distributed throughout the above-mentioned portion of the Great Plains.
The influences of prey abundance, within-field
vegetation, and composition and diversity of the surrounding landscape
matrix on communities of aphidophagous insects were studied in
wheat fields. Within field variables such as aphid abundance
and crop density were important for explaining variation in the
abundance of adult Coccinellidae in wheat fields. The density
of herbaceous and grassy weeds in fields did not influence the
abundance of any aphidophagous species. The proportion of cultivated
land and diversity of the landscape mosaic in the section (1.5
km2) surrounding the sampled field influenced the abundance
of some aphidophagous species, as did the proportion of cultivated
land in the eight sections immediately adjacent to the section
that included the sampled field. The influence of the mosaic
extended beyond the eight surrounding sections and was detectable
at a scale greater than 100 km2.
Evaluation of aphid natural enemy effectiveness.
Initial production of monoclonal antibodies for serological gut
analysis of aphid predators revealed a major cross-reacting
protein in several cereal aphid species. New fusions are planned
using greenbug and RWA homogenates from which the cross-reacting
protein has been removed by precipitation. A postdoctoral fellow
is being recruited to support the development of DNA hybridization
probes to detect endoparasitoids within aphid hosts. A colony
of Aphelinus albipodus was established to provide DNA for
this effort, and colonies of A. asychis and A. varipes
are being established.
A replicated study of spider species diversity and
abundance in relation to cereal aphids was begun in autumn 1996,
in Lamar, CO. Each replicate comprises two 1-ha wheat plots,
the first planted to TAM 107 and the second to HALT. Aphids were
counted by collecting tillers and multiplying the number per tiller
by the number of tillers per square meter. Spider densities were
obtained by sampling within one-half square meter sampling
frames by D-vac for foliage-inhabiting spiders, followed
immediately by hand search for those on the soil surface. Very
small numbers of spiders were collected throughout the autumn,
exclusively on the soil surface at first, but appearing later
also on the foliage. The families Lycosidae and Gnaphosidae predominated.
Aphids included the corn leaf aphid and bird cherry-oat
aphid.
Multitrophic interactions.
Modified cultural practices and control of volunteer wheat and
barley can be important in minimizing Russian wheat aphid infestations.
However, chemical control is the primary method used. The effect
of low concentrations of the newly developed systemic aphicides
CGA 215944 and Gaucho[theta]
(imidacloprid) on the feeding behavior of the RWA on wheat was
evaluated using electronic feeding monitors. Aphids began surviving
15 days after treatment with CGA 215944 (soil drench, 10 g ai/l)
and 45 days after planting on plants grown from seed treated with
Gaucho (1 fluid oz/cwt). Following these periods of acute toxicity,
CGA 215944 exhibited antifeedant effects on D. noxia that
were expressed by changes in the frequency and duration of different
feeding behaviors. Aphids on plants treated with CGA 215944 spent
significantly more time in nonprobing activities and had a much
higher frequency of leaf penetration, followed by significantly
shorter periods of phloem ingestion. Immediately after the period
of acute aphid toxicity, there were no substantial carryover effects
from CGA 215944 or Gaucho on the tritrophic relationship between
host plant, D. noxia, and Diaeretiella rapae McIntosh.
RWA genetics. Eleven
RWA clones, collected from five states (Colorado, Kansas, Nebraska,
Wyoming, and Washington) from 1994-95,
were evaluated for biotypic variation on four wheat (Pavon, PI
372129, STARS-9302W, and STARS-9501W) and two barley
(Wintermalt and STARS-9301B) germplasm entries. Although
statistical differences were detected in measurements of chlorosis,
leaf rolling, leaf number, tiller number, plant height, shoot
weight, root weight, aphid numbers, and aphid weight among some
clones, no clear differences in virulence properties were apparent.
Host responses to RWA infestation among the 11 clones were similar.
In addition, RAPD profiles of these 11 clones (plus several others
from Colorado, Kansas, and Oklahoma) revealed no variation. We
also assayed these clones for variation in the 18S region of the
rRNA cistron, but found none. All the clones tested were genotypically
and phenotypically equivalent. Ten years after its introduction
to the U.S. and before the commercial release of resistant cultivars,
the RWA has not exhibited any biotypic variation. Because of
the threat of other introductions, RWA should be periodically
monitored for biotypic variation, before and after the deployment
of resistant cultivars.
Evaluation of alternate hosts and determination
of economic injury levels. Greenbugs
collected over 35 counties in Oklahoma from 1995-96
wheat crops were identified to biotype and also to susceptibility
to phosphate insecticides. Biotype K, a recently identified greenbug
biotype that will kill biotype I-resistant grain sorghum germplasm,
was identified in greenbug collections from 12 Oklahoma counties.
This is important information, because commercial grain sorghum
companies are currently developing biotype I-resistant grain
sorghum varieties. Several of the greenbug collections were resistant
to phosphate insecticides. In cooperation with Kansas State University
scientists, work will continue to determine the distribution of
biotype K in the Midwest and to monitor the greenbug population
for insecticide resistance.
We completed a one-season test on the economic threshold
of greenbugs on winter wheat. Current thresholds are outdated,
because none relate aphid numbers/tiller to yield loss, control
costs, and monetary value of the wheat. Our studies utilized
control cost, monetary value of the crops, and number of aphids/tiller.
We will continue to evaluate the economic injury level of greenbugs
and other cereal aphids.
Different species of wheatgrasses continue to be
evaluated for resistance to the RWA. The mechanisms of the resistance
identified in the wheatgrass species also are being identified.
We recently evaluated all available crested wheatgrass entries
and results have been submitted to the Journal of Economic Entomology.
Western wheatgrass entries are currently being tested for resistance
to the RWA.
The known greenbug biotypes, B, C, E, F, G, H, I,
and K, are being evaluated against several species of grasses
to determine if different levels of susceptibility occur among
the grass species. Canada bluegrass is susceptible to biotype
F, although resistant to biotypes B, C, and E. No information
exists on the newer biotypes and their interaction with forage
grasses.
Personnel.
Dr. Dirk B. Hays has recently joined us as postdoctoral
research associate, and will be working on the biochemistry and
physiology of aphid resistance in plants.
Publications.
Baker CA, Porter DR, and Webster JA. 1996. Inheritance
and mechanisms of Russian wheat aphid (Homoptera: Aphididae) resistance
in PI 225217. Proc 20th Hard Red Winter Wheat Work Conf p. 106.
Baker CA, Porter DR, and Webster JA. 1996. Identification
of genetic diversity for Russian wheat aphid resistance in wheat.
Agron Abstr p. 93.
Burd JD and Elliott NC. 1996. Changes in chlorophyll
a fluorescence induction kinetics in cereals infested with Russian
wheat aphid (Homoptera: Aphididae). J Econ Entomol 89:1332-1337.
Burd JD and Elliott NC. 1995. The effect of Russian
wheat aphid feeding chlorophyll a fluorescence induction kinetics
of resistant and susceptible cereals. Eur J Plant Pathol, Proc
13th Inter Plant Prot Cong, The Hague, Abstracts. Abstr 1005.
Burd JD, Elliott NC, and Reed DK. 1996. Effects of the aphicides 'Gaucho' and CGA-215944 on feeding behavior and tritrophic interactions of Russian wheat aphids. Southwest Entomol 21:145-152.
Burd JD, Webster JA, Puterka GJ, Hoxie RP, and Wellso
SG. 1996. Effect of Russian wheat aphid on constituent nonstructural
carbohydrate content in wheat seedlings. Southwest Entomol 21:167-172.
Elliott NC and Michels Jr, GJ. 1997. Estimating
aphidophagous coccinellid populations in alfalfa. Biological
Control 8:43-51.
Elliott NC, Burd JD, Butts RA, Lee JH, Shufran KA,
Hein GL, Armstrong JS, Holtzer TO, Peairs FB, and Webster JA.
1997. Biology, ecology, and Management of the Russian wheat
aphid. In: Ecologically-Based IPM in Dryland Cropping
Systems, Proceedings of a Workshop (Holtzer TO and Peairs FB comp).
Colorado State University, Fort Collins. (In Press).
Elliott NC, Kieckhefer RW, and Obrycki JJ. 1996.
The influence of within patch and landscape factors on aphidophagous
insect communities in wheat. Program and Abstracts 11th Ann U.S.
Landscape Ecol Symp. p. 42.
French BW and Elliott NC. 1996. Permeability of
grassland-wheat field borders to ground beetles (Carabidae).
Program and Abstracts 11th Ann U.S. Landscape Ecol Symp. p.
49.
Gatschet MJ, Taliaferro CM, Porter DR, Anderson MP,
Anderson JA, and Jackson KW. 1996. A cold-regulated protein
from bermudagrass crowns is a chitinase. Crop Sci 36:712-718.
Greenstone MH. 1996. Serological analysis of arthropod
predation: past, present and future. In: The ecology
of agricultural pests-biochemical
approaches (Symondson WOC and Liddell E eds). Chapman
and Hall, London. Pp. 265-300.
Kindler SD and Hammon RW. 1996. Comparison of host
suitability of western wheat aphid with the Russian wheat aphid.
J Econ Entomol 89(6):1621-1630.
Michels GJ, Jr, Elliott NC, Romero RL, and Johnson
TD. 1996. Sampling aphidophagous Coccinellidae in grain sorghum.
Southwest Entomol 21:237-246.
Miller HL and Porter DR. 1996. A technique to quantitatively
measure the leaf streaking symptom of Russian wheat aphid infestation.
Crop Sci 37:278-280.
Mornhinweg DW, Porter DR, and Webster JA. 1996.
Effect of constant Russian wheat aphid (RWA) infestation on yield
and yield components of RWA-resistant and -susceptible
barleys. Agron Abstr p. 93.
Porter DR, Burd JD, Shufran KA, and Webster JA.
1996. Effect of wheat and sorghum resistance genes on the development
of new greenbug biotypes. Agron Abstr p. 79.
Webster JA, Porter DR, Burd JD, and Mornhinweg DW.
1996. Effect of growth stage of resistant and susceptible barley
on the Russian wheat aphid, Diuraphis noxia. J Agric Entomol
13(4):283-291.
Wratten SD, Elliott NC, and Farrell J. 1995. In:
Integrated pest management in Wheat (Dent D ed). Chapman &
Hall, London. pp. 241-279.
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