The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), and its associated pathogen "Candidatus Liberibacter solanacearum" (Ca. L. solanacearum), the putative causal agent of zebra chip (ZC) disease in potatoes (Solanum tuberosum L.), were sampled in commercial potato fields and untreated control plots for 3 yr in multiple locations in Texas, Kansas, Nebraska, and Colorado. Populations of the potato psyllid varied across years and across potato growing regions. However, the percentage of potato psyllids infected with Ca. L. solanacearum although variable across years, was consistently highest in the Lower Rio Grande Valley of Texas (LRGV), the reported overwintering location for this pest. The numbers of Ca. L. solanacearum-infected psyllids collected on field traps and large nymphs counted on leaf samples were both positively correlated with the final percentage of ZC in tubers. In the LRGV, where vector and disease pressure is the highest, population levels of immature life stages of the psyllid and percentage of ZC differed greatly between commercial and untreated fields. These results show that the pest management program that was used can be effective at controlling development of the psyllid and ultimately reducing the incidence of ZC.

The Dectes stem borer, Dectes texanus LeConte (Coleoptera: Cerambycidae), is an increasingly important pest of soybean and sunflower in central North America. Nine large-scale field trials were conducted over a 3-year period to determine if Dectes stem borer could be managed with insecticide treatments. Aerial applications of lambda on July 6, 12 and 15 were successful in significantly reducing adults, but applications on July 1, 20 and 24 were less successful. These data suggest that for central Kansas two aerial applications may be required to control Dectes stem borers in soybean. Based on our experience the first application should be made at the peak of adult flight about July 5(th) and the second application 10 days later. The local treatment schedule should be developed to follow the local Dectes stem borer adult emergence pattern. Treated aerial strips 59 m (195 ft) wide were not large enough to prevent reinfestation, but treated half-circles (24 ha or 60 acres) were successful in reducing in Dectes stem borer infestation of soybean. Sweep net samples of adults were not successful in identifying a treatment threshold, so treatment decisions will need to be based on field history of infestation. Further studies are needed to identify better sampling methods that can be used to establish treatment thresholds and to refine the best timing for treatments.

Each Field Day report consists of individual research reports on topics specific to the region, including cultural methods for most of the major crops grown in Kansas, mitigating the effects of weeds, insects, and disease associated with those crops, and irrigation. Research is conducted and reports written by staff of the K-State Research and Extension Southwest Research Extension Center.

The western corn rootworm (Diabrotica virgifera virgifera LeConte) is one of the most important insect pests of corn in North America. This insect costs farmers $1 billion or more annually in reduced yields and insecticide treatment costs (Metcalf 1986). Corn rootworm larvae damage the corn root system by feeding underground. The root feeding can cause physiological yield losses and make the plants susceptible to lodging and stalk rot fungi (Palmer and Kommedahl 1969). Corn rootworm beetles also cause damage by feeding on silks, which affects pollination and seed set. Corn rootworms traditionally have been managed on a field-by-field basis using crop rotation or insecticide applications. Crop rotation works because corn rootworm beetles tend to lay their eggs in corn fields. of treated areas. They also are seeking to use timely applications of environmentally friendly insecticides to replace standard foliar insecticide treatments. The USDA and cooperating university researchers have evaluated areawide management for controlling western corn rootworm beetles in several large, 41 km2 regions (16 mi2) (Faust and Chandler 1998, Wilde et al. 1998, Chandler 2003). The objective of these projects was to reduce the frequency and number of insecticide applications needed to achieve commercially acceptable suppression of western corn rootworm. The areawide management strategy requires information on corn rootworm populations within the managed area. One method of estimating corn rootworm beetle populations is for scouts to count beetles on corn plants at numerous locations in the The eggs overwinter and hatch in the spring when corn plants are growing rapidly. Crop rotation reduces the likelihood that corn will be planted in soil where large numbers of western corn rootworm eggs have been laid. In some areas, however, the economic advantage of corn production is so large that growers plant corn year after year in the same fields (known as continuous corn). In this case, growers use soil insecticides to protect the plant roots from corn rootworm feeding or foliar insecticide treatments to kill the beetles before they can lay their eggs in the field. Scientists have proposed using an areawide management strategy to manage corn rootworms (Wilde et al. 1998, Whitworth et al. 2004) by reducing insect populations (in this case beetles) over a larger geographical area to reduce the threat of reinfestation

Susceptibility of adult populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to several insecticides was evaluated in seven Kansas counties, including Dickinson, Ford, Finney, Pottawatomie, Republic, Riley, and Stevens, between 1996 and 2002. All populations surveyed were highly susceptible to methyl parathion with the largest difference in susceptibility of only three-fold based on 16 complete bioassays for the populations from six counties over a 5-yr period. Noticeable decreases in carbaryl susceptibility were found in populations collected from Republic County between 1997 and 2001 when the cucurbitacin-carbaryl-based bait SLAM was widely used as an areawide management approach for adult corn rootworm control. However, the lowered carbaryl susceptibility returned to previous levels 1 yr after the use of SLAM was halted in the managed (treated) cornfields. This change implies possible dispersal of insects into the relatively small managed area from surrounding untreated cornfields and/or some fitness cost associated with carbaryl resistance within the population. Relative susceptibility of western corn rootworm adults also was evaluated for seven commonly used insecticides, including bifenthrin, carbaryl, chlorpyrifos, cypermethrin, fipronil, malathion, and methyl parathion. They were tested with corn rootworm adults collected from a single cornfield. Methyl parathion and bifenthrin were highly toxic to corn rootworm, adults, and cypermethrin, chlorpyrifos, carbaryl, and malathion were only slightly less toxic. Although fipronil was highly toxic to adult rootworms, its activity was much slower than that of other insecticides. Thus, bifenthrin and methyl parathion were among the most effective in killing corn rootworm adults.

Banks grass mite (BGM): Oligonychus pratensis (Banks) Twospotted spider mite (TSM): Tetranychus urticae Koch Four miticides were evaluated at three application timings on field corn, (110-day maturity), planted 5 May with a John Deere Max Emerge 6 row planter at a rate of 36,000 seeds/acre in a furrow-irrigated field (Finnup #8) at the Southwest Research-Extension Center, Finney County, KS.The test was set up in a randomized complete block design with four replications.Plots were four rows (10 ft) wide and 50 ft long with 4-row (10 ft) borders of untreated corn on each side and 10-ft allies at each end.The treatments were applied with a high clearance sprayer using a 10-ft boom with two nozzles directed at each row (one on each side of the row on a 16-inch drop hose).The nozzles were directed up into the plant for the first treatment and at the ear zone for the other timings.The sprayer was calibrated to deliver 14 gpa at 2 mph and 40 psi.Treatments 2-4, 5-7, and 8-10 (Table 1) were applied on 5, 16, and 28 Jul respectively.Corn was in late whorl stage (4 ft tall), early tassel stage, and soft dough stage on 5, 16, and 28 Jul, respectively.An untreated check and a standard early season miticide, Comite II, was included with the whorl and tassel stage treatments and a standard late-season miticide, Capture, was included with the dough stage treatments.Spider mites infested the plots naturally from an adjacent wheat field.During the summer, spider mites were sampled in corn by collecting half the leaves from 4 plants (4 half plants = 2 plants) from the two center rows in each plot.The sample plant material was placed in large 76-liter Berlese funnels with a 100 watt light bulb to dry the vegetation and drive arthropods down into a collecting jar containing 70% methanol.The alcohol samples were filtered on ruled white filter paper and spider mites, predator mites and thrips were counted under a binocular microscope.A subsample of spider mites (about 20 for each plot) was mounted on a microscope slide and examined to determine the proportion of BGM versus TSM.Pre-treatment spider mite samples were collected 27 Jun and posttreatment samples were collected 9, 16, 23, 30 Jul, and 6 Aug. Spider mite counts were transformed with Taylor's power transformation for statistical analysis and converted to mites per 4 half-plants for presentation.On 12 Sep the plots were also rated for the number of green leaves.Grain yield was collected by machine harvesting the two middle rows from each plot and adjusted to 15.5% moisture.There was a significant yield gradient down the field that was associated with slope and furrow irrigation.We calculated the "field yield trend" by averaging the yield at each position down the field across 6 strips of plots.The position means were smoothed using rolling averages.Then this "field yield trend" was used as the covariate in the ANOVA of grain yield and number of green leaves.Means were separated using an

This trial was conducted to evaluate the efficacy of corn hybrids containing a Cry1Ab event for controlling SWCB with hybrids containing a Cry1Ab event stacked with a VIP3a event for controlling CEW. Experimental corn seed (supplied by Syngenta) and commercial standard seed (added by the authors) were machine-planted 10 Jun at the Southwest Research-Extension Center, Garden City, KS. The plots were 4 rows wide and 20 ft long. The seed was planted in a single row (row 2) and the other rows were planted to a commercial Bt corn seed. There were 10-ft wide alleys at each end of the plots. The design was a RCB design with four replicates. Four to 12 rows of Bt and non-Bt corn were planted around the experimental plots as a border and windbreak. One isoline and one Bt11 plot was treated for second generation SWCB and CEW with Warrior T using a 2-gallon hand sprayer. The plots were sprayed on 1 Aug (3 oz product/acre) and on 12 Aug (6 oz product/acre). The spray was directed at the plants while the nozzle was moved up and down to treat the whole plant. Each of the first 10 plants in each experimental row was infested with 5 to 10 SWCB neonates 9 - 13 Jul when the plants were in the 8 to 10 leaf stage. The second generation SWCB infestation resulted from free flying feral moths and moths emerging from the manually infested first generation. First generation SWCB leaf-feeding

While most Corn Belt farmers consider planting Bt corn to control European corn borer, southwestern Kansas farmers must also take into account an array of other insect pests, including corn rootworm, spider mites, and southwestern corn borer. This research uses a decision analysis framework to estimate the expected economic value of Bt corn in southwest Kansas. Mean per acre Bt values ranged from $12.49 to $34.60, well above the technology fee assumed to be $14 per unit, or $5.25 per acre at a seeding rate of 30,000 seeds per acre. The minimum value over all scenarios was $8.69 per acre. Using Monte Carlo simulation, it was shown that European and southwestern corn borer infestation probabilities, expected corn price, and expected pest-free yields are important determinants of the value of Bt corn.

We simulated the population dynamics and population genetics of two bivoltine species of corn borers, the European corn borer, Ostrinia nubilalis (Hübner), and the southwestern corn borer, Diatraea grandiosella Dyar, in a hypothetical region of irrigated transgenic and nontransgenic corn where insecticide was applied only to the nontransgenic refuge crop. Over the 100-yr time horizon, resistance developed quickly in both species and to both transgenic corn and the insecticide when the allele for resistance to the respective toxin was dominant. When the allele for transgenic resistance was not dominant and the refuge location was constant over the time horizon, spraying the refuge to control southwestern corn borer had no effect on how quickly resistance to the transgenic corn developed. In contrast, the European corn borer developed resistance to transgenic corn much sooner when the refuge was sprayed once per year, and the time to 3% resistance allele frequency decreased as efficacy of the insecticide increased. Only when the refuge was treated less than once every 5 yr (10 generations) did the frequency of application decline enough to permit resistance management for the European corn borer to approximate the effectiveness of an unsprayed refuge. A consistently sprayed refuge <40% of the corn acreage was an inadequate resistance management strategy for the European corn borer even when a low efficacy insecticide (70% mortality) was used. When assumptions about European corn borer adult behavior were changed and the adults behaved similarly to adult southwestern corn borer, the development of resistance to the transgenic crop was slowed significantly.

The population dynamics and population genetics of two bivoltine species of corn borers are modeled in a hypothetical region of irrigated transgenic and nontransgenic corn. European corn borer, Ostrinia nubilalis (Hubner), adults were assumed to disperse throughout the landscape for both mating and oviposition. Southwestern corn borer, Diatraca grandiosella Dyar, adults were assumed to have very localized dispersal behaviors. Resistance developed quickly in both species when the allele for resistance to the transgenic toxin was dominant. When the allele for resistance was not dominant and few or none of the heterozygous larvae survived the toxin, the behaviors of adult insects determined the speed of resistance development. With block refuges of 10-40% the European corn borer developed resistance within 15-38 yr, but the southwestern corn borer never developed resistance within the 100 yr simulated. A row-strip refuge configuration (lid not change the time for resistance to develop in the European corn borer; however, row-strip refuges cannot be recommended for the southwestern corn borer. Uncertainty about adult behaviors in irrigated corn led us to examine the potential impact of behavior on resistance development, Adult behaviors influenced resistance development more than refuge size. For instance, if the first flight of moths exhibit random mating and uniform oviposition throughout the landscape and the second flight exhibits localized mating and oviposition, resistance developed at least five times faster in the southwestern corn borer population and three times slower in the European corn borer population compared with our standard assumptions. We discuss the implications of adult behavior, refuge configuration, refuge placement within the landscape and year-to-year relocation on resistance management plans.

Laboratory bioassays were conducted to determine the toxicity of four insecticides (ethyl parathion, chlorpyrifos, malathion, and carbofuran) to insecticide-susceptible and resistant populations of greenbug, Schizaphis graminum (Rondani). These bioassays were used to develop and validate a discriminating concentration for assessing insecticide resistance in greenbug populations in the field. Samples from wheat and sorghum in two states, Oklahoma and Kansas, indicated that insecticide resistance persists in greenbug populations over a large area at a low level.

The success of managing greenbugs, Schizaphis graminum (Rondani), with plant resistance has been challenged by the repeated occurrence of resistance-breaking biotypes. Biotypes recognized as seriously damaging to sorghum, Sorghum bicolor (L.) Moench, hybrids are C, E, I, and K. In 1995, biotype K, which damages sorghum resistant to biotype I, was first identified in a biotype I greenbug colony being reared in the greenhouse. This colony originated from greenbugs collected in a field of wheat in Haskell County, Kansas, in April 1992, and was maintained on susceptible sorghum. Documenting the presence of biotype K in the field was imperative. Field samples of greenbugs collected from wheat and sorghum in Kansas and Oklahoma from 1996 to 1998 were identified to biotypes. These samples indicated that biotype I was the dominant biotype on both crops. Biotypes E and K were present in about 21 and 12% of the samples collected from sorghum in 1998, respectively. Biotype K was identified in samples collected from 11 counties in Kansas and 10 counties in Oklahoma during the sampling period. It is a potential threat to future sorghum hybrids that may rely on PI 550610 for protection against greenbug damage. Studies conducted at constant temperatures of 22, 27, and 32 degreesC indicated that biotypes C, E, I, and K had similiar reproductive capacity and survival at 22 and 27 degreesC.

Susceptibility of adult populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to carbaryl was determined by a survey in 1996 before the implementation of an areawide management program near Scandia in north central Kansas. Subsequently, the susceptibility of western corn rootworm adults to carbaryl has been monitored throughout the program from 1997 to 2000 in both control and managed areas. In 1996, adults were highly susceptible to carbaryl with a mean LC50 value of 0.64 microg/vial. This value was comparable to those for adults collected from other regions within Kansas. However, adult susceptibility to carbaryl decreased rapidly within the managed area, where the cucurbitacin- carbaryl-based bait SLAM has been used as the primary tool to control adults in this project since 1997. In 1999, adults collected from the managed area were 9- and 20-fold less susceptible to carbaryl at the LC50 and LC90 levels, respectively, than those evaluated in 1996. In contrast, adults collected from the control area were only 2- and 3-fold less susceptible to carbaryl at the LC50 and LC90 levels, respectively, than adults evaluated in 1996. Although field adult populations of western corn rootworm were relatively low in 2000, evaluations showed trends similar to those in 1999 regarding their carbaryl susceptibility in the managed and control areas. These results provide evidence that western corn rootworm has been evolving carbaryl resistance rapidly in response to the use of SLAM in areawide-managed cornfields near Scandia.

Comparative differences and similarities in prereproductive time (d), progeny production in a time equal to d (Md), and intrinsic rate of increase (rm) were established for one susceptible (S) and three resistant (R) strains of the greenbug, Schizaphis graminum (Rondani), reared on sorghum hybrids Dekalb G550E and Cargill 607E. The R strains showed three patterns of elevated esterase activity. Four R1 clones, four R2 clones, one R3 clone, and four S clones were evaluated. The interaction of sorghum hybrid and greenbug strain did not significantly influence any of the parameters measured. However, R1 greenbugs exhibited a significantly longer prereproductive period than the other strains. In addition, the R1 strain had a significantly slower intrinsic rate of increase than the R2 or S greenbug strains, but did not differ significantly from the R3 strain. These results suggest that R1 greenbugs may be less fit than the other strains studied.

In areas of finite groundwater resources, the groundwater used for irrigation must be used as efficiently as possible. Yields and water use characteristics of longer-maturity corn (Zea mays L.; 118-d relative maturity), shorter-maturity corn (97-d relative maturity), and grain sorghum [Sorghum bicolor (L.) Moench] under full and limited irrigation were evaluated from 1993 to 1996. Mean yield of longer-maturity corn was 15 bu/acre greater than that of shorter-maturity corn and 50 bu/acre greater than that of grain sorghum. Longer-maturity corn used the greatest amount of water, 3.4 in, greater than shorter-maturity corn or grain sorghum. Average water use rates were similar among the three crops. Mean water use efficiency for longer-maturity corn was not different from that of shorter-maturity corn; mean water use efficiency of grain sorghum was 1.4 bu/acre per in, less. Mean yield of fully irrigated crops was 15 bu/acre greater than that for crops under limited irrigation (replacing 70% of crop evapotranspiration [ET]). Water use efficiency of crops under limited irrigation was 0.7 bu/acre per in, greater than under full irrigation, but full irrigation of corn was more profitable than limited irrigation. These yields, average water use rates, and water use efficiencies indicate no justification for choosing shorter- over longer-maturity corn.

Kansas State University initiated a Rootworm Areawide Management Project (RAMP) under the auspices of the United States Department of Agriculture (USDA) in 1997. This 4-yr project is being conducted in north central Kansas with the cooperation of 47 owners or operators. The project is a concerted effort to suppress adult western corn rootworms, Diabrotica virgifera virgifera LeConte, over a large contiguous area of continuous corn (Zea mays L.) production by using the principles of integrated pest management (IPM), including carefully timed applications of the semiochemical insecticide-bait SLAM(R). In addition to this adult suppression program, technology is being developed or modified to determine treatment thresholds and application timing so that private consultants and growers can continue rootworm areawide suppression after the year 2000, when the intensive research program terminates. The managed area is located in 41.4-km(2) (16-mi(2)) of intensely irrigated corn-soybean production near Scandia, Kansas. A similar 10.36-km(2) (4-mi(2)) area near the town of Norway, Kansas, will serve as a control and will not be treated with Slam throughout the duration of this project. One hundred and twenty-one cornfields were monitored in 1997 with Pherocon AM(R) yellow sticky traps. Treatment thresholds were greater than or equal to 35 western corn rootworm adults per sticky trap per week or 0.6 western corn rootworm per plant based upon plant inspections that were used to supplement trap counts. One thousand one hundred and seventy-seven hectares required treatment (68.5% of the total from the managed area). The Slam application resulted in greater than or equal to 95% adult western corn rootworm control in all treated fields. Treated and untreated fields were selected for 10 additional experiments that were initiated to refine sampling technology necessary for adequate timing of insecticide applications. All experiments will be continued, with appropriate modifications, throughout the duration of the project.

Insecticide resistance in insects often is associated with elevated acetylcholinesterases and carboxylesterases. Three greenbug, Schizaphis graminum (Rondani), strains with different general esterase patterns were tested for differences in insecticide response. The standard strain had no noticeable elevated esterase activity. Pattern 1 and pattern 2 strains had different elevated esterase patterns. Toxicity of 5 organophosphorous (chlorpyrifos, dimethoate, disulfoton, malathion, and parathion) and 2 carbamate (carbofuran and methomyl) insecticides were tested using surface residue bioassays. Esterase pattern 1 greenbugs had significantly higher LC(50)s for each of the organophosphorous insecticides, but the LC(50)s for the 2 carbamate insecticides were not higher than the standard strain. Esterase pattern 2 greenbugs had significantly higher LC(50)s for 4 Of the 5 organophosphorus insecticides (chlorpyrifos, dimethoate, disulfoton, and parathion) and the 2 carbamate insecticides, but the LC50 for malathion was not higher than the standard strain. Pattern 2 greenbugs had significantly higher tolerance to disulfoton than did pattern 1 greenbugs. This indicates that certain strains of the greenbug are cross resistant to many of the organophosphorous and carbamate insecticides currently labeled for greenbug control in wheat and sorghum. There is an urgent need to find alternative control measures.