Economic impact of Hessian fly (Diptera: Cecidomyiidae) on spring wheat in Oregon and additive yield losses with Fusarium crown rot and lesion nematode

Damage caused by Hessian fly, Mayetiola destructor (Say), was quantified in spring wheat, Triticum aestivum L., trials near Pendleton and Moro, OR, during 2001 and 2002. Five field experiments were established to examine genetic resistance to Fusarium crown rot, Fusarium pseudograminearum (O'Donnell & Aoki), and economic damage by lesion nematode, Pratylenchus neglectus (Rensch, 1924) (Filipjev Schuurmanns & Stekhoven, 1941) and Pratylenchus thornei (Sher & Allen, 1941). Hessian fly became the dominant factor affecting grain yield in four experiments. Genotypes carrying the H3-resistance gene had grain yields 66 and 68% higher than susceptible genotypes in cultivar trials during 2001 and 2002, respectively. Yield reductions were detected when Hessian fly infestation rates exceeded 50% plants during 2001 and 15% plants (8% tillers) during 2002. In two trials during 2001, in-furrow application of aldicarb (Temik) at planting improved yields of four Hessian fly-susceptible cultivars by 72 and 144% (up to 1,959 kg/ha) and yields of one Hessian fly-resistant cultivar by 2 and 3%. Resistant cultivars and aldicarb improved grain quality as much as two market grades during 2001. The value of increased grain production with Hessian fly-resistant cultivars in four field experiments ranged from dollar 112 to dollar 252/ha, excluding price incentives for improved market quality. Yield reduction due to combined damage from Hessian fly and either Fusarium crown rot or lesion nematode was additive. This report seems to be the first quantitative yield loss estimate for Hessian fly in spring wheat in the semiarid environment of the inland Pacific Northwest.     

Effects of tillage on the activity density and biological diversity of carabid beetles in spring and winter crops

The effects of tillage regimen (conventional [CT] and no-tillage [NT]) on the activity density and diversity of carabid beetles (Coleoptera: Carabidae) was studied by pitfall trapping within a rain-fed cropping system in northwestern Idaho, 2000-2002. The cropping rotation consisted of a spring cereal (barley, Hordeum vulgare L., in 2000 and 2001; and wheat, Triticum aestivum L., in 2002), spring dry pea (Pisum sativum L.) 2000-2002, and wheat (T. aestivum), spring in 2000 and 2001, and winter in 2002. A total of 14,480 beetles comprised of 30 species was captured, with five numerically dominant species [Poecilus scitulus L., Poecilus lucublandus Say, Microlestes linearis L., Pterostichus melanarius Ill., and Calosoma cancellatum (Eschscholtz)], accounting for 98% of all captures. All species including the dominants responded idiosyncratically to tillage regimen. Adjusting for trapping biases did not significantly change seasonal activity density of Poecilus spp. or Pt. melanarius to tillage. More beetles were captured in CT than in NT crops because of the dominance of P. scitulus in CT, whereas species richness and biological diversity were generally higher in NT crops. Observed patterns suggest that direct effects of tillage affected some species, whereas indirect effects related to habitat characteristics affected others. CT may provide habitat preferable to xerophilic spring breeders. A relationship was found between beetle species size and tillage regimen in pea and to a lesser extent across all spring crops, with large species (>14 mm) conserved more commonly in NT, small species (<7 mm) in CT, and intermediate species (7-14 mm) conserved equally between tillage systems.     

Tillage affects the activity‐density,absolute density,and feeding damage of the pea leaf weevil in spring pea

Conversion from conventional‐tillage (CT) to no‐tillage (NT) agriculture can affect pests and beneficial organisms in various ways. NT has been shown to reduce the relative abundance and feeding damage of pea leaf weevil (PLW), Sitona lineatus L. (Coleoptera: Curculionidae) in spring pea, especially during the early‐season colonization period in the Palouse region of northwest Idaho. Pitfall traps were used to quantify tillage effects on activity‐density of PLW in field experiments conducted during 2001 and 2002. As capture rate of pitfall traps for PLW might be influenced by effects of tillage treatment, two mark‐recapture studies were employed to compare trapping rates in NT and CT spring pea during 2003. Also in 2003, direct sampling was used to estimate PLW densities during the colonization period, and to assess PLW feeding damage on pea. PLW activity‐density was significantly lower in NT relative to CT during the early colonization period (May) of 2001 and 2002, and during the late colonization period (June) of 2002. Activity‐density was not different between treatments during the early emergence (July) or late emergence (August) periods in either year of the study. Trap capture rates did not differ between tillage systems in the mark‐recapture studies, suggesting that pitfall trapping provided unbiased estimates of PLW relative abundances. PLW absolute densities and feeding damage were significantly lower in NT than in CT. These results indicate that NT provides a pest suppression benefit in spring pea.     

Population Dynamics of Heterodera glycines in Conventional Tillage and No-Tillage Soybean/Corn Cropping Systems

The effects of no-tillage (NT), conventional tillage (CT), and crop rotation on soybean yield and population dynamics of Heterodera glycines were compared during a 7-year study in a silty clay loam soil with 6% organic matter. Either H. glycines-resistant ''Linford'' soybean or susceptible ''Williams 82'' soybean was rotated with corn and grown on 76-cm-wide rows in both tillage systems. Soybean was planted in 1994, 1996, 1998, 1999, and 2000. Yield of Linford was significantly greater than Williams 82 in all years. Soybean yield was affected by tillage in 1999 and 2000. No-tillage production tended to support more reproduction (R = number of eggs at harvest/number of eggs at planting) on both cultivars. The largest R for Williams 82 were in 1998: 58.35 for NT plots and 11.78 for CT plots. For Linford, the largest R were 12.09 for NT plots in 1996, and 3.71 for CT in 1999. When corn was planted, R decreased more in NT. When soybean was planted in years subsequent to 1994, numbers of eggs at harvest (Pf) were greater for Williams 82 NT than for Williams 82 CT or Linford in both tillage systems; however, crop rotation with corn negated these population increases. The soil became suppressive to H. glycines in 1999 and was suppressive in 2000. After the 3 years of continuous soybean, Pf per 250 cm[sup3] soil were 2,870 for Williams 82 NT, 791 for Williams 82 CT, 544 for Linford NT, and 990 for Linford CT in 2000, compared with Pf of 13,100 for Williams 82 NT, 15,000 for Williams CT, 2,360 for Linford NT, and 2,050 for Linford CT in 1994. Describing population dynamics solely on the basis of R was not adequate, but also required independent examination of initial populations following overwintering and Pf after the growing season. Planting soybean either NT or CT in rotation with corn did not result in long-term increases in numbers of H. glycines eggs.     

Comparison of Polygonum aviculare L. seedling survival under different tillage systems in Mediterranean dryland agroecosystems

Weed community shifts in agroecosystems are influenced by multiple factors. Among them, tillage and crop rotation are very important. Polygonum aviculare survival at early plant stages and biomass and density at harvest time were compared under three tillage systems (conventional, CT; minimum, MT; and no tillage, NT). Field studies were conducted from 1997–1998 to 2000–2001, during a crop rotation (pea–wheat–wheat–barley). The layout of the tillage systems was not randomized, which led to confusion between the tillage effect and the site effect, although all three tillage systems were implemented as of 1993–1994 and the same agricultural practices had been employed in the entire field between 1981–1982 and 1992–1993. Seedling mortality was analysed in two monitored cohorts (2000 and 2001) using a generalized linear model of binomial probability distribution with a complementary log–log link function. Analyses of variance considering tillage system (or site) and block were performed on: (1) aboveground biomass at the harvest time of the four crops; (2) density and mean plant biomass at the end of the first two crops; (3) seedling density registered twice during the 1998–1999 campaign. The expected changes to estimated mortality showed that seedlings under NT had greater probabilities of failure than those growing under the other two tillage systems. These differences were found considering the tillage system apart from the crop and the accumulated precipitation effects, which also strongly affects seedling survival. Density, 1999–2000 biomass and 2000–2001 biomass were different under different tillage systems (P < 0.05), the lowest density occurring under NT and the lowest values of biomass under MT. Mean seedling densities were similar between CT and MT, but both were higher than densities under NT.     

Susceptibility of low-chill blueberry cultivars to Mediterranean fruit fly, oriental fruit fly, and melon fly (Diptera: Tephritidae)

No-choice tests were conducted to determine whether fruit of southern highbush blueberry, Vaccinium corymbosum L., hybrids are hosts for three invasive tephritid fruit flies in Hawaii. Fruit of various blueberry cultivars was exposed to gravid female flies of Bactrocera dorsalis Hendel (oriental fruit fly), Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), or Bactrocera cucurbitae Coquillet (melon fly) in screen cages outdoors for 6 h and then held on sand in the laboratory for 2 wk for pupal development and adult emergence. Each of the 15 blueberry cultivars tested were infested by oriental fruit fly and Mediterranean fruit fly, confirming that these fruit flies will oviposit on blueberry fruit and that blueberry is a suitable host for fly development. However, there was significant cultivar variation in susceptibility to fruit fly infestation. For oriental fruit fly, 'Sapphire' fruit produced an average of 1.42 puparia per g, twice as high as that of the next most susceptible cultivar 'Emerald' (0.70 puparia per g). 'Legacy', 'Biloxi', and 'Spring High' were least susceptible to infestation, producing only 0.20-0.25 oriental fruit fly puparia per g of fruit. For Mediterranean fruit fly, 'Blue Crisp' produced 0.50 puparia per g of fruit, whereas 'Sharpblue' produced only 0.03 puparia per g of fruit. Blueberry was a marginal host for melon fly. This information will aid in development of pest management recommendations for blueberry cultivars as planting of low-chill cultivars expands to areas with subtropical and tropical fruit flies. Planting of fruit fly resistant cultivars may result in lower infestation levels and less crop loss.     

Effects of tillage systems on wheat and weed water relationships over time when growing together,in semiarid conditions

Water availability directly influences interactions and competition between weeds and crops. This article is based on the idea that relative water content (RWC) indicates the water uptake within plants and that it is possible to explain the water relationships between plants that are growing together. A field experiment carried out for 3 years (2013–2014, 2014–2015 and 2015–2016) compared the short-term effects of years and tillage systems on wheat grain yield, weed density, wheat-RWC, weed-RWC and soil water content (SWC), at tillering and flowering stages in a winter wheat monoculture system. The three tillage treatments were conventional tillage (CT), minimum tillage (MT) and no-tillage (NT). Wheat grain yield was low all years of study, because of low interannual rainfall, and we did not observe differences between tillage systems. Weed density was also affected by year and not by tillage systems. Lowest winter rainfall (73.4 mm from Nov to Feb) in the last year of the study (2015–2016), decreased the weed density in all tillage systems. Despite the rainfall variability over the 3 years of study, the NT system presented higher weed density (73 plants/m²) than MT and CT systems (39.83 and 46.33 plants/m²). We also observed a higher number of weed species for the NT system, facilitated by a high soil water storage in this system. The wheat-RWC, at tillering stage, varied with years and tillage systems; we found that high winter rainfall (2013–2014) led to higher values in CT (64.5%) compared with MT (52.9%) and NT plots (52.9%). Weed-RWC values did not vary and SWC was greater in NT than in CT and MT. At flowering stage, the year (2015–2016) with highest spring rainfall favoured higher wheat-RWC in NT (56.9%) compared with CT (48.3%). However, the lowest spring rainfall coincided with the lowest weed-RWC, (18% in NT plots) and SWC was always higher in NT soils. The results showed that climatic conditions affected the water competence dynamics between weeds and wheat in different ways. Seemingly, weeds can tolerate a lack of water availability until crop tillering stage independently of tillage system; however, the competition for water was not a problem as crops overcame the high weed density by flowering stage.     

Biotypes of Hessian fly (Dipt., Cecidomyiidae) in Morocco

Hessian fly, Mayetiola destructor (Say), is the most important insect pest of wheat in Morocco, where host plant resistance has been used successfully for control. Our objective was to determine the frequency of Hessian fly virulence on H5, H13 and H22 resistance genes. Five Hessian fly populations from the principal cereal‐growing regions in Morocco were studied. The variability in percentage of susceptible plants across Hessian fly populations was highly significant (P < 0.01), indicating differences in virulence frequencies. Plants with the H13 gene had the lowest percentage of susceptible plants, 1.77 and 1.51%, when infested with Hessian flies from Fes and Marchouch, respectively. A low level of virulence to H22 was detected in Fes, Abda and Marchouch populations, 1.87, 1.54 and 1.99% susceptible plants, respectively. The level of virulence to H5 was low in all the five populations. The Beni Mellal population gave the highest percentage of susceptible plants carrying H13 and H22 genes, 6.43 and 7.28%, respectively. The size of live larvae on susceptible plants of the three cultivars carrying H5, H13 and H22 was similar to that of the susceptible check, indicating that a true virulence (biotype) is developing in Hessian fly populations in Morocco. Thus, continuous monitoring of the development of Hessian fly biotypes is essential for optimal deployment of resistance genes.     

Postharvest resistance in hard spring and winter wheat varieties of the northern Great Plains to the lesser grain borer (Coleoptera: Bostrichidae)

Wheat (Triticum aestivum L.) varietal resistance to the lesser grain borer, Rhyzopertha dominica (F), was evaluated in hard spring and winter wheat produced 1997, 1998 (Bozeman, Montana). We tested the hypothesis that six Montana-grown spring wheat varieties, 'Ernest', 'Scholar', 'Hi-Line', 'McNeal', 'Newana', and 'Amidon', were equally and strongly resistant to R. dominica at low moisture contents (9-10%). Mortality/Feeding damage occurred in all varieties. In most assays, Ernest had significantly greater feeding damage from R. dominica than other varieties, usually not significantly different from the susceptible control. Mean adult mortality was significantly greater in McNeal (93%) and Hi-Line (92%) than in Ernest (34%) and Montana-grown, soft white spring wheat (Penawawa), the susceptible control (36%). In 9 wk, twice as many adult progeny were produced on Ernest than on McNeal, Hi-Line, or Scholar. We also compared three Montana-grown winter wheat varieties for resistance to R. dominica attack at low moisture contents (9-10%). Significantly more mortality after 6 wk was associated with all winter wheat varieties than the susceptible control. In 'Nuwest', 'Rocky', and 'Vanguard', significantly fewer progeny were produced than in the susceptible control; these varieties appeared more resistant. 'Tiber' and 'Neeley', in contrast, appeared more susceptible than other winter wheat varieties evaluated. Susceptibility decreased significantly with a 1.2% decrease in moisture content. Percentage of total protein was positively correlated with percentage of sound kernels and negatively with total progeny (r2 = -0.69). Kernel hardness was positively correlated with percentage of sound kernels, but negatively correlated with total progeny (r2 = -0.87) and dry weight loss.     

First combined resistance to Hessian fly and Sunn pest identified in synthetic hexaploid wheat

Hessian fly, Mayetiola destructor (Say), and Sunn pest, Eurygaster integriceps (Puton), are the two most damaging insect pests of wheat in North Africa, West and Central Asia. Host plant resistance is the most environmental friendly, cost-effective and practical means of controlling insect pests. Twenty synthetic hexaploid wheat lines selected as resistant to Syrian Sunn pest in 2010 were screened for resistance to Moroccan Hessian fly biotype in 2016. The Hessian fly screening was carried out in standard greenhouse flats using a randomized complete block design with three replications, with susceptible and resistant checks in every test flat. The results showed that three synthetic hexaploid wheat lines exhibited resistance to both Moroccan Hessian fly biotype and Syrian Sunn pest. This is the first record of combined resistance to these two pests in wheat. Mapping populations using these sources of resistance are being developed using double haploid techniques for subsequent genetic characterization and identification of linked molecular markers for marker assisted selection.     

Ultrastructural changes in the midguts of Hessian fly larvae feeding on resistant wheat

The focus of the present study was to compare ultrastructure in the midguts of larvae of the Hessian fly, Mayetiola destructor (Say), under different feeding regimens. Larvae were either fed on Hessian fly-resistant or -susceptible wheat, and each group was compared to starved larvae. Within 3 h of larval Hessian fly feeding on resistant wheat, midgut microvilli were disrupted, and after 6 h, microvilli were absent. The disruption in microvilli in larvae feeding on resistant wheat were similar to those reported for midgut microvilli of European corn borer, Ostrinia nubilasis (Hubner), larvae fed a diet containing wheat germ agglutinin. Results from the present ultrastructural study, coupled with previous studies documenting expression of genes encoding lectin and lectin-like proteins is rapidly up-regulated in resistant wheat to larval Hessian fly, are indications that the midgut is a target of plant resistance compounds. In addition, the midgut of the larval Hessian fly is apparently unique among other dipterans in that no peritrophic membrane was observed. Ultrastructural changes in the midgut are discussed from the prospective of their potential affects on the gut physiology of Hessian fly larvae and the mechanism of antibiosis in the resistance of wheat to Hessian fly attack.     

Tillage differentially affects the capture rate of pitfall traps for three species of carabid beetles

The influence of tillage, gender, and microclimate on capture rates of pitfall traps for the beetles Poecilus scitulus LeConte, Poecilus lucublandus (Say), and Pterostichus melanarius Illiger (Coleoptera: Carabidae) were assessed in mark–release–recapture experiments in spring pea and spring wheat. Experiments were conducted during June, July, and August of 2003 in the Palouse region of northern Idaho, USA. Rates of capture in pitfall traps for the three carabid species were differentially affected by crop‐tillage systems. Capture rates for P. scitulus and P. lucublandus were higher in no‐till (NT) than in conventional tillage (CT) peas, whereas capture rates for P. scitulus and Pt. melanarius were higher in CT than in NT wheat. Ground‐level temperatures and relative humidity (r.h.) differed little among tillage systems. Nevertheless, capture rates were generally positively correlated with ground‐level temperature and negatively correlated with r.h., with correlations more often significant in NT than in CT systems. The response of the thermophilic Poecilus spp. to temperature provides a possible mechanistic explanation for capture rate patterns in legumes during June, but not in other months for peas or any month in wheat during the experiments. Movement impedance due to residue could explain lower capture rates of P. scitulus and Pt. melanarius in NT than in CT spring wheat. These results suggest that researchers using pitfall trapping for carabid populations should take into account potential capture biases their treatments can introduce.