Impact of Trichosirocalus horridus (Coleoptera: Curculionidae) on Carduus thistles in pastures

Trichosirocalus horridus (Panzer), a rosette-feeding weevil introduced from Europe, was released on musk thistle (Carduus thoermeri Weinmann), plumeless thistle (Carduus acanthoides L.) and mixtures of both thistle species from 1974 to 1976 in pastures in Virginia. The weevils became established at nine of the 10 release sites: three on musk, four on plumeless thistle and two on mixtures. Density of thistles was reduced in all established sites by 1981. Thistle reduction ranged from 1·3% for the most recently established site to 96·5% for the earliest established and most successful site, versus an 11·6% increase at the plumeless thistle site where T. horridus was not established, and a 9·7% increase at a mixed thistle site prior to establishment in 1980. A control musk thistle without any weevil release showed a 5·8% increase between 1976 and 1979, when Rhinocyllus conicus, a thistlehead weevil, which is well established in Virginia, dispersed into the area.     

Further tests on Ceutorhynchus trimaculatus F. as a candidate for the biological control of Carduus thistles

Tests were conducted on Ceutorhynchus trimaculatus F. (Coleoptera: Curculionidae), a candidate for introduction from Europe into North America, for the biological control of Carduus thistles which are major weeds in pastures, rangeland and interstate highway embankments. Host specificity tests conducted simultaneously in Blacksburg, Virginia and in Albany, California were to determine whether Cirsium species native to the USA, and considered to be endangered species, are acceptable as hosts to the weevil, and if there is any preference for the Cirsium over the Carduus thistle species. In Virginia, three Cirsium species were compared with Carduus thoermeri Weinmann (musk thistle) and, in California, four Cirsium species were compared with Carduus macrocephalus L. Adult weevils fed on all test species, to a greater extent on musk thistle than on the Cirsium spp. except for Cirsium discolor (Muhl.) Spreng. which was preferred to musk thistle. Cirsium arvense (L.) Scop., Cirsium discolor and musk thistle supported oogenesis of Ceutorhynchus trimaculatus, but the greatest number of eggs was in musk thistle. Ovipositional preference was also shown for musk thistle over the Cirsium spp. in comparison tests using leaf bouquets, although no distinct preference for oviposition on rosettes was found. Besides musk thistle, both Cirsium occidentale (Nutt.) Jepson and Cirsium brevistylum Cronq. supported development from first instar to the adult stage. These results indicate that several of the Cirsium species tested are acceptable as hosts of Ceutorhynchus trimaculatus under caged conditions. However, musk thistle was preferred for feeding, oogenesis and oviposition.     

Abundance of Sitona lineatus L. (Col., Curculionidae) in peas (Pisum sativum L.): Effects on yield parameters and nitrogen balance

In a four-year study, we investigated the relationship between the damage to root nodules of organically produced pea (Pisum sativum L.) by the larvae of the pea leaf weevil (Sitona lineatus L.) and the abundance of adult weevils. In addition to studying natural infestations, we established artificial infestations within cages to assess the impact of different weevil densities on yield parameters and determinants of the nitrogen balance. Densities of 0.2 adult S. lineatus per plant (20 individuals per m²) reduced the number of seeds and pods per plant by 18% and 15%, respectively; seeds per pod and thousand-seed weight remained unaffected. A three-fold or five-fold increase in weevil abundance (13–40 or 20 to 100 individuals per m²) did not result in an additional reduction in yield. Moreover, the higher weevil abundance did not adversely affect the N-harvest index or soil nitrogen content. We suspect that the impact of adult S. lineatus on yield and nitrogen parameters is limited by the density-dependent mortality of the larvae. Survival of larvae in turn depends on the nodulation of the plants, which is largely regulated by the supply of water. The assumption that organic cropping systems are at specific risk from the pea leaf weevil was confirmed by increasing population densities during the study period. However, yield losses were independent of adult attack within a wide range of weevil abundance, which indicates the complexity of assessing larval damage based on adult infestation level. An enhanced intraspecific competition among larvae may account for the absence of linear relationships, considering that especially young instars failed to establish in root nodules at higher densities. We found that adult densities of 0.2 individuals per plant and subsequent larval densities of 7 individuals per plant resulted in destruction of 37% of the root nodules on primary roots, which was much below destruction values reported in other studies. In conclusion, we recommend an early monitoring of weevils and early initiation of control strategies because yield losses were caused by even low weevil densities. Finally, the tolerance of P. sativum to S. lineatus was influenced by the yield level, i.e., tolerance to S. lineatus decreased as yield increased.     

Minimizing environmental impacts of grassland weed management: can Cirsium arvense be controlled without herbicides?

Invasion by undesirable plants, such as Cirsium arvense, can constrain attempts to conserve and restore biodiversity in extensively managed temperate grasslands, but control with herbicides can cause environmental harm. We contrasted herbicides with more environmentally sustainable weed control strategies. Six‐year, large‐scale randomized block experiments were established to determine optimum combinations of grazing management and mechanical or herbicide treatments to control thistles within lowland and upland grazing systems. Factorial combinations of tight vs. lenient grazing in spring and autumn with additional treatments of winter grazing were compared. Thistle control methods were applied in sub‐treatments for the first 2 years: cutting twice yearly, herbicide wiping, and cutting followed by herbicide application. Thistle abundance decreased under lenient grazing in spring, autumn and winter at the lowland site, under lenient spring and winter grazing in the uplands and under cattle compared with sheep grazing. Herbicide wiping was the most effective control measure and cutting the least, but effects of all weed control sub‐treatments were lost rapidly, so lenient grazing was sufficient to give long‐term thistle control. Lenient grazing and herbicide wiping also caused small declines in non‐target forb diversity. Control of creeping thistle can therefore be achieved without herbicides because lenient grazing in spring and autumn can decrease thistle populations to sufficiently low levels. Severe infestations can be more rapidly controlled using herbicides, but are better avoided at botanically diverse sites. Ecologically‐based weed control strategies have great potential, but require well designed field experiments, which run for sufficiently long periods to allow community‐level impacts to develop.     

Investigating phenotypic structures and allelochemical compounds of the fruits of Momordica charantia L. genotypes as sources of resistance against Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae)

Plant resistance is an important component of integrated management of the melon fruit fly, Bactrocera cucurbitae (Coquillett) owing to difficulties associated with its chemical control. Various biophysical traits including fruit length, fruit diameter, fruit toughness, number of the longitudinal ribs, height of the longitudinal ribs, number of small ridges, depth of small ridges and pericarp thickness, and biochemical traits including total chlorophyll, pH, tannin, flavanol, phenol, ash and silica contents of fruit were studied on six genotypes of bitter gourd (Momordica charantia L.) in relation to resistance against B. cucurbitae under field conditions in Pakistan. Faisalabad-long and Col-II were the most resistant whereas Chaman and Col-Vehari were the most susceptible among the tested genotypes. Fruit length, fruit diameter, number of the longitudinal ribs and number of small ridges had significant positive correlations whereas fruit toughness, depth of small ridges, height of the longitudinal ribs and pericarp thickness had significant negative correlations with the percent fruit infestation and larval density. Maximum variation in fruit infestation and larval density was explained by fruit toughness (63.4 and 49.2% respectively) followed by fruit diameter (23.2 and 22.4% respectively) and number of the longitudinal ribs (8.2 and 11.6% respectively) whereas the remainder of the physical traits explained <2.0% variation in fruit infestation. Total chlorophyll and pH were lowest in resistant and highest in susceptible genotypes whereas tannin, flavanol, phenol, ash and silica contents were highest in resistant and lowest in susceptible genotypes. Tannin and flavanol contents explained 96.5% of the total variation in fruit infestation and 97.7% of the total variation in larval density whereas rest of the biochemical traits explained <0.2% variation in fruit infestation.     

Resseliella sp. (Diptera: Cecidomyiidae) attacking field beans (Vicia faba L.)

In 1981 and 1982, the stems of Vicia faba in England were often infested by larvae of Resseliella sp. Attacks were widespread, most noticeable in June and July, and most frequent on winter beans, although the spring crop was also attacked. Larvae were associated with epidermal lesions, these usually being caused by Fusarium or Botrytis. It was concluded that attacks of the Cecidomyiid were secondary, exploiting existing injuries. Some insecticide treatments against Sitona lineatus also decreased infestation by Resseliella.     

Cultivation of milk thistle (Silybum marianum L. Gaertn.), a medicinal weed

Milk thistle (Silybum marianum L. Gaertn.) is the most researched plant for the treatment of liver disease. Its therapeutic properties are due to the presence of silymarin, a mixture of three flavonolignans (silybin, silydianin and silycristin). The seeds contain the highest amount of silymarin, but the whole plant is used medicinally. Milk thistle is grown successfully on a range of soil types, from sandy soils to much heavier clay soils. Milk thistle is directly seeded in soils. Sowing occurs in autumn and spring, and row spacing is usually 40-75 cm, with 20-30 cm between plants in the row. Nutrient requirements of this crop are low to moderate since it is adapted to poor quality soils and many different growing conditions. A limiting factor in milk thistle production is weed interference. Pendimethalin and metribuzin herbicides are safe for weed control in milk thistle, both alone and in combination. Milk thistle is considered drought resistant and normal rainfall will often suffice. In a Mediterranean environment, under severe drought conditions, the crops should be irrigated during seed growth and filling. Moreover, a few varieties of milk thistle have been developed. The silymarin content most often ranges from 1.0% to 3.0% of achene dry matter but can exceed 8%. Efforts should be made to develop varieties with high silymarin content.     

Rice striped stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), overwintering in super rice and its control using cultivation techniques

Super rice has the potential to deliver very high yields but is also susceptible to attack by the striped rice stem borer, Chilo suppressalis. In this study, surveys and field trials were performed to examine this problem and efficient ways were found to lower the borer’s population density. It was found that larger super rice plants provided more refuges for borers to evade insecticide contact and had a longer growth period allowing borers to complete their larval development in an intact environment. The current cultivation regime was shown to favour outbreaks of borers. Super rice is harvested leaving tall field stubbles until the following growing season, thus providing food and cover in which borers may successfully overwinter. We found that borer larvae were distributed to a greater height in the plants of super rice than in common rice, making control through agricultural operations more feasible. Burning fields after harvest, which killed 84.5% of borers, seemed the best remedy, though this practice is forbidden in China for ecological reasons. Leaving short stubbles followed by appropriate treatment of the rice straw killed 74.0% of the borer population. In addition, spring irrigation after the pre-pupation dispersal movements of borers killed more than half of the overwintering population. Pre-winter rotary tillage had little effect on borer numbers but enhanced the population reduction effect of irrigation the following spring. Based on the results obtained, efficient control of borers on super rice can be achieved by harvesting leaving short stubbles, followed by rotary tillage and spring irrigation. This regime can reduce the borer population by more than 98%, minimising chemical use and maximising use of a reduced agricultural workforce.     

Evaluation of seed treatment insecticides for management of the rice water weevil,Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), in commercial rice fields in Louisiana

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor^® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx^® Rice, Syngenta^® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside^®, Valent^® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.     

Body Size Plasticity of Weevil Larvae (Curculio davidi) (Coleoptera: Curculionidae) and Its Stoichiometric Relationship With Different Hosts

Parasites obtain energy and nutrients from the host, and their body size is also usually limited by host size. However, the regulatory mechanisms that control the plasticity of parasite body sizes and the stoichiometric relationships with their hosts remain unclear. Here we investigated the concentrations of 14 elements (C, H, O, N, P, S, K, Na, Ca, Mg, Al, Fe, Mn, and Zn) in the acorns of three oak species (Quercus spp.), in their endoparasitic weevil (Curculio davidi Fairmaire) (Coleoptera: Curculionidae) larvae and in the larval feces, and the weight of weevil larvae within different hosts in a warm-temperate zone of China. Our results showed that the three acorn species exhibited significant differences in C, H, O, P, K, Mg, and Mn concentrations. However, in the weevil larvae, only P, Mn, and C:P ratio revealed significant differences. Weevil larvae preferentially absorbed and retained N, Zn, Na, and P, whereas Mn, K, Ca, and O were passively absorbed and transported. The weevil larvae weight was associated with acorn stoichiometry, and positively correlated with acorn size. Weevil larvae P decreased, but Mn and C:P increased with their weight, implying highly variable in somatic stoichiometry are coupled with the plasticity of body size. Interestingly, weevil larvae weight was negatively correlated with acorn infection rate, indicating small-size parasitic insects might have higher fitness level in parasite–host systems than larger-size ones. Our results suggest that variation in P, Mn, and C:P in parasites may play critical roles in shaping their body size and in improving their fitness.     

Contributions of visual cues to cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), resistance in novel host genotypes

Herbivorous insects can demonstrate great selectivity among visual cues. The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) (syn. Ceutorhynchus assimilis (Paykull)) is also influenced by visual cues. Here, we present results of a study examining the attractiveness of flowers and foliage of Sinapis alba (a suboptimal host for larval development), Brassica napus (an excellent host for larval development) and novel lines derived from S. alba x B. napus; several of these have been demonstrated to be resistant in field and laboratory tests. Attractiveness, reflectance properties and resistance demonstrated in field trials were related. Responses to host plants differed among plant genotypes and were related to the amounts of UV and yellow reflected from flowers. Moderate UV reflectance greatly increased the attractive effects of yellow. Fewer weevils responded to test plants with greater or lesser floral UV reflectance.     

Efficacy of entomopathogenic nematodes (Nemata: Rhabditida) to control Brazilian apple leafroller Bonagota salubricola (Meyrick, 1937) (Lepidoptera: Tortricidae)

The Brazilian apple leafroller, Bonagota salubricola (Meyrick, 1937) (Bonagota cranaodes) (Lepidoptera: Tortricidae), is one of the main pest problems in apple orchards is Brazil. The purpose of this work was to evaluate B. salubricola larval and pupal susceptibility to different species of entomopathogenic nematodes, isolated in Rio Grande do Sul state in Brazil, under laboratory and field (apple orchard) conditions. Bioassays for isolates selection and determination of lethal concentration were performed in tubes of 1.5 ml (eppendorf), each containing one B. salubricola third instar larvae and filter paper. Field experiments were performed in commercial orchard, with application of 100 infecting juveniles (IJs)/cm² for each apple plant previously infected with five B. salubricola larvae covered with plastic trays containing thin cloth. Nematodes H. bacteriophora RS107 and H. bacteriophora RS57 had LC₅₀ of 13 and 4.5 IJs/larvae (4.3 and 1.5 IJs/cm²), respectively. In the field, H. bacteriophora RS107 and H. bacteriophora RS57, applied with sorbitol as an adjuvant, reached 70.2 and 61.1% larval mortality, respectively. The results showed that both isolates had biological activity against B. salubricola under laboratory and field conditions.     

Pest-damage relationships for Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on vegetative soybean

The response of vegetative soybean (Glycine max) to Helicoverpa armigera feeding was studied in irrigated field cages over three years in eastern Australia to determine the relationship between larval density and yield loss, and to develop economic injury levels. Rather than using artificial defoliation techniques, plants were infested with either eggs or larvae of H. armigera, and larvae allowed to feed until death or pupation. Larvae were counted and sized regularly and infestation intensity was calculated in Helicoverpa injury equivalent (HIE) units, where 1 HIE was the consumption of one larva from the start of the infestation period to pupation. In the two experiments where yield loss occurred, the upper threshold for zero yield loss was 7.51 ± 0.21 HIEs and 6.43 ± 1.08 HIEs respectively. In the third experiment, infestation intensity was lower and no loss of seed yield was detected up to 7.0 HIEs. The rate of yield loss/HIE beyond the zero yield loss threshold varied between Experiments 1 and 2 (−9.44 ± 0.80 g and −23.17 ± 3.18 g, respectively). H. armigera infestation also affected plant height and various yield components (including pod and seed numbers and seeds/pod) but did not affect seed size in any experiment. Leaf area loss of plants averaged 841 and 1025 cm²/larva in the two experiments compared to 214 and 302 cm²/larva for cohort larvae feeding on detached leaves at the same time, making clear that artificial defoliation techniques are unsuitable for determining H. armigera economic injury levels on vegetative soybean. Analysis of canopy leaf area and pod profiles indicated that leaf and pod loss occurred from the top of the plant downwards. However, there was an increase in pod numbers closer to the ground at higher pest densities as the plant attempted to compensate for damage. Defoliation at the damage threshold was 18.6 and 28.0% in Experiments 1 and 2, indicating that yield loss from H. armigera feeding occurred at much lower levels of defoliation than previously indicated by artificial defoliation studies. Based on these results, the economic injury level for H. armigera on vegetative soybean is approximately 7.3 HIEs/row-metre in 91 cm rows or 8.0 HIEs/m².     

Path analysis: a novel approach to determine the contribution of nematode damage to East African Highland banana (Musa spp., AAA) yield loss under two crop management practices in Uganda

Damage caused by plant-parasitic nematodes on East Africa Highland banana cultivar Mbwazirume was evaluated at Sendusu, Central Uganda. Banana plots were either nematode-infested or non-infested and received either continuous heavy mulch or were finger millet (Eleusine coracana) inter-cropped. An infestation with banana weevil, Cosmopolites sordidus, occurred naturally. Suckers detached from third crop cycle harvested plants were indexed for root and corm damage. Nematodes were extracted from the indexed roots. Banana weevil damage was observed in a cross-section through the corm of the harvested plant. Relationships between root damage, corm damage and nematode population densities were examined using correlation analyses. Path analysis was used to establish their relative effects on bunch weight. Independent of the type of crop management, percentage root necrosis, percentage dead roots, Radopholus similis and Helicotylenchus multicinctus population densities were each negatively correlated with bunch weight. Banana weevil damage and Pratylenchus goodeyi population densities were not correlated with bunch weight (P≤0.05). Path analysis revealed that root necrosis under heavy mulching and dead roots under finger millet inter-crop were the major factors associated with reduced bunch weight. Independent of the type of crop management, path analysis demonstrated that R. similis and then H. multicinctus contributed most, and to a lesser extent P. goodeyi, to root necrosis and dead roots. C. sordidus damage to the inner or outer corm appeared not to affect bunch weight.     

Wild safflower species (Carthamus oxyacanthus): A possible source of resistance to the safflower fly (Acanthiophilus helianthi)

Safflower (Carthamus tinctorius L.) is an important oil seed crop with growing importance in many countries around the world. However, safflower fly (Acanthiophilus helianthi Rossi) is one of the main limiting factors to expand the production area of the crop in several countries. Since host plant-resistance is the most efficient method for pest management, we evaluated a germplasm of wild accessions (Carthamus oxyacanthus Bieb.) with mostly brown–black seed coat color along with some white-seeded cultivated safflower genotypes for resistance to safflower fly. The results showed that there was a significant difference between two species for safflower fly damage with all cultivated genotypes being susceptible. However, for the accessions of C. oxyacanthus, a wide range of resistance was observed. In a choice experiment and natural infestation, 35.3–78.9 percent of heads per plant were infested in genotypes of C. tinctorius while for the accessions of C. oxyacanthus this was much smaller and ranged from 1.6 to 13.6%. In addition, percentage of seed yield loss per infested plant was more drastic in cultivated safflower (29.0–72.8%) than the wild accessions (0.0–21.4%). In the no-choice experiment, fly population was dramatically decreased in the wild accessions due to larval mortality and possibility of antibiosis. There was a strong relationship between brown–black seed coat color and resistance to safflower fly indicating the possibility of using this trait in breeding programs of safflower to develop fly-resistant cultivars.     

Portable acoustic device for detection of coconut palms infested by Rynchophorus ferrugineus (Coleoptera: Curculionidae)

Acoustic methods have been developed and used to detect insects in concealed habitats. The larvae of red palm weevil, Rynchophorus ferrugineus (Olivier), a serious pest of the coconut palm, Cocos nucifera L. feed on the soft tissues inside the stem and bud region. Detection of infested coconut palms in the early stages by the conventional method of checking for external symptoms is time consuming, labour intensive and costly. This paper describes the development of a portable and efficient acoustic device and its potential in detection of infested palms in the field. The device comprises a sensor to mount on the palm and to acquire the sounds of red palm weevil larvae, an electronic unit that processes the acquired sounds and a set of headphones to receive the output sound by the listener. It is light weight, user-friendly and powered by batteries. The highest accuracy of identifying infested palms was obtained when the palm was checked at four positions; either side of palm base and bases of the two lowermost leaves. The infested palms were detected with over 97% accuracy, while the probability of not detecting uninfested palms was over 92%. A second check increased the rate of accuracy. Many difficulties encountered with conventional methods could be overcome by the use of this device.     

Variation in C:N:S Stoichiometry and Nutrient Storage Related to Body Size in a Holometabolous Insect (Curculio davidi) (Coleoptera: Curculionidae) Larva

Body size can be an important factor controlling consumer stoichiometry. In holometabolous insects, body size is typically associated with nutrient storage. Consumer stoichiometry is known to vary within species across a range of body sizes; however, the contribution of nutrient storage to this variation is not well understood. We used the fifth-instar larvae of the oak weevil (Coleoptera: Curculio davidi Fairmaire), which is characterized by a high capacity for nutrient storage, to investigate the effect of shifts in nutrient storage with body mass on variations in larva stoichiometry. Our results showed that weevil larvae with larger body mass had a lower carbon (C) content, reflecting decreases in the sequestration rate of C-rich lipids. Larger larvae had elevated concentrations of nitrogen (N), sulfur (S), and protein. The similar patterns of variation in elemental composition and macromolecule storage with body weight indicate that the shift in nutrient storage is the main factor causing the variation in larval stoichiometry with body weight. This finding was further supported by the low variation in residual larval biomass C, N, and S concentrations after lipid extraction. These results help decipher the physiological mechanism of stoichiometric regulation in growing organisms.     

Evidence of genetic transmission of antibiosis and antixenosis resistance of sorghum to the spotted stemborer, Chilo partellus (Lepidoptera: Pyralidae)

Spotted stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), is the most important pest of sorghum in Asia and south and eastern Africa. Host plant resistance is an important control tactic for controlling this pest. Two breeding lines 27B × PB 15881-3 and 463B × PB 15881-3 with their parents, resistant and susceptible genotypes were evaluated in the field, glasshouse and laboratory for different resistance parameters. Breeding lines and genotypes varied significantly in foliar damage ratings, percentage of stem length tunneled, percentage of plants with deadhearts, larval survival, larval and pupal weights, larval and pupal duration, and percentage pupation and adult emergence in diets amended with leaf powder of different sorghum genotypes. The breeding lines 27B × PB 15881-3 and 463B × PB 15881-3 showed antixenosis and antibiosis to C. partellus in terms of reduced eggs per plant, larval survival and development. The levels of antixenosis and antibiosis of both breeding lines were similar to their resistant parents. Results indicate that transmission of characteristics responsible for resistance to the progeny from the resistant parent occurred.     

Cereal leaf beetle (Oulema melanopus (L.)) population densities and winter wheat yields

Grain yields of a soft white winter wheat cultivar, cv. Ionia, susceptible to cereal leaf beetle (Oulema melanopus (L.)), were determined when the crop was subjected to four controlled infestation levels of the beetle in caged plots over a 3-year period in Michigan. Although identical infestation procedures and insect numbers were used each year, the intensity of larval infestation and feeding damage varied with the year. Significant (P < 0·01) grain losses occurred in plots that had at least 9·0 larvae per stem. The greatest yield loss was 45% and occurred with 15 larvae per stem and 85% feeding damage. Beetle damage had a greater effect on kernel weight than on the other yield components. Although economic thresholds should be conservative to allow for environmental variations, it appears that soft white winter wheat can often withstand beetle infestation levels greater than the current economic threshold of three or more eggs and largae per stem before the boot stage or one or more large larvae per flag leaf during heading.     

First Report of Potato Psyllids, Bactericera cockerelli, Overwintering in the Pacific Northwest

Potato psyllids became a topic of interest at the end of the 2011 growing season in the Pacific Northwest when they were first documented to transmit ‘Candidatus Liberibacter solanacearum,’ the putative pathogen causing zebra chip disease in the region. Zebra Chip is characterized by above and below ground symptoms that cause significant yield loss. For many decades it has been unclear whether the potato psyllid migrates to states in the Pacific Northwest from large, well-documented infestation areas in California or Texas. Thus, we conducted a study in the spring of 2012 in the lower Columbia Basin (north east Oregon and south east Washington state), and in the fall, winter, and spring of 2012 in southwestern Idaho to determine if psyllids could be found overwintering. Potato psyllid was observed in November 2011 in southwestern Idaho and March 2012 in the lower Columbia Basin living on Solanum dulcamara L. (i.e., bittersweet nightshade), a perennial weed of wet habitats and riverbanks. Potato psyllids were collected and brought to the laboratory. Emerging adults from both locations (i.e., Columbia Basin and Idaho) were offered potato plants and they completed a second generation in approximately 15 days under similar environmental conditions. While overwinter survival of the potato psyllid in the Pacific Northwest is concerning for the potato industry, weather trends in the region were mild during the winter of 2012. It is unknown whether a colder or longer winter season would affect the overwintering biology we have observed. Observations through several coming winters are warranted.