Influence of host plant odours on invasion of the rice leaf bug Trigonotylus caelestialium into paddy fields

• 1 The host‐odour preferences of the rice leaf bug Trigonotylus caelestialium between the rice plant Oryza sativa L. and four species of graminaceous weeds, Poa annua, Alopecurus aequalis, Digitaria ciliaris and Eleusine indica, were investigated with an olfactometer aiming to clarify the influence of these odours on invasion of the bug to paddy fields at the flowering stage of rice.
• 2 Both female and male adults significantly preferred the graminaceous weed A. aequalis in the flowering stage to rice in the fifth‐leaf stage. The bugs also significantly preferred flowering P. annua and A. aequalis to rice in the panicle‐formation stage. However, the bugs showed no preferences between rice in the flowering and grain‐filling stages and the flowering graminaceous weeds P. annua, D. ciliaris and E. indica.
• 3 The preference of the rice leaf bug for the flowering graminaceous weeds before rice flowering coincides with the fact that these bugs mainly live on these weeds before rice flowering. It is considered that the bug's similar preference for flowering rice panicles as the flowering graminaceous weeds causes the intense invasion of the bug into paddy fields at this rice developmental stage.

     

Resistance to the rice leaf bug, Trigonotylus caelestialium, is conferred by Neotyphodium endophyte infection of perennial ryegrass, Lolium perenne

Neotyphodium fungal endophytes form mutualistic symbiotic associations with many grasses of the subfamily Pooideae, including important forage and turfgrass species. This relationship provides a competitive advantage to the host plant by increasing abiotic/biotic stress tolerance, such as its resistance to drought, diseases, and insect pests. The insect deterrent effects of endophytes are now receiving attention in Japan, as insect pests growing in meadows are causing problems in adjacent rice paddies. One of the most serious problems is the kernel spotting of rice grains caused by the rice leaf bug, Trigonotylus caelestialium Kirkaldy (Heteroptera: Miridae), which reproduces on Lolium species grown as forage. To determine the potential of Neotyphodium endophytes to reduce the invasion of rice crops by T. caelestialium from adjacent Lolium crops, we carried out choice and no‐choice feeding tests using endophyte‐infected and endophyte‐free clonal perennial ryegrass (Lolium perenne L.) (Poaceae). Our experiments revealed that the presence of the Neotyphodium endophyte strongly deterred the feeding of both first‐instar larvae and adults of T. caelestialium. These results show the potential of Neotyphodium endophytes to reduce the number of T. caelestialium in forage fields and grasslands, and thus to reduce the damage to rice grains caused by this insect pest.     

Fungal loline alkaloids in grass–endophyte associations confer resistance to the rice leaf bug, Trigonotylus caelestialium

Plant symbiotic fungi (endophytes) of the genus Neotyphodium [anamorphs, asexual derivatives of Epichloë (Ascomycota: Clavicipitaceae)] often associate with grass species of the subfamily Pooideae, which includes important forage and turf species. These endophytes are known to produce a range of alkaloids that enhance their host's resistance to insects or are toxic to grazing animals. Among the alkaloids, loline alkaloids (saturated 1‐aminopyrrolizidines) are generally observed in the highest concentrations in many Neotyphodium–grass symbiotic associations, and are known to be toxic to insects but not to mammals. Some Neotyphodium‐infected grasses have enhanced resistance to rice leaf bug, Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae), one of the major pests for rice production in Japan. Our laboratory experiments quantified the effects of purified loline (N‐formylloline) and in planta synthesis of loline alkaloids by meadow fescue [Lolium pratense (Huds.) S.J. Darbyshire (syn. Festuca pratensis Huds.)]–Neotyphodium uncinatum (Gams, Petrini & Schmidt) Glenn, Bacon & Hanlin and Italian ryegrass (Lolium multiflorum Lam.)–Neotyphodium occultans Moon, Scott & Christensen associations on the development and survival of T. caelestialium. No‐choice feeding assays with laboratory populations of the insect revealed that their growth was significantly decreased by the infected grasses, and the effect was greater for N. uncinatum than for N. occultans, in keeping with differences in N‐formylloline concentrations in the plants. Artificial feeding of N‐formylloline through feeding sachets indicated that the chemical has an adverse effect on survival of larvae, even at the lowest concentration tested (50 µg/g), which was considerably lower than the typical concentrations in many Neotyphodium–grass associations. The results confirmed the ability of Neotyphodium‐infected forage grasses to control T. caelestialium propagation in meadows, which may cause damages to nearby rice paddies.     

Reduction in the attraction of males to females after mating in the rice leaf bug Trigonotylus caelestialium

The influence of mating on the extent to which males are attracted to females in Trigonotylus caelestialium (Heteroptera: Miridae) was examined. No differences in attraction of males to mated and virgin females were observed within 3–5 h of mating, but males became less attracted to females 1 to 2 days after the first mating. The difference in male attraction to mated vs virgin females disappeared at 4 days after mating. These results indicate that reduced attraction of males to mated females occurs after a certain time interval, and persists for a few days. Furthermore, males were less attracted to females that had mated with virgin vs recently mated males, i.e. males that had just mated with another female at 1 and 2 days after mating. The ejaculate expenditure of recently mated males was less than that of virgin males. Hence, the amount of male ejaculate transferred to females during mating, rather than the act of mating, might influence the attraction of males to females. The results demonstrate that mating reduces the attraction of males to females in T. caelestialium on the basis of direct observation of male behavior.     

Effects of male mating interval on spermatophore formation,transfer, and subsequent female receptivity and fecundity in the sorghum plant bug,Stenotus rubrovittatus

Males of the sorghum plant bug, Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae), transfer a spermatophore to females during copulation. After a 1‐day interval between the first and second copulation, males transferred both sperm and a spermatophore to females during the second copulation. However, when male mating interval was <1 h, they transferred sperm but no spermatophores to females during the second copulation. Therefore, the male mating interval probably produces two types of mated females, those with and those without a spermatophore. Mated females of S. rubrovittatus do not remate for at least 3 days after mating, even when courted, and lay more eggs than virgin females at the beginning of the oviposition period. The effects of spermatophores on female sexual receptivity and fecundity were examined using mated females with or without a spermatophore. Only one of the 40 (2.5%) mated females with a spermatophore remated, whereas 10 of the 26 (38.5%) without a spermatophore remated. Furthermore, mated females with a spermatophore laid more eggs than those without a spermatophore. These results suggest that spermatophores participate in reducing female sexual receptivity and enhancing female fecundity in S. rubrovittatus.     

Spatio-temporal variation of natural and sexual selection in breeding populations of the coreid bug,Colpula lativentris (Heteroptera: Coreidae)

Spatio-temporal variations of lifetime reproductive succes (LRS) of both male and female individuals of a coreid bugColpula lativentris were measured and analyzed using the multiple regression method of Arnold and Wade (1984a, b). The standardized variance of LRS was larger in males than that in females as males often to secure mates for a long period whereas females could easily find mates and oviposit simply dependent on ovarial maturation. LRS was partitioned into 4 consecutive fitness components: (1) reproductive lifespan, (2) copulating efficiency, (3) guarding efficiency (for males) or oviposition efficiency (for females), and (4) number of eggs per clutch. In males copulating efficiency was the largest determining factor of LRS, whereas in females reproductive lifespan was the most important factor. Such tendencies were stable on both a yearly and local basis. Patterns of relative contribution of natural selection (reproductive lifespan and number of eggs per clutch) and sexual selection (copulating efficiency and guarding or oviposition efficiency) to LRS were clearly different between males and females. This sexual difference is, at least to some extent, thought to be brought about by sexual selection among males for mating opportunity, though no physical fight was observed among males. Directional selection on body length was found only in relation to the clutch size of females because large females tended to lay larger clutches. No significant directional selection was found in other fitness components.     

Interpopulation variation of hibernal-aestival-diapause in the egg parasitoid wasp Anagrus takeyanus: adaptation to seasonal host-plant alternation of the tingid host, Stephanitis takeyai

The egg parasitoid wasp, Anagrus takeyanus Gordh & Dunbar (Hymenoptera: Mymaridae), is one of the few natural enemies of the andromeda lace bug, Stephanitis takeyai Drake & Maa (Heteroptera: Tingidae). Studying this wasp in two habitats, I found that at Kyoto, where the bug alternates its host plants seasonally, most wasp individuals in the overwintering eggs of the bug entered summer diapause immediately after winter diapause. However, at Nara, where the bug does not alternate its host plant, the wasp proved to have no summer diapause. Changes in the parasitization rate between generations differed at the two study sites. In Kyoto, the overwintered generation suffered the highest parasitism among the three generations of the year. In contrast, the first and second generations suffered higher parasitization rates in Nara. This difference in level of parasitization between the two study sites corresponded to the different diapause regime of the wasp and the seasonal population trends of the lace bug. Laboratory experiments showed that short photoperiod in combination with low temperature could terminate the long diapause at the time the non-aestivating individuals terminate winter diapause. As a life cycle without host plant alternation is likely to be an ancestral character of the bug, the aestivation of the wasp is thought to have been appended to overwintering as an adaptation to the evolution of seasonal host plant alternation in the lace bug.     

Effects of seasonal variation in host quality and availability on parasitism by the egg parasitoid Telenomus coloradensis

Hemlock looper, Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), is one of the most important defoliator in North American forests. The common egg parasitoid Telenomus coloradensis Crawford (Hymenoptera: Platygastridae) plays a significant role as a natural control agent, with parasitism levels in spring typically higher than in fall. The objectives of this study were to quantify changes in host acceptance and reproductive performance of the parasitoid in relation to (1) host egg fertilization in fall, (2) host diapause status, (3) host embryonic development in spring, and (4) host deprivation during summer. Our results indicate that T. coloradensis do not have the capacity to develop in unfertilized host eggs, whereas early‐diapausing eggs are more suitable for the parasitoid than post‐diapausing eggs. Furthermore, the host physiological suitability decreases with embryonic development in spring. Finally, a host deprivation period during the summer tends to negatively affect the parasitic activity of T. coloradensis. These laboratory results confirm previous hypotheses concerning T. coloradensis seasonal ecology and contribute to a better understanding of the effect of hemlock looper egg physiology and availability on the reproductive potential of T. coloradensis.     

Effect of diapause status and gender on activity,metabolism, and starvation resistance in the plant bug Lygus hesperus

Lygus hesperus Knight (Hemiptera: Miridae), a key pest species distributed throughout the western USA, survives winter in a state of diapause. A laboratory population was examined to elucidate the changes in behavior and physiology linked to this period of dormancy and to determine how these changes are affected by gender. It was found that under starvation conditions, diapausers lived significantly longer compared to non‐diapausers in both genders. This may be attributable to the greater lipid reserves that diapausers have compared to non‐diapausers. Diapausers also spent more time at rest and less time feeding than non‐diapausers. Gender did not impact these behaviors. There was no difference in resting metabolic rate or flight activity between diapausers and non‐diapausers, however, there were significant gender differences when the data were pooled. Males had higher resting metabolisms than females, whereas females spent more time flying. Collectively, these results point toward a higher degree of resource conservation in diapausers. These differences may enhance resistance to starvation and dehydration conditions that L. hesperus are likely to encounter while overwintering.     

Effect of variation in photoperiodic response on diapause induction and developmental time in the willow leaf beetle, Plagiodera versicolora

The willow leaf beetle, Plagiodera versicolora (Coleoptera: Chrysomelidae) overwinters in adult diapause. In this study, the photoperiodic responses for diapause induction and developmental time were examined in the Ishikari (Hokkaido, Japan) population of P. versicolora. All females entered reproductive diapause under short daylength (L10:D14), but 31.7% of females did not enter diapause under long daylength (L16:D8). The developmental time from oviposition to adult emergence was significantly longer at L10:D14 than that at L16:D8. Norm of reaction curves illustrated variation among families in the photoperiodic responses for diapause induction and for developmental time. ANOVA indicated significant family × photoperiod interactions in the developmental time. At L16:D8, developmental time was positively correlated with the incidence of diapause in females. This means that a female having a longer developmental time tends to have a longer critical photoperiod. Such variation may be maintained by differences in selection pressures on the growth rate and the critical photoperiod for diapause induction between univoltine and bivoltine genotypes because Ishikari is located in a transitional area between populations with univoltine and bivoltine life cycles.     

寄主植物与温度对大豆食心虫滞育期间糖类和脂质含量的影响

【目的】本文探究了大豆食心虫Leguminirora glycinioorella(Mats.)Obraztsov进入滞育以后体内糖类、脂质和水分含量的变化,以及不同寄主植物和滞育诱导期温度对大豆食心虫体内糖类、脂质和水分含量的影响。【方法】通过蒽酮硫酸法和氯仿甲醇分离法测定了滞育前后、以大豆Glycine max(L.)Merr和野大豆Glycine soja Sieb.et Zucc.两种植物为寄主以及不同滞育诱导温度下的大豆食心虫体内脂质、水分、总糖、糖原和海藻糖的含量,结果利用SPSS17.0数据分析软件进行分析。【结果】进入滞育阶段的大豆食心虫体内脂质、总糖、海藻糖和糖原含量显著增加,含水量显著下降。以大豆为寄主的大豆食心虫在滞育阶段体内水分含量、总糖和糖原含量较野大豆寄主的高,海藻糖含量较野大豆的低,差异均显著。不同滞育诱导温度下的大豆食心虫体内生化物质含量基本一致。【结论】滞育前后大豆食心虫体内各种生化物质变化明显,以栽培大豆为寄主和以野大豆为寄主的大豆食心虫体内生化物质含量不同,而滞育诱导温度对大豆食心虫体内生化物质含量影响不大。     

Effect of land use types on stream water quality under seasonal variation and topographic characteristics in the Wei River basin,China

The effect of topographic characteristics of land uses on stream water quality must be addressed for a better understanding of the complex relationship between land use and stream water quality. In this study, Geographic Information System (GIS) and Pearson correlation analysis were used to determine whether there were relationship between land use types and stream water quality at the sub-basin scale in the Wei River basin, China, during the dry and rainy seasons in 2012. Temporal variation of these relations was observed, indicating that the relationships between water quality variables and different land uses were weaker in rainy seasons than that in dry seasons. Compared with other land uses, agriculture and urban lands had a stronger relationship with water quality variables in both rainy and dry seasons. Topographic characteristics of land use were employed to further analyze these relationships. The results showed that seasonal variation also occurred in the complex relationship, and land uses in steeper slopes generally had a stronger influence on stream water quality than those in flatter ones. For the riparian zone of each sampling site, the slope coefficients were weaker than those at the sub-basin scale. Land use type near stream water was generally a better indicator for the effectiveness of water quality. These results suggest that the slope and proximity should be taken into account for better land use management.     

Effects of genotype variation in the cultivated rice species on the biology and galling characteristics of the African rice gall midge,Orseolia oryzivora (Diptera: Cecidomyiidae)

This study assessed the effects of genotype variations in two cultivated rice species: Oryza glaberrima and Oryza sativa on the biology and galling characteristics of the African rice gall midge (AfRGM), Orseolia oryzivora Harris and Gagné. The study was conducted in the screen house at ambient temperature (27 ± 3°C), 70 ± 5% relative humidity and 12:12 h photoperiod. Shoot galling, the most visible response of rice genotypes to attack by the insect, was greatly suppressed, being only 0.7 cm long in the O. glaberrima genotypes compared to 34 cm in the O. sativa species. Larval mortality (70–88%) in the O. glaberrima genotypes was significantly higher at the first instar compared to O. sativa. Gall setting was confirmed to be an irredeemable tiller loss. Even in the susceptible O. sativa genotypes, where many larvae may colonize a tiller, only one survived to the second instar. Resistant and susceptible rice genotypes had significantly different effects on the development and reproductive anatomy of the AfRGM. The female reproductive anatomy which consists of two ovaries, each with a potential complement of 192 eggs was affected by interspecific variation in rice genotypes causing reduced potential fecundity (32); morphological distortion, 60% reduction of egg size of F1 emergent in O. glaberrima compared to emergent from the susceptible O. sativa genotypes.     

基于稳定同位素技术的海州湾海洋牧场食物网基础及营养结构的季节性变化

基于稳定同位素技术对2015年春季海州湾海洋牧场海域采集的中小型生物消费者,包括鱼类、虾类、蟹类、头足类、螺类和双壳类等与其潜在碳源样品进行分析,利用IsoSource模型计算该海域消费者碳源贡献率,并对2014年夏季生物学样品与2015年春季样品比较,分析食物网营养结构的季节性变化,根据稳定同位素测定结果绘制二维双标图,计算出6种营养结构的量化指标.结果表明: 2015年春季海州湾海洋牧场海域消费者的δ¹³C值范围为-18.9‰～-17.1‰,3种潜在碳源[浮游植物、悬浮颗粒有机物(POM)、沉积物(SOM)]的δ¹³C值范围为-18.1‰～-23.4‰,根据模型计算得出浮游植物对消费者的平均碳源贡献最大,为80.8%,其余依次为SOM和POM,分别为10.8%和8.4%.2014年夏季生物样品与2015年春季样品的δ¹³C值存在显著差异,而δ¹⁵N值无显著性差异;6种量化指标表明群落营养结构存在季节性差异, 2014年夏季的δ¹³C比值范围(CR)、总面积(TA)、平均最邻近距离(NND)和平均最邻近距离标准差(SDNND)均大于2015年春季,δ¹⁵N比值范围(NR)和平均离心距离(CD)无明显变化,夏季群落营养结构冗余度小于春季,且食源多样性水平高于春季,存在季节差异.     

Effect of the inclusion of food waste in pig diets on growth performance, carcass and meat quality

Food waste from fish and fruit shops was used as an alternative to the grain in grower-finisher pig diets. Two diets were formulated on an iso-nutrient basis (14 MJ digestible energy per kg, 160 g crude protein per kg on a dry-matter basis) to contain 0 g of food waste per kg in the control diet and 50 g of fish-shop waste per kg and 120 g of fruit-shop waste per kg in the experimental diet. In the study, 28 pigs per diet (seven pigs per pen) were fed ad libitum from 20 kg to 100 kg, then, they were slaughtered and the carcass characteristics determined. The inclusion of food waste in the diet had no significant effect (P>0.05) on average daily feed intake (2.12 v. 2.20 kg/day), average daily gain (0.74 v. 0.78 kg/day), or gain/feed (0.35 v. 0.35 kg per kg). In the case of the experimental diet, backfat thickness was significantly lower (18.0 v. 21.3 mm, P < 0.01). The results of the taste test indicated that the meat from food waste-fed pigs had acceptable organoleptic quality although a very light aroma to fish was observed in the bacon (P < 0.01).It was concluded that food waste from the fish and fruit shops could be included in grower-finisher pig diets without any detrimental effect on growth performance and only minor effects on carcass characteristics and meat quality.     

Effect of host plant resistance and chemical control of the head bug, Calocoris angustatus Leth., on grain quality and seedling establishment in sorghum

The sorghum head bug, Calocoris angustatus Lethiery (Hemiptera: Miridae), is one of the most important pests of grain sorghum in India. Studies were conducted to quantify the effect of head bug damage on grain quality and seedling establishment on head bug-resistant cultivars (IS 17610 and IS 21443), a moderately susceptible cultivar (IS 9692), and a susceptible commercial cultivar (CSH 11). Differences in 1000-grain mass, seed germination and percentage of floaters were significant between protected and unprotected plots in CSH 11 and IS 9692, but not in IS 17610 and IS 21443. Grain damage ratings were significantly lower in IS 17610 than in IS 9692 and CSH 11 across different protection levels. Head bug-damaged grain had greater protein content than the undamaged grain, possibly because of depletion in starch, and a marginal increase in soluble sugars. Amounts of proline and tyrosine were greater in the bug-damaged grain than in the undamaged grain, while the reverse was true for aspartic acid, methionine, leucine and lysine. Head bug damage also increased the tannin content in IS 9692 (which is a high-tannin genotype). Moisture regimes and insecticide protection levels significantly affected seedling emergence. Seedling emergence of CSH 11 was lower than that in IS 17610. In the latter genotype, the differences between protected and unprotected plots were not significant. Head bug damage thus not only leads to quantitative loss in grain yield, but also spoils the grain quality and renders the grain unfit for seed purposes. These qualitative effects should be taken into account while estimating losses due to bug damage and determining economic thresholds.     

Effect and design of buffer zones in the Nordic climate: The influence of width, amount of surface runoff, seasonal variation and vegetation type on retention efficiency for nutrient and particle runoff

Loss of nutrients and sediments from agricultural runoff causes eutrophication in surface water. Vegetated buffer zones adjacent to a stream can effectively remove and retain nutrients and sediments. It is, therefore, important to study design criteria which optimise the effect of buffer zones (BZ). This paper describes the influence of four criteria: (i) buffer zone width, (ii) amount of surface runoff water entering the BZ, (iii) seasonal variation and (iv) vegetation type. These parameters were studied after simulated and natural runoff at four different sites in Southern Norway with cold temperate climate. Surface runoff was collected before entering and after passing the BZs. The simulation experiments were short-term experiments carried out over a few days in 1992 and 1993. In the natural runoff experiments, volume proportional mixed samples were collected after each runoff period during 1992–1999. The results show significantly higher removal efficiency (in %) from 10 m wide BZs compared to 5 m widths, however, the specific retention (per m²) is higher in 5 m BZ. Buffer zones can receive particle runoff over several days without a significant decrease in their removal level. Retention efficiency between summer and autumn varied depending on the measured parameter (phosphorus, particles and nitrogen), and there were no significant differences in removal efficiency between summer and winter. The results show no significant differences between forest buffer zones (FBZ) and grass buffer zones (GBZ) regarding their retention efficiency for nitrogen and phosphorus. There was significantly higher retention efficiency in FBZ for particles. Average removal efficiencies from both simulated and natural runoff experiments varied from 60–89%, 37–81% and 81–91% for phosphorus, nitrogen and particles, respectively.