Fruits of apple and sweet persimmon are not essential food sources for Riptortus pedestris (Hemiptera: Alydidae) which causes fruit-spotting

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) has recently become an important fruit-spotting bug of apple and sweet persimmon trees in Korea. Although fruits of cultivated species are unsuitable food for some fruit-spotting bugs, the dietary importance of fruits of apple and sweet persimmon for R. pedestris is unknown. We evaluated harvested fruits of apple and sweet persimmon with or without soybean seeds as a food source for R. pedestris by investigating nymphal development time, immature mortality, preovipositional period, fecundity, and adult size in the laboratory. No first instars of R. pedestris that were fed only apple or sweet persimmon fruits became third instar nymphs. When supplemented with soybean seeds, both fruits supported nymphal development and reproduction of R. pedestris. However, fruits combined with soybean seeds were not a better diet than soybean seeds only. Therefore, apples and sweet persimmons are not essential food sources for the development and the reproduction of R. pedestris. These results suggest that R. pedestris may not reproduce on fruit trees, thus explaining the absence of eggs and nymphs of this bug on fruit trees in orchards. Management of nearby vegetation of fruit orchards would be important for reducing damage by adult R. pedestris.     

Evaluation of three plant seeds as potential pre-season diets for Riptortus pedestris

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a polyphagous pest causing serious economic damage especially in soybean (Glycine max L.). R. pedestris start to emerge earlier in spring when reproduction is not possible due to scarcity of nutritious food sources, thus host exploitation pattern is not well known. In order to understand the patterns of seasonal occurrence and how it relates to suitability of host plants in the spring, we evaluated the seeds of barley (Hordeum vulgare L.), sesame (Sesamum indicum L.), and black locust (Robinia pseudoacacia L.) as pre-season food sources for R. pedestris. A diet of soybean seed was also compared as a control. When nymphs fed sesame seeds only, R. pedestris never became third instars. Only 2.5 and 5% of R. pedestris fed on barley and barley + sesame, respectively, successfully became adults. Only when supplemented with soybean seeds could barley and sesame seeds support nymphal development and reproduction of R. pedestris. This indicates that neither barley nor sesame is adequate food sources for the development and the reproduction of R. pedestris even though they occur in those crop fields in spring and summer. However, seeds of black locust supported the complete development and reproduction of R. pedestris. Thus, black locust can be an additional leguminous host plant for R. pedestris during the period when suitable food sources are limited.     

Effects of combining releases of non-viable host eggs with insecticide application on Riptortus pedestris population and its egg parasitoids

Our previous study demonstrated that the release of refrigerated non-viable eggs of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) enhanced parasitism rates in soybean fields but did not result in the reduction of R. pedestris populations. This study was further conducted using an open-cage exclusion design in a soybean field in order to evaluate the compatibility of combining releases of non-viable host eggs with a single pre-harvest application of insecticide for the control of R. pedestris. Refrigerated eggs of R. pedestris were released twice in treatment plots, and fresh (< 1 day old) eggs of R. pedestris were deployed in all experimental arenas, every 6 days, for host resource and measurement of field parasitism. The releases of host eggs did not reduce the number of R. pedestris in any life stage except the adult stage on two sampling dates. However, parasitism by Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae) was higher in treated plots (9–25%) than in the control plots (1–9%). Statistical significant reduction was not found in the pest population, but parasitism rates significantly increased. Pesticide application did not reduce the bug population but did affect the parasitoids population. Pest management tactics, using both artificially deployed host eggs and insecticide, are discussed.     

Biological attributes of Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) reared on refrigerated eggs of Riptortus pedestris (= clavatus) Fabricius (Hemiptera: Alydidae)

Storing host eggs at low temperatures has been used to mass rear parasitoids of stink bugs, including Riptortus pedestris Fabricius (Hemiptera: Alydidae), a major soybean pest in Korea and Japan. However, no information on the effect of cold storage on parasitization by Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae), one of the major parasitoids of R. pedestris, has been published. In this study, we examined biological attributes, including parasitism rate, development time, sex ratio, adult size, and longevity, of O. nezarae when the adult parasitoids were provided with host eggs refrigerated for 0, 15, 30, 60, and 120 days at 2.0 °C. None of the attributes of the first or second generation of O. nezarae was negatively affected by host egg refrigeration up to 30 days. In addition, O. nezarae could parasitize refrigerated host eggs successfully for the first four days of post-refrigeration period when they were kept at 26.3 °C and 78.7% RH conditions. Therefore, refrigeration of R. pedestris eggs can be a good method to mass rear O. nezarae.     

Infestation of Riptortus pedestris (Fabricius) decreases the nutritional quality and germination potential of soybean seeds

The bean bug, Riptortus pedestris (Fabricius), is one of the major pests of soybean; this pest mainly feeds on soybean pods. Its population is highest when the soybean plants bear mature seeds. We aimed to determine the effect of bean bug infestation on soybean according to changes in nutrient levels and seed germination potential. Newly emerged adult males of R. pedestris (n = 5 per plant) were released into a meshed cage containing soybean plants at the R5 stage. Another meshed cage with soybean plants was treated as control. Healthy seeds harvested from control plants were selected and accounted as undamaged seeds and seeds from bug-released cages were visually categorized into 7 different classes according to the intensity of damage incurred due to bean bug infestation. The seeds were then compared in terms of changes in weight, protein, lipid, and carbohydrate content, and germination potential. Elevated protein levels were observed in seeds that showed a higher intensity of damage. On the other hand, the lipid and carbohydrate contents and germination potential were reduced in seeds showing a higher degree of damage. Germination potential in terms of lipid and carbohydrate loss caused by bug infestation is also discussed.     

cis-Jasmone indirect action on egg parasitoids (Hymenoptera: Scelionidae) and its application in biological control of soybean stink bugs (Hemiptera: Pentatomidae)

In many plants, the secondary metabolite cis-jasmone activates the metabolic pathway that produces volatile organic compounds attractive to natural enemies and, sometimes, repellent to herbivores. Previous studies indicate that the feeding damage caused by the herbivore Euschistus heros or the exogenous application of cis-jasmone in soybean plants induces the release of herbivore-induced plant volatiles (HIPVs) with a similar chemical profile and these compounds can attract the stink bug egg parasitoid Telenomus podisi (Scelionidae). Herein we tested in field conditions the effect of exogenous application of cis-jasmone in soybean plants on the parasitoid and stink bug community and on stink bug egg parasitism. In two areas, one within a soybean and another within a Crotalaria matrix, we randomly distributed 2 m² plots, with soybean plants induced (treatment, n = 5) or not induced by cis-jasmone (control, n = 5) in the field. We sampled the parasitoid community weekly with yellow sticky traps (n = 3/plot) and monitored parasitism with sentinel eggs of E. heros (n = 150/plot). We also monitored the population of stink bugs weekly, by sampling each plot with shake-cloth technique. The abundance of Scelionidae was highest overall and also in treated plots during the first four weeks in the area with a soybean matrix, but decreased thereafter. The richness of parasitoid families was similar between treatment and control plots in the area with a soybean matrix, but higher in control plots in the area with a Crotalaria matrix. Evenness was higher in control plots in the area with soybean matrix, whereas the reverse occurred in the area with a Crotalaria matrix. Results suggest that treatment with cis-jasmone effectively attracted and enhanced the population of scelionid parasitoids, but had no effect on the occurrence and intensity of parasitism and in the number of stink bugs.     

Evaluation of different leguminous seeds as food sources for the bean bug Riptortus pedestris

This study was conducted to determine the effects of six different leguminous seeds (cowpea, white kidney bean, soybean cultivars Cheongja and Daepung, mung bean, and azuki bean) on the life history traits of the bean bug Riptortus pedestris (F.) (Hemiptera: Alydidae). The total developmental time from the first instar nymph to adult ranged from 18 to 25 d; R. pedestris fed with white kidney beans were the slowest to develop. In addition, bugs fed with white kidney beans had the highest mortality (93%) and the shortest longevity (18 d). R. pedestris fed with cowpeas, soybeans, or azuki beans had high reproductive success, with the highest egg hatching success recorded in bugs fed cowpeas. The results suggest that cowpea may be a beneficial food source for the development and reproduction of bean bugs.     

Lethal and sublethal effects of synthetic insecticides on the locomotory and feeding behavior of Riptortus pedestris (Hemiptera: Alydidae) under laboratory conditions

The bean bug, Riptortus pedestris (Hemiptera: Alydidae) is a polyphagous insect pest and has a wide range of hosts including leguminous plants and tree fruits. Currently, the management of R. pedestris mainly relies on the use of insecticides, and most studies have focused on the lethal effects of insecticides. However, insecticides can not only kill insects directly, but can also affect behavioral changes of survivors when exposed to sub-lethal doses. In this study, we investigated locomotory behaviors (vertical movement, horizontal movement, and flight ability) and feeding behaviors (frequency of insects approaching dried soybean seeds and number of stylet sheaths left on the dried soybean seeds by insects) of surviving R. pedestris pre-exposed to five insecticide residues for 4 h. None of the three insecticides (bifenthrin, etofenprox, and acetamiprid) tested had significant effects on the locomotory behaviors of R. pedestris adults compared to the water-treated control group. Fenitrothion- and dinotefuran-treated groups showed a significant decrease in the vertical movement compared to the water-treated control, but the insects recovered mobility 24 h after the initial exposure. The frequency of R. pedestris approaching to dried soybean seeds was affected by four insecticides (fenitrothion, etofenprox, bifenthrin, and dinotefuran), but the actual feeding activity of R. pedestris determined by the stylet sheaths remaining on the dried soybean seed was only affected by fenitrothion treatment. Given the relatively low toxic effects of five insecticides tested, a better understanding of the impact of insecticides on the behavior of target species is needed for a more robust pest control strategy and a more effective use of insecticides in IPM programs.     

Attractiveness of conspecific stink bugs to adult stink bug-baited traps in soybean fields

The attractiveness of live adult stink bugs used as baits in traps in soybean fields, Milyang, Korea, to conspecific stink bugs was evaluated. Both sexes of bean bug, Riptortus pedestris Fabricius (Hemiptera: Alididae), and one-banded stink bug, Piezodorus hybneri Gmelin (Hemiptera: Pentatomidae), were attracted to conspecific male adults-baited traps. Likewise, both sexes of brown-marmorated stink bug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), and sole bug, Dolycoris baccarum L. (Hemiptera: Pentatomidae), were attracted to traps baited with conspecific male stink bugs. However, in Nezara antennata Scott (Hemiptera: Pentatomidae), both male and female used as baits in traps were attractive to conspecific adults. Accordingly, these results suggest that the only male adults of H. halys and D. baccarum and both sexes of N. antennata are attractive to conspecific male stink bugs.     

Ecotoxicological effect of insecticides on Ooencyrtus nezarae (Hymenoptera: Encyrtidae) reared from refrigerated and unrefrigerated Riptortus pedestris (Hemiptera: Alydidae) host

Due to increased field occurrence of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) on various crops including soybean, persimmon and apple in recent years in Korea, demand for insecticide applications to control the stink bug has increased. Acute toxicity of eight pesticides on Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae), a major egg parasitoid of R. pedestris, was compared in the laboratory. Fenitrothion, spinosad, cyfluthrin, etofenprox and carbosulfan caused 100% mortality of O. nezarae within 24 hours by topical application or exposure to residue. Fenitrothion was also highly toxic to the parasitoid when ingested orally. In a previous study, release of refrigerated inviable eggs of R. pedestris was found to increase field parasitism; therefore, we evaluated the sublethal effect of fenitrothion when O. nezarae parasitised refrigerated or unrefrigerated host eggs. Although parasitism rates on both kinds of eggs significantly decreased when O. nezarae were provided with host eggs sprayed with fenitrothion, no difference in parasitism rate, adult emergence, sex ratio, development time and longevity of O. nezarae was found between the refrigerated or unrefrigerated host eggs when the insecticide was treated either before or after oviposition. There was no significant sublethal effect when parasitised host eggs were treated with the insecticide. From these results, all the insecticides tested showed high, acute toxicity against O. nezarae with relatively lower sublethal effects. Refrigeration of host eggs did not affect the susceptibility of O. nezarae to insecticides.     

Effect of resistant and susceptible soybean cultivars on the attraction of egg parasitoids under field conditions

The association of resistant crop varieties and biological pest control has great potential for pest management, as resistant cultivars may affect herbivore population dynamics by interfering with their biology and search behaviour for host plants. In addition, resistant varieties can also affect the efficiency of natural enemies. The aims of this work were to evaluate the influence of the soybean cultivars Dowling (resistant), IAC 100 (resistant) and Silvânia (susceptible) under field conditions on: (i) the abundance of parasitoids in the Platygastridae family and the stink bug Euschistus heros and (ii) the parasitism of stink bug eggs by these natural enemies. There was no difference between cultivars in stink bug distribution in the field. The parasitoids Telenomus podisi, Trissolcus teretis, Tr. urichi and Tr. brochymenae emerged from the sentinel eggs of E. heros, and T. podisi was the most abundant species observed during the reproductive stage R6. The cultivars Dowling and IAC 100 attracted a higher number of Platygastridae parasitoids, T. podisi and Tr. teretis, and the abundance of these parasitoids during the period from R1 to R7 might have being sufficient to control the stink bug population. These results suggest that the cultivars Dowling and IAC 100 have important attributes that should be taken into account in the implementation and development of new cultivars in breeding programmes that aim to obtain plants more resistant to stink bugs and more attractive to natural enemies.     

Nutritional characterization of Mucuna pruriens: 3. Effect of replacing soybean meal with Mucuna on intake,digestibility, N balance and microbial protein synthesis in sheep

Mucuna pruriens seeds have relatively high crude protein (CP) concentrations, but little is known about their potential to replace commonly used CP supplements in ruminant rations. The aim of this experiment was to determine effects of replacing soybean meal (SB) with Mucuna on the performance of lambs. Forty Rambouillet lambs (33.2 ± 5.73 kg) fed a basal diet of maize grain, cottonseed hulls and urea were randomly assigned to one of four supplements formulated by substituting 0 (SB), 330 (Lo), 670 (Med) or 1000 g/kg (Hi) of soybean meal with rolled Mucuna seeds. Lambs were housed individually in metabolic crates and allowed ad libitum access to isocaloric (metabolizable energy=11.7 MJ/kg dry matter, DM) and isonitrogenous (CP = 146 g/kg, DM) diets for 14 d of adaptation and 7 d of total fecal collection. Fecal egg counts and coccidian oocyst scores were determined on d 14. Dry matter intake (1.7 kg/d versus 1.5 kg/d; P<0.05), CP digestibility (774 g/kg versus 714 g/kg DM; P<0.05) and N retention (28.0 g/d versus 20.4 g/d; P<0.01) were higher and amylase-pretreated neutral detergent fiber digestibility (617 g/kg versus 686 g/kg DM) was lower (P<0.05) in sheep fed SB versus Mucuna diets. However, supplementary protein source did not affect rumen pH, blood urea N or glucose concentration, or fecal egg counts. Increasing the level of Mucuna supplementation increased (P<0.05) level and efficiency of microbial protein synthesis, ruminal fluid acidity, total volatile fatty acid concentration, decreased (P<0.05) coccidian oocyst scores, and tended (P<0.10) to increase N retention. Therefore, SB is a better supplement than Mucuna to support performance of lambs. Nevertheless, Mucuna seeds are a promising CP supplement for situations where cost or availability precludes use of SB in ruminant rations.     

Biochemical characterization of digestive α-amylase, α-glucosidase and β-glucosidase in pistachio green stink bug,Brachynema germari Kolenati (Hemiptera: Pentatomidae)

The pistachio green stink bug, Brachynema germari, has 3–5 generations per year and causes severe damages to pistachio crops in Iran. Physiological digestive processes, such as digestive carbohydrases, can be used to design new strategies in IPM programs for controlling this pest. The enzyme α-amylase digests starch during the initial stage of digestion. Complete breakdown of carbohydrates takes place in the midgut where α- and β-glucosidic activities are highest. Alpha-amylase and α- and β-glucosidase activities were found in the midgut and salivary glands of pistachio green stink bug adults. Overall enzyme activities were significantly higher in the midgut than in salivary glands. The highest α-amylase and α- and β-glucosidase activities were in section v3, whereas the lowest activities were in section v4. V_max was higher and K_m was lower in the midgut than in the salivary glands for these enzymes. In the pistachio green stink bug, the optimal pH was pH 5–6.5 and the optimal temperature was 30 °C to 35 °C for these enzymes. Alpha-amylase activity in the midgut and salivary glands decreased as the concentrations of MgCl₂, EDTA and SDS increased. Enzyme activities in both midgut and salivary glands increased in the presence of NaCl, CaCl₂, and KCl. NaCl had a negative effect on alpha-amylase extracted from salivary glands.     

Population Dynamics of Dichelops melacanthus (Dallas) (Heteroptera: Pentatomidae) on Host Plants

The stink bug Dichelops melacanthus (Dallas) has become one of the major pests of corn and wheat in Brasil, mainly after a shift from the conventional tillage system to the no tillage cultivation system. This fact may be due to the simultaneous occurrence of second planting corn with wheat cultivation, and the presence of wild hosts. This study aimed to evaluate the population dynamics of D. melacanthus on wild hosts adjacent to areas cultivated with corn, wheat, and soybean during the season and off-season of soybean cultivation. Weekly surveys were conducted in the region of Londrina, PR, Brasil from the beginning of July 2007 up to the end of June 2008 using the square meter method. Corn (Zea mays), soybean (Glycine max), tropical spiderwort (Commelina benghalensis), hairy indigo (Indigofera hirsuta), crotalaria (Crotalaria pallida), wheat (Triticum aestivum), and signal grass (Brachiaria decumbens) were identified as hosts of D. melacanthus. Signal grass was the host in which stink bug adults were found in higher numbers, while nymphs and adults were consistently collected on tropical spiderwort. Although nymphs completed their development on tropical spiderwort seeds, this host was found less suitable than soybean seeds.     

Quality assessment of Riptortus pedestris (Hemiptera: Alydidae) eggs cold-stored at different temperature and relative humidity regime

Supplementation of host resource can be more economical method for the biological control of insect pest compared to direct release of adult parasitoids. Periodical release of non-viable cold-stored eggs of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) has been found to enhance parasitism of this pest in soybean fields. To find the optimum environmental conditions for cold storage of these host eggs, we evaluated nine different combinations of temperature (2, 6, and 10 °C) and relative humidity (high 90–95%, medium 70–75%, and low 30–35%). After 30 d of cold-storage, eggs were weighed and held at 26.6 °C and 75% relative humidity for 8 d before testing. To test the eggs’ suitability as hosts following cold storage, females of Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) were released individually onto batches of eggs, and parasitization rates and the development, emergence, sex ratio, adult longevity, and size of parasitoid progeny were examined. Eggs stored at high relative humidity showed less weight loss than those stored at low relative humidity. The number of eggs parasitized was highest (5.9/15) on eggs stored at 6 °C and high relative humidity. Developmental times and adult emergence were optimal on host eggs stored at 2 °C and high relative humidity. A significantly lower proportion of eggs produced male parasitoids when eggs were stored at 2 or 6 °C. Adult longevity was not affected by egg storage conditions, but adult size of progeny decreased in eggs stored at 10 °C. In conclusion, eggs of R. pedestris stored below 6 °C and with a high relative humidity maintained the best quality for parasitization by O. nezarae.     

Juvenile hormone-mediated reproduction induced by a sublethal concentration of imidacloprid in Cyrtorhinus lividipennis (Hemiptera: Miridae)

The Hemipteran predator, Cyrtorhinus lividipennis, feeds on the eggs and nymphs of rice planthoppers and leafhoppers. We previously demonstrated that sublethal concentrations of imidacloprid stimulated the reproduction of C. lividipennis. Considering the essential roles of juvenile hormone (JH) in insect reproduction, we speculated that sublethal concentrations of imidacloprid may stimulate the reproduction of C. lividipennis by regulating JH level. To test this, we cloned C. lividipennis JH acid methyl transferase (ClJHAMT) and JH esterase (ClJHE), which are responsible for JH biosynthesis and degradation genes, respectively. We then knocked down ClJHAMT by injecting dsRNA into C. lividipennis nymphs and found that emerging female adults exhibited 88.8% lower expression of the vitellogenin gene (ClVg) and the number of eggs was reduced by 41.5% as compared with controls. Silencing ClJHE increased ClVg mRNA expression by 275.0% but did not affect fecundity. A sublethal concentration of imidacloprid (LC₂₀) increased the JH titer in females by 35.3% and 60.6% at 24 and 48 h post-emergence, respectively. In treatments containing both imidacloprid and dsJHAMT, the silencing of CLJHAMT reduced the number of eggs produced by adult females by 21.4% as compared to the control (imidacloprid + dsGFP). Our results indicated that sublethal concentration of imidacloprid may induce C. lividipennis reproduction by upregulating JH level via JHAMT. The finding could provide valuable information for improved integration of C. lividipennis and insecticides in pest management.     

Predicted voltinism of the camellia spiny whitefly,Aleurocanthus camelliae (Hemiptera: Aleyrodidae), in major Japanese tea-producing districts based on life history parameters

We examined the temperature-dependent development, adult longevity, fertility, and sex ratio of the whitefly Aleurocanthus camelliae, which infests tea plants, under laboratory conditions. Eggs and nymphs were reared on tea shoots at 20, 22.5, 25, and 27.5 °C with a photoperiod of 15L:9D. The developmental zero of the egg, total nymphal stadia, and egg–adult duration of A. camelliae were 12.6, 11.6, and 11.9 °C, respectively, with thermal constants of 176.7, 394.7, and 569.9 d-degrees, respectively. The mean longevities of adult female and male A. camelliae were 4.4 and 2.7 d, respectively. These results suggested A. camelliae voltinism of two to three generations per year in Kanto, Tokai, and Kinki districts and three to five generations per year in the Shikoku and Kyushu districts, Japan.     

Nutritional characterization of Mucuna pruriens: 4. Does replacing soybean meal with Mucuna pruriens in lamb diets affect ruminal,blood and tissue l-dopa concentrations?

The harmful effects of the 3,4-dihydroxy-l-phenylalanine (l-dopa) in Mucuna pruriens (Velvet bean) seeds have limited its use as a protein supplement for monogastrics and humans. Little is known about the extent of metabolism of Mucuna l-dopa in ruminants or its accumulation in ruminant tissues consumed as food by humans. This study aimed to determine if replacing soybean meal (SB) with Mucuna increases concentrations of l-dopa in rumen fluid, blood and muscle tissue of lambs. Twenty-seven RM lambs (RM; initial body weight, BW = 33.8 ± 5.44 kg) and 12 Florida Native (FN; initial BW = 24.9 ± 8.63 kg) lambs were assigned to four treatments and fed a basal diet of coastal bermudagrass hay, corn grain, and liquid molasses for 42 (FN) or 49 days (RM) and then slaughtered. Dietary supplements were formulated by substituting 0 (SB), 330 (Lo), 670 (Med) or at least 1000 (Hi) g/kg of SB with rolled Mucuna seeds (l-dopa, 24 g/kg dry matter, DM). Body weight was measured weekly and carcass characteristics and concentrations of l-dopa in rumen fluid, blood and the sterno-mandibularis muscle were measured at slaughter when concentrations of blood urea N, glucose, haptoglobin and cerruloplasmin were also measured. Lambs fed SB had higher (P<0.05) average daily gain than those fed Mucuna (0.20 versus 0.15 kg/day for RM; 0.21 versus 0.14 kg/day for FN). However, concentrate protein source did not affect dressing and concentrations of blood urea N, or blood glucose. Feeding the Hi diet versus the SB diet did not increase concentrations of blood cerruloplasmin, or l-dopa or concentrations of l-dopa metabolites in blood. No l-dopa was found in the ruminal fluid of the lambs and l-dopa concentrations in the sterno-mandibularis muscle were low (i.e., <5 ng l-dopa/g), and unaffected (P>0.05) by diet. Ingested Mucuna l-dopa was extensively metabolized in lambs, and did not accumulate to toxic levels in muscle tissues.     

Influences of food sources on reproduction and aggregation pheromone production of Riptortus pedestris (Hemiptera: Alydidae) in its adult stage

The dietary importance of sweet persimmon fruit (SPF) was determined in adult bean bug, Riptortus pedestris, by investigating the effect of feeding SPF and soybean seeds and peanut on longevity, weight change, fecundity and ability for pheromone production in the bean bug. Adult female R. pedestris fed on SPF had significantly shorter lifespans than those fed on soybean, while in males there was no significant difference. Males and females fed on SPF were significantly lighter than those fed on soybean seeds. Females fed on SPF did not lay eggs at all, but those fed on soybean laid 155.8 eggs, and those fed on soybean seed complemented with peanut seed laid 120.8 eggs in 50 days. The amount of pheromone components (E)‐2‐hexenyl (E)‐2‐hexenoate and (E)‐2‐hexenyl (Z)‐2‐hexenoate produced by male R. pedestris fed on SPF was significantly less than that produced by males fed on soybean. Other pheromone components, tetradecyl isobutyrate and octadecyl isobutyrate, were not produced by adult males fed on SPF. This difference was apparent at one week after emergence and was more at three weeks after emergence. In the present study, we demonstrated that SPF had adverse effect on female survivorship, reproduction of female adults and production of the aggregation pheromone by adult males, compared to soybean food. These results suggested that SPF is unsuitable for adult R. pedestris. Management of nearby vegetation of fruit orchards may play an important role in reducing damage by adult R. pedestris.     

Evaluation of aggregation and alarm pheromones of <Emphasis Type="Italic">Riptortus pedestris</Emphasis> (Hemiptera: Alydidae) as a push–pull strategy in soybean fields

Aggregation pheromone traps designed to capture Riptortus pedestris (Fabricius) have recently been found to reduce neither the bug population nor crop damage in soybean fields. To improve trap efficiency, we first evaluated the effect of installation distance from the soybean field (trap distance). Additionally, push (one repellent) and pull (trap distance) strategies were evaluated together in a soybean field. While installation of aggregation pheromone traps 1 m outside of the field did not reduce the R. pedestris population at all, when the traps were moved to 5 m outside of the field, the field density of R. pedestris decreased, although this never became lower than when aggregation pheromone traps were absent. When the alarm pheromone was evaluated together with trap distance as a pull–push strategy in a soybean field, no additional reduction of the bug population was found compared to when only trap distance was changed. The number of bugs caught inside the aggregation pheromone traps was highest when traps were placed 10 m outside the field from August to October. In conclusion, despite some positive effect of installation distance, traps used both with and without alarm pheromone failed to reduce the bug population to the level found when traps were not used.