The ability of synthetic sex pheromone traps to forecast Plutella xylostella infestations depends on survival of immature stages

The potential for using synthetic sex pheromone traps as a simple and practical method of monitoring population densities of insect pests has been investigated in many crop systems. Yet, factors enabling the forecast of infestations based on pheromone trap catches are not fully understood. This study tested the prediction that high survival of immature stages of the target pest is a pre‐requisite for trap catches to correlate well with future infestations on the crop. The influence of parasitoids, as an important natural mortality factor of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), larvae and pupae in South Africa, on the ability of pheromone traps to forecast infestations was investigated continuously at weekly intervals over 6 years on unsprayed cabbage. During late October–May, when parasitism levels were high (≥50%), infestations and trap catches were significantly lower than during low parasitism (<50%) observed during June–early October. Because infestations were negatively related to parasitism level, trap catches correlated with infestations better when observations were made in the same week during periods of high parasitism. Conversely, when survival of P. xylostella immature stages was high due to low parasitism levels, trap catches correlated with future infestations well for up to 2 weeks. Thus, trap catches can be used to forecast infestations during September–October, a period that coincides with high P. xylostella infestations as a consequence of low natural control by parasitoids. This is the first study to show that the ability of pheromone trap catches to forecast infestations depends on survival of the immature stages of the target pest.     

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.     

Trichogramma pretiosum parasitism and dispersal capacity: a basis for developing biological control programs for soybean caterpillars

In order to succeed in biological control programs, not only is it crucial to understand the number of natural enemies to be released but also on how many sites per area this releasing must be performed. These variables might differ deeply among egg parasitoid species and crops worked. Therefore, these trials were carried out to evaluate the parasitism (%) in eggs of Anticarsia gemmatalis and Pseudoplusia includens after the release of different densities of the egg parasitoid Trichogramma pretiosum. Field dispersal was also studied, in order to determine appropriate recommendations for the release of this parasitoid in soybean fields. The regression analysis between parasitism (%) and densities of the parasitoid indicated a quadratic effect for both A. gemmatalis and P. includens. The maximum parasitism within 24 h after the release was reached with densities of 25.6 and 51.2 parasitoids per host egg, respectively, for the two pests. Parasitism of T. pretiosum in eggs of P. includens decreased linearly as the distance of the pest eggs from the parasitoid release sites increased. For P. includens, the mean radius of T. pretiosum action and the area of parasitoid dispersal in the soybean crop were 8.01 m and 85.18 m2, respectively. We conclude that for a successful biological control program of lepidopteran pests using T. pretiosum in soybean fields, a density of 25.6 parasitoids per host egg, divided into 117 sites per hectare, should be used.     

An evaluation of western bean cutworm pheromone trapping techniques (Lepidoptera: Noctuidae) in a corn and soybean agroecosystem

Pheromone traps can be used to monitor for adult western bean cutworms, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), and for the timing of field scouting. Understanding the effect that different trapping techniques have on adult captures could help corn (Zea mays L.) producers make better pest management decisions. Several approaches to trapping adults were evaluated in 2005 and 2006 by using two different pheromone traps (sticky wing and jug traps) in two different environments (corn or corn/soybean [Glycine max (L.) Merr.] at three different heights (0.6, 1.2, and 1.8 m). There was no significant difference in the trap catches by trap type in either 2005 or 2006. There were significantly more adults captured in traps placed between two cornfields than traps placed between corn/soybean fields during both years. Trap height also was significant, with the traps at 1.2 and 1.8 m catching more moths than traps at 0.6 m during both years. These results show that trapping techniques do affect trap catches and that either trap type placed between two cornfields at either 1.2 or 1.8 m above the ground will maximize trap catches.     

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.     

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.     

Evaluation of cold-stored eggs of Dolycoris baccarum (Hemiptera: Pentatomidae) for parasitization by Trissolcus nigripedius (Hymenoptera: Scelionidae)

Trissolcus nigripedius Nakagawa (Hymenoptera: Scelionidae) is an egg parasitoid of Dolycoris baccarum L. (Hemiptera: Pentatomidae), a polyphagous insect pest of many crops including soybean. As a method for mass-rearing to augment the parasitoid, cold storage of host eggs were evaluated in the laboratory. After 0 (control), 8, 20, 60, 90, and 120 days of refrigeration, host eggs were given to adult female T. nigripedius. Host acceptance behaviors of the parasitoid, categorized as drumming, oviposition, and marking, on the refrigerated eggs and biological attributes of offspring were assessed. Most of the attributes examined were affected by the refrigeration of host eggs. But host eggs could be refrigerated for up to two months without significant change in emergence rate and sex ratio and with 90% of parasitism. In addition, the second generation of the parasitoid was not negatively affected at all. However, frozen eggs of D. baccarum can not be used for rearing the parasitoid since parasitism rate decreased to 44% on host eggs frozen for 8 days. Refrigeration of D. baccarum eggs could be useful for mass-rearing and augmentation of T. nigripedius to control D. baccarum without reduction in the quality of parasitoid’s progeny. Furthermore, refrigerated eggs could be supplemented in the field to boost the population of T. nigripedius since immature D. baccarum can not hatch after 20 days of refrigeration.     

Refrigeration of Riptortus clavatus (Hemiptera: Alydidae) eggs for the parasitization by Gryon japonicum (Hymenoptera: Scelionidae)

Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae) is a solitary egg parasitoid of Riptortus clavatus (Thunberg) (Hemiptera: Alydidae) one of the most important pests in soybean in Korean and Japan. Refrigeration of R. clavatus eggs for up to 120 days was evaluated as a method of mass production of G. japonicum. The refrigeration reduced the eclosion of eggs, thus no nymph emerged after 30 days of egg refrigeration. Increased duration of host acceptance behaviors by G. japonicum and some detrimental effects on parasitism rate, developmental time, longevity, and adult size of the parasitoid were found in refrigerated host eggs. However, all the biological parameters of G. japonicum were unaffected by the refrigeration of up to 30 days. Gryon japonicum parasitized 16 and 14 host eggs daily that were refrigerated for 15 and 30 days, respectively, which did not differ from parasitization of fresh host eggs. Furthermore, refrigeration of host eggs did not reduce the reproduction of the emerged adult parasitoids and emergence and sex ratio of their progeny. Gryon japonicum also parasitized 14 and 13 refrigerated host eggs per day kept at 26.3°C and 78.7% RH for 2 and 4 days of post-refrigeration without significant reduction, respectively. These results show that refrigeration of R. clavatus eggs can be a good method for mass rearing of the parasitoid, and the host eggs killed by cold storage can be supplemented in the field to boost field parasitism.     

Pheromonal cross-attraction in true bugs (Heteroptera): attraction of Piezodorus hybneri (Pentatomidae) to its pheromone versus the pheromone of Riptortus pedestris (Alydidae)

We investigated the attractiveness of a synthetic form of the pheromone of the soybean stink bug, Piezodorus hybneri (Gmelin), under field conditions, and compared it with that of (E)-2-hexenyl (E)-2-hexenoate, a pheromone component of a competitor, Riptortus pedestris (Fabricius). Many adult stink bugs were attracted to traps baited with 100 mg of the synthetic pheromone (1: 1: one mixture of β-sesquiphellandrene, (R)-15-hexadecanolide, and methyl (Z)-8-hexadecenoate), but few were attracted to 1 or 10 mg. More than twice as many females as males were attracted to this male-produced pheromone. None of the individual pheromone components (30 mg) attracted conspecifics. In summer (June-July), when field P. hybneri were not in diapause, (E)-2-hexenyl (E)-2-hexenoate was more attractive to P. hybneri than the synthetic pheromone. The sex ratio of the adults attracted to the synthetic pheromone was highly female-biased, yet almost equal numbers of both sexes were attracted to (E)-2-hexenyl (E)-2-hexenoate. Most females attracted to both attractants were mated and had mature ovaries. However, adults attracted to (E)-2-hexenyl (E)-2-hexenoate were likely to have less food in their stomach than those attracted to the synthetic pheromone. In late autumn (October-November), when the bugs were in reproductive diapause, both attractants attracted many sexually immature female and male adults that had well-developed fat body. The synthetic pheromone also attracted a large number of conspecific nymphs. These results suggest that P. hybneri pheromone and R. pedestris pheromone component, respectively, have different functions for P. hybneri. The male-produced pheromone system of P. hybneri seems to be sex-related but to have other roles.     

卵跳小蜂Ooencyrtus nezarae Ishii对豆缘蝽和豆璧蝽卵的选择性和密度反应(英文)

本文研究了卵跳小蜂对豆缘蝽 (R .clavatusThunberg)和豆璧蝽 (P .hybneriGmelin)卵的选择性和密度反应。在自由选择试验中 ,两种豆蝽卵中羽化的卵跳小蜂在不同的卵密度和比例中均选择豆缘蝽 ;而在非选择性试验中 ,从豆璧蝽中羽化的卵跳小蜂同时选择豆缘蝽和豆璧蝽卵 ,寄生率较高 ;然而 ,从豆缘蝽卵羽化的卵跳小蜂对豆璧蝽卵的寄生率非常低。嗅觉试验表明 ,从豆缘蝽卵上释放的气味对卵跳小蜂的搜寻和寄生行为影响很大。卵跳小蜂寄生的卵数量随着豆缘蝽和豆璧蝽卵密度的增加而提高 ;然而 ,卵跳小蜂对豆璧蝽的寄生率随着卵的密度增加而降低 ,尤其是从豆缘蝽卵中羽化的寄生蜂。研究还表明 ,卵跳小蜂在大田中对豆缘蝽卵的寄生存在着空间或时间上的障碍。     

Decline of soybean aphid (Homoptera: Aphididae) egg populations from autumn to spring on the primary host, Rhamnus cathartica

Soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), is a severe pest of soybeans in North America. Soybean aphid populations cycle between a secondary summer host, where populations reproduce parthenogenetically and a primary host, where populations overwinter as eggs. In North America, the secondary host is soybean, and the primary hosts are Rhamnus cathartica L. (Rhamnaceae) and R. alnifolia L'Her. A location with abundant populations of soybean aphid on R. cathartica was identified near Guelph, Ontario, Canada, in October 2004, and eggs on trees were counted at multiple sites within that location each autumn and spring over the next 2 yr. Dynamics of naturally occurring soybean aphid populations on the primary host were assessed with respect to (1) decline of overwintering eggs from autumn to spring, (2) development of spring populations on R. cathartica, and (3) development of soybean aphid populations on soybean immediately adjacent to overwintering sites. Counts of aphid eggs declined by approximately 70% between autumn and spring sampling periods in 2004-2005. Significant differences in counts of aphid eggs relative to sampling height were observed in the canopy of R. cathartica. No edge effects were observed in the development of soybean aphid populations in soybeans adjacent to overwintering sites in this study. Very few eggs were collected at the same study location in the autumn of 2005, and no aphid eggs were collected from samples taken in the spring of 2006. Egg counts taken in the autumn of 2006 were intermediate in number relative to counts taken in the autumn of 2004 and 2005.     

Interspecific larval competition between two egg parasitoids in refrigerated host eggs of Riptortus pedestris (Hemiptera: Alydidae)

In a previous study, we found that soybean fields could be supplemented with refrigerated eggs of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) to enhance parasitism. As a part of a study to evaluate the effect of host egg refrigeration on parasitism, host acceptance behavior and interspecific larval competition between Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae) and Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) were studied in multiparasitized unrefrigerated and refrigerated eggs. O. nezarae showed complete host acceptance behavior when offered refrigerated host eggs that were preparasitized by G. japonicum. Adult emergence rate of O. nezarae was 43 and 74% when the interval between the first and second oviposition was 0 and 4 days, respectively, and was not different between refrigerated and unrefrigerated eggs. Refrigeration did not change host acceptance behavior of G. japonicum, but adult emergence declined from 80% in unrefrigerated eggs to 37% in refrigerated eggs that were pre-parasitized by O. nezarae on the same day. No negative effects of refrigeration on sex ratio, adult longevity, and adult size of the both parasitoids were found. Generally host egg refrigeration did not negatively affect host acceptance behavior of the both parasitoids on preparasitized eggs or larval competition between the two parasitoids in multiparasitized host eggs with exceptions in the development time and emergence rate of G. japonicum. Therefore, host egg refrigeration may not interrupt interactions between the parasitoid populations in the field.     

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.     

Enhancement of Riptortus clavatus (Thunberg) (Hemiptera: Alydidae) egg parasitism by a component of the bug's aggregation pheromone

Egg parasitism of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), was surveyed using individual egg bags in a sweet persimmon orchard and at Gyeongsang National University (GNU) campus, Korea in 2006. The effect of (E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), one component of R. clavatus aggregation pheromone, on the parasitism enhancement was tested at GNU campus and in a soybean field in 2005 and 2006, respectively. In 2006, two egg parasitoid species, Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae), emerged from R. clavatus eggs. Parasitism by O. nezarae was 9.4–48.3% in mid August to mid September in GNU campus and 6.7–30.0% at the orchard. Total parasitism by G. japonicum (2.5%) at both sites throughout the experimental period was lower than that by O. nezarae (12.5%). This survey revealed nearly no activity of the two species after October at both sites. G. japonicum was solitary and O. nezarae could be either solitary or gregarious. From a single R. clavatus egg, one female or one male G. japonicum emerged. However, an average of 4.3 O. nezarae emerged from one host egg. It took 12.6 d for G. japonicum and 12.0 d for O. nezarae to emerge from R. clavatus eggs in the laboratory. Treatment with E2HZ3H increased parasitism by O. nezarae in both years, but did not increase parasitism by G. japonicum. This suggests that E2HZ3H can be used as a kairomone to reduce the density of R. clavatus in the fields where natural parasitism by O. nezarae is high.     

Pan trapping soybean aphids (Hemiptera: Aphididae) using attractants

Since its introduction into the United States in the past 10 yr, soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has been a damaging pest to soybean, Glycine max (L.) Merrill. During 2008 and 2009, fields in central and north central Iowa experienced pockets of high soybean aphid populations. Electroantennograms have shown that soybean aphid alatae are capable of detecting host plant volatiles and sex pheromones. Here, we evaluated baited pan traps as a potential soybean aphid attractant. Yellow pan traps were placed in soybean fields after planting along with lures that contained plant volatiles and sex pheromones in 2008 or sex pheromones only in 2009. Pan trap contents were collected weekly, and plant counts also were conducted. Aphids were identified, and soybean aphids were counted to determine whether one chemical lure was more attractive to spring migrants than other lures. In both years, soybean aphids collected in pan traps with lures were not significantly different from the other products tested.     

Pest phenology and evaluation of traps and pheromone lures for monitoring flight activity of obliquebanded leafroller (Lepidoptera: Tortricidae) in Minnesota apple orchards

The efficacy of two trap designs (Pherocon 1C "wing" trap versus Pherocon VI "delta" trap) and two pheromone blends for monitoring obliquebanded leafroller, Choristoneura rosaceana (Harris), was evaluated in Minnesota apple orchards during the 2001 and 2002 field seasons. Two distinct flight periods of C. rosaceana were recorded yearly in Minnesota. Overwintered C. rosaceana larvae resumed activity in the spring at approximately 60 degree-days (DD) base 10 degrees C, whereas adult emergence began approximately 275 DD base 10 degrees C. To determine the optimal pheromone blend for monitoring C. rosaceana in Minnesota, traps were baited with either a three-component pheromone blend (Z11-14:Ac, E11-14:Ac, and Z11-14:OH) produced by females in eastern North America, or a four-component blend (Z11-14:Ac, E11-14:Ac, Z11-14:OH, and Z11-14:Al) commonly produced by females in western North America. Of the four pheromone-baited traps evaluated, delta traps baited with the four-component western pheromone lure captured the highest number of C. rosaceana males, followed by wing traps baited with western lure. Male C. rosaceana were less attracted to traps containing the three-component eastern lure, and both lure types seemed to be considerably selective against sympatric redbanded leafroller, Argyrotaenia velutinana (Walker). These results suggest that the pheromonal response of the predominant endemic population of C. rosaceana in Minnesota is similar to the response of the pest in many parts of western North America. The delta trap baited with western pheromone lure of C. rosaceana is recommended for monitoring the pest in Minnesota, and the results are discussed in relation to the development of effective management strategies against this important pest of apple.     

Seasonal abundance of two armyworm species, Spodoptera exitgua (Hübner) and Spodoptera litura (F.) in the Philippines

The two armyworm species Spodoptera exigua (Hübner) and S. litura (F.) are Important pests on several agricultural crops in the tropics. Knowledge about species abundance is important for the development of integrated pest management strategies. During 1998 and 1999 population densities were recorded weekly using pheromone traps at San Leonardo and Munoz (Province Nueva Ecija, 150 km north of Metro Manila) on the Philippine island Luzon. Furthermore, meteorological conditions and natural enemies were observed. Both armyworm species were present year-round at both observation sites. No differences in numbers of male insects trapped in pheromone traps between seasons were found for S. litura. Contrary, numbers of male S. exigua trapped during rainy season was significant higher than during dry season. Rainfall explained between 30 and 40% of trapped moths and has to be considered when monitoring population density with pheromone traps. Parasitism rates were below 5% in both years and for both species and can not explain the high variation observed in population densities.     

大豆荚发育程度对点蜂缘蝽成虫寿命及生殖力的影响

【目的】为明确大豆荚发育程度对点蜂缘蝽Riptortus pedestris成虫存活及生殖力的影响。【方法】在室内24℃±1℃恒温下,用不同日龄(5, 15, 25, 35和45日龄)离体鲜豆荚饲喂点蜂缘蝽,测定成虫寿命、产卵前期、产卵期、单雌产卵量等生物学参数和不同日龄豆荚籽粒中脂肪、总蛋白和总糖含量,分析点蜂缘蝽成虫的生物学参数与不同日龄豆荚籽粒中主要营养成分含量之间的相关性。【结果】随着所取食豆荚日龄的增加,点蜂缘蝽成虫的平均寿命、产卵期、单雌产卵量呈先增加然后下降的趋势,而产卵前期的变化趋势则相反。当饲喂35日龄豆荚时,点蜂缘蝽成虫寿命最长(56.90±9.47 d),产卵前期最短(6.00±0.58 d),产卵期最长(29.67±6.61 d),单雌产卵量最高(129.56±36.53粒),且与取食其他日龄豆荚的成虫之间存在显著差异。点蜂缘蝽成虫寿命、产卵期、单雌产卵量均与豆荚籽粒脂肪和总蛋白含量呈显著正相关,产卵前期与豆荚籽粒脂肪和总蛋白含量呈显著负相关。【结论】大豆荚发育程度对点蜂缘蝽成虫寿命及生殖力等生物学参数具有显著的影响,35日龄豆荚对点蜂缘蝽成虫存活和繁殖最为有利。     

Sex pheromone for monitoring flight periods and population densities of the pine sawfly, Diprion jingyuanensis Xiao et Zhang (Hym., Diprionidae)

Abstract:  The pine sawfly, Diprion jingyuanensis Xiao et Zhang, is a serious pest of Chinese pine ( Pinus tabulaeformis Carr.) in the northern parts of China. The general biology of this recently described sawfly species is little known and in the present study we used a synthetic pheromone to monitor its flight period and to evaluate the possibility to use pheromone traps as a tool for estimating and predicting population densities. The attractant pheromone of D. jingyuanensis is (1 S ,2 R ,6 R )-1,2,6-trimethyldodecyl propionate and in this study we used a four-isomer threo-mixture containing the active attractant. Both doses tested, 1 and 2 mg/trap, revealed the same seasonal flight pattern, the higher dosage demonstrating more clear flight peaks. The first flight peak of D. jingyuanensis occurred in mid-June during all 3 years, 1997–1999, and in 1997 and 1998 a second flight peak was also recorded in mid-July. The flight period was similar in time for populations located at higher (1400 m) and lower altitude (1100 m), from early June to late July or early August. Temperature was the main weather factor-affecting trap catches. Diurnal flight activity began at 9.00, peaked at 13.00 and lasted until 20.00. A series of tests with traps in different positions within stands and trees were conducted and the results demonstrated the importance of standardizing the trapping protocol in population monitoring studies. By using traps with 2 mg baits it is possible to detect sawfly occurrence at very low population densities, not detectable by other means. Strong positive correlations between trap catch and relative population density were found in 2000 and 2001, but not in 1998, when only few sites were monitored and the population was in a decreasing phase. The results are promising for future large-scale use of pheromone-based monitoring of D. jingyuanensis .     

Combining pheromone-baited and food-baited traps for insect pest control: Effects of additional control by parasitoids

Two age-structured population dynamic models are analyzed in which pheromone-baited trapping and food-baited trapping are used simultaneously to eradicate an insect pest. The pest species is assumed to be under partial control by a host-specific parasitoid species. The two models assume that density-dependent population regulation is accomplished either by host larval competition or by means of oviposition interference among the parasitoids. The two trap types interact in a positive synergistic manner and this combination appears to be very promising as a useful combination of pest control methods. Several features of the system are examined; the feature which appears to cause the greatest problem is the possibility of the parasitoids being attracted to the pheromone or the food traps. In either case, the degree of attraction does not have to be very great to undermine the control effort. It is seen that food trapping becomes indispensible if host pheromone is used by the parasitoids as a host-locating kairomone. If odor in the food traps is used by the parasitoids as kairomone, then the situation appears more optimistic, as the reduction in efficiency of the food traps appears much less than with the pheromone traps when pheromone acts as kairomone.