Short- and long-term control of Vespula pensylvanica in Hawaii by fipronil baiting

BACKGROUND: The invasive western yellowjacket wasp, Vespula pensylvanica (Saussure), has significantly impacted the ecological integrity and human welfare of Hawaii. The goals of the present study were (1) to evaluate the immediate and long‐term efficacy of a 0.1% fipronil chicken bait on V. pensylvanica populations in Hawaii Volcanoes National Park, (2) to quantify gains in efficacy using the attractant heptyl butyrate in the bait stations and (3) to measure the benefits of this approach for minimizing non‐target impacts to other arthropods. RESULTS: The 0.1% fipronil chicken bait reduced the abundance of V. pensylvanica by 95 ± 1.2% during the 3 months following treatment and maintained a population reduction of 60.9 ± 3.1% a year after treatment in the fipronil‐treated sites when compared with chicken‐only sites. The addition of heptyl butyrate to the bait stations significantly increased V. pensylvanica forager visitation and bait take and significantly reduced the non‐target impacts of fipronil baiting. CONCLUSION: In this study, 0.1% fipronil chicken bait with the addition of heptyl butyrate was found to be an extremely effective large‐scale management strategy and provided the first evidence of a wasp suppression program impacting Vepsula populations a year after treatment. Copyright © 2011 Society of Chemical Industry     

The efficacy of Vespex® wasp bait to control Vespula species (Hymenoptera: Vespidae) in New Zealand

ABSTRACT

Transitioning from trials to pest control tool, the efficacy of controlling wasps Vespula vulgaris and V. germanica using Vespex® wasp bait was tested in 2015. Vespex® is a protein-based bait matrix with 0.1% fipronil. Five sites ranging <300 to >2000 ha and over 5500 ha in total had bait stations placed 300 × 50 m apart and received one application of Vespex®. Wasp nest traffic rates declined 93% in four days at one site, and over 97% after 20–38 days at all other sites. Measured honeydew availability also improved post wasp control. Further demonstrating feasibility, five different agencies worked closely with government leading many programme aspects. Vespex® was made more widely available in New Zealand towards the end of 2015. Web page information showed ～30% of all territorial authorities nationally are engaging in pest wasp problems. This signals a future potential in the way that pest wasps might be managed in a community context for social, economic and biodiversity conservation objectives.     

Potential manageable exploitation of social wasps,Vespula spp. (Hymenoptera: Vespidae), as generalist predators of insect pests

A manageable, generalist, predatory insect has to date been considered to be unavailable anywhere for pest insect control. Polistes spp. wasps showed promise, but are limited by small numbers of wasps per nest and short nest life. Social Vespula spp. wasps appear to possess the necessary attributes which will allow their development as manageable, generalist predators of a wide range of pest insects. They have a large number of foragers per nest, a high demand for invertebrate protein, a very wide range of prey, an ability to tolerate low temperatures, a tolerance of nest manipulation, and a colony life cycle that can span at least two summers. High numbers per nest and high nest densities can lead to the consumption of many kilograms of prey per hectare per year. Successful development of characteristics desired of a manageable predator, such as the ability to increase colony numbers by dividing and re-queening, and enhancement of multi-year colony existence, could result in management procedures for Vespula spp. wasps that are similar to those used for honey bees. Farmers could have wasp nests available when and where required and in the numbers desired. Wasps would be especially valuable for growers of some ‘organic’ crops in which conventional pesticides are not permitted.     

黏虫幼虫体表挥发物成分鉴定及其对中红侧沟茧蜂寄主定位行为的影响

为提高中红侧沟茧蜂Microplitis mediator田间寄生效率，对黏虫Mythimna separata 1～5龄幼虫体表挥发物进行提取，采用气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）技术对其成分进行分析，采用气相色谱-触角电位（gas chromatography-electron antenneal detection,GCEAD）技术确定引起中红侧沟茧蜂触角电位（electroantennogram,EAG）反应的挥发性物质，同时通过Y型嗅觉仪测定中红侧沟茧蜂对其的选择反应。结果显示，中红侧沟茧蜂雌成蜂对黏虫1～3龄幼虫体表粗提物有显著的选择反应，反应率分别为60%、68%和56%；中红侧沟茧蜂触角对黏虫体表粗提物中的2,4-二甲基庚烷、5-乙基-2-甲基辛烷、十二烷、1,3-二叔丁基苯、2,4-二甲基十一烷、十六烷、2,6,10,15-四甲基十七烷和抗坏血酸二棕榈酸酯10种物质均有电生理反应，EAG反应随浓度升高而增强；中红侧沟茧蜂雌雄成蜂对这10种物质的选择反应存在性别差异；其中中红侧沟茧蜂对其中的8种物质及...     

Development of semiochemical attractants for monitoring bean seed beetle, Bruchus rufimanus

BACKGROUND: Bruchus rufimanus is a serious pest of field beans. The objective here was to develop a semiochemical‐baited trapping system to facilitate monitoring of the pest. RESULTS: Volatile compounds that were electrophysiologically active with the antennae of B. rufimanus females were identified from headspace samples of Vicia faba flowers and from male B. rufimanus. Selected headspace samples and synthetic compounds were tested in olfactometer bioassays. The semiochemicals were then formulated in lures for traps and evaluated in a field trapping experiment. Cone traps baited with a three‐component blend of floral volatiles, releasing (R)‐linalool (17.7 mg day^?1), cinnamyl alcohol (0.4 mg day^?1) and cinnamaldehyde (0.77 mg day^?1), caught significantly more of both sexes of B. rufimanus than unbaited control traps. A male volatile, 1‐undecene, was EAG active with female antennae. It was attractive to females in an olfactometer, indicating that it is a sex pheromone. However, in the field it only enhanced trap catches if it was released together with the floral volatiles. CONCLUSION: The blends of semiochemicals identified were shown to be attractive in cone traps under field conditions. The prototype trapping system developed could be used as a monitoring tool to determine infestation levels of B. rufimanus in bean fields. Copyright © 2011 Society of Chemical Industry     

Screening of chemical attractants for second-stage juveniles of Meloidogyne species on agar plates

The attractiveness of 60 aromatic compounds, mainly carboxylic acids, alcohols, aldehydes, and phenols, to second-stage juveniles (J2) of four Meloidogyne species (M. hapla, M. incognita, M. javanica, and M. marylandi) was evaluated based on the relative density of J2 attracted to a test compound on an agar plate in an 8.5-cm Petri dish. Three types of nematode responses were observed in the single-compound assays: attraction, in which J2 were attracted to test compounds; concentration-dependent attraction, in which J2 were attracted to the zone located 1–2 cm from test compounds; and no response. None of the test compounds effectively attracted M. incognita or repelled J2 of any species. Thirty-five compounds attracted J2 of at least one of the other three nematode species. Highly effective attractants were trans-cinnamic acid, salicylic acid, 4′-hydroxy-3′-methoxyacetophenone, o-vanillin, carvacrol, 3-methoxybenzyl alcohol, 2-methoxycinnamaldehyde, trans-p-methoxycinnamaldehyde, 4-methoxy-3-methylbenzaldehyde, 2-methoxy-4-propenylphenol, and thymol. Salicylic acid dissolved in the agar reduced the attraction of M. marylandi J2 to salicylic acid and to o-vanillin. Two- and three-compound assays revealed differences in attractiveness to M. marylandi J2 between or among structural isomers of the attractants. o-Vanillin and salicylic acid were much more attractive to M. marylandi than vanillin and the two isomers of salicylic acid, respectively. It is not clear whether nematodes utilize the attractants found in the study for locating hosts in nature, but the attractants may have potential for use in nematode control.     

绿盲蝽对七种锦葵科植物挥发物的EAG和趋向行为反应

研究绿盲蝽Apolygus lucorum(Meyer-Dür)对锦葵科植物挥发物的EAG和趋向行为反应,为研发绿盲蝽引诱剂或驱避剂策略提供科学依据。田间采用动态顶空采样方法收集了7种锦葵科植物的挥发物,通过室内气相-质谱联用系统(GC-MS)进行物质鉴定及定量分析,最终测定了雌、雄绿盲蝽成虫对11种候选特征挥发物的触角电位(EAG)反应和嗅觉趋向选择行为。结果表明,7种锦葵科植物的挥发物种类和含量有较大差异,而且4种棉花品种之间的挥发物差异也很显著。棉花石远321的挥发物总量最大,其中4,8-二甲基-1,3,7-壬三烯(DMNT)含量最高,壬醛和罗勒烯其次。蜀葵的挥发物种类和含量均最少。11种候选特征挥发物均能够引起绿盲蝽雌、雄成虫EAG反应,且雄性成虫的反应值大都高于雌性成虫。其中,绿盲蝽雌、雄成虫触角对反-2-己烯酸丁酯EAG反应值最大,芳樟醇、乙酸叶醇酯、甲基庚烯酮及DMNT也能够激发绿盲蝽较大的EAG反应。在趋向行为检测中发现,DMNT及柠檬烯等对雄性成虫具有吸引作用。对雌性成虫有吸引作用的物质有γ-萜品烯、DMNT、月桂烯、α-石竹烯、罗勒烯及乙酸叶醇酯等,其中γ-萜品烯和乙酸叶醇酯对雌性成虫具有极显著吸引效果。锦葵科候选植物挥发物对绿盲蝽雌、雄虫具有不同EAG和趋向行为反应影响,候选气味化合物可以作为设计绿盲蝽引诱剂组分进行害虫防控田间实践。     

Controlling yellow jackets with fipronil-based protein baits in urban recreational areas

ABSTRACT

The western yellow jacket, Vespula penyslvanica (Saussare), is a serious seasonal pest of outdoor venues in the western United States. In the spring, queens and low numbers of workers were captured in heptyl-butyrate-baited traps until early July, when the number of foragers dramatically increased. Microsatellite data suggest that 18 colonies were actively foraging within the park in 2012. Foragers from 11 different colonies were collected at one trap site. In 2012 and 2013, sufficient numbers of foragers were not captured until early August when baiting trials were initiated. Baits were prepared with canned chicken mixed with fipronil for a final concentration of 0.025%. In 2012, a single baiting provided >96% reduction of foragers for at least two months. A second baiting late in the season provided >80% reductions. In 2013, one baiting trial resulted in a 74% and a 93% reduction. A bait acceptance study was conducted in 2014 to test a bait consisting of the juices from canned chicken and 0.025% fipronil incorporated into a hydrogel, and provided a much longer lasting bait in the field.     

灰茶尺蠖为害诱导茶树释放的互利素的鉴定

为鉴定灰茶尺蠖为害诱导茶树释放的互利素,遂以SDE法提取灰茶尺蠖为害茶梢和正常茶梢挥发物,经GC-MS检测,分别鉴定出31和25种组分,二者总含量相对于等剂量内标的含量分别是1863.8%和1124.6%。与正常茶梢相比,灰茶尺蠖为害茶梢挥发物中苯甲醛、反-2-癸烯醛、吲哚、水杨酸、反-2-己烯醛和己醛含量显著增加。将灰茶尺蠖为害茶梢挥发物的18种主要组分分别溶于液体石蜡制成10^-4g/mL味源,以Y形嗅觉仪检测茶尺蠖绒茧峰对味源的趋性;与液体石蜡相比,苯甲醛、水杨酸、反-2-己烯醛和己醛诱效显著,反-2癸烯醛、4-庚烯醛和吲哚的诱效明显,其他11组分无明显诱效。再将前7种组分配成10^-2g/mL引诱剂,分别载于橡皮头制成诱芯,附于芽绿粘板上,在茶园茶尺蠖绒茧蜂盛发期实施诱捕,携带前4种诱芯的芽绿粘板诱捕的蜂数明显多于后3种、且显著多于无诱芯的芽绿粘板,而且携带10^-2g/mL苯甲醛、水杨酸和反-2-己烯醛等量混合物诱芯的诱效最强。认为苯甲醛、水杨酸、反-2-己烯醛和己醛是灰茶尺蠖取食诱导的茶树互利素。     

Biology,revised taxonomy and impact on host plants of<Emphasis Type="Italic">Ophelimus maskelli</Emphasis>, an invasive gall inducer on<Emphasis Type="Italic">Eucalyptus</Emphasis> spp. in the Mediterranean Area

Ophelimus maskelli (Ashmead) (Hymenoptera: Eulophidae), an invasive species in the Mediterranean area that occurs naturally onEucalyptus camaldulensis at Wagga Wagga in New South Wales, was studied in Israel on the same host plant. The most distinctive characteristic ofO. maskelli as compared with other congeners is the presence of only a single seta on the submarginal vein.O. maskelli shows a clear tendency to oviposit in developed, immature leaves, and it prefers to oviposit on an area of the leaf blade near the petiole. The female lays an average of 109 eggs when maintained on water alone. The egglaying distribution tended towards aggregation, and the same tendency has also been observed within and among trees. The wasp prefers to attack the lower canopy. The gall diameter ranged from 1.2 to 0.9 mm, and gall density from 11.5 to 36.0 galls cm⁻², respectively. The typical color of the gall appeared as soon as third instar larva developed. Galls on shaded leaves remained green or greenish-yellow, whereas those that were exposed to the sun were reddish.O. maskelli produces three generations per year in Israel. High flight occurs among the spring generations, starting in early March. The wasps were attracted to green sticky plates much more than to the other tested colors. Heavy galling byO. maskelli results in premature shedding of the leaves, soon after the emergence of the wasps. Among the 84 eucalyptus species tested, the following 14 species were found to be suitable hosts:E. botryoides, E. bridgesiana, E. camaldulensis, E. cinerea, E. globulus, E. gunii, E. nicholii, E. pulverulenta, E. robusta, E. rudis, E. saligna, E. tereticornis andE. viminalis. This study focused on morphological and development characters that can clearly distinguishO. maskelli fromOphelimus eucalypti Gahan, and on examining the effect of crossing between eucalyptus species on the development possibilities of the wasps. Also considered were the effect of the food on adult survival, the competition between the eulophid gall makerLeptocybe invasa Fisher & LaSalle andO. maskelli, the heavy damage inflicted on eucalyptus, and the health problems and nuisance to people caused by the wasp near heavily infested trees during the mass emergence of adults. http://www.phytoparasitica.org posting Dec. 5, 2006.     

Ecdysteroid receptor docking suggests that dibenzoylhydrazine-based insecticides are devoid of any deleterious effect on the parasitic wasp Psyttalia concolor (Hym. Braconidae)

BACKGROUND: The moulting accelerating compounds (MACs) or ecdysteroid agonists represent a selective group of insecticides acting upon binding to the ecdysteroid receptor (EcR) and leading to lethal premature moulting in larval stages and aborted reproduction in adults. Psyttalia concolor Szèpl. is a useful parasitic wasp attacking important tephritid pests such as the medfly and olive fruit fly. RESULTS: Contact and oral exposure in the laboratory of female parasitic wasps to the dibenzoylhydrazine‐based methoxyfenozide, tebufenozide and RH‐5849 did not provoke negative effects. No mortality and no reduction in beneficial capacity were observed. The ligand‐binding domain (LBD) of the EcR of P. concolor was sequenced, and a homology protein model was constructed which confirmed a cavity structure with 12 α‐helices, harbouring the natural insect moulting hormone 20‐hydroxyecdysone. However, a steric clash occurred for the MAC insecticides owing to a restricted extent of the ligand‐binding cavity of the PcLBD‐EcR, while they did dock well in that of susceptible insects. CONCLUSIONS: The insect toxicity assays demonstrated that MACs are selective for P. concolor. The modelling/docking experiments are indications that these insecticides do not bind with the LBD‐EcR of P. concolor and support the theory that they show no biological effects in the parasitic wasp. These data may help in explaining the compatible use of MACs together with parasitic wasps in IPM programmes. Copyright © 2012 Society of Chemical Industry     

Automated detection of the yellow-legged hornet (Vespa velutina) using an optical sensor with machine learning

BACKGROUND

The yellow-legged hornet (Vespa velutina) is native to Southeast Asia and is an invasive alien species of concern in many countries. More effective management of populations of V. velutina could be achieved through more widespread and intensive monitoring in the field, however current methods are labor intensive and costly. To address this issue, we have assessed the performance of an optical sensor combined with a machine learning model to classify V. velutina and native wasps/hornets and bees. Our aim is to use the results of the present work as a step towards the development of a monitoring solution for V. velutina in the field.

RESULTS

We recorded a total 935 flights from three bee species: Apis mellifera, Bombus terrestris and Osmia bicornis; and four wasp/hornet species: Polistes dominula, Vespula germanica, Vespa crabro and V. velutina. The machine learning model achieved an average accuracy for species classification of 80.1 ± 13.9% and 74.5 ± 7.0% for V. velutina. V. crabro had the highest level of misclassification, confused mainly with V. velutina and P. dominula. These results were obtained using a 14-value peak and valley feature derived from the wingbeat power spectral density.

CONCLUSION

This study demonstrates that the wingbeat recordings from a flying insect sensor can be used with machine learning methods to differentiate V. velutina from six other Hymenoptera species in the laboratory and this knowledge could be used to help develop a tool for use in integrated invasive alien species management programs. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Effects of organic‐farming‐compatible insecticides on four aphid natural enemy species

BACKGROUND: The toxicities of pyrethrins + rapeseed oil, pyrethrins + piperonyl butoxide (PBO), potassium salts of fatty acids and linseed oil were assessed in the laboratory on the parasitic wasp Aphidius rhopalosiphi (Destefani‐Perez), the ladybird Adalia bipunctata (L.), the rove beetle Aleochara bilineata (Gyll.) and the carabid beetle Bembidion lampros (Herbst.). The methods selected were residual contact toxicity tests on inert and natural substrates. RESULTS: Both the pyrethrin products led to 100% mortality in the adult parasitic wasps and ladybird larvae on glass plates and plants. The pyrethrins + PBO formulation was toxic for B. lampros on sand and natural soil, but the pyrethrins + rapeseed oil formulation was harmless for this species. Insecticidal soaps were harmless for all these beneficial species. None of the tested products significantly affected the parasitism of the onion fly pupae by A. bilineata. CONCLUSION: The results indicated the potentially high toxicity of natural pyrethrins for beneficial arthropods. Although this toxicity needs to be confirmed in field conditions, the toxicity levels obtained in the laboratory were similar to or higher than those of several synthetic insecticides known to be toxic in the field. Insecticidal soaps could be considered as an alternative for aphid control in organic farming in terms of selectivity. Copyright © 2010 Society of Chemical Industry     

Recovery from inhibition of photosynthesis by metamitron in various plant species

Inhibition of photosynthesis by metamitron in the rooting medium and its subsequent recovery after transfer of the roots to herbicide-free nutrient solution was measured in eight plant species. Fast and complete recovery within a few hours after treatment showed that metamitron, once absorbed, was rapidly and completely inactivated in the leaves of sugar beet (Beta vulgaris L.). Inactivation in perennial ryegrass (Lolium perenne L.) was slower and incomplete. It was low in Echinochloa crusgalli (L.) P.B., Amaranthus retroflexus L., Alopecurus myosuroides Huds. and bean (Phaseolus vulgaris L.), and undetectable in maize (Zea mays L.) and Portulaca oleracea L. From the transpiration rate and the concentration of metamitron in the nutrient solution that just did not cause inhibition of photosynthesis in sugar beet, uptake and inactivation rates per unit leaf area were calculated to be at least 18·5 ng/cm²/h. The same external concentration markedly depressed photosynthesis in the other more susceptible species. After leaf sprays sugar beet plants gradually resumed the normal rate of photosynthesis, but bean plants did not recover.     

Competitive interactions in mixtures of broccoli and Chenopodium album grown at two UV-B radiation levels under glasshouse conditions

Ultraviolet-B radiation effects on intra- and interspecific competition in broccoli (Brassica oleracea) and Chenopodium album were studied using bivariate factorial experiments. A randomized block design was used in which three monoculture densities for each species [144 (low), 256 (medium), and 400 (high) plants m⁻²] and all binary combinations were grown in a glasshouse at two (4 and 7 kJ m⁻² day⁻¹) UV-B_BE radiation levels for 4 weeks in 1999 and 5 weeks in 2000. Inverse yield–density relationships were more discernible at 4, compared with 7 kJ m⁻² day⁻¹ UV-B_BE radiation. Substitution rates, indicating the balance of intra- to interspecific competitive effects, declined for broccoli at 7, compared with 4 kJ m⁻² day⁻¹ UV-B_BE radiation, largely because of reduced interspecific competitive influences. Conversely, substitution rates increased for C. album grown at 7 kJ m⁻² day⁻¹ UV-B_BE radiation, as a result of both decreased intraspecific and increased interspecific competition. Interspecific competitive effects were influenced more than intraspecific competitive effects by UV-B radiation. Based on relative magnitude of substitution rates, C. album was a stronger competitor than broccoli at 4 kJ m⁻² day⁻¹ UV-B_BE radiation in both years, and at 7 kJ m⁻² day⁻¹ UV-B_BE radiation in 1999. In 2000, broccoli was the stronger competitor at 7 kJ m⁻² day⁻¹ UV-B_BE radiation. Overall, the relative competitiveness of broccoli was enhanced, while that of C. album diminished at 7, compared with 4 kJ m⁻² day⁻¹ UV-B_BE radiation. These findings indicate that above-ambient UV-B radiation has the potential to alter crop–weed competitive interactions, which could change acceptable weed threshold levels.     

Uptake, translocation and fate of 2,4-D and chlorsulfuron in Silene vulgaris (Moench) Garcke

Experiments were conducted to examine the up take, translocation and metabolism by S. vulgaris of two distinctly different herbicides: 2,4-D, a phenoxyalkanoic acid with growth regulator activity to which this species exhibits complete tolerance, and chlorsulfuron, a sul-fonylurea to which S. vulgaris is highly sensitive. Despite their structural dissimilarities 2,4-D and chlorsulfuron was readily absorbed by S. vulgaris with 65 and 69%, respectively, of the applied dosage being absorbed within 72 hours after treatment. Approximately 35% of the 2,4-D and 10% of the chlorsulfuron label was translocated out of the treated leaf after 72 hours. Neither herbicide accumulated in the terminal bud. Seventy-two hours after treatment 63% of the recovered ¹⁴C remained as unaltered 2,4-D in S. vulgaris, while in tomato, a 2,4-D sensitive species, 65% of the recovered ¹⁴C remained as intact herbicide. In S. vulgaris approximately 86% of the radioactivity remained as intact chlorsulfuron 72 hours after treatment compared to 12% in the tolerant wheat. The tolerance of S. vulgaris to 2,4-D could not be accounted for by limited absorption, translocation nor metabolic degradation of the herbicide. The sensitivity of S. vulgaris to chlorsulfuron would appear to be related to the inability of this species to metabolize the herbicide molecule.     

Combining visual cues and pheromone blends for monitoring and management of the tarnished plant bug Lygus lineolaris (Hemiptera: Miridae)

BACKGROUND

The tarnished plant bug Lygus lineolaris (Palisot de Beauvois) is considered the most damaging pest of cotton (Gossypium hirsutum L.) in the mid-southern United States. Previous studies have reported the role of different ratios of volatile metathoracic gland components such as hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal in eliciting low-level attraction of L. lineolaris. In this study, we tested different visual cues (colored sticky cards) in combination with olfactory cues (pheromone blends) to optimize the attraction and capture of L. lineolaris in the field.

RESULTS

Red-colored sticky cards were more attractive to L. lineolaris adults than white, blue or yellow cards. Red sticky cards combined with blends of three potential pheromone components attracted significantly more L. lineolaris adults than sticky cards without a blend added. Traps baited with a blend of hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal in 4:10:7 ratio, respectively, caught a significantly higher number of L. lineolaris than those baited with 10:4:2 or 7:10:4 blends or an unbaited control in the first week of the experiment.

CONCLUSIONS

Combining visual cues (red color) with olfactory cues (pheromone blends) significantly increased the capture of L. lineolaris in the field. This device or a future iteration could contribute towards sustainable and environmentally appropriate early-season monitoring and management of L. lineolaris in the field. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.     

Differential effect of diclofop-methyl on fatty acid biosynthesis in leaves of sensitive and tolerant plant species

The herbicide diclofop-methyl caused an early and pronounced inhibition of the incorporation of [¹⁴C]acetate into leaf lipids of the sensitive plant species maize (Zea may L.), wild oat (Avena fatua L.), and barnyardgrass (Echinochloa crus-galli L.). With an EC₅₀ value of approximately 10^?7M inhibition was already apparent 0.5–4 hr after herbicide application. The fatty acid biosynthesis of tolerant bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), and soybean (Glycine max L.) was not affected, with one exception [wheat (Triticum aestivum L.) belongs to the more tolerant species]; the inhibition of fatty acid biosynthesis, however, was in the same order of magnitude as in sensitive plants. More detailed studies showed that in wheat a recovery from inhibition of fatty acid biosynthesis occurred. Four days after herbicide application (0.18 kg diclofop-methyl/ha) in wheat normal fatty acid biosynthesis was restored, whereas in sensitive maize a 60% inhibition was maintained over the whole experimental period (8 days). The results support the view that tolerance of wheat to diclofop-methyl is based on its inactivation in leaves, whereas the tolerance of dicotyledonous species may probably lie at the level of the site of action of diclofop-methyl. In experiments with intact leaves, the inhibition of fatty acid biosynthesis resulted in an enhanced flow of [¹⁴C]acetate into organic acids and amino acids. This effect, however, was not always reproducible in experiments with leaf pieces or isolated root tips.     

Attraction ofTrichogramma platneri to eggs of some lepidopterous pests of avocado

The attraction ofTrichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) to eggs of two lepidopterous avocado pests,Boarmia sel-enaria (Schiffermüller) (Geometridae) andCryptoblabes gnidiella (Millière) (Phycitidae), was evaluated in olfactometer tests. The mobility of the wasp as measured by a mobility index was 0.6 for males and 1.8 for females; the males had a lower mobility and a lower search capacity index than the females. Frozen and fresh youngB. selenaria eggs had the greatest attraction forT. platneri, which diminished with increasing age of the eggs. The eggs ofC. gnidiella were also attractive to the parasitoid. Contribution from the Agricultural Research Organization. No. 2704-E, 1989 series.     

The importance of reduced light intensity on the growth and development of six weed species

Crops limit light for photosynthesis and growth of weeds. We studied the effect of reduced light on performance of six weed species [one invasive species (Amsinckia micrantha), three common species (Veronica persica, Capsella bursa‐pastoris, Viola arvensis) and two less common weeds (Anagallis arvensis and Scleranthus annuus)]. In two glasshouse experiments, six light levels were achieved aiming at 0%, 20%, 50%, 80%, 90% and 95% reduction of light and corresponding with daily light integrals (DLI) of 12.4, 9.63, 7.13, 2.74, 0.95 and 0.69 mol m^?2 day^?1 in experiment 1 and 21.2, 18.0, 10.7, 3.71, 1.64 and 1.20 mol m^?2 day^?1 in experiment 2. The number of leaves was strictly controlled by DLI. Chlorophyll content index, maximum photochemical efficiency of photosystem II (F_v/F_m), stomatal conductance, flowering and dry matter were strongly reduced when DLI was reduced to 0.69–3.71 mol m^?2 day^?1 for all species. Threshold DLI for flowering was ca. 3.71 mol m^?2 day^?1 for S. annuus, V. arvensis, A. arvensis and V. persica, while C. bursa‐pastoris deviated by flowering at DLI of 0.95 mol m^?2 day^?1. This may explain why C. bursa‐pastoris is common in the seedbank of Danish arable soils in spite of intensive farming with well‐fertilised and dense crops.