Survival and food choice of the grey field slug (Deroceras reticulatum) on three different seed types under laboratory conditions

In Ireland, the grey field slug (Deroceras reticulatum) is the predominant slug pest species in arable crops. It can cause enormous damage, but the knowledge about its feeding biology is limited.Adult species were reared under laboratory conditions, and the survival, feeding activity, and weight change of slugs when feed on maize, peas, or wheat seeds were investigated. An especially high mortality was experienced in the wheat treatment. It was hypothesised that the high mortality was due to a Fusarium species, however, a Fusarium infection of the wheat seeds was not confirmed. The weight change of the slugs was very variable due to a high egg production of some slugs.     

Damage by pod‐sucking bugs on cowpea when intercropped with maize

Abstract

Agroecosystems in the tropics include growing two or more crops in diverse polycultural patterns. In Kenya, cowpea Vigna unguiculata (Walp.) is grown in combination with cereals such as maize and sorghum, perennial legumes such as pigeon peas and root crops such as cassava and sweet potatoes. In the present investigations, field experiments were conducted to study the incidence and damage caused by Clavigralla tomentoscollis Germ, and C. shadabi after flowering, on cowpea intercropped with maize. It was evident from the present studies that C. tomentoscollis and C. shadabi were more prevalent on cowpea during the first season rather than during the second season. Both species had a preference for feeding on cowpea intercropped with maize than when it was grown in pure stands. Consequently more pod damage was recorded on cowpea planted with maize. It was therefore concluded that this agricultural system, which is commonly practised by small‐scale farmers in Kenya, is undesirable from the point of view of bug damage.     

Host plant preference of Diuraphis noxia (Kurdj.) (Hom., Aphididae)

Host plant preference of the Russian wheat aphid Diuraphis noxia (Kurdj.) was studied on 11 cultivars of 9 plant species: winter barley, spring barley, winter wheat, spring wheat, rye, oat, Triticale, canary grass, red millet yellow millet and maize. Seeds of the host plants were sown in a circle near the edge of pots. The host plant choice was evaluated 24 hours after releasing 55 Diuraphis noxia female adults in the middle of each pot. The suitability of different hosts for aphid development was evaluated 2, 7 and 14 days after infestation based on the mean number of Russian wheat aphid individuals per plant. Red millet, yellow millet and maize were chosen by significantly fewer aphids than grain crops. Winter and spring barley were chosen as hosts most frequently, and the progeny production was also the highest on these plants. The growth rate of D. noxia was significantly affected by the host plants and the date of assessment and their interaction.     

Prediction of yield loss caused by Orobanche spp. in carrot and pea crops based on the soil seedbank

Root parasites of the genus Orobanche cause serious losses in many subtropical crops. Direct control options are very limited and crop yield loss can reach 100%. Prediction of potential damage in a crop before sowing or planting would support farmers in their choice of crop. This paper discusses the relationship between the number of Orobanche spp. seeds in the field and yield loss in peas (Pisum sativum L.) and carrots (Daucus carota L.) in Israel. Yield loss due to Orobanche crenata Forsk. in peas was 100% at high infestations, whereas in carrots when O. crenata and O. aegyptiaca were present it stabilized at about 50% for moderate infestations of 200 seeds per kg of soil. Statistical analyses related the yield loss from parasitism in peas and carrots to the numbers of Orobanche seeds remaining in the soil. A rectangular hyperbolic model, previously applied to competition data, fitted the data well. Confidence intervals for per cent yield loss were calculated using the bootstrap method. The practical applications of these models in predicting yield loss are discussed.     

Survival and food choice of the grey field slug (Deroceras reticulatum) on three different seed types under laboratory conditions

In Ireland, the grey field slug (Deroceras reticulatum) is the predominant slug pest species in arable crops. It can cause enormous damage, but the knowledge about its feeding biology is limited.Adult species were reared under laboratory conditions, and the survival, feeding activity, and weight change of slugs when feed on maize, peas, or wheat seeds were investigated. An especially high mortality was experienced in the wheat treatment. It was hypothesised that the high mortality was due to a Fusarium species, however, a Fusarium infection of the wheat seeds was not confirmed. The weight change of the slugs was very variable due to a high egg production of some slugs.A second experiment examined the food choice and feeding activity of D. reticulatum when offered a choice of the three seed types. Most of the slugs preferred to feed on a mixture of seeds, but the highest feeding activity was recorded on the pea seeds.     

Modelling the effects of Elymus repens (L.) Gould competition on yield of cereals, peas and oilseed rape

Effects of Elymus repens (L.) Gould competition on yield of winter rye (Secale cereale L.), winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), peas (Pisum sativum L.), and spring oilseed rape (Brassica napus L.) were studied in field trials conducted on the same location through 3 years. The competitiveness of the five crops against E. repens could be ranked as follows, with the most competitive crop mentioned first: rye wheat, barley rape, peas. Yield losses ranged from 8% in rye to around 35% in peas and rape at a density level of 100 primary shoots m^?2 in spring. The different prevailing climatic conditions in the growing seasons had no effect on the yield-density relationships in rye, peas, and barley, whereas significant interactions were found in wheat and rape. The cumulative emergence patternsof primary shoots were described in the spring-sown crops, and models were derived to simulate the sensitivity of competition parameters to the actual time of shoot recording. The importance of choosing the right time for shoot emergence counts in relation to threshold recommendations and other aspects is discussed. Modélisation de l'effet de la concurrence de Elymus repens (L.) Gould sur les rendements de céréales, de pois et de colza Nous avons étudié au champ les effets de la concurrence de Elymus repens (L.) Gould sur le rendement du seigle d'hiver (Secale cereale L.), du blé d'hiver (Triticum aestivum L.), de l'orge de printemps (Hordeum vulgare L.), du pois (Pisum sativum L.) et du colza de printemps (Brassica napus L.). Les essais ont été conduits durant trois ans sur le même site. L'aptitude à la concurrence des cinq cultures à l'égard de E. repens peut être classée ainsi, en ordre décroissant: seigle blé et orge colza et pois. Les pertes de rendement allaient de 8% chez le seigle à environ 35% chez le pois et le colza, à un densité de pousses primaires 100 m^?2, mesurée au printemps. Les différentes conditions météorologiques ayant régné lors des périodes de croissance n'ont eu aucun effet sur les relations densité-rendement chez le seigle, le pois et l'orge, alors que des interactions significatives ont été observées chez le blé et le colza. Le patron cumulatif de l'émergence des pousses primaires a été décrit pour les cultures de printemps, et des mode les en ont été déduits pour simuler la sensibilité des paramètres de concurrence à la date à laquelle les levées sont enregistrées. L'importance est discutée du choix d'une date correcte pour les comptages de levées dans l'optique de recommandations de seuils de densité. Modellierung der Wirkung der Konkurrenz von Elymus repens (L.) Gould auf den Ertrag von Getreide, Erbse und Raps Die Wirkung der Konkurrenz der Gemeinen Quecke (Elymus repens) auf Winterroggen (Secale cereale L.), Winterweizen (Triticum aestivum L.) Sommergerste (Hordeum vulgare L.), Saat-Erbse (Pisum sativum L.) und Sommerraps (Brassica napus L.) wurde in Feldversuchen über drei Vegetationsperioden am selben Ort untersucht. Für die Konkurrenzkraft der fünf Kulturen gegenüber der Quecke ergab sich folgende Reihenfolge: Roggen Weizen, Gerste Raps, Erbse. Die Ertragsverluste lagen bei einer Dichte von 100 Queckenhalmen m² im Frühjahr zwischen 8 % beim Roggen und rund 35 % bei Erbse und Raps. Die verschiedenen Witterungsbedingungen in den Versuchsjahren blieben ohne Einfluß auf die Ertrags-Dichte-Beziehungen bei Roggen, Erbse und Gerste, während bei Weizen und Raps eine signifikante Beeinflussung gefunden wurde. Das Austriebsverhalten der Queckentriebe wurde in den Sommerkulturen festgehalten, und es wurden Modelle entwickelt, um die Empfindlichkeit der Konkurrenzparameter in Abhängigkeit vom Zeitpunkt der Zählung der Triebe zu simulieren. Die Bedeutung der Wahl des richtigen Zeitpunkts für die Erfassung des Austriebs der Quecke hinsichtlich der Empfehlung von Schwellenwerten und anderen Aspekten wird diskutiert.     

Herbicide antidotes—A review

The history of herbicide antidotes is reviewed, beginning with the exploration of compounds to protect wheat (Triticum aestivum L.) against barban in the early 1960s, and the later introduction of naphthalic anhydride (NA, naphthalene-1, 8-dicarboxy-licanhydride) as a seed dressing for protecting maize (Zea mays L.) against EPTC. This compound was largely replaced by Stauffer's R-25788 (N, N-diallyl-2, 2-dichloroacetamide) which has continued to be widely used in conjunction with EPTC and butylate in maize. This compound is highly specific to maize and can thus be applied in admixture with the herbicide, but has not proved of practical value on other crop species. NA on the other hand is less specific and is of potential value on sorghum [Sorghum bicolor (L.) Moench] and rice (Oryza sativa L.); experimental work continues on these crops. The only other antidote to be marketed so far is cyometrinil as a seed dressing for protecting sorghum against metolachlor and related herbicides. Other compounds are under development. Mode of action and structure-activity relations are discussed, as well as the current and future potential for antidotes in respect of the control of weed species in closely related crops, the increased options for herbicide use in minor crops and the possibility of reduced costs for broad spectrum weed control in major crops.     

Attempts to transfer paraquat resistance from barley grass (Hordeum glaucum Steud.) to barley and wheat

A paraquat-resistant biotype of barley grass (Hordeum glaucum Steud.) was hybridized with barley and wheat in an attempt to transfer paraquat resistance to these crops. Although hybridizations with barley did not result in the production of a plant, cytological evidence of chromosome elimination of one parent, presumably of H. glaucum, was obtained from squash preparations of young F₁ embryos. Hybridizations of wheat with both diploid and tetraploid H. glaucum resulted in the production of wheat haploids. These results indicate that it may not be possible to transfer paraquat resistance to barley and wheat using conventional hybridization techniques.     

Sorghum (Sorghum bicolor) as a bean intercrop or rotation crop contributes to the survival of bean root rot pathogens and perpetuation of bean root rots

Root rots (RR) are the main cause of declining bean (Phaseolus vulgaris) production in southwestern Uganda. Here, beans are mainly intercropped/rotated with maize (Zea mays), sorghum (Sorghum bicolor), sweet potato (Ipomoea batatas), potatoes (Solanum tuberosum) and garden peas (Pisum sativum). These crops also suffer from RR and bean RR pathogens have been isolated from some of these crops. This study aimed to determine the extent of RR on maize, sorghum and peas, and their potential to contribute to the survival of bean RR pathogens. Therefore, experiments were carried out in bean RR‐infested farmers’ fields as well as soils inoculated with bean RR pathogens (Pythium spp. and Fusarium spp.) under screen house conditions and a susceptible bean cultivar served as a control. High RR incidence/severity scores were recorded in beans and sorghum in both farmers’ fields and screen house experiments. The high field RR incidence/severity in sorghum correlated with the screen house scores. This study shows that RR is also a problem to other crops, especially sorghum, warranting attention. The findings also imply that sorghum plays a potential role as an alternate host to bean RR pathogens, increasing inoculum density of bean RR pathogens and potentially negatively impacting the bean RR problem. Intercropping or rotating beans with sorghum in this region is not recommended. However, maize was RR‐resistant and therefore appropriate as an intercrop/rotational crop to beans in the system. A holistic rather than commodity approach is recommended for managing RR in this cropping system.     

Phenology and growth of Orobanche crenata Forsk (broomrape) in four legume crops

Studies were conducted in the field in 2 years comparing the phenology and growth of Orobanche crenata (Forsk) (crenate broomrape) in lentils (Lens esculenta L.) cv. Castellana, peas (Pisum sativum L.) cv. Orix, vetch (Vicia sativa L.) cv. comun and broadbean (Vicia faba L. cv. Alameda. First attachment of O. crenata to these crops took place 9–14 weeks after mid-November planting and earlier after later plantings, Differences in the first O. crenata attachment dates and in the duration of the underground growth period of O. crenata were much greater between years for any given crop than between crops in a given year: both attributes were apparently affected more by seasonal climatic conditions than by crop species, Furthermore, there was no consistent relationship found between crop growth stages and time after first attachment of the parante. This occurred in lentils and vetch while they were vegetative, in peas at late vegetative-early flowering stages, and at widely varying growth stages in broadbean, depending on planting dates and years. The maximum number of O. crenata plants successfully attached to each individual crop plant decreased in the order: peas > broadbean > lentil > vetch, with 21, 14, 10 and 8 per plant, respectively, averaged over the two seasons. Similarly, plant parasites: host dry weight ratio were 1.0, 0.7, 0.3 and 0.2 For each of these crops, respectively.     

Efficacy of Surface Dust Treatments of Pirimiphos-Methyl and Etrimfos when Applied to Commercially Stored Wheat and Barley

Commercially stored wheat and barley were surface treated with dust formulations of pirimiphos-methyl and etrimfos at the manufacturer's recommended application rate. Samples were taken at four-weekly intervals for 32 and 16 weeks for wheat and barley respectively. Pesticide efficacy was determined using insect bioassays and chemical analysis of residues. There was no evidence to suggest a decline in residue levels of either pesticide over the experimental period. However, considerable variation was observed in the residue levels recorded at different sample points and also between residue levels recorded for the same point over the trial period. Control of susceptible strains of Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.) and Sitophilus granarius (L.) was achieved where recovered pesticide residues remained above 1 mg kg⁻¹ pirimiphos-methyl and 1·6 mg kg⁻¹ etrimfos.     

Influence of 1-aminobenzotriazole (ABT) derivatives on the toxicity of EPTC to monocotyledonous plants

The effect of l-aminobenzotriazole (ABT) and EPTC mixtures on plant growth was investigated in greenhouse experiments by presowing application in sand. The concentration of ABT for 50% shoot growth inhibition (I₅₀) was about 1 mM in the monoctyledons investigated. Both subtoxic and toxic doses of ABT were antagonists of EPTC in maize (Zea mays L.) However, subtoxic doses of ABT were syner-gists of EPTC in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.). No correlation between ABT and EPTC sensitivity of monocotyledonous plants was found. Some of the C- and N-substituted ABT derivatives (e.g. N-methyl or N-benzyl-ABT) completely reversed the effect of toxic dose of EPTC in maize. These results are considered as indirect evidence for the hypothesis that oxidation by cytochrome P-450 enzymes is the biochemical target of EPTC and is involved in the mode of action of EPTC safeners.     

Spring aphid-parasitoid (Hom., Aphididae, Hym., Braconidae) associations and interactions in a Mediterranean arable crop ecosystem, including Bt maize

Conspecific and heterospecific associations of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) were used to determine the interactions between crops forming the main arable crop ecosystem (wheat, alfalfa, isogenic and [Bt Bacillus thuringiensis] transgenic maize) in an irrigated area in Catalonia, Spain. Species composition and instars of parasitized aphids (mummies) were used to detect the parasitoid population movements between the crops and proved interactions (alternation) between the crops, including transgenic maize. Parasitoid interactions were species-dependent, appearing in the movements between alfalfa-wheat-maize in the individual species. Aphidius ervi Hal., A. rhopalosiphi DeSt.-Perez, A. uzbekistanicus Luzh., Lysiphlebus testaceipes (Cress.) and Praon volucre (Hal.) were classified as key-stone species in the target agroecosystems in the area. No differences were found in aphid-parasitoid associations on Bt transgenic maize and isogenic maize for aphid species composition and associated parasitoid guild.     

Nitrogen effect on competition between winter cereals and littleseed canarygrass

Field experiments were conducted in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between littleseed canaryglass (Phalaris minor Retz.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare =distichum L.) or triticale (Triticosecale). The presence of 400P. minor plants per square meter until early March did not have an adverse effect on dry weight of any crop. However, their further presence significantly reduced dry weight of wheat and triticale, but not that of barley. Grain yield of wheat and triticale was reduced 48% and 47%, respectively, by season-long competition ofP. minor, whereas the corresponding reduction for barley was only 8%. Crop yield reduction due toP. minor competition resulted mainly from reduction in ear number and less from reduction in 1000-grain weight. Nitrogen fertilization (150 kg N ha⁻¹), compared with control (0 kg N), slightly increased yield of all crops grown without weed competition. The same treatment also increased dry weight and competitive ability ofP. minor against wheat and triticale, compared with that of control (0 kg N); the split application of nitrogen (50 kg N ha⁻¹ before crop sowing and 100 kg N ha⁻¹ in early March) caused a slightly greater increase inP. minor dry weight than did 150 kg N ha⁻¹ applied once before crop sowing. Dry weight ofP. minor grown with barley was not affected by nitrogen fertilization, but it was severely reduced compared with that ofP. minor grown with wheat or triticale. http://www.phytoparasitica.org posting April 22, 2003.     

Real-time weed detection, decision making and patch spraying in maize, sugarbeet, winter wheat and winter barley

Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Most of all, it allows a potential reduction in herbicide use, when post‐emergence herbicides are only applied to field sections with weed infestation levels higher than the economic weed threshold; a review of such work is provided. This paper presents a system for site‐specific weed control in sugarbeet (Beta vulgaris L.), maize (Zea mays L.), winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.), including online weed detection using digital image analysis, computer‐based decision making and global positioning systems (GPS)‐controlled patch spraying. In a 4‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 60% for herbicides against broad‐leaved weeds and 90% for grass weed herbicides. In sugarbeet and maize, average savings for grass weed herbicides were 78% in maize and 36% in sugarbeet. For herbicides against broad‐leaved weeds, 11% were saved in maize and 41% in sugarbeet.     

Response of spring cereal crops to soil residues of ethofumesate*

For evaluation of soil residues of ethofumseate [(±)2-ethoxy-2,3-dihydro-3,3-dimethylbenzofuran-5-yl-methylsulphonate], spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) were sown in soil planted 11 months previously with sugar-beet (Beta vulgaris L.) and previously treated with band or broad-cast applications of the herbicide at rates of 1.68-4.48 kg/ha. The height of barley and wheat was suppressed only where ethofumesate was applied broadcast and the soil was not ploughed after sugar-beet harvest. Three months after sowing, the 4.48 kg/ha rate suppressed the height of barley 18% and wheat 34%. In another experiment, barley grew normally on soil treated the previous year with pre-planting and post-emergence applications of ethofumesate where ploughing followed sugar-beet harvest. For all treatments, yields of straw and grain were not significantly lower than those of the untreated check plots. The dissipation of ethofumesate 24 weeks after application to sugar-beet was 89–100% when applied on a band compared to 85-95% when applied broadcast.     

Continuous Cereal Growing in Denmark; Experimental Results1

In Denmark, results from 3 long-term trials showed that yields from barley monoculture were satisfactory on clay soil provided that sufficient nitrogen was supplied. Root diseases, in particular take-all (Gaeumannomyces graminis (Sacc.) Arx et Olivier), often stabilized at a rather low level after a period of decline. Mono-culture of winter wheat gave poor yields compared with barley monoculture. Break crops of white mustard and oats in barley monoculture had a beneficial effect, especially on sandy soil.     

Modelling the economics of herbicide treatment in wheat and barley using data on prevented grain yield losses

Losses in grain yield prevented by controlling weeds were measured in 59 fields of (southern hemisphere) spring-sown wheat (Triticum aestivum L.) (cv, Otane) and 45 fields of spring-sown barley (Hordeum vulgare L.) (cv. Corniche) in five consecutive growing seasons from 1988/89 until 1992/93 in the Canterbury region of New Zealand. The losses were measured as the differences in yield between weeded and non-weeded plots located in randomly positioned pairs in the fields. In the first 2 years, the weeding was by push hoe in‘organically grown crops. For the last 3 years, the fields were under prophylactic herbicide regimens with nonweeded plots created by excluding commercial herbicide applications (made mostly in October for wheat and November for barley) with polyethylene sheets placed temporarily over the plots. For each season the distributions of yield losses were modelled using the normal distribution and probabilities of ‘breaking even’ on herbicide use derived by substituting cumulative probability density functions into a simple break-even model for herbicide use. The model assumed that herbicide application in the current crop has no flow-on economic effect for succeeding crops. The mean annual yield losses prevented by herbicide application were positively correlated with September and October rainfall for wheat and bailey respectively. As a consequence, the probabilities of breaking even on herbicide use increased with increasing spring rainfall. Using historical rainfall records, probabilities of breaking even were estimated for each of the 48 years from 1947 to 1994. Averaging over these years, the analysis revealed that at current grain prices prophylactic use of the commonly applied herbicides is likely to be uneconomic in 24% (95% confidence limits 6% and 50%) of fields of average-yielding Otane wheat and in 26% (95% confidence limits 1% and 91 %) of fields of average-yielding Corniche barley in Canterbury. It was concluded that there is potential for withholding herbicide treatments without jeopardizing profitability in these crops, particularly in seasons with low spring rainfall.     

Integrated pest-management approaches in orchard,cereal and potato protection in Poland1

With its total area of 312,683 km² and a population of about 39 million people, the area of agricultural land per person in Poland is about 0.47 ha. The yields of basic crops are rather low and the losses due to pathogens, animal pests and weeds are high. The use of pesticides is about 1.0–1.3 kg a.i. per ha and this gives a good starting point for integrated pest management (IPM) in the production system of various crops. IPM in glasshouse crops reached the level of 500 ha per year. An IPM approach against codling moth (Cydia pomonella) in orchards allowed a reduction by 70% in the number of insecticide treatments. In the case of apple scab (Venturia haequalis), the IPM approach allowed a reduction in the number of fungicide treatments by 30% on an area of 100,000 ha. In respect to small grains, the IPM approach concerns rational use of fungicides and herbicides in winter wheat and barley. In potato protection, the IPM approach mainly concerns Colorado beetle (Leptinotarsa decemlineata), which at present is controlled by chemical insecticides on 77% of the potato area. Special research and demonstration IPM programmes sponsored by USDA/AID in Central and Eastern Europe will be operational during 1992/1995 and will concern orchards (apple, pear), small grains (wheat, barley) and potatoes.     

Field experiments to investigate long-term effects of repeated applications of MCPA, tri-allate, simazine and linuron: II. Crop performance and residues 1969–78

In four field experiments begun in 1963, each of four herbicides was applied to plots planted wilh the same crop each year. The annual treatments were: MCPA at 17 kg/ha to barley (Hordeum sativa Jess) and wheat (Triticum aestivum L.) at growth stage 15. tri-allate at 17 kg/ha pre-emergcnce to barley and wheat, simazine at l7kg/ha pre-emergence to maize (Zea mays L.) and linuron in two applications of 084 kg/ha pre- and post-emergence to carrots (Daucus carota L.). MCPA did not affect growth or yield of either barley or wheat. In general tri-allate also did not aftect the crops although wheat yield was depressed in 1978, wheat 1000 grain weight was reduced in 1972 and barley germination percentage was increased in 1973. Simazine did not influence the height, yield or appearance of maize. Linuron normally produced no effect on carrot yield, density and size. However, in 2 years when the post-emergence application was late, density but not yield was lower than in control plots. There was no accumulation of residues of any of these compounds in the soil. Rates of loss were similar to those predicted on ihe basis of laboratory experiments. In a fifth experiment these herbicides were applied twice per year (3 times in the case of linuron) at double the rales above on each occasion to bare plots. These applications ceased in 1968 (1969 for MCPA) but residues were monitored until 1972 except in the case of MCPA. Disappearance rates were similar to those in the cropped plots and residues were largely confined to the top 10 cm. The plots treated with MCPA had developed an enhanced ability lo degrade il prior to 1968. This persisted for 5 years after the final application.