Cauliflower Fields Research Articles

Spatial distribution of small white butterflyPieris rapae(L.) in the cauliflower fields of Tehran

One of the most basic information to understand insect population dynamics is the pattern of their spatial distribution. This study was conducted on spatial distribution of the small white butterfly, Pieris rapae (Lepidoptera: Pieridae), in the cauliflower fields in the south of Tehran from late May until October 2011. Each cauliflower plant was presumed to be a sampling unit. The pattern of spatial distribution was determined for each development stage of P. rapae by using regression models (Taylor’s power law and Iwao’s patchiness regression). The results indicated that the spatial distribution pattern was clumped for all life stages of P. rapae. In Taylor’s and Iwao’s models, the slopes of regression lines were more than one for all life stages. Also, population fluctuations of different stages of this pest were high during the season. The spatial distribution pattern can be used to improve the sampling programme, estimate the exact population density and to plan and perform integrated management of th...

Diel Activity and Behavior of <I>Bagrada hilaris</I> (Hemiptera: Pentatomidae) on Desert Cole Crops

Patterns of diel activity and behavior of the Bagrada bug, Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae), were investigated in a series of field and greenhouse experiments in Yuma, AZ. Adults of B. hilaris were monitored by on-site direct observation on broccoli and cauliflower plants in large-block experimental plots at various intervals throughout consecutive 24-h periods. In the field trials, mean number of B. hilaris adults differed among sampling times, with peak abundance observed consistently between 1300 and 1800 hours. There was a positive correlation between temperature and numbers ofB. hilaris adults in all fields, and a negative relationship between humidity and adult numbers in 7 of 12 fields. Significant relationships between temperature and B. hilaris numbers were revealed in regression models for all trials. Slopes were not significantly different among all broccoli blocks or in three of the four cauliflower fields. In greenhouse studies, mating occurred throughout the day but peaked between 1000 and 1600 hours. Females of B. hilaris caused more feeding damage than males on the first true leaf of broccoli, and additional differences in behavior between sexes were observed. Our results suggest that higher temperatures increase field activity and influence the behavior of adult B. hilaris, and temperature is a more reliable indicator to predict the activity of B. hilaris than other environmental parameters measured. The implications of these findings for developing monitoring and management programs for B. hilaris in cruciferous crops are discussed.

Natural parasitism of the diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) by a larval parasitoid wasp, Diadegma anurum on different cauliflower cultivars

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), is the most serious pest of cauliflower fields in central Iran and its control is primarily based on pesticide sprays. Over the past years, a number of new pesticide compounds were introduced onto the market and some of them may cause adverse effects on natural populations of parasitoids associated with DBM. Excessive use of insecticides against the pest did not produce satisfactory results but has caused concerns about environmental pollution and increased pest resistance to chemicals. This research aims to study natural parasitism of pest on different cauliflower cultivars in the fields of south of Tehran. Dominant species of parasitoids include Diadegma anurum, Cotesia plutellae and Oomyzus sokolowskii. The highest parasitism rate was observed by D. anurum that was recorded on Buris cultivar (19.92 ± 1.06) and White cloud cultivar (16.20 ± 1.49) and the lowest parasitism rate was observed on Snow crown cultivar (3.42) and SG cultivar (5.00) during the season.

New Record of Brachymeria albicrus (Klug) (Hymenoptera: Chalcididae), A Pupal Parasitoid of the Cabbage White Butterfly, Pieris rapae (linnaeus) from Iran

Small cabbage white butterfly, Pieris rapae is the most important insect pest of the plants belonging to family Brassicaceae. In order to identify its parasitoids, sampling was made in the cauliflower fields of southern Tehran from June until October 2011. The pupae were collected from fields and then reared under controlled conditions of 27°C, 60±10% Rh and 14L:10D photoperiod until the emergence of parasitoid adults. These parasitoids were put in alcohol 75°. One parasitoid wasp specimen was collected from the pupal samples. This parasitoid was identified as Brachymeria albicrus (Klug) (Hymenoptera: Chalcididae). This species is a new host record from P. rapae and distribution record from Tehran for the fauna of Iran.

Seasonal population fluctuations of the diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) on different cauliflower cultivars

The diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, it has been identified as a serious pest of the cauliflower fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported until now. According to many researchers, to solve the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. Despite this condition, it seems that the use of resistant cauliflower cultivars is an appropriate policy for integrated control of the pest in the field. In order to identify the most resistant cultivar in the field, eight cauliflower cultivars in a completely randomised design with five replicates were planted at the Shahed University research field (south of Tehran). Density of eggs, larvae and pupae of P. xylostella were measured every 10 days in these cultivars. The results showed that there is no significant difference between numbers of eggs per plant on different cultivars. But number of larvae and pupae per plant were significantly different among different cultivars. Smilla and Snow mystique cultivars had the highest number of larvae and pupae. On the other hand, Buris and Snow crown cultivars had the lowest number of pupae and Snow crown and SG cultivars had the lowest number of larvae per plant. According to the results, the Buris and Snow crown cultivars had the lowest infestation and had a kind of resistance to pest.

A methodological approach to assess the combined reduction of chemical pesticides and chemical fertilizers for low-carbon agriculture

The extensive use of synthetic chemicals for pest control is recognized as a major threat to ecosystem integrity and the realization of low-carbon agriculture. There have been many studies of agrochemical reduction technologies, but little work to date has been done to achieve a combined reduction of chemical pesticides and chemical fertilizers. This fact has led us to the conception of assessment methodologies and the establishment of a relevant ecological model. A significant challenge to the development of assessment methodologies is agro-ecosystem complexity. In this study, we explain the agro-ecosystem as one composed of various social, economic and natural factors that can be defined using a comprehensive positive/negative effect evaluation index system, which is based on fuzzy theory and can be used to assess combinations of technologies for reduced use of chemical pesticides and fertilizers in cauliflower fields. On this basis, a technology using 14% calcium superphosphate 750kghm−2, 46% urea 825kghm−2, 12% granular boron fertilizer 4.5kghm−2, active pesticides 3.09kghm−2 and hanging sex pheromone lure on the watermelon–cauliflower rotation mode resulted in the largest index evaluation value (0.3795) and was considered the best combined reduction technology in Chongming Eco-island, Shanghai of China. The results of our study should be of interest to policy makers and environmental managers who seek to realize low-carbon agriculture and to farmers who seek to optimize application technology in practice.

Detection and Characterization of Wolbachia in Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae), a Parasitoid of the Diamond Back Moth Plutella xylostella (Linn.)

Cotesia plutellae (Kurdjumov) is an indigenous, larval endoparasitoid that attacks mid instar larvae of the diamond back moth (DBM). Although the parasitoid is distributed widely, not all local populations appear to be equally effective in controlling the DBM. Bacterial endosymbionts may play regulatory role in determining their efficiency. Field collected C. plutellae populations from cauliflower fields were assessed for the prevalence of the bacterial endosymbionts. Bacterial endosymbionts in the genus Wolbachia were detected in the populations obtained from Hoskote (Karnataka) and Thirupathi (Andhra Pradesh). PCR amplification using specific primers for Wolbachia revealed 528 and 518 bp for the populations, respectively. Sequencing of the Wolbachia surface protein, wsp, revealed Wolbachia infection to be related to Wolbachia endosymbiont of Cotesia glomerata outer surface protein, wsp gene (Genbank Accession No. AB094202) with maximum identity of 99% with BLAST search of NCBI. The sequence was submitted to the GenBank with the Accession No. JF421566. The detection of Wolbachia in the parasitoid signifying its role in biological manipulations of the parasitoid for enhanced efficiency is discussed.

Effects of limestone applications on soil pH and extractable elements in a cauliflower field study

The pH and Mehlich-3 extractable concentrations of a variety of elements including those that were study treatments (Ca, Mn and Zn) and those that were expected to be influenced by the treatments (Mg, Sr, K, Rb, Na, Al, Fe, Si and Cu) were determined in soil samples from a cauliflower field trial conducted between 1979 and 1985. The treatments were limestone applied to the soil at three rates (0, 9 and 19 Mg ha-1) and Zn and Mn foliar applications. The pH of air-dried samples varied only slightly when analysed within each year of sampling versus as one batch after the trial was completed, which showed that the samples were stable over the long time the samples had to be stored through the field trial period and until the samples were analysed. Being able to do all the analyses in one batch also facilitated the application of quality control to ensure comparability of results. There were differences in the soil measurements of most of the elements taken pre-plant versus post-harvest, showing that the time of sampling must be consistent for experimental and soil test interpretations. Post-harvest samples (i.e., focusing on residual effects of limestone application) were selected to examine the treatment effects. Limestone application had wide-ranging and variable effects on extractable elements in the soil. Soil pH and extractable Ca increased with increased limestone rate as expected, while the amount of extractable Mn, Zn, K, Mg, Na, Al and Fe decreased. Extractable Sr, Si and Cu increased with limestone applications. Extractable Ca, Zn, Mg, Al and Si were affected to 15-30 cm depth, and pH and extractable Mn, Rb and Fe were affected to 30-60 cm. Subsurface (>15 cm depth) Sr, K, Na and Cu were not influenced by the limestone treatments. The effect of limestone on the elements tended to correspond to the effect previously observed on the contents of these elements in cauliflower plants. The ability of Mehlich-3 extract solution to reflect the availability of elements to plants and the effect of limestone applications on other elements simultaneously showed the potential for this soil test solution to predict the need for nutrient amendments to prevent lime-induced deficiencies.

Occurrence and Diversity of Xanthomonas campestris pv. campestris in Vegetable Brassica Fields in Nepal.

Black rot caused by Xanthomonas campestris pv. campestris was found in 28 sampled cabbage fields in five major cabbage-growing districts in Nepal in 2001 and in four cauliflower fields in two districts and a leaf mustard seed bed in 2003. Pathogenic X. campestris pv. campestris strains were obtained from 39 cabbage plants, 4 cauliflower plants, and 1 leaf mustard plant with typical lesions. Repetitive DNA polymerase chain reaction-based fingerprinting (rep-PCR) using repetitive extragenic palindromic, enterobacterial repetitive intergenic consensus, and BOX primers was used to assess the genetic diversity. Strains were also race typed using a differential series of Brassica spp. Cabbage strains belonged to five races (races 1, 4, 5, 6, and 7), with races 4, 1, and 6 the most common. All cauliflower strains were race 4 and the leaf mustard strain was race 6. A dendrogram derived from the combined rep-PCR profiles showed that the Nepalese X. campestris pv. campestris strains clustered separately from other Xanthomonas spp. and pathovars. Race 1 strains clustered together and strains of races 4, 5, and 6 were each split into at least two clusters. The presence of different races and the genetic variability of the pathogen should be considered when resistant cultivars are bred and introduced into regions in Nepal to control black rot of brassicas.

Effect of host plants on life-history traits of Spodoptera exigua (Lepidoptera: Noctuidae)

Host plants play an important role in population increases and outbreaks of cosmopolitan polyphagous insect pest, such as Spodoptera exigua (Hubner; Lepidoptera: Noctuidae). We investigated the impact of various host plants (cauliflower, peas, and wheat) on fitness and relative growth rate of S. exigua and intrinsic rate of population increase. The S. exigua population was collected from cauliflower fields from Multan, Pakistan. Comparison of various life-history traits on three different host plants revealed significant differences that might be correlated with the fitness costs. The mean number of eggs laid by female reared on cauliflower was significantly greater than on peas or wheat. Similarly, eggs viability, intrinsic rate of population increase, adult eclosion, and adult’s longevity were significantly higher on cauliflower than on peas and wheat. The low survival on peas and wheat suggest the unsuitability of these host plants, while the higher pupal weight on cauliflower suggest that it provides better food quality to S. exigua compared with peas and wheat. On peas and wheat, fitness declined with each generation suggesting that the average fitness of individuals may decline due to the elimination of insects with higher fitness. Our results suggest that cauliflower was the most nutritive and preferred host plant. Such results could be useful to design cultural management strategies, which may include trap cropping.

Characterization and pathogenicity of Rhizoctonia isolates associated with cauliflower in Belgium

Sixty‐two isolates of Rhizoctonia spp. were collected from Belgian cauliflower fields during 2005 and 2006. The majority of the isolates (60 out of 62) had multinucleate cells and were identified as Rhizoctonia solani. Characterization of anastomosis groups (AGs) was performed using pectic zymograms, PCR‐RFLP and sequencing of the rDNA‐ITS region. The most prevalent AG was AG 2‐1 (55% of isolates), followed by AG 2‐1 subset Nt (11%), AG 1‐1C (8%), AG 5 (8%), AG 4 HGII (6%), AG 3 (5%) and AG 1‐1B (3%). Pathogenic potential towards different vegetable crops and towards maize was determined. Damage to cauliflower and endive was caused by different AGs, with the isolates aggressive towards cauliflower belonging to AG 2‐1, AG 2‐1 subset Nt, AG 4 HGII, AG 1‐1C, AG 1‐1B and AG 2‐2, and those aggressive towards endive belonging to AG 1‐1B, AG 1‐1C, AG 2‐1 subset Nt, AG 2‐2, AG 4 HGII and AG 5. The most aggressive isolates towards bean belonged to AG 2‐1 subset Nt and AG 2‐2, for lettuce to AG 1‐1B and AG 2‐1, on carrot to AG 4 HGII and towards maize to AG 2‐2. Within the isolates of AG 2‐1, variability was observed in PCR‐RFLP pattern and in aggressiveness towards several crops, indicating this subgroup to be heterogeneous. This is the first study concerning the occurrence of R. solani AGs causing wirestem in Belgian cauliflower fields and the first report of aggressive isolates of AG 1‐1C, AG 2‐1 subset Nt and AG 4 HGII associated with cauliflower.

Severe and Widespread Clubroot Epidemics in Nepal.

Cultivation of brassica vegetables has the highest potential for generating income among more traditional rice and maize farmers in Nepal. Among brassica vegetables, the most important are cauliflower (Brassica oleracea var. botrytis L.) and cabbage (B. oleracea var. capitata L.). Although clubroot disease, caused by Plasmodiophora brassicae Woronin, has been observed in Nepal since 1993, severe and widespread epidemics have been observed since 2004 in the Bhaktapur, Kathmandu, Lalitpur, and Palung Valley production areas. Typical disease symptoms (1) are widespread, and disease severity has been particularly severe in the Kathmandu Valley and Palung/Daman area of the Makwanpur District. Many cauliflower fields in these areas have had as much as 100% yield loss between 2004 and 2006 with an estimated 40% overall loss from clubroot. Estimates from interviews with growers in the Palung production area during an intensive farmers' interaction program indicated that cauliflower production was reduced from 5 to 6 metric tons per household (1,500 m2) prior to 2004 to <300 kg per household in 2004 and beyond. The economic loss in this area alone was estimated at $1.4 million in 2004 and 2005. Examination of transplant nurseries indicated that frequently >80% of the seedlings have symptoms of clubroot at the time of transplanting. Soil samples from throughout the production areas indicated that the sandy loam soils were predominately acidic (pH range of 4.2 to 7.2 with >90% below 6.0). Several management practices are being employed to reduce disease severity, including the use of clubroot resistant cultivars, raising the soil pH to >7.0 by using dolomitic lime, testing of the fungicide flusulfamide (Nebijin) and biopesticide Sanjeevani (Trichoderma viride), and biofumigation and solarization of the nursery beds in an effort to reduce disease pressure on transplant material.

Levantamento da intensidade da alternariose e da podridão negra em cultivos orgânicos de brássicas em Pernambuco e Santa Catarina

O objetivo deste trabalho foi avaliar a intensidade da alternariose, causada por Alternaria brassicicola e/ou Alternaria brassicae, e da podridão negra, causada por Xanthomonas campestris pv. campestris, em cultivos orgânicos de brássicas em Pernambuco e Santa Catarina. Os levantamentos foram realizados no período de novembro de 2001 a fevereiro de 2002, num total de 103 cultivos orgânicos de várias espécies de brássicas. Foram registradas elevadas prevalências das doenças nos estados, com exceção em couve-chinesa em Santa Catarina. A prevalência da alternariose foi 100% nos cultivos de brócolis em Pernambuco, bem como em couve-flor nos dois estados, enquanto a podridão negra atingiu esse nível nos cultivos de brócolis e couve-flor em Santa Catarina. Na média das diferentes espécies de brássicas, as doenças foram mais prevalentes em Pernambuco que Santa Catarina. Entretanto, as médias de severidade de cada doença no conjunto das brássicas não foram diferentes entre os estados, embora as condições climáticas tenham sido nitidamente distintas. A severidade da alternariose variou entre as espécies de brássicas somente em Pernambuco, com a menor severidade registrada em couve-manteiga. Em relação à podridão negra, apenas em Santa Catarina houve diferença na severidade entre as brássicas, sendo registrados os menores níveis em couve-chinesa. Não foram constatadas correlações significativas entre os níveis de severidade da alternariose e da podridão negra, bem como da severidade destas com o número total de plantas e a idade das plantas nos cultivos.

Reservoir Weed Hosts for Turnip mosaic virus in Iran.

During the summer of 2003, weed samples of Rapistrum rugosum and Sisymbrium loeselii showing severe mosaic, malformation, and stunting were collected from cauliflower fields in Tehran Province of Iran. Using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with specific polyclonal antibodies, the samples were tested for the presence of Beet western yellows virus, Cauliflower mosaic virus, Radish mosaic virus, Turnip crinkle virus, Turnip mosaic virus (TuMV) (DSMZ, Braunschweig, Germany), Cucumber mosaic virus, and Tobacco mosaic virus (Sanofi Diagnostics Pasteur, Marnes-La-Coquette, France). Leaf extracts were used for mechanical inoculation and they produced chlorotic local lesions on Chenopodium amaranticolor, necrotic lesions on leaves and shoot apex necrosis on Nicotiana glutinosa, leaf deformation, mosaic, and stunting on Petunia hybrida, and severe mosaic, distortion, and stunting on Brassica rapa. These symptoms were similar to those that were described previously for TuMV (4). ELISA results showed that the original leaf samples and inoculated indicator plants reacted positively with TuMV antibodies, but not with antibodies for any of the other viruses listed above. Also, reverse transcription-polymerase chain reaction of total RNA extracted from the collected leaf samples using the universal primers for potyviruses (3) resulted in the amplification of two fragments of the expected sizes, approximately 700 and 1,700 bp. TuMV, a member of the genus Potyvirus in the family Potyviridae, is transmitted by aphids in a nonpersistent manner (4). This virus is geographically widespread with a wide host range that can infect 318 species in 156 genera of 43 plant families including, Brassicaceae, Chenopodiaceae, Asteraceae, Cucurbitaceae, and Solanaceae (2,4). R. rugosum and S. loeselii, two annual or biennial plants in the Brassicaceae family, were common and widely distributed in the fields surveyed. The presence of TuMV-infected weed hosts in cauliflower fields may impact disease management strategies. TuMV was first observed on stock plants (Matthiola sp.) in Iran (1). To our knowledge, this is the first report of natural occurrence of TuMV on weed hosts in Iran.

Lignin is involved in the reduction of Verticillium dahliae var. longisporum inoculum in soil by crop residue incorporation

Verticillium wilt is an increasing problem in European cauliflower production. In this study, several crop residues were screened for their ability to reduce the viability of microsclerotia when incorporated into soil. In addition, the role of fungitoxic volatiles and lignin in the crop residue-mediated reduction in microsclerotia viability was studied. Broccoli ( Brassica oleracea var. italica), cauliflower ( B. oleracea var. botrytis), Indian mustard ( Brassica juncea), ryegrass ( Lolium perenne) and corn ( Zea mays) were incorporated in naturally infested soil samples collected from two cauliflower fields in Belgium, labelled Is1 and S3. The effectiveness in reducing the viability of microsclerotia depended on the soil sample and on the type of residue. In the Is1 soil, broccoli, cauliflower and ryegrass incorporation significantly reduced the inoculum level by more than 90%, while Indian mustard significantly reduced numbers of viable microsclerotia by 50%. In the S3 soil, broccoli, cauliflower and Indian mustard were not effective, whereas ryegrass and corn incorporation reduced the microsclerotia level by 50% or more. In conclusion, incorporation of ryegrass and corn was more effective than incorporation of crucifer residues. In the conditions tested, fungicidal volatile compounds did not play an important role in Verticillium microsclerotia reduction in soil. Volatiles from broccoli and cauliflower did not affect microsclerotia viability in an in vitro bioassay, whereas the volatiles from Indian mustard killed the microsclerotia. Indian mustard incorporation in soil, however, only had a minor effect on microsclerotia viability. In the S3 soil, 1% (w/w) Kraft pine lignin, a waste product of the paper industry, had to be added to observe a significant reduction on the viability of microsclerotia, whereas in the Is1 soil, a significant effect was observed when 0.1% (w/w) Kraft pine lignin was added. Acid-insoluble lignin was extracted from all crop residues previously tested. Crop residues with high lignin content seemed to be more effective than crop residues with low lignin content. The reduction of Verticillium microsclerotia viability depended on lignin type and on crop structure, since lignin extracted from cauliflower leaves was more effective than lignin extracted from cauliflower stems and corn leaves were more effective than corn roots. Microsclerotia reduction was higher after fresh residue incorporation than after incorporation of their extracted acid-insoluble lignin, indicating that the effect of crop residue incorporation on microsclerotia viability cannot be explained solely by the effects of lignin. Incorporation of lignin-rich substrates in soil may open up new perspectives for integrated control of Verticillium.

Measured and Simulated Nitrate Leaching on an Organic and a Conventional Mixed Farm

ABSTRACT A number of fields on an organic (a potato field, a pasture and a field with red cabbage) and a conventional mixed farm (a potato field, a pasture and a field with cauliflower) were compared with respect to nitrate leaching in winter, using both soil mineral N measurements and a simulation approach. Soil organic matter N mineralization rates of the surface layers were determined during laboratory incubations. Mineral N contents of the 0–90 cm layer of each field were monitored during the period October-March. A coupled N mineralization—leaching model was used to simulate NO3-leaching over this period. Calculated NO3-leaching was in the same range on most fields, between 66 and 87 kg NO3-N ha−1, except for the conventional pasture, which had smaller losses (35 kg NO3-N ha−1), and the conventional cauliflower, which had very large losses (293 kg NO3-N ha−1). The contribution of N mineralization during autumn and winter to NO3 leaching was important, and could only be taken into account explicitly using simulation models. The most remarkable difference with respect to N leaching was observed between the conventional cauliflower and organic red cabbage field, both with very high N fertilization rates. This was attributed to the differences in type of fertilizer applied, with N fertilization on the conventional fields much more conducive to N losses. The average NH4 +-N concentrations during the field experiment were larger on the organic fields than on the conventional fields. This indication for a retardation or inhibition of nitrification in the organic fields is an important observation, which obviously could have important implications for NO3 − leaching, but needs to be further investigated and quantified before it could be incorporated into simulation models.

Binomial sampling as a cost efficient sampling method for pest management of cabbage root fly (Dipt., Anthomyiidae) in cauliflower

A binomial (presence–absence) sampling plan has been developed based on the relationship between the proportion of cauliflower plants having visible cabbage root fly eggs (Delia radicum L.) exposed on the soil surface around the plant stem and the mean density of eggs per plant. The Kono–Sugino’s model was fitted to a total of 125 population estimates, each based on 10 plant samples collected from cauliflower fields in 1994 and 1995 (P=0.001; R2=0.64). When the model was compared with an independent data set consisting of 39 population estimates collected in 1995, an analysis of covariance showed no significant differences between the regression lines. The efficiency of the binomial method was compared with absolute sampling in terms of relative precision and cost efficiency. The binomial method had a high coefficient of variation, RV≈ 0.85, due to large biological error. In spite of this, binomial sampling was more cost efficient than the applied soil sampling when between 10 and 30 plants were examined for the presence of visible eggs.

Rodents in cauliflower and cabbage: Population, damage and control

Mus musculus, Bandicota bengalensis, Rattus meltada and M. booduga were the major rodent species in the cauliflower fields, comprising 26 .87, 23.47, 16.40 and 13.23%, respectively, of the total rodent population in the curd crop and 27 .09, 22.96, 18.12 and 13.98%, respectively, in the seed crop. These fields supported 53 to 57 active rodent burrows per hectare. Rodent damage occurred from the curd formation stage onwards and varied from4 .44 to 11.37% in the curd crop and 8.36 to 13.94% in the seed crop. B. bengalensis and R. meltada appeared to be the most damaging species as their burrows were located in the fields either at the base or in the near vicinity of the plants, whereas burrows of mice were at the periphery of the fields. Burrowbaiting with 0 .005% flocoumafen and 0 .005% bromadiolone yielded 76 .9 and 76.1% control success, respectively. Pulsed-baiting with 2 .5% zinc phosphide applied in burrows, followed by bromadiolone provided 83 .4% control success. Such a treatment (pulsed-baiting) resulted in a saving of up to 1080 kg curd and up to 25 .028 kg seed/ha in cauliflower curd and seed crop, respectively.

Herbicides interactions with cow manure and field soil organic matter

Abstract The direct interaction of the herbicide metazachlor ‐chosen as an example‐ with the soil organic matter has been studied by laboratory incubation of old and young cow manures containing metazachlor. The extraction efficiencies of solvents of increasing polarities indicated the formation of association compounds by bonds weaker than covalent between metazachlor and the organic matter: electron donor‐acceptor complexes, hydrogen bonding complexes, and complexes by both bonding types. Laboratory incubation of metazachlor in soil of low organic matter content indicated that the soil mineral part only had a diluting effect on the soil organic matter capacity to adsorb metazachlor. Similar association compounds were observed in the soil of a cauliflower field crop. Their concentrations were greater in the plots treated with organic fertilizers than in the organic fertilizers untreated plots. The free‐ unbound metazachlor was faster metabolized than the one bound to the soil organic matter, explaining why the organic fertilizer treatments slow down the herbicide soil biodegradation during the main first crop period. Inclusion of metazachlor in the field soil humic acids lattice ‐another kind of herbicide association compound with the soil organic matter‐ occurred at crop end when most of the metazachlor was metabolized; the soil concentrations of this kind of association compound thus was low, so that the release after crop of metazachlor in the environment has no practical significance.

Insecticide soil persistence and efficiency in cauliflower field crops: Influence of organic fertilizer and organic matter properties

Cauliflower crops were treated some days after planting against the root fly by pouring onto soil around the plant stem an emulsion of chlorpyrifos or of carbofuran in water. The fields were divided into plots; each plot was treated with one of the organic fertilizers: cow manure, city refuse compost, or mushroom cultivation compost; there were also control plots not treated with organic fertilizers. During the first 50 days crop period, the insecticide soil persistence was greater in the organic fertilizers treated plots—relative to the untreated control plots—probably giving better insecticide protection of the young plants. Thereafter and till harvest, the soil insecticide concentrations became similar in the organic fertilizers treated plots and in the controls. The organic fertilizer soil treatments increased—relative to the controls—the total soil organic matter and the humic acids soil concentrations, and the humic acids nitrogen content. The organic fertilizer soil treatments generated humic acids which contained—according to their 13C NMR spectra—more ketonic, carboxylic acid and ester, aromatic phenolic and amines, and aromatic carbons, relative to the humic acids from the controls. These chemical functions are able to bind insecticides in soil. This fact supports the hypothesis that the organic fertilizer soil treatments increase the pesticide adsorption onto the soil organic matter, protecting the insecticides against the metabolizing soil microbial activity.