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1.
Abstract

The distribution, hosts, phenology and abundance of Athesapeuta cyperi, an insect enemy of purple nutgrass, Cyperus rotundus, in Pakistan are given. Its biology and damage to C. rotundus in the laboratory are also reported. Usually one egg was laid in a tuber. When two eggs were present, only one reached maturity. The infested tuber was completely hollowed out and failed to regenerate. Thus, 100% plants infested with A. cyperi were killed. In host specificity tests larval development occurred on Cyperus spp. and Fimbristylis ferruginea but oviposition was restricted to Cyperus spp. However, C. rotundus was preferred to other species of Cyperus both for oviposition and development.  相似文献   

2.
Control options for Cyperus rotundus and Cyperus esculentus (purple and yellow nutsedge) were evaluated within three cropping systems in the low desert of southern California: (1) standard vegetable crop rotation (weed‐free, uncontrolled nutsedge and cultivation) with spring cantaloupe (Cucumis melo) – summer fallow – winter broccoli (Brassica oleracea), (2) cover crop rotation (halosulfuron and smother crop) with spring wheat (Triticum aestivum)/corn (Zea mays) – summer sudangrass (Sorghum sudanense) – Winter Fallow, (3) rotation with solarization (non‐solarization and solarization) with spring wheat – summer fallow/solarization – winter broccoli. After two growing seasons, broccoli was planted without Cyperus control, to study the effect on yield. Cyperus rotundus tubers increased from 0.66 tubers per m2 to 1260 tubers per m2 in the uncontrolled treatment over two seasons. Cultivation during the growing season reduced C. rotundus tubers by 93% compared with the uncontrolled plots. Cover crop rotation did not reduce the number of C. rotundus tubers significantly, despite the dense sudangrass canopy shading the soil during most of the summer. Cyperus rotundus was effectively controlled by the solarization treatment. All methods controlled C. esculentus, especially when there were no crops growing in the summer. When broccoli was grown after two years of various management strategies, the cultivation treatment showed a 44% yield reduction compared with the weed‐free control, while the solarization treatment increased broccoli yield by 64% compared with the non‐solarization treatment. Rotations that included sudangrass had low broccoli yield when either C. rotundus or C. esculentus were present.  相似文献   

3.
Established Greenhouse grown plants of cogongrass Imperata cylindrica (L) Beauv.) and purple nutsedge (Cyperus rotundusL.) were given three different soil moisture regimes; field capacity, moderate stress and extreme stress, followed 6 weeks later by glyphosate [(N-phosphonomeihyl) glydne] applications to the shoots at 0.2,0.4 and 0.8 kg/ha for Imperata and 0.3,0.6 and 1.12 kg/ha for Cyperus. Field capacity watering stimulated most vegetative growth in hoth species. Glyphosate given at field capacity decreased shoot dry weight in both species, and rhizome length, rhizome dry weight and total carbohydrate in Imperata and total number of tuber-bulbs in Cyperus. In contrast. at extreme soil moisture stress, glyphosate showed reduced activity which appeared to be related to the physiological and morphological behaviour of the plants arising from the drought trealment. Application of waier to the roots of the plants grown at soil moisture stress. I week before and I week afler glypbosate spraying, enhanced glyphosate activity, probably because of the recovery of processes disturbed by ibe soil moisture deficit.  相似文献   

4.
A survey of weeds and weeding practices was carried out by a team of agricultural economists and agronomists on 283 farms in five Cassava growing regions of Colombia at three times during a cropping season. Seventy-one to 78% of all weed species present were broadleaved species. As cassava grew older, grass species were present to a greater and sedge species to a lesser relative frequency. Surprisingly Pteridiumaquilinum (L.) Kuhn was the most frequently listed species and Bidens pilosa L. and Cyperus rotundus L. were other frequent problems. Regional variations in the most frequently encountered species were found but several of the weeds were common to many zones. The most frequently encountered species did not usually have the highest plant populations. Most of the annual grasses, sedges and broadleaf weeds found can be controlled by currently recommended herbicides for cassava but further research is needed on Imperata cylindrica (L) Beauv., Melinis minutlftora Beauv., P. aquilinum and Sida spp. The average number of manual weedings was 3.3 per crop, occupying 48 man-days/ha which is 50% of the total labor requirements for cassava production, and more than one-third of the total costs. Reasons for not using herbicides were (1) relative costs of herbicides and labor. (2) lack of information, (3) lack of capital, (4) right herbicides were not available, and (5) herbicides were not available in small packages. This survey has usefully identified new field problems and has suggested further research programs to solve them.  相似文献   

5.
Abstract

Results are given of a trial in which trifluralin, incorporated in the soil, at rates of 0.5 and 0.75 kg/ha, was combined with fluometuron at 1.6 kg/ha, and with prometryne at 1.0 kg/ha, both incorporated, pre- and post-em. and with noruron + MSMA (1.0:2.2) at 1.7 kg/ha post-em.

Best results were given by incorporated treatments of trifluralin + fluometuron (0.5 + 1.6) kg/ha, or by trifluralin incorporated at 0.5 or 0.75 kg/ha + fluometuron applied pre-em. at 1.6 kg/ha, or by trifluralin incorported at 0.75 kg/ha + prometryne applied pre-em. at 1.0 kg/ha.

It is recommended that noruron + MSMA (1.0:2.2) at 1.7 kg/ha be applied post-em. as a complementary treatment to trifluralin at 0.5 kg/ha in fields where Cyperus spp. are a problem.  相似文献   

6.
Summary. The response of tubers to low temperatures was investigated to gain insight into a physiological basis for the differential distribution of Cyperus esculentus L. (yellow nutsedge) and C. rotundus L. (purple nutsedge) in the United States. Only C. esculentus tubers survived the winter of 1968–69 in the field at Urbana, Illinois. Less than 10% of C. rotundus tubers survived at 2°C for 12 weeks, whereas more than 95% of C. esculentus tubers survived this treatment. Exposures to -2°C for 4 h or longer killed 50% of C. rotundus tubers, whereas - 6·5°C was required to kill 50% of C esculentus tubers. C. rotundus distribution is restricted to regions where the soil seldom freezes, whereas C. esculentus is distributed in regions where the soil temperatures often get below freezing. Survival of C. esculentus tubers in soil which frequently freezes may account for its wide distribution. Death of C. rotundus tubers in soils which freeze apparently is the reason why the species is restricted to the southeastern and southwestern regions of the U.S.A. L'Influence de la température du sol sur la répartition différentielle de Cyperus rotundus et de Cyperus esculentus aux Etats-Unis  相似文献   

7.
During a 3-year field study on two vineyards of north-eastern Croatia, the qualitative and quantitative composition as well as the vertical dynamics of Xiphinema spp. were determined each month. The greatest number of fertile X. vuittenezi females was noted in August-September at a soil moisture of 18–20%. The greatest number of larvae of this species was determined in September-October in a temperature range of 14–18°C and soil moisture of 18–22%. The development cycle of X. vuittenezi lasts about 24–33 months under natural conditions and that of its larval stages 3–8 months. The nematodes of this species are susceptible to high temperatures (above 20°C) and drought (under 13%). The greatest number of fertile females of X. pachtaicum was determined in July at a soil temperature of 20–24°C, absolute soil moisture of 16–20%. The greatest number of larvae was noted in September-October at a soil temperature of 16–21°C and soil moisture of 13–23%. The development cycle of X. pachtaicum in field conditions lasts about 12–13 months and that of the larval stages 2–3 months. This species demonstrated reduced activity at soil temperatures under 10°C and at soil moisture under 13%; larvae were less active than females at temperatures over 20°C. On the basis of the results obtained, it is suggested that sampling of vineyards to determine the distribution and population density of the two Xiphinema spp. should be performed at depths down to 50 cm in spring and autumn, which are also the most favourable times for nematicide application.  相似文献   

8.
Imperata cylindrica and Cyperus rotundus were grown under three different light regimes; unshaded, 50% shade, and 75% shade and no shade plus 75% shade before and after spraying, (temporary shade) in a heated greenhouse. Six weeks after the start of the experimenis, glyphosate was applied to the plants at 0·2, 0·4 and 0·8 kg/ha (for Imperata) or 0·3, 0·6 and 1·2 kg/ha (for Cyperus). Glyphosate toxicity was enhanced as shade increased. In Imperata, all shade regimes at all rates of glyphosate eaused greater damage to the plants than the unshaded regime. The reduction in shoot dry weight, rhizome dry weight and total carbohydrate content of Imperate rhizotties at 75% continuous and temporary shaiie conditions, with the lowest rate of glyphosate, was almost twice as much as the reduction in the same features m the unshaded plants caused by the highest rate of glyphosate. In Cyperus. glyphosate at the intermediate and highest rates decreased the shoot dry weight at 75% continuous shade by 79% and 98% respectively. Plants in 50% shade were significantly affected only at the highest rate of glyphosate. Sprouting ability of the tubers al 75% continuous shade was inhibited when the tubers were replanted for recovery. Enhanced toxicity of glyphosate in reduced light intensity was attributed to the morphological changes in the nature of the leaves caused by shade.  相似文献   

9.
Abstract

In the Punjab province of Pakistan, cotton is subject to attack by three major bollworm pests: Pectinophora gossypiella, Earias vittella and £ insulana. Because of the difficulty of controlling these pests once their larvae have penetrated the bolls, early season control is essential. A non‐toxic method is desirable if beneficial insects are not to be destroyed. Tests with a Mitsubishi ‘twist‐tie’ pheromone formulation containing the major components of Pectinophora and the two Earias spp. achieved almost complete trap suppression of all three species for up to eight weeks duration following a single application at the pin‐square stage. Visual observations confirmed a complete lack of moth activity indicating that control by mating disruption was attainable.  相似文献   

10.
Decline of newly planted, grafted grapevines is a serious viticultural problem worldwide. In the Riverina (New South Wales, Australia), characteristic symptoms include low fruit yields, very short shoots and severely stunted roots with black, sunken, necrotic lesions. To determine the cause, roots and wood tissue from affected plants in 20 vineyards (Vitis vinifera cv. Chardonnay grafted to V. champini cv. Ramsey rootstock) were assayed for microbial pathogens. Ilyonectria spp. (I. macrodidyma or I. liriodendra, producers of phytotoxin brefeldin A, BFA, and cause of black foot disease of grapevines) and Botryosphaeriaceae spp. (predominantly Diplodia seriata) were isolated from rootstocks of 100 and 95% of the plants, respectively. Togninia minima and Phaeomoniella chlamydospora (cause of grapevine Petri disease) were isolated from 13 and 7% of affected plants, respectively. All Ramsey rootstock stems of grafted plants sampled from a supplier nursery were infected with Ilyonectria spp. and D. seriata. Diplodia seriata, but not Ilyonectria spp., was also isolated from 25% of canes sampled from the rootstock source block. Root inoculation of potted, disease‐free Chardonnay plants with Ilyonectria isolates from diseased vineyards caused typical disease symptoms, while co‐inoculation with Botryosphaeriaceae spp. increased disease severity. This is the first study to show that a major cause of young grapevine decline can be sequential infection by Botryosphaeriaceae from rootstock cuttings and Ilyonectria spp. from nursery soil. Although the Petri disease fungi were less common in young declining grafted grapevines in the Riverina, they are likely to contribute to the decline of surviving plants as they mature.  相似文献   

11.
The control of weeds and nematodes by solar heating of the soil using transparent polyethylene (PE) sheets was studied in the field during the summer of 1990. PE mulching for 32 days decreased the emergence from seed of the dominant weeds Dactyloctenium aegyptium (L.) P. Beauv., Acrachne racemosa (Roem. & Schult.) Ohwi, Trianthema monogyna L. and Cyperus rotundus L. by over 90%. Emergence of C. rotundus from tubers was increased by the mulching treatments. Mulching for 16 days also decreased weed emergence but to a lesser extent than the 32-day treatment. The main solarization effect was restricted to the 0–5 cm layer of soil. Solarization reduced the population of plant-parasitic nematodes (Tylenchus, Heterodera, Xiphinema, Hoplolaimus, Pratylenchus and Ro-tylenchus spp.) by about 90% and of saprophytic nematodes by about 60% but, after 70 days, the nematode levels had largely recovered. The mean maximum soil temperatures recorded at 5 cm were higher when mulching followed irrigation. Data are given on the soil temperatures recorded over the 32-day period. The growth of soybean was improved and seed yield increased by up to 78% following solarization. Effet de la solarisation du sol sur les mauvaises herbes et les nematodes en conditions tropicales indiennes La lutte contre les mauvaises herbes et les nématodes par solarisation du sol à l'aide de films de polyéthylène transparent (PE) a étéétudiée au champ pendant l'été 1990. Trente deux jours de solarisation diminuaient de plus de 90% la levée à partir de graines des mauvaises herbes dominantes Dactyloctenium aegyptium (L.) P. Beauv., Acrachne racemosa (Roem. & Schult.) Ohwi, Trianthema monogyna L. et Cyperus rotundus L. La levée de C. rotundusà partir de tubercules était accrue par la solarisation. Seize jours de solarisation diminuaient aussi la levée des mauvaises herbes, mais dans un moindre mesure. L'effet de solarisation s'exerçait principalement dans les 5 centimètres superficiels du sol. La solarisation réduisait d'environ 90% la population de nématodes parasites des plantes (Tylenchus, Heterodera, Xiphinema, Hoplolaimus, Pratylenchus et Rotylenchus spp.) et d'environ 60% la population des nématodes saprophytes. Après 70 jours, les populations de nematodes étaient pratiquement reconstituées. Les moyennes des températures maximales du sol enregistrées à 5 cm de profondeur étaient plus élevées quand l'installation du film polyéthylène suivait une irrigation. Des données concernant la température du sol sur 32 jours sont communiques. La croissance du soja était accrue et le rendement en grains augmentait jusqu'à 78% après solarisation. Wirkung der Bodensolarisation auf Unkräuter und Nematoden unter tropischen Bedingungen Die Bekämpfung von Unkräutern und Nematoden durch Solarisation mittels farbloser Polyethylenfolia (PE) wurde im Sommer 1990 im Freiland untersucht. Nach 32tägiger Solarisation nahm die Keimung der vorherrschenden Unkräuter Dactyloctenium aegypticum (L.) P. Beauv., Acrachne racemosa (Roem. & Schult.) Ohwi, Trianthema monogyna L. und Cyperus rotundus L. um über 90% ab. Der Austrieb von Cyperus rotundus aus Knollen wurde gefördert. Eine l6tägige Solarisation war nicht so wirkungsvoll. Die Wirkung war auf die oberste Bodenschicht bis 5 cm Tiefe beschränkt. Gegen pflanzenparasitische Nematoden (Tylenchus, Heterodera, Xiphinema, Hoplolaimus, Pratylenchus und Rotylenchus spp.) betrug die Wirkung der Solarisation etwa 90%, gegen saprophytische Nematoden rund 60%, aber nach 70 Tagen hatten sich die Nematodenpopulationen wieder weitgehend erholt. Nach Bewässerung wurde in 5 cm Tiefe eine höhere Bodentemperatur erreicht. Für die 32-Tage-Periode werden die Temperaturdaten wiedergegeben. Nach der Solarisation war das Wachstum von Sojabohne verbessert, und die Erträge stiegen um bis zu 78%.  相似文献   

12.
The acidic ether fraction of methanol extracts from Cyperus rotundus L. (purple nutsedge) tubers contained inhibitory substances described hereafter as inhibitor β. Inhibitor β inhibited sprouting of excised C. rotundus buds and also the elongation of wheat coleoptiles. The inhibition of bud sprouting by inhibitor β was reversed by the application of N-6-benzyl adenine (BA). Applications of abscisic acid (ABA) also inhibited sprouting of the excised buds and this was similarly reversed by BA applications. Chromatographic evidence suggested that inhibitor β mainly consisted of phenolic materials and possibly ABA as a minor component. The role of BA in enhancing sprouting of C rotundus tubers is discussed. Inhibition des bourgeons de bulbes de Cyperus rotundus L. par I'inhibiteur β ou l'acide abscissique et réversion de ces effects par la N-6-benzyl adénine La fraction éther acide d'extraits, par le méthanol. de bulbes de Cyperus rotundus L. contient des substances inhibitrices decrites ci-après comme I'inhibiteur β. Cet inhibiteur β a inhibé la germination de bulbes isolés de C. rotundus ainsi que l'élongation de coléoptiles de blé. L'inhibition de la germination des bourgeons par I'inhibiteur βété renversée par l'application de la N-6-benzyl adénine (B.A.). Des applications d'acide abscissique (ABA) ont également inhibé la germination de bourgeons isolés et cet effet a été lui aussi renversé par des applications de B.A. Les chromatogrammes suggèrent que l'inhibiteur β est principalement constitué par des composés phénoliques et peut-être par I'ABA comme composant mineur. Le rôle de la B.A. dans l'inhibition de la germination des bulbes de C. rotundus est discuté. Knospenhemmung der Knollen von Cyperus rotundus L. durch Hemmstoff β oder Abscisinsäure und die Umkehrung dieser Effekte durch N-6-Benzylmlenin Die saure Fraktion aus methanolischen Extrakten von Cyperus rotundus L.-Knollen enthielten Hemmstoffe, die im folgenden als Hemmstoff β bezeichnet werden. Hemmstoff β hemmte das Sprossen isolierter C. rotundus-Knospen und die Streckung von Weizenkoleoptilen. Die Hemmung der Knospensprossung durch Hemmstoff β wurde durch An-wendung von N-6-Benzyladenin (BA) aufgehoben. Abscisinsäure (ABA) hemmte auch das Sprossen isolierter Knospen; durch BA wurde es auf ähnliche Weise aufgehoben. Der chromatographische Befund deutet darauf hin. Daß Hemmstoff β sich hauptsächlich aus phenolischen Verbindungen zusammensetzt und möglicherweise in gering-em Unfang ABA enthält. Die Rolle von BA auf die Förderung der Keimung von C. rotundus-Knollen wird diskutiert.  相似文献   

13.
Nuclear polyhedrosis virus (NPV) and Bacillus thuringiensis (Bt) are the most commonly used biopesticides for the control of Helicoverpa spp. larvae on cotton crops in Australia. The performance of NPV and Bt against Helicoverpa spp. larvae on cotton crops, is inconsistent and at times totally unsatisfactory against high densities of Helicoverpa spp. larvae. We determined the effect of mixing petroleum spray oils, containing ultra-violet light absorbing compounds, with NPV and Bt for efficacy against Helicoverpa spp. larvae, levels of cotton plant damage, and persistence of efficacy. The study showed that the efficacy and persistence of NPV and Bt were increased when mixed with petroleum spray oil (PSO?–?Canopy®) at the rate of 2% (v/v). In the field experiments, mixing NPV with 1 and 2% (v/v) PSO, increased Helicoverpa spp. mortality from 25.9 to 31.5 and 44.8%, respectively. Similarly, the mortality caused by Bt, when mixed with 1 and 2% (v/v) PSO, was increased from 31.5 to 36.0 and 48.2%, respectively. In addition, 1 and 2% PSO mixtures with NPV increased persistence of efficacy from 1.1 to 1.6 and 2.5 days, respectively, whilst persistence of Bt was increased from 1.5 to 1.8 and 2.6 days, respectively. In another study using potted cotton plants, in which the plants were left outdoors throughout the study, the average NPV induced mortality of first instar Helicoverpa larvae was increased from 20.9% to 35.9 and 43.4% by 1 and 2% (v/v) PSO, respectively. Persistence of NPV efficacy was enhanced by 2 and 3.1 times by 1 and 2% (v/v) PSO, respectively. Similarly, Bt induced mortality of Helicoverpa larvae was increased by 1 and 2% PSO from 68.1 to 78.8 and 83.2%, respectively, and the persistence of Bt efficacy was enhanced 1.3?–?2.0 times, respectively. In a mesh house study, young cotton plants, treated with a PSO/biopesticide mixture, suffered less leaf damage than cotton plants treated with the biopesticides alone. In conclusion, the results of this study showed synergies from the combined use of UV protected PSO and NPV or Bt, against Helicoverpa spp. larvae on cotton. Such a biopesticide-PSO combinations could be a useful tool for IPM program in cotton.  相似文献   

14.
不同食料对黄地老虎生长发育和繁殖的影响   总被引：3，自引：1，他引：2  
幼虫在不同食料饲养中,以灰藜最好,苘麻最差。前者幼虫期平均23～30.9天,脱皮4～5次,自然死亡率4.3～8.0％;后者则各为46.1～47.1天、6～7次、45％。各种食料饲养的蛹重,以白菜和灰藜较重,马铃薯较轻。蛹重不是决定成虫产卵高低的主要因子,而与幼虫取食食料种类关系较为密切。如幼虫取食白菜、棉花及玉米、马铃薯混杂草者,较取食旋花、马铃薯及玉米者产卵量高0.15～2.23倍,产卵期和寿命亦较长。取食混合食料的幼虫,发育速度和成虫产卵量,一般均较取食单纯一种食料为高。在成虫取食各种花蜜饲养中,以供食蜂蜜红糖水、马蔺花和向日葵花者产卵率和产卵量最高,白菜花、苜蓿花和清水者最低,前者为后者产卵量的1.99～14.06倍,雌蛾产卵率高11.1～35.7％,产卵期和寿命亦以前者为长。从幼虫和成虫取食不同营养对产卵量的对比来看,成虫期补充营养较幼虫期营养更为重要。因而某一地区蜜源植物的种类、分布密度以及蜜源植物花期与成虫发生期的符合程度,是决定某地区黄地老虎种群密度高低、为害轻重的最主要因素之一。  相似文献   

15.
Abstract

The effect of weeds on crops is discussed, with particular reference to the Commonwealth Caribbean. The most serious weeds in the region are Cyperus rotundas, Cynodon dactylon, Commelina spp., Parthenium hysterophorus, Portulaca oleracea, Cleome spp. and Amaranthus spp. Serious weeds include Eleusine indica, Echinochloa colonum, Euphorbia spp., Brachiaria mutica, Paspalum conjugatum, Sporobolus indicus and Ipomoea tiliaceae. Brief notes are given for these species and also for the locally serious weeds, Rottboellia exaltata, Digitaria sanguinalis, Mimosa pudica, Scleria reflexa, Cenchrus echinatus. Control measures include macheting, hand weeding, flooding, mulching and short-term fallows. Herbicides are used especially by larger vegetable growers and in sugarcane and citrus groves. Paraquat is the most widely used. Other chemicals used in specific situations are listed. Knapsack sprayers are the commonest application method but granular and c.d.a. application is likely to increase. Weed control research in the Commonwealth Caribbean is also briefly reviewed.  相似文献   

16.
Black-headed caterpillar, Opisina arenosella Walker (Lepidoptera: Crytophasidae) is an endemic, frequently outbreaking pest of coconut in India and Sri Lanka. It also occurs in Bangladesh and Myanmar. Two larval parasitoid wasps Goniozus nephantidis (Muesebeck) (Bethylidae) and Bracon brevicornis Wesmael (Braconidae), are widely employed, either singly or in combination, for the biological control of O. arenosella in India. The co-occurrence of G. nephantidis and B. brevicornis in the field indicates the potential for competitive interactions which may interfere with pest suppression. In order to study the outcome of competitive interactions between these parasitoids, host larvae were exposed to the parasitoid species either alone or in combination. Females of G. nephantidis and B. brevicornis did not discriminate between unparasitised hosts and hosts parasitised by the other species. Survival of G. nephantidis and B. brevicornis from eggs to adult eclosion was 89.6 and 81.8%, respectively, when larvae of O. arenosella were exposed to these parasitoids individually. When both species were released simultaneously, the survival of G. nephantidis was 86.8% and females of that species chased B. brevicornis females, attempting to bite and sting them. The mean percentage of progeny obtained was significantly higher for G. nephantidis than for B. brevicornis. G. nephantidis dominated due to its parental care behaviour producing 87.0% of progeny and a sex ratio (proportion of females) of 0.79, whereas B. brevicornis produced 84.0% progeny and a sex ratio of 0.36. Although parental care by G. nephantidis females serves to protect the progeny from intruders, it may be disadvantageous from the standpoint of pest suppression under field conditions especially, when the pest population density is high.  相似文献   

17.
Abstract

We determined fall armyworm abundance, infestation and damage on maize in smallholder farmers’ fields in the Zambezi Valley in northern Zimbabwe. Data were collected through field measurements at four sites and interviews with 101 farmers. Fall armyworm abundance ranged from 13.7 to 33.3 larvae per 30 plants, with infestation exceeding 94% and leaf, silk and tassel damage levels ranging between 25 and 50%. Most larvae on maize plants (P?<?0.05) were at instar stages 2 to 3. Estimated grain yield decrease was 58%. Echinochloa colona and Amaranthus spp. were also damaged by fall armyworm. Farmers experimented with 28 combinations of pesticides, ash, and washing powders. Sixty five percent of the farmers used restricted to highly restricted pesticides. High fall armyworm abundance, infestation and maize damage levels suggest that the Zambezi Valley could become a fall armyworm hotspot. Sequential damage of plant parts signified the persistence of this pest in the study area. We recommend large-scale interventions that include chemical and biological control methods as well as destroying ratoon hosts, publishing information about locally available pesticides for the control of fall armyworm, and farmer training on fall armyworm biology and correct use of pesticides.  相似文献   

18.
Abstract

The biology and host specificity of the beetle, Gastrophysa atrocyanea Motch were studied in the laboratory in Nanchang, China. This univoltine insect completed its immature stage in 32–39 days with adult overwintering in soil. A total of 35 plant species from 21 families were tested. Both larvae and adults attacked Rumex japonicus and Rumex acetosa with R. japonicus the main host. Larvae also attacked two Polygonum species, P. hydropiper and P. perfoliatum. But the adults are not concurrent with the two Polygonum species. Though oviposition occurred on five other plant species, none of them supported larval development. Field observations showed that G. atrocyanae caused a progressive decline in natural R. japonicus populations. Thus it is recommended as a valuable biological agent for this weed.  相似文献   

19.

The strategy for the control of cotton pests, notably Helicoverpa spp., in Australia is insecticide-dependent with limited consideration of the role of beneficial insects. A programme for the development of an integrated pest management (IPM) approach commenced in cotton fields at Norwood near Moree in New South Wales in 1992. In this approach, an alternative crop, lucerne (Medicago sativa), was used in an interplant system plus spraying of cotton with a supplementary food (Envirofeast®), which served to attract and retain predators in treated plots. The predator complex consisted of predatory beetles, bugs, lacewings and spiders. The deployment of these two components, interplants and predator retention, reduced the number of Helicoverpa spp. eggs, very small and small larvae (first, second and third stages), medium and large larvae (fourth and fifth stages) and resulted in a cotton yield (2.72 bales ha?1) that was significantly higher (p < 0.01) than the yield from the untreated control plot (0.59 bales ha -1 ). However, the yield from the interplants and food sprayed plot was significantly lower (p < 0.01) than in the insecticide-managed plot (7.12 bales ha?1). Whenever the ratio of predators to Helicoverpa spp. (pests) per metre row of cotton was S 0.5, Helicoverpa pest numbers were maintained below the economic damage threshold. Though not successful in suppressing Helicoverpa spp. numbers, to avoid significant yield loss, further improvement could be made by introducing other potential components to the IPM strategy.  相似文献   

20.
Abstract

Early work on chemical weed control in the fallow towards the end of the Second World War is reviewed briefly. Attempts to use contact residual herbicides as pre-emergence applications in the early 1950s are also described.

Pre-sowing applications of residual herbicides were found more phytotoxic to cotton than pre-emergence applications. The closer the time of pre-sowing application to cotton sowing, the more effective was suppression of weeds competing with cotton.

Mechanical cultivations and particularly disc ploughing and rotovation to a depth of more than 15 cm were found more effective in the control of Cynodon dactylon than pre-sowing herbicide applications.

Fluometuron, noruron and prometryne were found very effective as pre-emergence herbicides. Optimum rates of application were found to be only 25-50% of rates recommended for the USA and other countries. Resistant weeds included Cyperus rotundus, Cynodon dactylon, and Rhyncosia memnonia.

A large-scale trial with fluometuron, covering 125 feddans at Wad el Nairn showed that yields obtained were equal to those with normal weeding. Costs of herbicide treatments were also comparable to costs of hand-weeding in a year of exceptionally low hand-weeding costs.  相似文献   

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