摘要:

Hand held electrically driven spinning disc atomizers are capable of applying herbicides more efficiently than with hydraulic nozzles, because the narrower droplet spectra they produce reduce drift and wastage of chemical. Despite these savings, however, farmers are frequently reluctant to use such methods because of poor reliability, and high maintenance costs of the electrical drive systems. Therefore an alternative drive system has been examined, which uses a jet of the pesticide fluid to power the atomizer. Experiments were carried out to increase understanding of the processes involved, and an optimum design has been produced, which is suitable for attaching to a knapsack sprayer in place of a hydraulic nozzle. The fluid drive mechanism is comparable to that of a Pelton wheel; driving torque arises from a change in momentum of a fluid jet as it strikes the inside of a cup, causing it to rotate. The fluid is emitted from grooves and teeth to form ligaments which produce uniform droplets. Peripheral distribution of fluid is made uniform by a series of slotted weirs on the inside wall of the cup. Spectral and deposit characteristics are satisfactory for CDA herbicide application with water‐based formulations, but an antifoaming agent must be added to formulations containing surfactant. Typical volume median diameters are of the order of 250 μm, and optimum swath width is 1.2 m for an intended application rate of 30–40 litres/ha.

ISSN:0143-6147    

DOI:10.1080/09670879209371676

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

AZabrotes subfasciatus‐resistantvariety ofPhaseolus vulgaris(RAZ 2) developed at CIAT in Colombia was compared with local susceptible varieties from Colombia and Uganda using strains of insect from both locations. Two bioassay methods were used to measure relevant parameters. RAZ 2 proved highly resistant to both insect strains. The response of both strains to the resistant cultivar was consistent with the mechanism proposed for the action of the antimetabolite, arcelin 1. Inter‐strain differences and disparity in results from the two bioassay methods were detected and their significance is discussed. ClAT's Z.subfasciatus‐resistant varieties have the potential to markedly reduce losses caused by this pest to beans in tropical farm storage.

ISSN:0143-6147    

DOI:10.1080/09670879209371677

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A line ofPhaseolus vulgarisbred for resistance toZabrotes subfasciatus(RAZ 2) was tested in parallel in Uganda and Colombia to determine whether resistance identified in laboratory bioassays reflected in reduced losses when beans were stored for periods ranging from 4 months in Uganda to 8 months in Colombia. RAZ 2 was highly resistant to both insect strains. As compared to local susceptible cultivars, significantly lower numbers of insects emerged from RAZ 2. As a result, seed damage and weight losses in the resistant line were negligible. Results of the storage trials confirmed those of laboratory tests and illustrated the potential of resistance as a method of control to reduce losses caused byZ. subfasciatusin beans in the tropics.

ISSN:0143-6147    

DOI:10.1080/09670879209371678

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The neem tree,Azadirachta indicais the source of azadirachtin and other compounds with potent insecticidal, feeding deterrent, and insect growth regulator activity. This study investigated the effects of a commercial insecticide formulation (Margosan‐O) containing 0.3% azadirachtin and 14% neem oil on orientation, tunnelling, and feeding behaviour of the Formosan subterranean termite,Coptotermes formosanus.In short‐term orientation assays, termite workers did not avoid papers treated with a 1000 ppm solution of azadirachtin. Termite workers also readily penetrated sand containing 20, 100, or 500 ppm azadirachtin, although significant mortality occurred in the 100 ppm treatment. However, subsequent observations indicated that termites avoided long‐term contact with the treated sand. In two multiple‐choice feeding assays, C.formosanusworkers fed significantly less on papers containing azadirachtin concentrations >100 ppm. Azadirachtin, and possibly other neem oil components, thus show some toxicity, long‐term repellency, and feeding deterrent activity towardsC. formosanusalthough the threshold for antifeedant effects is relatively high in comparison to thresholds for other insect species.

ISSN:0143-6147    

DOI:10.1080/09670879209371679

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The prevalence of guava(Psidium guajavaL.) fruit anthracnose was surveyed in three major guava‐producing areas of Bangladesh during 1987 and 1988. One hundred percent of plants and 90–100% of fruits were severely diseased. Disease severity was higher in 1987 than in 1988.Pestalotiopsis psidiiPat.,Colletotrichum gloeosporioidesPenz. andBotryodiplodia theobromaePat. were established as causal organisms. Inin vitrotests Topsin M, Rovral wp and Rovral FLO completely inhibited mycelial growth of three fungi, while Dithane M‐45 and Macuprax proved ineffective. When applied on plants, Topsin M significantly reduced fruit infection and disease severity (89.5%) followed by Rovral FLO (87.0%), Rovral wp (80.0%) and Dithane M‐45 (73.0%) over control. The use of a sticker and increasing the number of sprays from four to seven resulted in significantly greater reduction of fruit infection.

ISSN:0143-6147    

DOI:10.1080/09670879209371680

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The microbial insecticide,Bacillus thuringiensisBerliner var.kurstaki(Dipel 10G), was effective against larvae of the maize stalk borer,Busseola fusca(Fuller), in two separate trials in Kitale, Kenya during the 1987 growing season. In the first trial,B. thuringiensisapplied at different times, was compared against DDT (5% dust), endosulfan (Thiodan 3G), trichlorphon (Dipterex 2.5G), ash, diatomaceous earth, and an untreated control. The level of suppression provided by the laterB. thuringiensistreatments was equivalent to DDT and trichlorphon but inferior to endosulfan. Ash and diatomaceous earth treatments proved ineffective. In the second trial, destructive sampling ofB. thuringiensis‐treatedplots and untreated control plots was used to assessB. thuringiensis'sImpact on the nature and degree of stalk borer infestation. Four developmental categories were assigned to larvae of various head capsule widths and pupae comprised a fifth category. Significantly(P <0.05) fewer individuals of all but the first developmental category were found in the plants treated withB. thuringiensis.Results suggest thatB. thuringiensismay have residual activity againstB. fuscalarvae for at least 3½ weeks after application when applied directly in whorls.

ISSN:0143-6147    

DOI:10.1080/09670879209371681

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Laboratory studies were conducted to evaluate the efficacy of neem,Azadirachta indicaagainst corn earworm (CEW),Heliocoverpa zeafall armyworm (FAW),Spodoptera frugiperdasugarcane borer (SCB),Diatraea saccharalissouthwestern corn borer (SWCB),Diatraea grandiosellamaize weevil (MW),Sitophilus zeamaisand larger grain borer (LGB),Prostephanus truncatus.Neem seed powder at the rate of 5 g and 10 g, and neem seed oil at the rate of 1 ml per kg of meridic diets, were incorporated into the diet of CEW, FAW, SCB and SWCB. Maize grain was treated with 5 and 10 ml neem seed oil per kg of grain and infested with adult MW and LGB. The presence of neem seed powder and neem seed oil in the diets significantly reduced the survival and growth of CEW, FAW, SCB and SWCB. Neem oil also had significant effects on the survival of MW. In the case of LGB the effects of neem oil, however, were not profound. Results indicate that neem has good potential to be used as a control agent for the CEW, FAW, SCB, SWCB and MW.

ISSN:0143-6147    

DOI:10.1080/09670879209371682

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Studies were conducted to develop a pheromone‐trap monitoring system for the sweet potato weevil, Cylas formicarius (Fabricius), in sweet potato,Ipomoea batatas(L.) Lam., fields in four states: Florida, Louisiana, North Carolina, and Texas. The present studies examined the attractiveness of sex pheromone synthesized by two sources (USDA and AgriSense) and pheromone of different purities (75–99%) to weevils in the field. In all but one trial, weevil counts did not differ between traps baited with pheromone from the two sources for each of two doses (10 and 100 μg).Percentages of weevils caught per replicate per sample date were not consistently positively correlated with purity (significant in four of 10 trials); however, slope estimates were steeper in regions with lower trap counts (North Carolina and Louisiana) than in those with higher trap counts (Florida). Because the pheromone will be used to monitor weevils In both weevil‐free and weevil‐infested regions, the use of pheromone with a purity level >99% is most appropriate. The importance of these data in pheromone‐trap monitoring programmes for this weevil worldwide is discussed.

ISSN:0143-6147    

DOI:10.1080/09670879209371683

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Five grasshopper species were caged over milk stage millet panicles to determine relative damage rates.Psalydolyttaspp. blister beetles were caged over flowering stage millet panicles. The grasshopperHieroglyphus daganensiswas caged on flowering, milk and dough stage panicles. The standard treatment used was two insects caged per panicle for 4 days. Highest damage rates per insect were obtained fromPsalydolyttaspp., at 10.3 cm2millet surface area per day,Kraussaria anguliferaat 4.3 cm2per day, andCataloipus cymbiferusat 3.3 cm2per day. The average insect weight was correlated with damage rate (r = 0.93), and the number of insects requiring replacement was negatively correlated with damage rate (r = —0.69). Damage per insect dry weight (g) was highest forPsalydolyttaspp. and the smaller grasshoppersKraussella amabileandOedaleus senegalensisat 25.8, 7.9, and 6.4 cm2/g per day, respectively. Highest damage levels fromH. daganensisoccurred during the early and middle milk stage. Damage rates were relatively low during the early flowering and mid‐late dough stages. The percentage weight of grain kernels remaining after grasshopper feeding was 35–70% when exposed to grasshoppers during late milk and dough stages and 10–35% when exposed during the early milk stage. A formula and example calculations for estimating economic injury levels are provided.

ISSN:0143-6147    

DOI:10.1080/09670879209371684

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Most cocoa plantations in the eastern region of Sierra Leone are ageing, with a gradual drop in the yield. The main problem is due to high pest and disease incidence. A trial to determine the effect of Kocide 101 (copper oxide) and Kokotine (Lindane) on rehabilitating (bringing back into bearing) the old plantations was carried out in a site spreading in the three districts of Kailahun, Kenema, and Kono. The profitability analysis showed that a rehabilitatedtreeproduced about 94% more healthy pods than a non‐rehabilitated tree.

ISSN:0143-6147    

DOI:10.1080/09670879209371685

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor