Jointness in farmers' decision to apply pesticides in multiple crops and its determinants at the farm level in Bangladesh

Decision about pesticide application for pest control is an issue of major concern, but research on factors affecting decision-making is limited. This study investigates jointness in farmers' decision to apply pesticides in multiple crops and socio-economic determinants of pesticide use across crops using a survey of 2083 farms from 17 districts in Bangladesh applying a multivariate Tobit model. Overall, 75.4% and 12.7% of the farmers applied pesticides in one and two crops, respectively. The decision to apply pesticides in multiple crops was found to be negatively correlated, providing evidence of jointness. Also, individual socio-economic factors exerted variable influences on pesticide use in different crops. Output price significantly increases pesticide use whereas the influence of fertilizer price and labour wage is varied. Educated farmers use significantly more pesticides in rice and oilseed. Marginal and small farmers use significantly less pesticides in wheat/maize and pulse. Policy implications include price policies to reduce fertilizer prices and engaging agricultural extension agencies and non-governmental organizations to disseminate information on specific crop combinations which will synergistically reduce pesticide use.     

An integrated approach to weed management practices in direct-seeded rice under zero-tilled rice–wheat cropping system

An increasing water crisis as well as shortage of farm labor farmers in many Asian regions is forcing a shift from puddled transplanted rice to direct-seeded rice. The weeds, however, are a major constraint to the production of direct-seeded rice. In this perspective, a field study was carried out to evaluate various pre- and post-emergence herbicides and different possible integrated weed management practices in zero-till direct-seeded rice. Weed infestation decreased the rice yield by near about 75%. Co-culture rice with Sesbania followed by (fb) pendimethalin fb 2,4-D effectively reduced the total weed population (65.1%) and biomass (86.7%) at 30 days after sowing (DAS). The lowest total weed dry biomass at 60 DAS was recorded from bispyribac-sodium+azimsulfuron-treated plot and such tank mix application of herbicide performed better against diverse weed flora as compared to a single herbicide. Higher yield and more profit from zero-till direct-seeded rice were obtained with the application of bispyribac-sodium+azimsulfuron herbicides as a tank mixture or an integrated approach through cowpea green-manuring fb 2,4-D+glyphosate fb bispyribac-sodium by effective management of versatile weed flora.     

Farmers' perspectives on the biotic constraint of Striga hermonthica and its control in western Kenya

Witchweed, Striga hermonthica (hereafter, referred to as “Striga”), is a major biotic constraint to cereal production in sub‐Saharan Africa. The parasitic plant is a socioeconomic problem that has forced some resource‐poor farmers to abandon their farms due to high infestation. This study was designed in order to elucidate farmers' perceptions of Striga control measures and to determine their potential adoption in two villages in western Kenya. Participatory rural appraisals and individual interviews were conducted in 2009 and 2010 in a sample of 128 and 120 households in Kaura and Kogweno‐Oriang villages in Homabay and Rachuonyo districts, respectively. The results revealed that crop production was the main occupation in most households. The farmers identified Striga as one of the major constraints to maize, sorghum, and finger millet production. According to the farmers, the most popular control measures were hand‐pulling, crop rotation, and intercropping, even though rotational systems might need a longer timeframe to reduce the soil seed bank of Striga. Although the level of Striga infestation and damage were increasing in the farmers' fields, the adoption of the control options was limited. The reason for the low adoption level of the control methods by the farmers is because they are “too risky” as there is no guarantee of a direct pay‐off in increased crop yield. Farmer‐led evaluation and adaptation of the various Striga control technologies in real‐life situations will facilitate the choice of appropriate options and facilitate their uptake.     

Weedy rice: An expanding problem in direct‐seeded rice in the Philippines

Weedy rice is morphologically similar to cultivated rice (Oryza sativa L.). It has biological characteristics that identify it as a weed. Its important weedy characteristics, that is, early and heavy seed shattering, makes it very difficult to control. Weedy rice has not been reported to be an important weed problem in transplanted, flooded rice. However, the shift to direct‐seeded rice (DSR) due to water issues and high costs of labor has increased reports of weedy rice becoming an expanding important problem in Vietnam, Malaysia, Thailand, and the Philippines. Experts believe that the growing adoption of DSR in Asian countries will result in the rise of weedy rice as one of the top troublesome weeds in rice production. Early and recent surveys in the Philippines have indicated the urgent need to increase awareness of weedy rice among farmers to allow the implementation of a number of effective location‐specific weed management strategies. These surveys and other studies conducted since weedy rice was first reported in 1991 confirmed that weedy rice and grass weed species caused major problems in DSR areas. About 35% of the 4.56 M ha harvested area in the country is planted with DSR. As cultivated and weedy rice are close relatives, it would be very difficult to implement management options very early in crop growth. However, a deeper understanding of the underlying traits of weedy rice can help develop a holistic approach toward effective and economic weed management.     

A survey of weed seed contamination of rice paddy in Cambodia

Cambodia has experienced a rapid shift from transplanted to hand broadcast seeded rice, with a consequent increase in seeding rates from 25–30 to 100–200 kg ha^?1. To reduce costs, farmers keep their own seed for sowing with the risk of greater weed seed contamination of the sowing seed. A survey of weed seed contamination in harvested rice paddy was conducted in two provinces of Cambodia (Battambang and Takeo) at the end of the wet season in 2016. Farmers were interviewed about rice‐seeding practices, and a total of 110 farmers' fresh paddy samples were inspected for weed seed contamination from the two provinces. Sowing seed samples collected from 28 seed producer lots and 71 samples of farmer‐kept seed were also analysed for weed seed contamination. In both provinces, the majority of farmers kept their own seed or bought seed from a neighbour. Farm‐kept seed for sowing accounted for 88% of sown seed in Battambang and 89% in Takeo. Seeds of 41 different weed species from 13 plant families were found in the farmers' freshly harvested paddy samples. Overall, farmers managed to reduce the number of weed propagules by 60% and seed producers by 95%. There was no significant difference between farmer‐kept seed and seed producer/seed company seed for the total number of weed seeds present. When shown photos, farmers' rankings of the 10 most common weed species found in freshly harvested paddy did not closely correspond to the actual weed seed frequency in the paddy. When farmers were asked to rank the frequency of weeds in their fields without the option to choose from a list, they ranked the weeds differently. Farmers ranked Ischaemum rugosum, Echinochloa spp. and Fimbristylis miliacea as the three most frequent weed species in their fields. The most frequent weeds in harvested paddy, apart from weedy rice, were I. rugosum and Melochia corchorifolia. Farmers did not rank M. corchorifolia as a frequently occurring weed, and most farmers could not recognise M. corchorifolia from photographs. The priority for improved seed hygiene is to place the emphasis on assisting farmers to further improve their seed purification techniques and to caution them to inspect seed before purchasing from neighbours, seed producers and seed companies in the absence of the implementation of seed certification regulation.     

Use of phytotoxic rice crop residues for weed management

There is a general perception among Cambodian rice (Oryza sativa) farmers that, after harvesting, rice crop residues that are incorporated into the field benefit the growth of the subsequent rice crop. However, the effect of this action upon weed establishment and growth has not yet been considered. A series of pot and field trials were conducted to determine whether such action could inhibit weed establishment and/or growth. The pot studies first evaluated the response of the test plant (rice line ST‐3) and three weed species, barnyardgrass (Echinochloa crus‐galli), small umbrella sedge (Cyperus difformis), and water primrose (Ludwigia octovalves), to the residue of 16 rice lines and the field trials were later conducted to evaluate the response of the same test plants to the residue of seven putatively allelopathic rice lines and one non‐allelopathic rice line. The residue of all the studied rice lines, depending on how long they had been incorporated into the soil, reduced the establishment and growth of all three weed species, as well as the rice crop. However, if the residue's incorporation was delayed by 2 weeks or only a proportion of the residue was incorporated, the rice crop could withstand the growth‐inhibiting effect, while the inhibition of the establishment and growth of the three weed species was retained. These responses of rice and the weeds to rice crop residues might provide a basis for a weed management strategy, particularly in the resource‐poor rice‐production systems of Cambodia.     

Development of herbicides for paddy rice in Japan

The history of the development of herbicides for mechanized paddy rice production in Japan can be characterized by a combination of products with several ingredients, by large availability in formulation, and by application methods for labor saving in accordance with natural and social conditions of the country, for instance, around 40% of national land located in hilly and mountainous areas, small size paddy fields consolidated in approximately 0.3 ha on average and so on. As for combination products, one‐shot herbicides that can control both annual and perennial weeds, including grasses, sedges and broadleaved weeds, mainly with sulfonylureas have been a major means of rice production since the 1980s. One‐shot herbicides have been improved by using newly developed chemicals with excellent herbicidal efficacy, such as acetolactate synthase (ALS), 4‐hydroxyphenylpyruvate dioxygenase (4‐HPPD), protoporphyrinogen oxidase (PPO) and very‐long‐chain fatty acid elongase (VLCFAE) inhibitors, and by combining ingredients that are effective against sulfonylurea‐resistant (SU‐R) biotypes of lowland weeds. The latest type of one‐shot herbicides can control noxious species such as Eleocharis kuroguwai as well as other ordinal species. Regarding herbicide formulation, “1 kg granule,” “Jumbo,” “Flowable,” “Diffusion granule” and so on have been developed to save farmers the troubles of applying herbicides. As for application methods, “at‐transplanting application,” “at‐irrigation inlet application” and utilization of radio‐controlled helicopters or boats were put into practical use as labor‐saving technology. As a result, farmers were spared the severe hand‐weeding work under blazing heat during the summer season. Japan Association for Advancement of Phyto‐Regulators (JAPR) have promoted and contributed to the development of herbicides through collaboration with agrochemical companies and research organizations since it was founded in 1964. In this paper, I explain the development progress of herbicide using materials on the mode of action, the trend of one‐shot herbicides, the feature of a labor‐saving formulation and the working hours for weed management in rice production.     

Herbicide‐resistant weeds in the Philippines: Status and resistance mechanisms

Two major weeds in rice in the Philippines, Sphenochlea zeylanica Gaertn. and Echinochloa crus‐galli (L.) Beauv., are controlled with chemical and cultural methods. In the 1980s, after >10 years of continuous use of 2,4‐D, S. zeylanica evolved resistance to the chemical in those rice fields that had been treated with 2,4‐D once or twice every cropping season. In the 1990s, E. crus‐galli evolved resistance to butachlor and propanil in rice monocrop areas where both herbicides were used continuously for 7–9 years. Rice farmers continue to use 2,4‐D, butachlor and propanil extensively and are often unaware of herbicide resistance or the potential for cross‐resistance, its causes or its implications. In order to control herbicide‐resistant E. crus‐galli, farmers are shifting to locally available herbicides with different modes of action, such as bispyribac, an acetolactate synthase inhibitor, and cyhalofop, an acetyl coenzyme A carboxylase inhibitor. Follow‐up manual weeding or rotary weeding after herbicide spraying, a common farmers’ practice, removes the susceptible and resistant biotypes and could help to delay or prevent the evolution of resistance. Although the resistance mechanisms of both weeds are not determined yet, they could be related to enhanced degradation that is similar to the mechanisms that are shown by the resistant biotypes in other countries.     

超高效液相色谱-串联质谱法同时检测大米中15种常用农药的残留

建立一种超高效液相色谱-串联质谱同时检测大米中甲氨基阿维菌素苯甲酸盐等15种常用农药残留的方法,考察了基质效应、提取溶剂种类、提取方法以及不同净化方法对15种农药回收率的影响。样品经V (乙腈) : V (丙酮) : V (水) = 16 : 2 : 2混合溶液匀浆提取,分散固相萃取法净化,电喷雾正离子 (ESI+) 模式电离,多反应监测 (MRM) 模式检测,外标法定量。结果表明:在0.005~1 mg/L范围内,甲氨基阿维菌素苯甲酸盐等15种农药的质量浓度与对应的峰面积间线性关系良好,相关系数 (r) ≥ 0.99;在0.01、0.1、1和4 mg/kg 4个添加水平下,15种农药在大米中的平均回收率在82%~116%之间,相对标准偏差在1.2%~12%之间 (n = 5)。方法检出限为0.000 5~0.005 mg/kg,定量限为0.01 mg/kg。用该方法对上海市郊20个批次的大米样品进行测定,均未检出农药残留超标。该方法操作简单、快速、准确,适用于大米中甲氨基阿维菌素苯甲酸盐等15种常用农药残留的同时检测。     

Farmers’ perceptions of sorghum production constraints and Striga control practices in semi-arid areas of Tanzania

The objectives of this study were to investigate constraints affecting sorghum production and farmers' approaches of Striga management in the semi-arid regions of Tanzania. Focus group discussions based on a semi-structured questionnaire and observations following transect walks were used for data collection. Only 35%, 15%, and 10% of the farmers from Igunga, Kishapu, and Meatu districts, respectively, reported growing newly released varieties. The major constraints affecting sorghum production in the study areas included Striga infestation, drought, storage pests, damage by birds, a lack of access to improved varieties, and a lack of access to production inputs, such as fertilizers, insecticides, fungicides and herbicides. Hand weeding, crop rotation, fallowing, intercropping, and organic manure application were the most common practices of farmers for reducing Striga infestations, but most farmers (79.7%) had little knowledge of the best recommended Striga management practices. About 65% of the farmers did not use fertilizers and herbicides for soil fertility improvement and weed management, respectively, creating favourable conditions for Striga infestation. A systematic breeding programme aiming at improving sorghum varieties for Striga resistance, including farmers' preferred traits, should be designed and implemented to increase the adoption of these new varieties by the farmers.     

Rice seedbeds as a source of primary infection by Rice yellow mottle virus

The effect of contamination of rice seedlings by Rice yellow mottle virus (RYMV) in seedbeds on the onset and spread of rice yellow mottle in the field was investigated. Rice seedlings were artificially contaminated in seedbeds at different rates (0.1, 0.5, and 2.5%) and pooled in bundles before transplantation, as done by farmers. RYMV was successfully transmitted through contaminated hands and bundling healthy and diseased seedlings together. Hand contamination was responsible for 4.5% infection. Disease incidence in the field after secondary spread reached 32% for 2.5% seedbed contamination rate but remained limited (less than 10%) for all other rates. Eradicating infected plants from seedbeds lessened disease incidence in the field. This technique may be used in conjunction with other prophylactic measures to efficiently control rice yellow mottle disease.     

Grassy Stunt,Ragged Stunt and Tungro Diseases of Rice in Indonesia

Abstract

Grassy stunt disease, ragged stunt virus and rice tungro virus, are among the most widespread and damaging rice diseases in Indonesia. Yield losses due to grassy stunt and the brown planthopper (Nilaparvata lugens) in the period 1974–77 were more than US$510 million. Ragged stunt virus is a new disease which is widespread in Indonesia and has been reported in several rice growing countries in Asia since 1977. Loss figures for ragged stunt are not available, however, individual farmers have suffered 100% yield loss in infected fields. Tungro and grassy stunt are controlled by resistant varieties but there are no commercially available varieties with resistance to ragged stunt.     

Chemical weed control in irrigated direct-seeded rice in the Sudan Gezira

Unrestricted weed growth resulted in serious yield losses (60–75%) in rice (Oryza saliva L.). Hand-weeding once at 2 weeks after crop emergence was ineffective, but weeding at 2 and 2 weeks after crop emergence brought yield losses down to 20%. Pre-emergence application of bifenox and oxadiazon (12 l) and post-emergence application of molinate + propanil gave crop yields comparable to that of the clean weeded control (91–129%). Grain yields obtained with pre-emergence application of oxadiazon (25 EC) and post-emergence applications of propanil, bentazone + propanil, and bifenox alone or as a tank mix with propanil or bentazone were considerably less than those obtained from the clean weeded plots. Bifenox, oxadiazon (12 l) and propanil + molinate gave adequate and persistent weed control (72–97%), and did not damage rice. Oxadiazon (25 EC) gave good weed control but resulted in a serious stand reduction. Post-emergence application of propanil, propanil + bentazone bifenox alone or as a tank mix with propanil or bentazone had no adverse effect on crop stand, but gave poor control of grasses (0–40%).     

Identification of the pathotype of Synchytrium endobioticum,causal agent of potato wart disease,present in Georgia

Potato wart is one of the most important quarantine diseases of potato in the world. In Georgia, symptoms of wart were first seen in 2009–2013 during observations on potato in home gardens in Khulo district, although they may have been present since 2006. However, potato wart presence was only confirmed by PCR in 2013. Isolates pw13N and pw13 of Synchytrium endobioticum collected from the infested area of the village Didadjara, Khulo municipality were tested using laboratories in Georgia and the Netherlands in the framework of collaboration between scientists of Batumi State University and the National Plant Protection organization of the Netherlands. Additionally, pot tests were carried out in Georgia. Based on the results obtained, the pathotype found in Georgia is not known from Europe, and based on its reactions this pathotype resembles pathotype 38 (Nev?ehir) detected in (the non‐European part of) Turkey.     

Farmers' knowledge,attitudes and practices of rice crop and pest management at Ifugao Rice Terraces,Philippines

A survey of 150 rice farmers in three municipalities of the Ifugao Rice Terraces, Philippines, carried out in June 1998, aimed to assess the farmers' knowledge, attitudes, and practices of rice crop and pest management. The survey revealed that: 54% of the farmers fall within a narrow age range (31-50 years), the majority having 11-30 years of rice farming experience; they are of average literacy; and they have large households. Non-farm activity such as woodcarving was the most common source of additional income. The majority of farmers planted a single crop of rice per year and followed traditional cultivation practices. Major rice crop production constraints were drought due to the El Nino phenomenon and insufficient irrigation infrastructure. Zinc deficiency was widespread. Major, non-insect pests known to farmers were earthworms, rats, golden apple snails, and house sparrows. These pests damage either the rice plant or the terrace wall. Earthworm damage to the terrace wall is most obvious. Farmers had very little exposure to integrated pest management and new rice technologies.     

水稻孕穗期稻茎毛眼水蝇经济阈值的研究

试验表明，水稻孕穗期每丛水稻茎毛眼水蝇卵数（Ｘ_１）、被害穗数（Ｘ_２）与产量损失（Ｙ）的关系符合下列方程：Ｙ＝－２．０１＋４．５２４Ｘ_１±２．２，ｒ＝０．９９１４；Ｙ＝－０．０７６＋４．９１２Ｘ_２±２．７８，ｒ＝０．９８６３。产量损失的主导因素是水稻受害后，早稻实粒数减少，晚稻总粒数和实粒数减少。根据防治费用，稻谷价格等，导出孕穗期稻茎毛眼水蝇的经济阈值为每丛禾１．９粒卵或１．３４株受害穗。经大田验证，与实际基本相符。     

Weedy rice represents an emerging threat to transplanted rice production systems in Japan

Weedy rice is a conspecific weed of cultivated rice (Oryza sativa L.) and is a primary weed of direct‐seeded rice production systems worldwide. The shift in the method of establishing rice, that is, from transplanting to direct seeding, is considered the main reason for the emergence of weedy rice in Asia and, more recently, Japan. Japan has increasingly adopted directly seeded rice, even though this practice remains limited. In this study, I confirmed the relationship between weedy red rice emergence and the adoption of direct‐seeded rice in Japan. Twenty‐seven areas from eight prefectures infested with weedy rice were selected to confirm the relationship between the rice planting method and the emergence of weedy rice. Fields that were severely infested with weedy rice were selected as survey fields for this study. I found no relationship between the method of planting rice and weedy rice emergence. Changes to herbicide application, duration of rice production and hand weeding also contribute to the emergence of weedy rice in transplanted rice fields in Japan. The results of this study indicate that weedy rice could become a serious problem in Japan, even in transplanted rice fields.     

不同地理种群二化螟对诱集植物香根草的选择趋性比较

为明确不同地理种群二化螟Chilo suppressalis对香根草选择趋性的差异,通过室内盆栽试验测定了3个省份共8个地理种群二化螟成虫对水稻和香根草的选择趋性及产卵选择性。结果表明:8个地理种群中,选择香根草栖息的二化螟雌、雄蛾比例分别为50%~70%和50%~80%。接入二化螟成虫后第1天,除温岭、乐清、萧山种群外,其它种群雌成虫对香根草和水稻的选择性存在显著差异。金华、衡阳、温岭、衢州种群雄成虫对香根草和水稻的选择性存在显著差异。接入二化螟成虫后第2天和第3天,所有种群雌成虫对香根草的选择性均显著高于对水稻的选择性。除乐清和萧山种群外,其它种群雄成虫对香根草的选择性也显著高于对水稻的选择性。8个不同地理种群二化螟在香根草上的产卵量比例为35%~70%,是水稻上产卵量的1.17(温岭)~2.33(衡阳)倍,均显著高于在水稻上的产卵量。结果表明,香根草对不同地理种群二化螟成虫均具有较好的诱集效果。     

The role ofPseudomonas spp. and competition for carbon,nitrogen and iron in the enhancement of appressorium formation byColletotrichum coccodes on velvetleaf

Colletotrichum coccodes is currently being investigated as a mycoherbicide against the weed velvetleaf (Abutilon theophrasti). Two isolates ofPseudomonas spp. (Ps2 and Ps5) reduced the percentage of germ tubes and increased appressorial formation ofC. coccodes on detached leaves of velvetleaf. A study was conducted to see whether this effect could be attributed to competition for nutrients or iron betweenC. coccodes andPseudomonas spp. Ps2 and Ps5 had no effect on early spore germination, but reduced the percentage of germ tubes at 24 and 30 h, compared to the nontreated control. This reduction was diminished by the addition of nutrients but not Fe³⁺. Ps2 and Ps5 stimulated the formation of dark-coloured appressoria without germ tubes (AWGT), but this stimulation was diminished by the addition of nutrients or Fe³⁺. Germ tube branching at 30 h was also inhibited by the bacteria, but was not diminished by the addition of nutrients or iron. EDTA stimulated conidial germination at 10 h, which was reduced by the addition of Fe³⁺. However, EDTA did not stimulate the formation of appressoria (AWGT). These results suggest that the reduction in the percentage of germ tubes and the increase in the percentage of appressoria induced by the bacteria may be due to the competition for carbon or nitrogen. Iron competition may also be involved in the stimulation of appressorial formation, but not in the reduction in germ tube percentage and branching. Phylloplane bacteria may compete for carbon, nitrogen and iron, limiting the saprophytic phase of the pathogen on the phylloplane and accelerating the development of the parasitic phase. This may enhance the field efficacy ofC. coccodes as a biocontrol agent against velvetleaf.     

Biological Control of Lantana

Abstract

Experiments conducted at the International Rice Research Institute (IRRI) in the Philippines, showed that all commonly marketed formulations and derivatives of 2,4-D and MCPA were equally effective in controlling barnyard grass [Echinochloa crusgalli (L.) Beauv.] and other annual weeds in transplanted rice (Oryza sativa L). In the Philippines, these phenoxy acid herbicides cost US$2.50/ha as liquid formulations and US$5.50/ha as granular formulations. These low-cost herbicides provide excellent alternatives to hand weeding in transplanted tropical rice. Other herbicides which can control weeds before or after the weeds emerge are more expensive than 2,4-D or MCPA. Some of these selective herbicides, such as butachlor and TCE-styrene + 2,4-D, are in the Philippine market. Their prices vary from US$8 to US$12/ha.

For direct-seeded flooded rice, granular formulations of several new herbicides, such as butachlor, benthio-carb and C-288 (chemistry not yet disclosed), were highly selective in controlling barnyardgrass and other annual weeds under tropical conditions. C-288 controls algae in addition to annual weeds in direct-seeded flooded rice. Of these three promising herbicides, only butachlor is marketed in the Philippines at US$8/ha. For upland rice, the chemicals which look promising are butachlor, benthiocarb and fluorodifen. Butachlor liquid is available to rice farmers in Asia at about US$16/ha. These herbicides provide an excellent alternative to hand weeding. Generally a complete job of weed control in upland rice requires more than one hand weeding.