Integrated pest management (IPM) can simply be defined as a systematic approach including cultural, mechanical, biological and chemical methods that are least toxic to suppress or keep the population of a pest(s) within an acceptable level. IPM encompasses methods used to control pests in an environmentally responsible manner that reduces the dependence on pesticides thereby saving cost and protecting man’s health. In other words, it is a system that encourages reduction in the use of pesticides and increased utilization of non-chemical control methods (Yorobe et al., 2011). As an alternative approach to reach farmers with pest management solutions, IPM systems has evolved to participatory methods focusing to biological and management-intensive methods (Norton et al., 1999). According to Norton et al. (1999), some of the problems involved in the use of pesticides such as high pest management costs, lower incomes and greater risk of health (health hazards) and other wildlife and environmental problems.
In addition, IPM system has been disseminated in Southeast Asia through farmer’s field schools by the FAO as a strategy to introduce farmers to participatory and discovery-based learning of pest management issues (Yorobe et al., 2011).
Sustainable agriculture is one that is ecologically sound, economically viable, socially just and humane and IPM is considered a key component of a sustainable agriculture system.
IPM is a phenomenon in crop protection science that combines the effective use of short and long-term production strategies that optimizes profit and minimizes the risk of undesirable environmental impacts. IPM can be simplified as a process that
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involves the application of all applicable cultural, biological and chemical strategies to eradicate or reduce the population of the targeted pest to acceptable levels and this usually involves a prerequisite evaluation before a suitable control measure is decided upon. A wide range of pest control techniques are available to farmers, some of which are old and others new.
There is need to conduct an IPM evaluation with farmers enabling them to understand the evaluation process and the results. According to Peshin and Dhawan (2009), this can be achieved only if the IPM participants are fully engage in program evaluation. Farmers’ understanding of the value of IPM is an important prerequisite to achieve the sustainability of IPM programs. In addition, identification of key stakeholders that include policy makers, extension workers, researchers and farmers is also necessary for IPM evaluation. IPM evaluation usually starts with the identification of observable indicators, on-farm practices, testing of participants knowledge, attitudes, skills and recording participants aspirations (Peshin and Dhawan, 2009).
IPM comprises integrated use of physical, biological, genetic modification and chemical control techniques. Vegetable growers carry out intensive use of pesticides to manage disease occurrence as well as to protect the cultivated crops. Vegetables are perishables and the market price relies on the eye-catching value.
In this chapter, IPM practices in the vegetable production systems described in the previous chapters (1 and 3) were diagnosed and evaluated in the two year study period.
Following the participatory methodology that was employed in this study; information gathered from farmers reveals that the four main diseases those affecting yield and farm incomes are;
Verticillium yellows of Chinese cabbage (Verticillium dahliae)
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Clubroot disease of the crucifers (Plasmodiophora brassicae)
Root rot lettuce (Fusarium oxysporum f. sp. lactucae)
Cobb’s root lesion nematode of lettuce (Pratylenchus panetrans) 4.1.1 Verticillium yellows of Chinese cabbage
Verticillium wilt is mainly caused by a soil borne pathogenic fungus Verticillium dahlia Kleb. V. dahlia has a wide range of host consisting of herbaceous annuals, perennials and woody plants (Kemmochi and Sakai, 2004; El-Bebandy et al., 2011). V.
dahlia can survive in the soil for several years in the form of a microsclerotia and may become stimulated by root exudates resulting to the germination of the microsclerotia, developing hyphal branching that invades and colonizes the root cortex of appropriate hosts (Lopez-Escudero et al., 2007). Asexual reproduction of this fungus commences when the hyphae penetrate the xylem vessels producing conidiospores that subsequently germinate and penetrate other vessels. Symptoms include chlorosis and necrosis of the foliage, discoloration of the vascular system resulting to wilting and stunted growth of infected plants (Huang et al., 2006; El-Bebandy et al., 2011).
Current integrated disease management strategies to control Verticillium wilt include fumigation (Hirota and Miyagawa, 1988; El-Bebandy et al., 20011) , soil solarization, crop rotation, use of tolerant varieties in the absence of resistant ones (El-Bebandy 2011), organic amendments of botanical species (Lopez-Escudero et al., 2007) including wild oats green manure to suppress Verticillium wilt (Konagai et al., 2005).
In addition, Chloropiclin injection in mulched ridge has been found to be efficiently control Chinese cabbage yellows disease without chemical injury (Shimizu et al., 1983).
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4.1.2 Clubroot disease of the crucifers (Plasmodiophora brassicae)
Clubroot disease is caused by an obligate parasitic eukaryote Plasmodiophora brassicae (Hirai, 2006; Kowata-Dresch and May-De Mio, 2012). It is one of the most serious diseases of Brassica crops worldwide and was recorded in Japan in the 1890s and is now one of the major problems in cabbage and Chinese cabbage production systems (Hirai, 2006).
The infection process is thought to occur through two phases. The resting spores germinate and the resultant zoospores attack the root hairs of the crucifers. The zoospores grow into multi-nucleate plasmodia (primary plasmodia) in the root hairs.
The plasmodia undergo further division to form secondary zoospores that migrate to the root cortical tissue and induce abnormal growth of tissue forming a distorted massive gall called a club (Hirai, 2006; Niwa et al., 2007).
Although breeding of highly clubroot resistant cultivars is an ideal strategy to overcome this disease, several techniques to suppress the disease have been conducted and reported, some of which are practically used in agriculture. Most control measures alter the environmental conditions and inhibit the germination of the resting spores (Takahashi, 1994; Hirai, 2006). Control of soil pH is effective, since the infection occurs in acidic pH, and does not found in alkaline pH (Hirai, 2006; Kowata-Dresch and May-De Mio, 2012). Several agrochemicals have been effective to control this pathogen. Flusulfamide has been reported to be effective and widely used in Japan (Hirai, 2006) and elsewhere (Kowata-Dresch and May-De Mio, 2012). Other agrochemicals including lime, some fungicides can control clubroot, but they have limited efficacy when there is a high density of resting spores and highly virulent populations of P. brassicae (Kowata-Dresch and May-De Mio, 2012). Quintozene
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which contains pentachloronitrobenzene (PCNB), is a standard commercial chemical that has been used for clubroot control on cruciferous crops in Japan.
Murakami et al. (2000) working on two types of soils collected from Fukushima, Japan, indicated the simultaneous effects of both biotic and abiotic factors involved in the suppressiveness of clubroot disease in Low-humic Andosols. In this study, sterilized and unsterilized soils diluted with sterilized soils in the less suppressive Haplic Andosols revealed that biotic factors play an important role in disease suppression even under favorable conditions. Biologically, the endophytic fungus, Heteroconium chaetospira was reported to suppress the club formation. The Japanese radish (Raphamus sativum) which is resistant to the pathogen, but facilitates germination of the resting spores in the soil, is being used as a cleaning crop in the contaminated soil (Hirai, 2006).
In Nagano Prefecture which is a central area of successive cropping of Chinese cabbage (Brassica campestris L. pekinensis group), there are many problems related to clubroot. Because of the spontaneous germination of P. brassicae resting spores and the short-lived character of the primary zoospores without hosts, rotation of susceptible crops with non-cruciferous crops could control clubroot. The most highly used strategy is the intensive use of lime to raise the pH of the soil, thus suppressing the germination of the resting spores.
4.1.3 Root rot lettuce (Fusarium oxysporum f. sp. lactucae)
Nagano is the highest lettuce-producing prefecture in Japan with about 32% of Japanese total production in 2011 (Tsuchiya et al., 2004). Lettuce has been grown mainly in summer and fall by taking advantage of Nagano’s cool climate in highland areas as earlier mention in the general introduction section of this study. The lettuce cultivation in Nagano reached 5,770 ha in 2011 (www.pref.nagano.lg.jp/nousei/engei/).
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The pathogen Fusarium oxysporum f. sp. lactucae was first observed in Japan in 1955 (McCreight et al., 2005). In 1995, lettuce seedlings showed symptoms of wilt disease immediately after planting in Kawakami, Nagano. In 1996, the same symptoms were observed in Shiojiri, Nagano. The symptoms were so severe that the lettuce could not be harvested. Following these disease incidence, pathogenic fungi were isolated by conducting physiological specialization and re-inoculation tests (Fujinaga et al., 2001). Results confirmed that the root rot of lettuce was the cause of the wilt disease and the causal organism was Fusarium oxysporum f. sp. lactucae found only on butter-head type lettuce (Lactuca sativa var. capitata L.). Similar results were also obtained in Italy confirming the high susceptibility of butter-head type lettuce to the root rot of Fusarium oxysporum f. sp. Lactucae (Garibaldi et al., 2004).
The incidence of this disease in Nagano was confirmed for the first time on the crisp-type lettuce (Lactuca sativa var. capitata L.) grown outdoors in Japan. Resistant tests by seeding in infested soils and fields were carried and this lead to the identification of two races (race 1 and race 2) in Nagano (Fujinaga et al., 2001). In addition Fujinaga et al. (2001) reported the presence of third race Fusarium oxysporum f. sp. Lactucae (McCreight et al., 2005).
In 1997, disease control measures using soil disinfectants such as chloropicrin were tested and confirmed effective. However, fumigation methods are difficult to implement, simplify the microflora phase in the soil, not cost effective and raises environmental concerns (Tsuchiya et al., 2004). Therefore, repressing the incidence of root rot of lettuce (RRL) by resistant varieties was crucial.
Yamaguchi (2001) divided isolates of Fusarium oxysporum f. sp. lactucae obtained from six locations in Japan into three pathogenicity groups: group 1 (race 1) was highly pathogenic to lettuce cultivars of crisp-head and red leaf types and less
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pathogenic to butter-head and green leaf type cultivars; group 2 (race 2) was highly pathogenic to the butter-head type and less pathogenic to crisp-head and leaf types;
group 3 (race 3) was less pathogenic to all lettuce types compared to groups 1 and 2.
According to Tsuchiya et al. (2009), RRL caused by Fusarium oxysporum f. sp.
lactucae (FOL) race 2 occurs only in Nagano Prefecture, Japan. The area infested area reached 17 ha in 2003. ‘Chouya No.37’ crisp-head type lettuce, which is adaptable to summer cultivation (slow bolting), was bred with resistance to FOL race 2. The maternal line selected to breed a resistant cultivar was “Kikugawa No.102” as a genetic resource with resistance to FOL race 2 and was crossed with a selection line of crisp-head lettuce with slow bolting. The progeny was selected by various methods up to the F6 generation and “Chouya No. 37” was bred (Tsuchiya, 2009). “Chouya No.37’ is as highly resistant to FOL race 2 as its maternal line. Its resistance is superior to that of other lettuce cultivars that are adaptable to mid-summer cultivation in Nagano.
In 2007, Shinano Hope crisp-head lettuce was bred that is resistant to F. oxysporum f.
sp. Lactucae race 1 and adaptable to summer cultivation. “Shinano Hope” is a hybrid between two crisp-lettuce; paternal line offering the slow bolting selection line and the maternal line from a race 1 resistant selection line (Tsuchiya et al., 2004).
In addition, Scott et al. (2010) reported that growers can reduce the risk of damage by Fusarium wilt by avoiding susceptible cultivars during the warmest planting periods.
4.1.4 Cobb’s root lesion nematode (Pratylenchus panetrans)
Plant-parasitic nematodes are invertebrate worm-like animals that require a susceptible host plant on which to feed in order to complete their life cycles (McBride et al., 2000).
Root-feeding nematode is one of the major groups of belowground herbivores that
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have a profound influence on productivity and species composition of plant communities (Piśkiewicz et al., 2008). Amongst nematode species that infect and cause damage to vegetables are Meloidogyne species, Rotylenchulus reniformis, Pratylenchus thornei, Belonolaimus ongicaudatus, and Paratrichodorus species but in this study, we focused Cobb’s root lesion nematodes (Pratylenchus penetrans).
The root-lesion nematodes, Pratylenchus spp. are among the most economically damaging plant-parasitic nematodes (Khan et al., 2006). Pratylenchus penetrans (Cobb) is the most common root-lesion nematode in the north of Japan. In potato and adzuki bean yield losses of 14% to 20%, respectively, due to nematodes has been reported in the Tokachi area of Hokkaidoi (Sakuma et al., 2011). Nematodes are small, rather stocky migratory endoparasites and polyphagous differing in host preference among the species (Khan et al., 2006).
In vegetable cultivation, nematode management is traditionally achieved by application of nematicides, the market of which is estimated to be around
$800,000,000 for vegetables alone (Vos et al., 2013). However, growing concerns about human and environmental safety have led to the withdrawal of several commonly used nematicides and soil fumigants. For a long time, producers used methyl bromide, a broad-spectrum fumigant that is efficacious on fungi, nematodes, insects and weeds and effectively controlled nematodes in vegetable production systems. Methyl bromide was identified as a contributor to the depletion of the stratosphere ozone layer in 1992 and was scheduled for worldwide phase out by 2005 (Monfort et al., 2007). Several alternative techniques were considered, including sanitation, soil management, organic amendments, fertilization, biological control, and heat-based methods (Collange et al., 2011). These methods encompass the four main processes for controlling nematodes; (i) Killing nematodes in the soil with thermal or
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chemical agents, (ii) breaking the nematode biological cycle to limit female reproduction potential or delay reproduction sequences, (iii) enhancing competition from other microorganisms in the soil to reduce nematode populations by predation, trophic competition, or parasitism and (iv) limiting dissemination from a contaminated to an uncontaminated area (Collange et al., 2011)
In the north of Japan, the effects of fallow on Tratylenchus penetrans and Avena strigosa planting on the population density of Pratylenchus penetrans were studied in a field experiment in Hokkaido. The results showed that planting of A. strigosa for 60 days or Tagetes erecta (marigold) for 100 days strongly suppressed the growth of Pratylenchus penetran (Narabu et al., 2002). Yamada et al. (2000) examined the parasitism of M. incognita, M. arenaria, P. penetrans and P. coffeae on five hybrid sorghum, four gramineous plants (guineagrass, oat, sudangrass and Italian ryegrass) and crotalaria. Results revealed that sorghum strain SS701 named Tuchitaro was the most effective as an antagonistic green manure plant for the control of M. incognita and M. arenaria. Wild oats showed that population densities of P. penetrans and P.
gregata f.sp. adzukicola in soil remained low, and infection and damage degree of post-crop adzuki bean by the brown stem rot (BSR) of adzuki bean was so low and resulted to high yield (Yamada, 2005). In addition, the effective use of frozen soil has been tested on the survival of P. penetrans in Tokachi district, Hokkaido (Narabu and Sekiguchi, 2005). Interactions between techniques are a key factor in nematode management as highlighted by Collange et al. (2011).
In this chapter, we evaluated the various techniques and interactions of pest managements in the four farms (A, B, C and AFC) to diagnose the most effective strategy through disease incidence evaluation. The results obtained provide vital information of farmer’s practices that will be incorporated in the IPM component of
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the model farm for leafy vegetable production systems. Other diseases such as bacterial and fungal diseases and their control measures were diagnosed and evaluated.