Diseases of Pulses
Seventy-nine diseases have been recorded on chickpea (Cicer arietinum L.), lentil (Lens culinaris Medic) , black gram (Vigna mungo (L.) Hepper), mung bean (Vigna radiata (L.) Wilczek), and khesari (Lathyrus sativus L.) in Bangladesh up to 1988. Of these, 54 are caused by fungi, 9 by nematodes, 1 by a bacterium, 11 by viruses, and 4 by mycoplasma (Ahmed et al. 1982; BARI 1982, 1983, 1984; Bakr and Zahid 1986; Fakir 1983). There are some diseases that are greatly influenced by environmental conditions. It appears from various records available in. the country that chickpea suffers from 11 diseases, lentil from 17, mung bean from 16, black gram from 21, and khesari from 14. Among the 11 diseases of chickpea, the most important are wilt (Fusarium oxysporum), collar rot (Sclerotium rolfsii), and gray mold (Botrytis cinerea). As many as 17 different diseases affect lentil. Of these, rust (Uromyces vici-fabae), foot rot (Sclerotium rolfsii), wilt (Fusarium oxysporum) and stemphylium blight (Stemphylium sp) are the most destructive. Of the 16 diseases of mung bean, the most important are: yellow mosaic (virus), powdery mildew (Odium sp), and leaf spot (Cercospora cruenta). Black gram is affected by 21 different diseases: yellow mosaic, leaf spot, and powdery mildew are the most important. Recently root-knot nematode (Meloidogyne sp) occurrence in the field has also become quite common. In khesari, 14 diseases were recorded. Of these, downy mildew (Peronospora viciae) and collar rot occur more often.
Yield Reduction due to Disease Yield losses in pulses caused by different diseases in the country have not been investigated. The plant pathology divisions at Bangladesh Agricultural Research Institute ( BARI) and the Bangladesh Agricultural University (BAU) have estimated yield losses by a few diseases like collar rot, and wilt of chickpea, powdery mildew, and yellow mosaic of mung bean and black gram (BARI 1987,1988; Bakr and Ahmed 1988; Fakir 1983). Collar rot caused 84.4% yield loss, while wilt caused 6 0 % loss in chickpea. Powdery mildew caused 26% yield loss in mung beans and 26.5% yield loss in black gram. Yellow mosaic caused 16% yield loss in mung bean and 10% yield loss in black gram.
Disease Control through Host Resistance Management of crop diseases through host resistance is economical and practical. To develop resistant cultivars, many cultivars and germplasm lines of chickpea, lentil, mung bean, black gram, and khesari were evaluated during 1983-1987 ( B A R I 1988; Rahman and Ahmed 1985; Dey et al. 1988). Efforts were made to locate resistant sources through artificial inoculation. A screening experiment was conducted against chickpea wilt with many exotic and local entries in wilt nurseries both at Joydebpur and Ishurdi. A highly susceptible check entry (ICC 4951) was sown after every two test entries and so far, we have obtained 41 resistant lines. In lentil 13 entries resistant to foot rot; 19 entries resistant to rust; 17 entries resistant to stemphylium blight; and 4 entries resistant to root rot were found. Several screening experiments against a yellow mosaic of mung bean and black gram were conducted at BARI and the Bangladesh Institute of Nuclear Agriculture ( BINA). In mung bean, only 2 entries ( BM 84-2-7- 5, BM 84-2-18-6) were found resistant, while only 2 mutants M 25 and M 26 were resistant to yellow mosaic in black gram ( BINA 1988). In the case of root-knot (Meloidogyne sp), 1 entry was found resistant in mung bean, and 4 entries in black gram, ( BARI 1984). Regarding the diseases of khesari, 1 entry was resistant to root-knot, 49 to foot rot, and 4 to downy mildew ( BARI 1984, 1986, 1988).
Seedborne Diseases
Field fungi associated with seeds cause deterioration of quality, affect the viability and reduce germination of seeds. Many studies were done at the Plant Pathology Divisions of B A R I and B A U to investigate the prevalence of fungi in seeds. Ten fungi were detected in chickpea, 5 in lentil, 17 in black gram, and 9 in khesari. Eleven seed-borne diseases were reported in four pulses. They are: blight, wilt, and seed rot of chickpea, rust of lentil, leaf spot and seed rot of mung bean, and seedling blight, anthracnose, foot rot, leaf spot, and seed rot of black gram.
Storage Pathogens Most storage pathogens are species of Aspergillus, Penicillium, and Rhizopus. The storage fungi may cause a decrease in germination, discoloration of seed, various biochemical changes that may make grains unfit for food, and toxins that are a health hazard for humans and animals. The factors that mainly determine infection by storage molds are the moisture content of seed and type of storage containers. Effect of moisture content on the prevalence of fungi in stored chickpea seeds was studied by maintaining 3 levels of moisture: 8%, 12% and 16%. Relatively lower levels of mold incidence and higher germination were recorded at the lowest level of moisture content. Of the storage containers, kerosene tin, plastic bag, and bamboo 'dole' were found promising (BARI 1984).
Disease Control through Plant Treatment Several fungicidal trials were conducted at BAU and BARI to determine effective treatments against different foliar diseases of black gram, mung bean, lentil, and khesari. Results showed that powdery mildew of mung bean and black gram can effectively be controlled by spraying either Thiovit® -(0.2%) or Karathane® (0.1 %) or Tilt 250® EC (0.1%) (Goswamietal. 1988). Similarly, cercospora leaf spot of mung bean and black gram can be controlled by Bavistin (0.1 %) or Bayleton® (0.2%) ( BARI 1988). Rovral® 50 WP (0.2%) was effective in controlling stemphylium blight of lentils. Leptosphaerulina leaf blight of khesari can be controlled by spraying either Dithane M-45® (0.2%) or Trimiltox forte® (0.2%) or Topsin M® (0.1%) or Copperoxychloride (0.3%) (BAU 1986).