Some of the common pests in Soybean are American bollworm, Tobacco caterpillar, Semi looper, Hairy Caterpillar and Girdle beetle. Among them, the attack of a Semi looper is considered to be severe.
Common preventive Practices are:
Management:
Management:
The adults emerge in March. The female lays 410 to 1250 light green spherical eggs, in clusters on the underside of leaves. The eggs hatch in 8-13 days. The larvae become full grown in 28 to 56 days. The pupation takes place in plant debris or in soil for 7 to 14 days. The full life-cycle is completed in 42 to 84 days. There are three to four generations in a year.
After emergence, the young larvae feed gregariously on the green portion of the leaf. Caterpillars eat leaves and soft portions of stems and branches. In the case of severe infestation, the plants may be completely defoliated.
Management:
The beetle makes semi circular holes on the stem and feeds on the main stem and branches. Due to internal feeding, the branches start drying up. The adult beetle has a hard shell-like exterior and rather long antenna. The freshly emerged adult is yellow, red, brown on the head, thorax and bases of upper wings. The larva is a creamy white, soft body worm with a dark head. To locate the larva, cut open the stems where girdling has occurred; the presence of larva could be seen. The insect remains active from July – October damaging most severely during August – September.
Management:
The adult flies are shining black and about 2 mm long. The damaging stage is maggot (larva) which is white in colour and remains inside the stem. It remains active from sowing to harvesting. The eggs are laid on leaves. After hatching from the egg, yellowish maggots bore the nearest vein of the leaf. The maggot then reaches the stem through the petiole and bore down the stem. If the infected stem is opened by splitting a distinct zig zag, a reddish tunnel can be seen with maggot or pupa inside. In severe cases the maggots bore into the tap root and kill the plant.
Management:
Management:
Soybean is mainly affected by soil borne diseases. Some are seed borne. Hence, while selecting seed, precaution should be taken to get good seed from disease free areas.
Curative methods:
The pathogen survives in crop residues. Disease is favoured by high humidity and temperature, more severe in high rainfall areas. Affected plants show brown necrotic spots with concentric rings on the leaves. Infected leaves later turn dry and drop prematurely. The seed becomes small and shriveled. Dark irregular spreading sunken areas occur on the seed.
Seeds may develop raised or sunken lesions and become shriveled and discoloured. Small angular, translucent, water-soaked, yellow to light brown spots appear on leaves. Young leaves are most infected and are destroyed, stunted and chlorotic. Angular lesions enlarge and merge to produce arge, irregular dead areas. Early defoliation of lower leaves may occur. Large black lesions develop on stems and petioles.
The infected young plants are stunted. The main symptom is the curving of terminal buds to form a hook. Later, other buds on the plant become brown, necrotic and brittle. When cut open, the stem and branches show a brown discoloration.
This virus is seed and sap transmissible. Under cooler weather (<25 degree Celsius) and water stress conditions this becomes severe.
Infected leaves appear leathery, dark, reddish purple. Lesions on petioles and stems are slightly sunken, reddish purple. Later, blighting of young, upper leaves over large areas occurs. Severe infection causes rapid chlorosis and necrosis of leaf tissues resulting in defoliation. High humidity and warm weather (23-27 degree Celsius) especially during flowering and maturing stage favour this disease spread.
This disease occurs when the plants are under moisture stress or under nematode attack or through soil compaction or may be through nutrient deficiencies. This is a most common basal stem and root disease of soybean plant. Lower leaves become chlorotic and wilting. Ultimately drying is apparent. If the plant stem is cut open, grayish discolouration is seen in the diseased tissues. Blackening and cracking of roots is the most common symptom of the disease.
The fungus survives in soil and crop debris under dry conditions. Dry conditions, relatively low soil moisture and nutrients and temperatures ranging from 25 degree C to 35 degree C are favorable for the disease to spread.
Infection usually occurs at or just below the soil surface. Sudden yellowing or wilting of plants is observed. Light brown lesions which quickly darken, enlarge until the stem is girdled. Leaves turn brown, dry and often cling to dead stems. Numerous fungal outgrowths are formed in the infected plant material.
Symptoms appear at the time of flowering. Intensive proliferation of buds occurs and flowers are not formed. The pods are either not formed or pods get deformed. Senescence is delayed.
White powdery patches/lesions are formed on leaves, stems and pods. In severe conditions, all above ground parts are covered with white powdery mass.
The pathogen survives through plant debris. Warm conditions develop disease development.
Infected seeds have irregularly shaped tan or light brown sunken lesions. Infected leaves appear as water soaked at first instance. They soon take on a greenish brown to reddish brown appearance. The infected portion later turns tan brown or black in colour. Under high rainfall or high humid conditions, a web-like mycelial growth of fungus forms on the leaves. Dark brown fungal growths (sclerotia) are formed on leaves and petioles.
The pathogen survives as sclerotia in soil. Humid and cool (24-32o C) are favourable weather condition.