Oilseeds: Groundnut, Soybean, Sunflower, Sesame, Safflower

I. SOYBEAN – PESTS AND DISEASES:

Pests:

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:

• Crop rotation;
• Deep Summer ploughing;
• Understanding the life cycles of the pests and acting accordingly;
• Application of neem cake @ 100 kg in two equal split doses – one along with the manure; application and the next, one month after the first application;
• Establishment of bird perches @ 10 per acre covering the entire field;
• Establishment of light trap (100 watt capacity) @ 1 per acre with a water trough underneath and switched on from 6.30 pm-8.30pm in the evening;
• Jowar/maize as a border crop-obstructs entry of pests and increases natural enemies.

1. American Bollworm (Helicoverpa armigera):

• Life cycle: The adult emerges from the resting pupa with the onset of rains. Adult stage is for about 8-10 days.  Adult moths are grey to brown in colour and have dark spots on the front wings. The young larvae vary in colour from bright green, pink and brown to black, with a lighter underside. Alternating light and dark bands run lengthwise and the head is yellow. The larvae feed on tender leaves, buds and flowers and later bore into the pods. They deposit feces at the base of the entrance hole. The eggs are pinhead size, yellowish in colour and found singly laid on the tender shoots, flowers and pods. Larval stage is for 12-20 days. Mature larvae drop to the ground and pupate in the soil. Pupal stage is for 8-15 days. 

Management:

• 2-3 rows of trap cropping with Marigold or Lady’s finger around the Soybean (Marigold should come to flowering before the Soybean, as Marigold flowers act as traps for the moths to lay eggs)
• Intercrop with groundnut/cowpea/green gram/soybean helps in the growth of beneficial insects like chrysopa, syrphid fly etc., which parasitise the larvae.
• Monitor the pest (Helicoverpa) by installing pheromone traps @ 4/acre. The lure has to be changed every 3 weeks.
• Release Trichogramma @ 40000/acre, 3-4 times during the egg stage (about 45 days).
• Application of 5% NSKE during flowering to prevent the moth from laying eggs, preventing the young larvae from eating the leaves, flowers and pods.
• Application of chilli-garlic extract when the larval size is about 5 cm or big or during heavy infestation.
• Application of Dashparni extract to prevent larval damage.
• Application of HA NPV 200LE per acre.

2. Tobacco Caterpillar (Spodoptera litura):

• Life cycle: The moth lays eggs on the underside of the leaves in groups (100-300) and are covered with buff coloured scales and hairs. Each female lays 1000-2000 eggs in life cycle. The eggs hatch in 3-5 days. The larval stage is completed in about 20-30 days. Pupation takes place in the soil and pupal period lasts for about 7-12 days. The longevity of an adult is 5-10 days. It has 6-8 generations in a year. The early instar larvae feed gregariously on the under surface of the leaf leading to skeletonisation of the leaves. Later they disperse, become solitary and nocturnal. They also feed on the flower buds, flowers, calyx, squares and bolls. The pest is polyphagous in nature.

Management:

• Collection and destruction of egg masses and skeletonised leaves with first stage 
• Grow Castor as trap crop: collect and destroy larvae and eggs.
• Establishing pheromone traps, (Spodoptera sp) with the onset of flowering, @ 4 per acre. The lure has to be changed every 3 weeks.
• Application of 5% NSKE during flowering to prevent the moth from laying eggs, preventing the young larvae from eating the leaves, flowers and pods.
• When the larvae are grown in size, application of chilli-garlic extract would minimize the population.
• Bacillus thuringiensis var. kurstaki spray @ 2g (2 ml) per litre.
• Spraying of SL NPV 200LE per acre.
• Application of Dashparni extract to prevent larval damage.

3.Hairy caterpillar (Spilosoma obliqua): 

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:

• Use light traps for the catching adult moths as these moths are attracted to light
• As they are gregarious, young larvae can be destroyed by plucking the infested leaves or by pulling out the infested plants and bury them underground
• The grown up larvae are a bit difficult to manage as their body is covered with hairs. NSKE 5% spray will make the larvae starved for food. If at all ingested, the larvae may not be able to go to the next stage of its life.
• Application of chilli-garlic extract if the larvae are grown up

4. Girdle beetle:

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:

• Collect and destroy infested plants and egg masses.
• Application of NSKE 5% or pongamia seed kernel extract 5% to prevent the adults laying eggs.
• Spray Neem oil 2.5 l per acre to affect the young grubs before boring into the plant and preventing the adults from making girdles.

5. Stem fly (Melanagromyza sojae): 

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:

• Collection and destroying the affected plants
• Application of NSKE 5% or pongamia seed kernel extract 5% to prevent the adult from laying eggs
• Neem oil @ 2.5 l per acre spray to prevent the hatched maggots boring into the petioles or stem.

6. Sucking pests (Aphids/jassids/whiteflies/thrips): 

Management:

• Encouraging natural enemies by growing intercrops like cowpea, maize etc;
• Application of cow dung ash;
• Establishing Light trap (for jassids);
• Application of vitex decoction;
• Application of ipomea decoction;
• Application of entomopathogens like Beauveria bassiana

Diseases: 

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. 

• Crop rotation
• Clean cultivation (removal of crop debris, previous year’s stubbles etc.)
• Maintaining optimum plant population
• Use of resistant varieties
• Seed treatment with Trichoderma viride or Trichoderma harzianum @ 5g per kg seed to be done to prevent the soil borne fungal pathogens attacking the young seedlings. 
• Similarly , application of Pseudomonas fluorescens @ 2kg per acre at the time of manure application during ploughing, will minimize the soil borne diseases.
• In case viral diseases uproot the affected plants and destroy them; vector control needs to be done (mostly sucking pests, hence application of vitex decoction spray or tobacco decoction spray would be ideal. While spraying tobacco decoction, care needs to be taken to cover nose and mouth to prevent the inhalation of the strong narcotic smell)

Curative methods:

• Application of sour buttermilk @ 6 l per acre (in 100 liters of water) 
• Cow dung + urine spray with asafetida – 100 g reduces the infection.

1. Alternaria leaf spot (Alternaria tenuissima):

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. 

2. Anthracnose/pod blight (Colletotrichum truncatum): 

• Infected seeds become shriveled, mouldy and brown. On cotyledons, the infection appears as dark brown sunken cankers. In early stages, irregular brown lesions do appear on leaves, stems and pods. In advanced stages, the infected tissues are covered with black fruiting bodies of fungus. High humidity favours the disease and veinal necrosis, leaf rolling, cankers on petioles and finally leads to premature defoliation.

3. Bacterial blight (Pseudomonas syringae pv. Glycinea):

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 pathogen is seed borne and survives in plant debris too. The spread occurs with windy rainstorms and also during cultivation when foliage is wet.

4. Bud blight (Peanut Bud Necrosis Virus / Tobacco RingSpot Virus (TRSV)):

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. 

5. Cercospora leaf blight, leaf spot and Purple seed stain (Cercospora kikuchii):

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.

6. Charcoal rot, ashy or stem blight or dry root rot (Macrophomina phaseolina):

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.

7. Collar rot / Sclerotial blight (Sclerotium rolfsii):

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.

• The pathogen survives mainly in soil.
• Disease occurs in hot (25-35 degree Celsius) and humid weather. Sandy soil, sandy loam soil, high soil moisture, high plant population, dense crop canopy and presence of undecomposed organic matter will favour the disease occurrence.

8. No podding or Bud proliferation (MLOs and nematodes – Rhabditis, Pratylenchus, Heterodera):

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.

9. Powdery mildew (Microsphaera diffusa):

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. 

10. Rhizoctonia aerial blight / web blight (Rhizoctonia solani): 

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.

11. Rust (Phakopsora pachyrhizi):

• The disease begins with small water soaked lesions which gradually increase in size, turning from grey to tan or brown. Tan to dark brown or reddish brown lesions appear on the underside of leaflets. Lesions may also appear on petioles, pods and stems. In severe cases, leaf necrosis and complete death of infected areas may result.
• The pathogen survives through a collateral host. Mean daily temperature 22-27 C accompanied 80-90% RH and long periods of leaf wetness occurring throughout the growing season.

12. Soybean Mosaic (Soybean Mosaic Virus (SMV) – belongs to Potty virus):

• Infected seeds get mottled. Diseased plants are usually stunted with distorted (puckered, crinkled, ruffled, stunted, narrow) leaves. The parts are often stunted. Flattened or curved and contain fewer and smaller seeds. Infected seeds fail to germinate or they produce diseased seedlings.
• Soybean mosaic virus is seed borne. The SMV can be transmitted through sap, 32 aphid species and seed. Cool (around 18o C) and humid are favourable.

13. Yellow Mosaic (Mung Bean Yellow Mosaic Virus (MBYMV)):

• Characteristic symptom is conspicuous systemic bright yellow mottling of leaves. The yellow areas are scattered or occur in indefinite bands along the major veins. Rusty necrotic spots appear in the yellow areas as the leaves mature.
• This virus has a wide host range and is not sap or seed transmissible. Insect vector for MBYMV is whitefly. (Bemisia tabaci). Early infection may cause severe losses.