Learn about the pests that damage castor and its control.
1. Castor Whitefly, Trialeurodes Ricini Misra (Hemiptera: Aieyrodidae):
The castor whitefly has been reported from India and Pakistan. It is primarily a pest of castor but the nymphs also feed on the leaves and stems of Breynia rhamnoides and Achras zapota. The nymphs are translucent, light yellow in colour and are covered with thick waxen filaments. The adults are pale yellow with white wings covered with waxy powder.
Life-Cycle:
This pest is active from February to November. The eggs are laid in small clusters on the under surface of tender leaves. On emergence, the nymphs attach themselves to leaves and become full-grown after four moultings. The life-cycle is completed in 19-21 days during July, August and September.
The lady birds, Cryptognatha flavescens Motsch., Brumoides suturalis (Fabricius) and Sticholotis sp. (Coccinellidae); a drosophilid fly, Acletoxenus indica (Drosophilidae) and the lygaeid bug, Geocoris bicolor Fabricius (Lygaeidae) are predacious on the nymphs of this pest. Encarsia lahorensis Howard and Aphelinus fuscipennis (Aphelinidae) parasitize the nymphs.
Damage:
As a result of sucking of sap by the nymphs the leaves show yellow patches initially. Later on, there is a gradual drying of the leaves and ultimately the plants die.
Control:
Spray one litre of malathion 50 EC or 625 ml of dimethoate 30 EC or oxydemeton methyl 25 EC or formothion 25 EC or 200 ml of phosphamidon 100 EC in 625 litres of water per ha and repeat at 2-3 week intervals.
2. Castor Semilooper, Achaea Janata (Linnaeus) (Lepidoptera: Noctuidae):
This is a serious pest of castor in all parts of India and Pakistan and has also been reported from Sri Lanka and Thailand. While occurring in large numbers the semiloopers strip the castor plant bare of all foliage. Unlike most of other noctuid moths which do not feed on fruits, the adults of this species are fruit sucking moths and cause serious damage to citrus.
The adult of A. janata is a pale reddish brown moth with a wing expanse of 6-7 cm. The wings are decorated with broad zig-zag markings, a large pale area and dark brown patches. The full-grown larva is dark and is marked with prominent blue-black, yellow and reddish stripes and has a pair of reddish processes and also a dorsal hump near the head end of the body. There is a characteristic white mark on the head. The colour patterns of the larvae of the third and fourth instars are so variable that they have been mistaken for four different varieties of caterpillars. They are highly conspicuous on the green plants.
Life-Cycle:
The moths are active at dusk and lay scattered eggs on tender leaves. A female can lay up to 450 eggs during its life span. The egg, being about 1 mm in length, is fairly large and also has on its surface a few ridges and furrows which radiate from the circular depression at the apex.
Yet it is difficult to locate it on the foliage as it is bluish-green. The larva emerges by cutting a hole in the egg-shell in 2-5 days and devours it immediately. Then, it starts feeding on the foliage. The first stage larva measures 3.5 mm. It feeds and moults 4-5 times and becomes full-grown in 15-20 days.
The grown-up larva prepares a loose cocoon of coarse silk and some soil particles, and pupates under the fallen leaves on the soil, usually at the edge of the field. In some cases, pupation also takes place within the folded leaves on the plant itself. The pupal stage lasts 10-15 days and the moths, on emergence, feed on the soft fruits of citrus, mango, etc. There are 5-6 generations in a year.
Trichogramma minutum Riley (Trichogrammatidae) parasitizes the eggs. Various larval parasitoids recorded on this pest are Apanteles sudanus Wilk., A. ruidus Wil., Microgaster maculipennis Szep., M. eusirus Lyle, M. similislyle and Rhogas percurrens Lyle (Braconidae); Euplectrus leucostomus Rohwer and Tetrastichus ophiusae (Eulophidae).
Damage:
The caterpillars feed voraciously on castor leaves, starting from the edges inwards and leaving behind only the midribs and the stalks. Damage is maximum in August-September and with the excessive loss of foliage, the seed yield is reduced considerably. Although the semilooper feeds on a variety of plants, it seems to prefer castor.
Control:
Apply 625 ml of methyl parathion 50EC in 625 litres of water per ha.
3. Castor Capsule Borer, Conogethes Punctiferalis Guenee (Lepidoptera: Pyralidae):
This borer is distributed throughout India wherever castor is grown. The damage is caused by the caterpillars, which bore into the main stem of a young plant and ultimately into the capsules. The full-grown caterpillar measures 25-30 mm in length, is reddish brown, with black blotches all over the body and a pale stripe on the lateral side. The moths are orange yellow, with black markings on both the wings.
Life-Cycle:
The moths lay eggs on leaves and other soft parts of the plant. The eggs hatch in about a week. The larvae pass through 4-5 instars and are full-fed in 2-3 weeks. Pupation takes place inside the seed or sometimes in the grass that collects after feeding. The pupal stage lasts about one week. The life-cycle is completed in 4-5 weeks and 3 generations are completed in a year. The pest is active on castor from September to March.
The larvae are parasitized by Diadegma ricini Row & Kurian, D. trochanterata (Morley) and Theronia sp. (Ichneumonidae); and Apanteles sp. and Bracon hebetor Say (Braconidae).
Damage:
The attack by this borer is recognized from a distance by the webbed capsule heads. The yield is reduced considerably since the capsules and the seeds within are damaged.
Control:
(i) It is advisable that the infested shoots and capsules may be collected and destroyed,
(ii) Spray 2.5 kg of carbaryl 50WP in 625 litres of water per ha and repeat at 15-day intervals.
4. Castor Hairy Caterpillar, Euproctis Lunaca Walker (Lepidoptera: Lymantriidae):
The castor hairy caterpillar, which is widely distributed in India along with an allied species, Euproctis fraterna Moore, is a serious pest of this oilseed. It has also been observed feeding on linseed, groundnut, guara (Cyamposis tetragonoloba ) and grapevine.
Damage is caused by the larvae which measure 35-40 mm when full-grown and are dark grey, with a wide white dorsal stripe, and have long hair all over body. The moths are pale yellow and are seen sitting on castor and other plants during the day time.
Life-Cycle:
This pest is active throughout the year but its speed of development is considerably reduced during the winter. Moths emerging in February lay a large number of eggs in clusters on the underside of leaves. The eggs are covered with the female anal tuft of brown hair. They hatch in 5-7 days and the young larvae feed gregariously for the first few days. Later on, they disperse and feed individually.
They pass through six stages and are full-fed in 2-3 weeks. The full-grown caterpillars make loose, silken cocoons in the plant debris lying on the ground and pupate inside. The pupal stage lasts about one week in the summer. During the winter months, the egg, larval and pupal stages may last 10, 85 and 20 days, respectively. The pest passes through several generations in a year.
The parasites, Telenomus euproctiscidis (Mani) (Scelionidae) and Trichogramma minutum Riley (Trichogrammatidae) are associated with the eggs. Apanteles colemani Viereck and A. euproctisiphagus Muzaffar (Braconidae) parasitize the larvae of this pest.
Damage:
Caterpillars feed on the leaves of various host plants and in case of severe infestation, they may cause complete defoliation. The attacked plants remain stunted and produce very little seed.
Control:
Spray 625 ml of methyl parathion 50EC in 625 litres of water per ha.
5. Castor Slug, Parasa Lepida (Cramer) (Lepidoptera: Limacodidae):
Although commonly called slug, it is an insect larva that causes damage to the leaves of host plants. It is a serious pest of sporadic occurrence on castor, mango, pomegranate, citrus, coconut, palm, rose, wood apple, country almond, etc., in India, Malaysia and Sri Lanka.
The full-grown larva is flat, fleshy and greenish in colour with white lines on the body. It is covered with spines having red or black tips. The moth is short and stout with forewings predominantly green in the middle and brownish at the end.
Life-Cycle:
The female moths lay flat shining eggs in batches of 15- 35 on the under surface of the leaves of host plants. The eggs hatch in 7 days and the young larvae start feeding in clusters on the under surface of leaves. The larva passes through five instars and is fully developed in 40-42 days. It then pupates in a hard shell-like greyish cocoon on the tree trunk. The pupal stage lasts 20-28 days and the life cycle is completed in about 10 weeks. The pest remains active throughout the year.
The larvae are heavily parasitized by Clinocentrus sp. (Braconidae), Eurytoma parasae G., and E. monemae Rusch (Eurytomidae) and Apanteles sp. (Braconidae).
Damage:
The young caterpillars feed gregariously by scraping the undersurface of the leaves. The loss of sap from plant tissue reduces the vitality of plants and the leaves dry up. As the larvae grow, they get scattered and feed on the entire leaf and cause defoliation.