Pests On Tuber Crops – Potato, sweet potato – Insects study materials

PESTS ON TUBER CROPS

POTATO

Cutworms,    Noctuidae: Lepidoptera

Common cutworm,     Agrotis segetum 

Black cutworm, Agrotis ipsilon 

Spotted cutworm, Xestia C-nigrum 

Variegated cutworm, Peridroma saucia

• Feed on foliage
• Cut tender stem
• Larvae remain in soil
• Larva dark brown in colour 
• Pupates inside the soil
• Adult – brown fore wings with spots and markings

Potato Tuber moth, Phthorimaea operculella Gelechiidae: Lepidoptera

• Causes problem both in field and storage
• Larvae mine into leaves, tender shots and developing tubers 
• Eggs laid on the leaves or on the exposed tubers
• Larva yellow with brown head. Pupates in soil. 
• Hibernates either in larval/ pupal stage. 
• Moth small dark brown

White grubs Holotrichia spp. Melolonthidae : Coleoptera 

Lady bird beetle     Epilachna vigintioctopunctata  Coccinellidae : Coleoptera 

Green leaf beetle  Chalaenosoma metalicum  Chrysomelidae : Coleoptera 

Bihar hairy caterpillar Spilosoma obliqua Lymantriidae : Lepidoptera

Weevil  Myllocerus subfasciatus     Curculionidae : Coleoptera 

Brinjal fruit borer Leucinodes orbonalis Pyraustidae : Lepidoptera

Aphid Myzus persicae, Lipaphis erysimi, Aphididae : Hemiptera 

Leafhoppers Amrasca devastans, Empoasca kerri, Cicadellidae : Hemiptera 

Whitefly Bemisia tabasi Trialeurodes vaporariorum Aleurodidae : Hemiptera 

Thrips Solenothrips indicus Thripidae : Thysanoptera 

Potato Golden nematode

• Two species commonly called “golden nematode” produce cysts on potato roots: Globodera rostochiensis (the actual ‘golden nematode’) and Globodera pallida (the pale cyst nematode).
• Plants are stunted and yellow, and may die off completely, usually in patches in the field. Potato tubers from affected plants are usually small, but show no other symptoms.

SWEET POTATO

Sweet potato Weevil – Cylas formicarius, Curculionidae: Coleoptera

• The adult stage of the sweet potato weevil is a reddish-black that looks like a large ant. 
• When an adult weevil is disturbed, it plays dead. 
• Male weevils are active at night. During the day the weevils hide under leaves or in soil cracks. 
• The root is preferred for feeding and egg-laying at the beginning of growing season, when the plants have not produced any storage roots.
• Adult weevils live on the stem and leaves. The adults feed on foliage, lay its eggs on the vines and leaves, and the larvae feed on the stem or the leaf and pupate inside the vines.
• When the adult female finds a sweet potato root, it will make feeding and egg laying punctures. 
• The punctures containing eggs can be distinguished by their dark color because the eggs are covered with weevil frass (insect excrement). 
• Both the feeding and egg laying punctures lower the quality of the root, and can lower the market price. 
• After hatching from eggs on leaves and stems, larvae feed and develop in the stems of sweet potato vines, causing thickening and malformation. 
• Larvae emerging from eggs laid on the root surface tunnel into the roots and feed with in them until they are ready to pupate. The tunnels are full of weevil frass.
• Black rot infection is common in weevil-damaged roots, because the roots are more susceptible to the black rot fungus after feeding or egg-laying punctures have been formed by the weevils.
• The sweet potato weevil is a severe pest throughout the tropical world. 

Stem borer-   Omphisa anastomosalis Pyraustidae : Lepidoptera

• The female lays eggs individually or in small groups on the leaves near the veins. 
• After hatching, the tiny larva bores into the closest leaf stem (petiole). 
• Leaf turns yellow and dies, as the larva grows, it migrates to a vine, consuming its tissue and often migrating towards the base of the plant. 
• A pile of excrement under the base of the plant is a typical sign of infestation by the stem borer. 
• The pupae are formed within tunnels made in the stem and they are covered with brown webbing. 
• Leaves that become yellowing and die may indicate the presence of newly hatched larvae. Thickening and swelling of the base of the sweet potato plant and piles of light brown frass on the ground under the plant are typical signs of sweet potato borer infestation.

Tortoise beetles                 

• The damage to the stem tissue interferes with the transportation of water, nutrients and organic matter within the plant. Seriously, affected plants may wilt and die.

Tortoise beetles,    Aspidomorpha miliaris, Cassida circumdata, 

Chirida bipunctata     Cassidae : Coleoptera

• The tortoiseshell beetles and their larval stages leave round holes in sweet potato leaves as they feed.  
• Tortoiseshells lay eggs in a series of tissue-like layers that form a box-like mass.
• The larvae are flattened and spiny, and some hold their tails up over their bodies as they walk about. 
• The pupa is less spiny than the larva and is fixed to the leaf. 
• All the life stages are found on both sides of sweet potato leaves.
• The life cycle ranges from 3 to 6 weeks, depending on environmental conditions. 

Blue pansy, Precis orithya 
Nymphalidae : Lepidoptera

• Larva is a leaf feeder.
• Blue Pansy, a sexually dimorphic butterfly, is found throughout India, more in dry open plains than in forests. 
• The male is a unique color combination of blue and black, while the female is purple-brown color. 
• During daytime, it is very active.
• Head and body of the larva very dark shining black shading into brown, latter of an orange colour for a short distance; Body covered with perpendicular spines armed with strong radial hairs.

TAPIOCA

Cassava Scales: Aonidomytilus albus (Diaspididae : Hemiptera)
                            Parasaissetia nigra  (Coccidae : Hemiptera)

• Hosts of scale include Anthurium, bamboo, coffee, cotton, croton, eggplant, fig, edible ginger, guava, macadamia, ornamentals, and pineapple.
• The scale feeds from the phloem of the host plant, yellowing, defoliation, reduction in yield, and a loss in plant vigor may result.
• Adult females vary from dark brown to shiny black in color. 

Whitefly  – Bemisia tabaci Aleurodidae : Hemiptera

• Cassava Mosaic Disease and Cassava brown streak virus disease are spread through infected cuttings and by whiteflies (Bemisia tabaci).

Thrips – Rhipiphorthrips cruentatus Thripidae : Thysanoptera

YAM

ARUM, ALOCASIA AND COLACASIA