There was a minor incidence of the following insects and diseases in gladiolus fields in Goa over a period of five years. Aphids (Aphis gossypi, Aphis craccivora): Aphids suck the sap from tender parts of the plant and the infected plants become weak and get deformed. They excrete honey dew which attracts sooty mould and ants. Incidence of aphids is commonly seen during February and March. It can be controlled by spraying of Malathion 0.1 % or Rogor 0.1 % at fortnightly interval.
Thrips (Taeniothrips simplex):
This is a major pest in gladiolus and causes serious damage to the crop. Yellow nymphs and black adults damage leaves and spikes by rasping tissue and sucking the sap. Affected leaves and spikes develop silver co loured streaks which later turn brown, get deformed and dry if the damage is severe. attacks corms in storage and infected corms become sticky, shrivel and produce weak plants when planted. It can be controlled by weekly spraying ofRogor 0.2%. or Malathion 0.1 %.
Cut worms (Agrostis segetum):
Incidence of cut worms is normally observed in the first month of crop. Eggs of moth are seen near the ground level on plant parts. Larvae feed on emerging shoots and cut the plants at the ground level during night. Some times they damage under ground corms and developing spikes. Spraying of Methyl Parathion 0.05% or Quinolphos 0.05% at fortnight interval provides protection.
Leaf eating caterpillar (Spodoptera litura):
Egg masses covered with hair are seen on under surface of the leaves. Early instar larvae feed on lower surface ofleaves by scraping while mature larvae eat leaves voraciously during night time. Skelitenization of leaves is the main symptom. Spraying ofQuinolphos 0.05% or Chlorpyriphos 0.05% or Carboryl 0.1% at 10 days interval controls the incidence effectively. Neem oil 1% or neem kernel
extract 4% checks damage caused by early instar larvae.
Both nymphs and adults attack corms by sucking sap causing shriveling and drying of affected corms in severe cases. Incidence of mealy bugs starts in the field during dry conditions and then it is carried to the storage. Movement of ants on plants is the sign of mealybug infestation. Methyl Parathion 0.04% or Di Methoate 0.04% or Acephate 0.1 % at fortnight interval can be applied to effectively control mealy bug.
Borer (Heliothis armigera):
Larvae feed on leaves and unopened buds. Spraying ofThiodon 0.5-0.8%, Endosulphon 0.07% or Methyl Parathion 0.05% or Ekalux 0.5- 0.8% at fortnight interval can control the pest. Neem kernel extract 4% or neem oil 1% can also control the pest.
Wilt (Fusarium oxysporium f.sp.gladioli):
Wilt is a major fungal disease in gladiolus. It is soil borne and spread through corms from season to season. High temperature, high level of nitrogen,anaerobic condition and accumulation of carbon dioxide (C02 ) favour the fungus. Yellowing of older leaves, browning of vascular tissue and wilting of whole plant are the symptoms of the disease. Roots can not absorb nutrients and water due to damage of vascular tissues. Soil solarization is reported to give good results but it is laborious and not practical in large areas. The best way to control the wilt is to plant healthy corms and follow crop rotation. Farmers should avoid the use of infected/ sick soils for cultivation. Treat corms in hot water (38-400C) containing 2.5g each of Benlate and Captan for 30 minutes for effective management of wilt.
Corm rot is a common problem caused by group offungi namely Fusarium, Curvularia, Stromatinia and Penicillium spps. It causes heavy loss particularly during storage. Anaerobic conditions, storage in air tight rooms and more humidity favour the infection. Black, brown, greenish or yellowish mouldy growth on corms is seen during the storage. Under poor air circulation the corms may rot and emit foul smell. Hot water treatment (38- 40° C) containing 2.5g each of Ben late and Captan for 30 minutes has been quite effective. Damage to corms at the time of lifting, improper curing and dampness in storage should be avoided.
It is caused by many fungi but the most important are Curvularia trifolii and Curvularia ergrostidis. Water soaked oval to elongated brownish spots appear on leaves sheaths and petals and later they coalescein advanced stage. The patches turn to brown and finally black. Moist and warm conditions spread the blight very fast. It is effectively controlled by Mancozeb 0.2% spray at 10 days interval.
- Central Coastal Agricultural Research Institute, Ela, Old Goa, Goa