Managing insects in monsoon crops

Climate change has become a reality, and this year’s prolonged dry spells between periods of rain have allowed insect populations to multiply.

The white-winged caseworm moth lays its eggs on rice paddy leaves. The caterpillars that hatch feed on the leaves, rolling them into cigar-shaped cocoons or ‘cases’. They then cut themselves free from the plant to pupate. Damage caused by the caseworm is often mistaken for grazing by small animals until the floating ‘cases’ are seen on the water in the field. Running a rope over the plants helps dislodge the cases, which then float towards the outlet when the field is drained. They can be collected using an empty onion sack or a piece of shade net. Care should be taken to drain the field only when rain is expected; otherwise the crop may suffer from water stress if left dry.

The monsoon is also the season when the GI-tagged Khola chilli thrives. If you are growing chillies, capsicum, tomato or brinjal (aubergine), the whitefly Bemisia tabaci is a common pest. It not only damages plants by sucking sap from the undersides of the leaves but also spreads several plant diseases. Symptoms include leaf curl, reduced leaf size and generally unhealthy-looking plants. The problem is often worsened by mealybugs, which resemble flour or a white fungal growth on young shoots and leaves. A thorough spray of Beauveria bassiana suspension, commonly available under the brand name Baba, is usually sufficient to control both pests. To help prevent soil-borne fungal diseases that can cause plants to wilt and die at flowering time, apply 10 ml or 10 g of Trichoderma viride, which is available in Goa in both liquid and powder forms.

Ladyfinger, or ‘bhendi’ (Abelmoschus esculentus), is a popular monsoon vegetable. Varieties available through Government sources include ‘JK-62’ and ‘Radhika’, while seeds of the local ‘Sath Xirancho Bhendo’ are sold by private dealers. The Elephant Tusk bhendi from Kerala is available in Tivim and is sold on Friday mornings near the ZAO office in Mapusa. This is a good time to sow the crop if you did not plant it in May or June. Do not be tempted to spray chemical pesticides if caterpillars make holes in the leaves. Dusting wood ash onto wet leaves provides an effective repellent. Otherwise, the damage can usually be ignored.

This is also the right time to sow cluster beans, or ‘tiddki’, by direct seeding, as with ladyfinger. Being legumes, cluster beans enrich the soil by fixing atmospheric nitrogen through a symbiotic relationship with Rhizobium bacteria. However, they often attract aphids once flowering begins. These soft-bodied insects can cover the pods, giving them a grey or black appearance. Ladybird beetles feed on aphids naturally, while dusting the plants with wood ash also helps control infestations. When grown using organic manures, cluster beans have a superior flavour. Consumers recognise the difference and are often willing to pay a premium for locally grown tiddki beans produced without chemical insecticides.

Learn to manage pests naturally this monsoon and enjoy a healthier, more productive vegetable garden.

~ MIGUEL BRAGANZA