Mango
Mango Stem Borer
Batocera rufomaculata
Insect
In a Nutshell
- Holes in bark.
- Weak branches may break.
- Wilted trees.
Can also be found in
Mango
Symptoms
The bark of twigs is gnawed and growing tips are chewed. Patches of bark become detached. Under severe infestation the wood becomes so weak that branches may break or the main stem collapses. Branches or even the entire tree may appear wilted. Ejected frass can be found in bark cracks or at the base of the tree. Exit holes in tree bark are indicators for infestation. Foliage and fruit production will also be affected by the infestation and can lead to yield losses. Most damage is caused by the larvae that initially bore into the sub-cortex of the tree and later move deeper into the tree. The adults chew on the green growing tips and on the barks of twigs. Grub tunnels in the sapwood on the trunk or branches. Grub bore into the sapwood and make irregular tunnels. They feed on the vascular tissues and as a result in interruption of nutrient and water transport on the tissue. Drying of terminal shoot in early stage. Frass comes out from several point and at times sap oozes out of the holes. Wilting of branches or the entire tree in case of young plants or if there are many grubs in a single trees.
Recommendations
Organic Control
Metarhizium anisopliae or Beaveria bassianna can be used to manage the pest population.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments if available. Insecticides like organophosphates should be applied to the main trunk, branches and exposed roots when adult beetles have been spotted. Clean entry holes and fill them with cotton wool soaked in emulsion of carbofuran (3 G at 5 g per hole) and plug them with mud. Older larvae hiding in their burrows can be killed in situ by the injection of a volatile liquid or fumigant. Apply bordeaux paste up to one meter high on the trunk from ground level which will prevent egg laying. Padding with Monocrotophos (36 WSC 10 ml in 2.5cm/tree) and soaked in absorbent cotton. Apply Copper Oxychloride paste on the trunk of the tree if infestations are high.
What caused it?
The damage is caused by the larval and adult stage of Batocera rufomaculata. The beetles are 25-55 mm long with body long antennae and nocturnal. The female beetle cuts in the bark of damaged or stressed trees and lays its eggs in these areas. Alternatively eggs are laid in roots that are exposed by soil erosion. Larvae feed under the bark of main stems, larger branches or exposed roots. At a later larval stage they also bore deeper into the wood and pupate there. The adults emerge from an exit hole and feed on the bark of twigs and growing tips. Adults are 3-5 cm, grayish brown, with 2 kidney shaped orange-yellow spots on the sides of the thorax. Fully grown larvae are cream colored with a dark brown head and are up to 10 cm long. Larval development often requires more than one year. The larvae bore through the sapwood and because of their size, the large tunnels adversely affect foliage and fruit production. Pupation takes within the stem, the adult beetles emerging in late summer. They are nocturnal, may live for several months and can fly for long distances, facilitating their dispersal. The pest has only a single annual generation.
Preventive Measures
- Use tolerant varieties if available.
- Use a knife or a piece of wire to destroy larvae and eggs in the entry holes in the bark.
- The holes can then be filled with cotton wool soaked in kerosene oil, crude oil or formalin which is able to kill the larvae.
- Remove severely affected branches and cut down heavily infested trees.
- Remove alternate host plants from and around your field.
- Clean out entry holes with an iron hook or wire and plug holes with cotton wool soaked in kerosene oil, crude oil or formalin which is capable of killing the larvae.
- Other methods involve cutting down infested trees, sawing off severely affected branches and the removal of alternate hosts plants.
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