Banana weevil borer – monitoring

Posted on by Better Bananas

Banana weevil borer Cosmopolites sordidus

Monitoring

Adult banana weevil borer activity increases during warm and/or wet weather and decreases during cold and/or dry conditions. Periods of greatest adult activity are in spring (September-October) and autumn (March-April). If blocks are suspected of infestation, trapping should concentrate on these times to determine whether chemical treatments are needed or not. In addition, it is advisable to set traps prior to a new planting or during the fallow period. This is to ensure that any banana plant material has decomposed entirely, eliminating the possibility of any remaining adult banana weevil borers being present in residues that might affect the new crop.

If infestations are suspected adult banana weevil borer monitoring should be carried out every month, except during the colder months when the time frame can be extended to six weeks. Banana weevil borer numbers at baits placed during adverse conditions may not accurately reflect actual adult population levels, as it has been shown that only 5-15% of the actual population will appear on baits under these conditions.

There are a few main methods of monitoring banana weevil borers, which are outlined below:

Bait trapping

Adult banana weevil borer numbers can be monitored by baiting (trapping). Baits are made by cutting a fresh pseudostem into slices about 10cm thick . The pseudostem material selected for making baits should ideally be taken from the lower portion of the stem of freshly harvested plants. One bait is placed close to the base of each plant, with one cut surface in full contact with the ground, and covered with leaves to prevent the bait from drying out. Twenty or more baits should be used in known hot spots to obtain a good indication of banana weevil borer numbers. The ground directly beneath the bait should be cleared of any weeds or plant material that can shelter adult banana weevil borers and hinder rapid checking of the baits. After three to four days, the baits are turned over and the adult banana weevil borers are counted (Hint! Look for banana weevil borers on the ground where the bait was resting as well as the base of the bait in contact with the ground).

Adult banana weevil borer numbers are recorded from each bait and, knowing the total number of baits set and banana weevil borers counted, the average number of adults per bait can be calculated by dividing the total number of banana weevil borers by the number of baits set.

Banana weevil borer BWB bait trapping
Banana pseudostem placed near the base of a banana plant to trap banana weevil borer.
Banana weevil borer BWB bait trapping
Banana pseudostem covered with a leaf to prevent drying out.
Traditional pitfall trap that is used with pheromones. Here the lid has been removed to count the number of banana weevil borer’s present.

Pheromone trapping

Another option for monitoring is the use of pheromone-baited traps, which contain a substance (sordidin) that specifically attracts adult banana weevil borers. These baits attract both male and female banana weevil borers and can attract individuals up to 20m away from the trap, however, this efficiency is reduced by rainfall. Baits need to be replaced every 30 days, as lures run out (depending on lure concentration – read labels for specifics). Different types of traps are commercially available for growers.

Corn damage assessment

Larval damage can be assessed by rating the percentage of tunnelling in the corm of harvested plants.

The larger the area affected the higher the pressure of banana weevil borers. This monitoring is destructive and requires the cutting of plants, and is more encouraged as a monitoring tool to see how known infestations are responding to treatment, rather than a diagnosis of infestations.

Download this information as a factsheet

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
07 4220 4177 or email betterbananas@daf.qld.gov.au 

This information is adapted from: Pinese, B., Piper. R 1994, Bananas insect and mite management, Department of Primary Industries, Queensland and Treverrow, N., Pearley D., and Ireland, G 1992 Banana weevil borer : a pest management handbook for banana growers. : NSW Agriculture, North Coast Region; NSW Banana Industry Committee; Horticultural Research & Development Corporation.
This information has been updated as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.
Hort innovation logo

Banana weevil borer – general information

Posted on by Better Bananas

Banana weevil borer Cosmopolites sordidus

General information 

Description and life cycle

The eggs of the banana weevil borer can be found in a pit that has been chewed into the side of the pseudostem. The site of egg laying is nearly impossible to find due to banana sap congealing and covering the hole. The larvae continuously feed within the corm producing distinctive tunnels until they are almost 2cm long when they move towards the outer edge to pupate.

The lifecycle of banana weevil borers (particularly egg and larval periods) is extremely temperature dependent and is shorter in warmer conditions. The total time from egg hatching to adult emergence can be as short as 12 weeks in ideal conditions in northern Queensland.

Banana weevil borer lifecycle
Lifecycle of the banana weevil borer (arrow indicating part of plant affected).
banana weevil borer egg
Banana weevil borer egg in banana tissue, egg circled in red.

Newly emerged adults are reddish brown but quickly assume their characteristic shiny black appearance as their exoskeleton hardens. The adults are sluggish and fake death if disturbed. However, it can be determined whether they are indeed alive, by gently blowing on them as live adults will wiggle their legs and snouts.

Banana weevil borers have functional wings, however, they rarely, if ever, fly. Instead, they can travel by walking up to 6-7 metres between plants at night, resulting in a very slow spread. Movement is reduced during dry weather, as adults remain in the corm to avoid desiccation. Dispersal of banana weevil borers over larger distances is primarily by the introduction of infested suckers and bits at planting.

Banana weevil borer
An adult banana weevil borer with scale.

Occurrence & seasonality

Banana weevil borer is found in all major banana growing areas throughout the world. Bananas and other species of the genus Musa are the only known hosts. First recorded at Mackay in 1896, the banana weevil borer has since spread to all major banana growing areas in Australia.

It has been observed that there are two distinct peaks in the emergence and activity of adults– the first in spring during September and October, and the second in autumn, during March and April. These peaks are particularly evident in subtropical regions where activity almost ceases during winter. In the Far North Queensland tropics, where winter temperatures are not as low, activity continues throughout the year although at a reduced rate in winter. In Far North Queensland, dry conditions greatly reduce adult activity, as adults remain in the corm to avoid desiccation, whereas rainfall may be a major factor in increasing adult activity.

 

Damage 

Most of the damage is done by the tunnelling of the larvae which occurs exclusively within the corm. Evidence of larval tunnelling is not noticeable since all the tunnelling is confined to the corm below the surface. In heavy infestations, tunnelling will extend for a short distance up the pseudostem; the presence of tunnels can be seen if the pseudostem is cut close to the soil surface. In plants that have fallen out or snapped off the pseudostem may decay more slowly and tunnelling may extend a greater distance up the pseudostem.

Newly planted blocks are more vulnerable to infestations of banana weevil borer as they don’t yet have a substantial corm (especially tissue-cultured plants), meaning tunnelling will cause proportionally more damage.

BWB larvae
Banana weevil borer larval stage (in red) on banana roots

Tunnelling in young plants can cause the death of the cigar leaf if banana weevil borers damage the primary meristem, which is especially likely if tunnelling has extended into the lower pseudostem. However, healthy, fast-growing plants can withstand considerable infestation without showing obvious signs of reduced vigour. 

Typical symptoms of a severe infestation are reduced plant growth, choking, yellow leaves and weak or dying suckers. Environmental stress has been shown to exacerbate the symptoms of banana weevil borer infestations. Plants under attack are also prone to falling out (particularly in windy weather) but the root system of fallouts must be inspected carefully to ascertain the cause. Fallouts can occur from both banana weevil borer and burrowing nematode damage. When banana weevil borer is the cause there is an obvious breakage with the lower part of the rhizome and roots are often retained in the ground (snapped off). Whereas if burrowing nematode is the cause the entire corm is exposed along with stubby roots (‘roll-out’).

Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.
Dark tunnelling pattern from banana weevil borer shown throughout corm cut close to the soil surface.

Note: Banana weevil borers will be at higher pressure after weather events that cause serious plant damage, or in blocks that use cultural practices that encourage damage or breakages, such as desuckering, as they are attracted to fresh exposed plant volatiles.

Download this information as a fact sheet

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
07 4220 4177 or email betterbananas@daf.qld.gov.au 

This information is adapted from: Pinese, B., Piper. R 1994, Bananas insect and mite management, Department of Primary Industries, Queensland and Treverrow, N., Pearley D., and Ireland, G 1992 Banana weevil borer : a pest management handbook for banana growers. : NSW Agriculture, North Coast Region; NSW Banana Industry Committee; Horticultural Research & Development Corporation.
This information has been updated as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.
Hort innovation logo

Banana weevil borer – management

Posted on by Better Bananas

Banana weevil borer Cosmopolites sordidus

Management

Cultural

The use of clean (banana weevil borer-free) planting material and maintenance of trash and weed-free areas near plants are two important factors in reducing the impact of this pest in bananas. Ideally, planting material should be obtained from an accredited QBAN nursery. If you are unable to use tissue culture the next best option is to use planting material from your own farm that is sourced from a block that is clean from pest and disease.

When planting into old banana land, allow at least six months of fallow after all old banana material has rotted down. This will help to prevent a carryover of weevil borer adults. Cut up all fallen and harvested pseudostems to prevent banana weevil borer breeding. This is particularly important in subtropical regions where drier, cooler conditions result in slow breakdown of plant material. Glyphosate injection for crop removal is encouraged to ensure adequate plant destruction to reduce weevil population levels.

Tissue culture plants
Banana planting material from clean sources, such as accredited plant nurseries, ensures that no banana weevil borers are present.
beauveria bassiana infected banana weevil borer adult BWB
Dead adult banana weevil borer infected with the fungus Beauveria bassiana.

Biological

A large range of general predators including flatworms, ants, beetles and cane toads assist in reducing banana weevil borer numbers. Research is being undertaken to determine the effectiveness of insect parasitic nematodes, which could prove suitable as biological control agents for banana weevil borer control.

Some international research, and research in NSW have shown some success using laboratory assays of entomopathogenic nematodes, Steinernema spp. and Heterorhabditis spp. However, to date, Queensland-based research has been unable to replicate positive results in the field, instead showing no difference between treated plants and untreated (control) plants, indicating that more in-field research is still needed.

Initial research in Australia shows that some insect diseases (entomopathogens) such as the fungus, Beauveria bassiana, have the capacity to reduce banana weevil borer populations, but more research is still needed.

Chemical

If the average banana weevil borer counts from bait trapping are more than two per trap (subtropics) or more than four per trap (tropics), registered chemical treatments should be applied according to label directions. If average counts are less than these, treatment is not considered necessary. Pheromone trapping doesn’t currently have a threshold value.

When choosing a chemical, it is essential to consider the life stage and behaviour of the banana weevil borer. The adults typically move around corms during spring and autumn to feed and lay eggs. To achieve optimal control, it is recommended to apply chemicals during these peak activity periods, using banded or butt spray applications that apply insecticides adjacent and/or onto the plants . By comparison, injection treatments aim to control larvae within the corm and therefore may have more flexibility in when they can be applied. However, some of these chemicals should not be applied during the dry season, as these chemicals have shown an increased incidence of mite flares. Always check the product label for guidance.

Chemical options are generally older chemistries that are disruptive to integrated pest management and/or other insects present throughout blocks. When trying to control banana weevil borer, certain chemicals have been known to cause mite flares. Therefore, it is crucial to only use spray treatments when the infestation has reached critical levels. Insecticide resistance is a threat with current options available, so chemical choices and modes of action should be rotated to reduce the risk of resistance. Always check the APVMA website for current chemical registrations before use. All chemical applications should be made according to the directions on the label. Resistance management plans should be followed to reduce insecticide resistance risk, see CropLife plans here.

Banana weevil borer BWB chemical options

Download this information as a factsheet

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
07 4220 4177 or email betterbananas@daf.qld.gov.au 

 
This information is adapted from: Pinese, B., Piper. R 1994, Bananas insect and mite management, Department of Primary Industries, Queensland and Treverrow, N., Pearley D., and Ireland, G 1992 Banana weevil borer : a pest management handbook for banana growers. NSW Agriculture, North Coast Region; NSW Banana Industry Committee; Horticultural Research & Development Corporation.
This information has been updated as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.
Hort innovation logo

Banana weevil borer Cosmopolites sordidus

Posted on by Better Bananas

Banana weevil borer

Banana weevil borer is found in all major banana growing areas throughout the world. Bananas and other species of the genus Musa are the only known hosts.

Often infestations of banana weevil borer will go unnoticed until the plant falls out, as most of the damage is done by the tunnelling of the larvae within the corm. In heavy infestations, tunnelling will extend for a short distance up the pseudostem, the presence of tunnels can be seen if the pseudostem is cut close to the soil surface. Other typical symptoms include reduced plant growth, choking, yellowing leaves, and weak or dying suckers. If infestations are detected, monitoring is essential to determine the levels present and appropriate management actions. 

Planting with clean material is essential to prevent banana weevil infestations. Plants from an accredited nursery are optimal, or the next best option is using clean planting material from your own farm.

Banana weevil borer
An adult banana weevil borer with scale.
Always use clean planting material to reduce the risk of a banana weevil borer infestation.

More information

For a general description for identification and detailed life cycle, seasonality and the damage that banana weevil borers can inflict on bananas click here. 

Monitoring should occur in peak times to determine whether chemical treatments are needed or not. To learn more about types of traps that are available for monitoring click here.

For information on how to manage banana weevil borer infestations and how to avoid infestations to begin with click here.

This information is adapted from: Pinese, B., Piper. R 1994, Bananas insect and mite management, Department of Primary Industries, Queensland and Treverrow, N., Pearley D., and Ireland, G 1992 Banana weevil borer : a pest management handbook for banana growers. : NSW Agriculture, North Coast Region; NSW Banana Industry Committee; Horticultural Research & Development Corporation.
This information has been updated as part of the National Banana Development and Extension Program (BA19004) which is funded by Hort Innovation, using the banana industry research and development levies and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture. The Queensland Government has also co-funded the project through the Department of Agriculture and Fisheries.
Hort innovation logo

Corm smelly, rotting or discoloured

Posted on by Better Bananas

Corm smelly, rotting or discoloured

Panama disease (Fusarium wilt) (discoloured)

Biosecurity Alert

Cause: The fungus Fusarium oxysporum f. sp. cubense which is a soil-borne organism. It is spread in water, soil and planting material. It enters the plant through the roots, and blocks the conducting tissue within the plant resulting in wilting, yellowing of leaves, splitting of pseudostem and death of the plant.

 

Solution: There is no cure for affected plants. Use only approved planting material and do not plant in previously infested areas. 

Biosecurity obligation: Panama is a notifiable disease and you must report any suspicious plants. If you suspect Panama disease you must notify Biosecurity Queensland immediately (13 25 23). 

More info:

The rotting corm has a strong odour.

Bacterial corm rot (smelly, rotting, discoloured)

Cause: The bacteria Pectobacterium spp. (formerly known as Erwinia spp.) that are common soil inhabitants. Plants that are stressed during the dry season can succumb to invasion during the wet season. 


Solution: No chemical treatments are available. Ensure adequate moisture levels are maintained during the dry season and provide good drainage during prolonged wet seasons.

Moko disease (discoloured)

Biosecurity Alert

Cause: The bacteria Ralstonia solancearum race 2. Moko is a soil-borne disease and is spread with soil, in water, on implements, in planting material and by insects from flower to flower. The infection enters the plant through the roots and spreads through the host, blocking conducting tissue and resulting in plant yellowing, wilting and death.


Solution: There is no chemical control for Moko. All plants plus an adequate buffer zone around the diseased plants must be destroyed. The area must be quarantined and only non-host plants grown.  

Biosecurity obligation: If you suspect Moko disease you must notify Biosecurity Queensland immediately (13 25 23). 

More info:

Note discoloured edge of corm.

Burrowing nematode (discoloured)

Cause: Burrowing nematode feeding in the banana corm. Planting nematode-infected corm pieces is the most common method of spread to new areas.


Solution: Do not use banana corms with visible signs of nematode damage as planting material.  

Tunnelling in corm

Posted on by Better Bananas

Tunnnelling in corm

Severe infestation reduces plant vigour and the tunnelling allows the entry of rot organisms, which result in faster corm breakdown.

Banana weevil borer

Cause: Tunnelling by larvae of Cosmopolites sordidus.


Solution: Use stem baits to establish the severity of the infestation. If necessary treat with an appropriate chemical. Follow label directions regarding application method and timing to maximise the effectiveness of the treatment. 

Damaged roots or no root hairs

Posted on by Better Bananas

Damaged roots or no root hairs

Note burnt root tips.

Fertiliser burn, drought or water-logging, poor drainage, air burn, soil compaction.

Cause: There are several causes of root tip burn. They include fertiliser burn from too much fertiliser or poor placement; aluminium or manganese toxicity caused by low soil pH; and soil drying out or staying too wet for too long. As well as these causes, air burn or soil compaction can cause root hairs to be lost. 

Solution: Determine the cause with soil and tissue analyses. Broadcast fertiliser evenly and at recommended rates. Watering heavily to leach salts out of the root zone can alleviate problems of excess fertiliser. Maintain soil pH between 5 and 6 and avoid planting in areas with poorly drained soils. 

Note chewed roots.

Greyback cane beetle

Cause: Chewing by larvae (cane grubs) of Dermolepida albohirtum. 

Solution: Correct timing of insecticide application is crucial. The chemical must be applied when larvae are close to the surface between November and January. 

 
Note lumps (galls) within roots and missing root hairs.

Root-knot nematode

Cause: Meloidogyne spp. Root-knot nematode invades the root when young. When mature the females form special feeding cells that appear as galls within the roots. 

Solution: Root-knot nematode is not usually an economic problem to banana production in the tropics. Most mature banana plants with adequate irrigation and fertilising can compensate for any damage. Root-knot nematode may become a problem in very young plants, or on very sandy soils.