IPDM – Better Bananas

Insect sanctuaries for beneficial predators and parasites

Posted on 2024-10-25 by Sarah Williams

Insect sanctuaries for beneficial predators and parasites in bananas

By Daniel Farrell

Beneficial insects are species that provide a positive effect or interaction in an ecosystem, such as pollinators, predators, or decomposers. Predators and parasites, known collectively as natural enemies, play a critical role as beneficial insects by suppressing and controlling pest insects in ecosystems.

In most agricultural ecosystems, including bananas, beneficial insects aren’t considered in management programs. Farming practices, for instance, pesticide usage, monocropping, tillage, and weed control along with the lack of suitable habitat can cause these ecosystems to be unhabitable for beneficial insects to remain, thrive and continue to provide biological control.

Insect sanctuaries are areas of non-harvested companion plants grown free from disturbances of farming practices and grown to encourage and attract beneficial insects to establish and remain in the ecosystem. Insect sanctuaries may consist of flowering or herbaceous plants, native shrubs or trees, or areas of specific weeds and grasses.

Insect sanctuaries are important for creating an agricultural ecosystem that is sustainable and suitable for beneficial insects by providing them with alternative food sources including important proteins and carbohydrates. In addition, sanctuaries provide harbourage and shelter increasing insect longevity and reproduction. An ecosystem with high biodiversity is generally more resilient to changes and less likely to experience pest outbreaks as natural enemies are available.

Insect sanctuaries can be planted externally or internally in existing production systems, as interrow or guard row (strips), or as a border or hedgerow (see below). Multiple small insect sanctuaries are just as significant to beneficial insects as large-planted areas, as they provide greater cross-over throughout the crop to optimize pest control and safe areas.

This DAF innovation-funded project aimed to use a Conservation IPDM approach to alter the banana ecosystem to provide more favourable conditions to enhance the population of beneficial insects. Seven flowering plants were evaluated including dill, fennel, Salvia, lemon balm, Thai chilli, garlic chives, and Impatiens (pictured).

These treatments were compared to a bare-ground control to determine if the composition of the insect community could be altered by incorporating additional plant biodiversity. The abundance (how many individuals) and diversity (how many different species) of insects attracted to each treatment were monitored in March – September 2022 using sticky traps, pitfall traps, and physical observations at the South Johnstone research facility. Collected insects were identified to the species level and then sorted into groups based on their role in the system as beneficial (predators, parasites, decomposers, etc) or pest (sap-feeders, herbivores, omnivores, etc) insects.

In general, the results found that insect diversity and abundance significantly increased over the trial duration. This could be due to either a combined treatment effect where the addition of all insect sanctuaries increased diversity and abundance to the trial site, or a general increase in abundance and diversity over time (i.e. warmer weather). From data models, we were able to devise some general relationships between treatments and the attraction or suppression effect they had on the insect groups (see below).

From these trial findings, Salvia and Impatiens would likely be suitable plants for insect sanctuaries in bananas, due to their high attraction for natural enemies and suppression of some pests. Dill would also seem suitable due to its good attraction to predators and suppression effect on pests; however, noting it was not a preferred host by parasites. Interestingly, Salvia, Thai chili, and Garlic chives were all suppressive to Thysanoptera (Thrips), further research could be useful to provide an alternative suppression option for banana rust thrips and banana flower thrips.

Finding the high attraction of beneficial insects to Salvia and Impatiens suggests that further studies in this area would be useful. Ideally, larger plantings with assessments for bunch pests on fruit should be conducted to explore pest-controlling relationships. Ultimately, a list of suitable plants for incorporation into insect sanctuaries associated with banana plantations considering seasonality and soil types could provide growers with options for dedicating an area on their farm for beneficial insect conservation.

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
13 25 23 or email betterbananas@daf.qld.gov.au

This project was funded by the Department of Agriculture and Fisheries through an Agri-Science Queensland innovation grant.

A growers’ guide to ant related problem and their management

Posted on 2024-10-25 by Sarah Williams

A growers' guide to ant related problems and their management

By Daniel Farrell, Richard Piper, David East and Kathy Grice

Ants are commonly found in commercial and backyard plantings of bananas across Australia. Ants find suitable sites to nest including in the ground, behind old leaf sheaths, inside decaying pseudostems or on weeds and leaf trash surrounding the plants. Depending on the species, ants play a different role on the farm and have a different effect on production.

Ants – Good and bad

Different species of ants can co-exist in bananas, however, depending on management practices and the surrounding environment, only one or two species typically dominate at any given time. Ants can be broadly split into two groups, based on their food preferences, either sugar feeders or protein feeders.

Protein feeders including green tree ants, Argentine ants, and coastal brown ants can be useful biological control agents as they prey on pest insects including banana scab moth, cluster caterpillar, banana weevil borer and thrips.

Sugar feeders on the other hand, can be detrimental as they aid the build-up of sap sucking insects such as aphids, scale insects and mealybugs, which they protect (‘farm’) in return for their sugary secretions. Many species are involved, and they are commonly referred to as sugar or tramp ants.

Exotic Electric ant species farming a mealybug in bananas. (Credit: Hawaii Ant Lab.)

Sugar ants farming a colony of banana aphids. (Photo courtesy of Australian Banana Growers Council)

Invasive ant species (Electric ants, fire ants and yellow crazy ants) are also be present in Queensland. Contact Biosecurity Queensland on 13 25 23 if you suspect you have exotic ants on your farm.

Ant problems

Ants generally aren’t considered a major pest for bananas, however, damage to fruit associated with abdominal spray secretions, secondary infections and pests, or nest construction in the bunch can be an issue.

Several species of ants spray formic acid from their abdomens when disturbed, which can damage the fruit. This damage appears as dark brown to black sunken trails or marks on the fruit skin.

Ants protecting sap sucking insects in the bunches can lead to black fungal growth known as sooty mould developing on the fruit. Sooty mould is caused by a fungus growing on the honey dew produced by sap sucking insects, for example scale insects, mealybugs and aphids. This mould is superficial, but difficult to remove from fruit. If banana aphids are present, they may also transmit the virus that causes bunchy top disease.

During wet weather ants can build nests by carrying soil and debris up into the bunch. This contamination can result in marking of the fruit when it is harvested and transported to the shed.

Ants also pose an occupational health and safety hazard to workers, with risks of biting, stinging or injury from formic acid sprays. Ants can also cause indirect problems such as damaging and blocking irrigation lines.

Ant management

Ants can be difficult to manage, however, they are generally suppressed with insecticide treatments used against other pests. Ground spray applications for banana weevil borer or banana rust thrips control will reduce populations and bunch protection applications will protect the fruit.

For more information contact:

The Better Bananas team
Department of Agriculture and Fisheries
South Johnstone
13 25 23 or email betterbananas@daf.qld.gov.au

This information has been updated as part of the Banana Integrated Pest and Disease Management Program (BA21004) 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.