Banana Rust Thrips(Chaetanaphothrips signipennis)

Early symptoms appear as water-soaked smoky areas where the colonies congregate to feed and oviposit between touching or adjacent fruit (left); these areas then develop the typical rusty-red to dark brown-black discolouration (right).Top hands are usually the most seriously affected. This pest produces distinctive localised damage that must not be mistaken as maturity bronzing. In severe cases the skin develops longitudinal cracks and damage may extend to cover most of the fruit surface.

This species is particularly troublesome in red soil areas, plant crops and where bunch bagging is not carried out. Fruit that develops during the warmer early months of the year is most at risk. The superficial damage does not reduce the fruit eating quality. However, 'rusty' fruit can be downgraded or rejected, depending on the severity of damage and the current market supply conditions.

Examine five immature (one third to half filled) bunches per hectare for rust thrips on a fortnightly basis throughout the year.

Under heavy infestations, rust thrips can produce characteristic V-shaped rust coloured markings on pseudostems as a result of their feeding where the petiole meets the pseudostem. If these marking are observed, the presence of thrips should be confirmed by gently pulling the leaf petioles away from the stem and inspecting these sites with a x10 hand lens.

Obtain thrips-free planting material and, if possible, hot water treat prior to planting out. Destroy all volunteer plants and old neglected plantations that harbour the pest and that could act as a source of thrips to spread to other plantings.

Sound (unbroken) bunch covers (which cover the full length of the bunch) do provide some protection if applied very early. These cannot be relied upon to fully protect fruit, particularly during severe infestations. Regular checking of fruit under the bunch covers is essential to ensure that damage is not occurring. Ensure treatments are applied immediately after detection to prevent further damage.General predators such as lacewings and ladybird beetles exert some control over rust thrips on the plant, and ants may be effective in removing some of the pupae in the soil.

.Chemical control should be directed at both the soil-dwelling pupal stage and the adults and larvae on the fruit and plant. Failure to control the pest at both sites will result in continuous reinfestation, especially during the hot, humid periods of the year.

 

 

 

The moth is small (25 mm wingspan) tan to light brown with small black spots on the wings.

The flattened eggs are laid in clusters ranging from a few to 30 eggs. The eggs resemble shiny overlapping fish scales. The yellow to orange larvae grow to about 25 mm before pupating.

Larval feeding causes superficial scarring on young fruit. Damaged areas form a black callous, rendering the fruit unmarketable. Feeding is generally confined to the curve of the fruit adjacent to the bunch stalk and between the fingers. Damage ceases after the hand lifts. Mature larvae can be found under the bracts enclosing the male flower or 'bell'.

This pest is most active during the hot wet summer months but sudden outbreaks can occur throughout the year in some localities. Damage occurs progressively as the hands lift and increases in severity towards the lower hands.

This pest is very damaging and to protect all emerging bunches, treatment must start when activity is first noticed. A decision on action should be made depending on the expected bunching rate and weather conditions, rather than on scab moth populations as these are difficult to predict from monitoring alone.

A range of spiders and other general predators exert a measure of natural control.

To promote biological control of scab moth and other pests, bunch injection is recommended and should be used in preference to aerial or bunch spraying. To be effective, injection must be carried out when the bunch is still upright in the throat of the plant. Dilute insecticide solution is injected approximately a third of the way down from the top of the upright bunch or 'spear'. Injections below this will damage fruit and if done above this area, the dense 'bell' will prevent entry of the chemical.

Adult weevils are about 10-12mm long, hard shelled and have the pronounced snout typical of weevils. The newly emerged weevil is reddish brown but soon becomes uniformly dull black. The weevils are nocturnal and hide during the day in or around corms or in moist areas near the plant and in the trash. Unusually sluggish in their movements, they feign death when disturbed and seldom fly. Natural spread is very slow. Dispersal is primarily by the introduction of infested suckers and bits for planting.

usually minor and frequent in northern Queensland but has a greater impact in southern areas. It can become an important pest in poorly managed plantations.

The larvae tunnel within the corm that lies below the soil surface. When there are large populations, tunnels are found through most of the corm tissue and a short distance up the pseudostem. This tunnelling weakens the plant and renders it susceptible to 'blowdown' in windy weather. Heavy infestations interfere with the movement of nutrients to the plant, and plants appear unthrifty. In severe cases the young suckers whither and fail to develop.

In some situations it is difficult to determine if weevils are the main cause or a symptom of plantation decline, since other factors (primarily burrowing nematodes) may be contributing to poor growth. Because of slower growing conditions in south-east Queensland, this pest can become a major pest, reducing plant growth and causing extensive plant fall outs.

At monthly intervals during March to April and September to October monitor populations using 100 mm thick pieces of cut pseudostem as baits during periods of adult activity. At other times 6-weekly intervals would be sufficient. The pseudostem material selected for making baits should be taken from the lower part of the stem of freshly harvested plants. Place at least 20 baits at the base of 20 randomly selected plants and with the cut surface in full contact with the soil after removing any weeds and debris. They should be covered with leaf material to prevent drying out. Count weevils after 3-4 days and treat if the average count is greater than two adults per trap (in south east Queensland) i.e. greater than a total of 40 adults over 20 trap baits. In northern Queensland an average count above four per trap would be more appropriate. Concentrate baits in known 'hot spots'.

Adult weevil activity increases during warm and/or wet weather and decreases during cold and/or dry conditions. Consequently, weevil borer numbers at baits placed during adverse conditions may not accurately reflect actual population levels.

Regular monitoring of adults will give information on weevil borer trends that can be useful in targeting the correct time for treatment. Chemical control measures will achieve the best result if applied during periods of high adult activity, because more weevil borers will come in contact with the lethal dose of insecticide.

 

Banana-silvering thrips are small (1.5 mm long), slender, brown insects with a darker abdomen and pale yellow hind wings that appear as a yellow line down the back of the body when the insect is at rest. Adult thrips have characteristic wings; the transparent wings have a fringe of hairs around the outside edge standing out in the same plane as the wing.

 

To prevent this insect spreading, do not use planting bits and suckers from areas infested with silvering thrips. Control important weed hosts, such as cobbler's pegs, in plantations to reduce infestations.

General predators such as ladybird beetles and lacewings keep silvering thrips in check.

Spot spray if damage becomes excessive.

 

 

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The vast majority of the bananas currently grown and consumed were not conventionally bred but are selections made over probably thousands of years from naturally occurring hybrids. Cultivated bananas are very nearly sterile and as a consequence are not propagated from seed but rather through vegetative propagation, primarily suckers as well as more recently micropropagated or tissue cultured bananas. These factors, very old selections, near sterility and vegetative propagation, mean that these bananas have not been genetically improved either for resistance or improved quality and are becoming increasing in affected by serious pests and diseases.

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