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Apple leaf curling midge (Dasineura mali)


Apple leaf curling midge or Dasineura mali is a species of midge that was introduced to New Zealand in the 1950s and is a threat to Apple trees in New Zealand. The midge originated in the palaearctic region and is common across Northern Europe and North America. Dasineura mali is part of the cecidomyiid family of Diptera which encompasses thousands of species. The midge has the ability to damage apple crops and trees as it attacks the shoots and leaves of young apple trees leaving the leaves curled and affecting crop yield and even affecting photosynthesis. Dasineura mali has the ability to cause quarantine issues with export apples that are infected by Dasineura mali. Dasineura mali was regarded as a minor pest in New Zealand until the 1990s, where (particularly in northern regions) surveys showed increased damage by the Dasineura mali larvae. Some larvae moved onto fruit where it pupated before harvest.

Description:

Dasineura mali is a small fly with four distinct life stages in a short space of time. The female Dasineura mali is between 1.5 and 2.5mm in length with a red abdomen; The female is also covered with black scales on its back. The legs and thorax of the insect are a Brownish colour. The male Dasineura mali is smaller in size than the female and also lacks the red colour on its abdomen. The female lays around 100 to 200 eggs which are orange in colour and generally cigar shaped; These hatch into Maggots after around 3-5 days. The larvae/maggots are what causes the most problems for apple plants as the legless maggots feed on the young leaves.

Distribution

Dasineura mali is not a native or endemic species to New Zealand. It arrived into New Zealand around 1950 and the species is native to the Palaearctic region. The small fly spreads across North America, Argentina and Northern Europe. Dasineura Mali is also Present in parts of Asia. Dasineura mali is located in many regions across New Zealand and most commonly in the major apple growing regions located around the country. Dasineura mali is common in Hawkes bay and Nelson, New Zealand's largest apple growing regions as well as being found in areas less known for apple tree growth such as Canterbury, central Otago and Manawatu. Since Dasineura mali relies on apple trees for survival it is only natural that it is found in areas with apple produce.

Life cycle

Dasineura Mali has four distinct life cycles. The four different stages of life are egg, larvae, pupae and adult. The lifespan in typically short for an adult Dasineura mali. The lifespan of an adult is generally around 3-5 days. Adult Dasineura mali are stong flyers. Dasineura mali females lay eggs only on actively growing shoot tips and eggs hatch in 3–5 days, depending on the temperature. Larval feeding on the young leaves causes them to roll, producing leaf galls on their outer edge which affects photosynthesis and yield. The pupal period lasts for 13 to 18 days on average but lasts for many weeks during the winter generations.

In general Dasineura mali completes four generations per year. The most damaging of these generations are often the 2nd or 3rd generation of the year and are typically most damaging to plants over the spring and summer months. This coincides with when trees are making their maximum growth. In some regions they can complete up to 5 life cycles depending on the climate. In New Zealand, the third adult emergence period happens in January and February. This occurs just before harvest of the apples. It is the larvae from the third generation that infect and infest the apple fruit.

Interactions

The main interactions Dasineura mali has are with apple trees. They are a common pest to the New Zealand apple industry and have the potential to ruin harvests and disturb the short and long term health of these trees. Dasineura mali typically only affect young and growing apple tree shoots and leaves and do little damage to established apple trees. It overwinters as cocooned larvae in the soil beneath the apple trees. Winged adults emerge in spring to mate and lay eggs on the young growing shoots. During early stages of infestation, the feeding larvae cause the leaves to become tightly rolled and red in colour. On completion of the feeding period the infested leaves are hard and brittle, and brown in colour. The Dasineura mali population is controlled by a number of factors; It is generally controlled by insecticides and by apple washers after the fruit has been harvested and Dasineura mali also has biological control by the parisitic was Platygaster demade, native to Europe but also in New Zealand. Predators such as Earwigs and phytoseiid mites are natural predators of Dasineura mali and help to control the population naturally.

Further information:

Dasineura mali has no cultural uses; They are considered a pest all around the world and therefore offer no value for any cultural purposes. During attempts to gain data and knowledge on Dasineura Mali, groups used pheromone lures to catch adult Dasineura mali. This mass trapping Dasineura mali to try and see whether the population in a specific orchard could be reduced and stabilised. Studies in New Zealand date back to the 1950s thanks to D.H Todd and his study on Dasineura mali in 1959 which helped to further understand the patterns and life stages that helped to clear a future for dealing with the pest. Modern ways to deal with Dasineura mali are to spray the trees at greentip with lindane, which helps to control the Dasineura mali impact on young trees.