False Codling Moth

Pests of Field Crops in Southern Africa

FALSE CODLING MOTH

(Lepidoptera: Tortricidae)

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Text Box: The false codling moth, Thaumatotibia (=Cryptophlebia) leucotreta has always been a sporadic pest of deciduous and citrus orchards, although in recent years it has become an increasing problem in commercial paprika plantations. It is usually encountered in infested fruits in the form of a pinkish larva with a dark brown head. The moths are 7 to 8 mm in length, have a wingspan of about 17 mm, and are fairly insignificant, slender, mottled brownish creatures. The forewings have darker brown markings and white patches, while the hindwings are uniformly pale brown. The eggs are oval, flattened and translucent white in colour and they give rise to tiny larvae with brown heads. These later develop to a rose-pink colour and reach about 15 mm in length. They should not be confused with bollworms, which are much larger and more variously coloured, or the headless and legless fly maggots, which follow when a fruit is damaged and rotting for some other reason. The pupae are 5 to 7 mm long and pale brown, and are found in loose cocoons constructed of soil and leaf fragments. TOP

Text Box: False codling moth has a wide host range, and besides being found on many cultivated fruits such as citrus (not lemon or grapefruit), cape gooseberry (Physalis sp.), peach, plum, guava, pomegranate, avocado, apricot and macadamia, they are also occasionally found on paprika, coffee berries, cotton bolls and numerous wild fruits. Amongst the latter are the fruits of Pseudolachnostylus maprouneifolia, Ziziphus mucronata and Z. mauritania, Capparis tomentosa, Diospyros lycioides, Ximenia caffra, Schotia afra, Combretum apiculatum and Sclerocarya caffra. TOP

Text Box: Feeding by the larvae causes premature ripening and fruit drop. In citrus fruits they feed on the inner rind and pulp, ignoring the juicy flesh which is presumably too wet. Infested fruits can often be recognised by the small area of prematurely coloured rind where the larva entered the fruit. In cotton, the larvae feed mainly in the seeds, and prefer the soft, partly grown bolls to very young or fully mature bolls. In gooseberries and peppers, the entrance is through a small, round hole near the calyx end. Infestation is often followed by secondary rotting. TOP

Text Box: The eggs are laid either singly or in small groups on the fruit surface. In warm weather they hatch in 4-8 days, but take up to 14 days in the cooler months. The newly-emerged larvae wander over the fruit before entering it and during this period they may feed on other eggs that are present, resulting in the fact that there is seldom more than one larva per fruit. They mature in 3-4 weeks, leave the fruit and spin a silken cocoon on the soil surface. The slender, brown pupae last 2-3 weeks in the warm months, but may take up to 40 days in the cool months. The moths that emerge from them are nocturnal and not greatly attracted to lights. They are good fliers and the females start laying eggs a few days after emergence, each producing up to 100 eggs. They are able to breed throughout the year, taking advantage of a continuous range of fruiting hosts. There are probably five to six generations per year, but these are not clear-cut and there is much overlapping of generations. TOP

Text Box: Control of this pest has never been really satisfactory, and has relied largely on orchard sanitation, where the aim is to prevent the completion of the life cycle. In citrus, this requires careful monitoring of the orchard and removal, then destruction or burial of infested fruit on and under the trees. Even small citrus fruits can be infested, and the egg-laying moths are especially attracted to fruits with wounds or splits. In the very hot months, monitoring should be increased to twice a week, and since the larvae often leave the fruit before it drops, attention should be paid particularly to infested fruit still on the trees. If this is done regularly, the levels of false codling moth will be reduced, but in a crop which produces lots of fruit rapidly and throughout the season (like paprika), this is much more difficult. If there are nearby indigenous fruit trees, the sanitation process should also include these! Pheromone traps are regularly used in citrus orchards, but are not in themselves a control measure, merely a means of monitoring the pest population so as to time the insecticide sprays. In terms of chemical control, there are few insecticides which have shown total control, but some success has been achieved in citrus by sprays of triflumuron or teflubenzuron, both insect growth regulators. Spray coverage needs to be as thorough as possible, so that there is little chance of an egg hatching on an unsprayed portion of the fruit. It should be applied as soon as the moths are known to be on the wing, a fact which may be ascertained by the use of pheromone traps. Once the larvae enter the fruit, they are out of reach of chemical control. There have been signs of resistance developing even to insect growth regulators, which means that over-application of these producst must be avoided. In some cases overall sprays of synthetic pyrethroids are used, but their timing must be careful and they shouold never be used where red scale is under biological control, or where scale insect or red mite infestations are present as they are so detrimental to natural predators. TOP

False codling moth larva.

False codling moth larva on Cape Gooseberry

False codling moth adult. (Photo: Pest and Disease Image Library, Bugwood.org.)