Leucoptera coffeella
| Leucoptera coffeella | ||||||||||||
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| Leucoptera coffeella | ||||||||||||
| ( Guérin , 1842) |
Leucoptera coffeella is a butterfly ( moth ) from the family of lyonetiidae (Lyonetiidae). Like Leucoptera caffeina and related species, theanimal isa leaf borer of the coffee bush ( Coffea ), an economically important pest .
features
These small butterflies are crepuscular and have a wingspan of 6.5 millimeters. They have fringed fore and hind wings of a brownish-white color. Their caterpillars mine in the leaves of the coffee plant. These have a length of 3.5 millimeters before pupation (four molting stages).
distribution
The area of origin of this species is not exactly known, today its occurrence extends to the Caribbean islands and South America . The large coffee-growing areas in Brazil are particularly affected by this leaf miner, which has become the main pest in coffee production.
The German-Brazilian biologist Hermann von Ihering suspected in 1912 that Leucoptera coffeella might have been introduced with young plants from the Antilles around 1851 . He must have come there with coffee plants from Africa . The caterpillars of Leucoptera coffeella specialize in coffee plants.
Reproduction and development
The females of the leaf miner lay their eggs on top of the leaves of the coffee bush. The eggs have a gelatinous shell and are difficult to see with the naked eye. The number of eggs depends heavily on environmental conditions. Under laboratory conditions at a constant temperature of 27 ° C and almost saturated humidity, the females laid over 60 eggs over a period of 13-14 days. The time it takes for the caterpillars to hatch also depends on ecological factors and can be between 6 and 20 days.
The caterpillars of L. coffeella hatch into the tissue of the coffee leaf right on the underside of the egg, which is attached to the epidermis of the leaf. There they feed on the palisade parenchyma located below the upper epidermis and dig tunnels through the palisade tissue, which is important for the assimilation of the plant.
The caterpillar development takes 7 to 11 days at high temperatures (27 ° to 30 °), but 16 to 26 days at temperatures around 20 °. The caterpillars then leave the leaf and pupate in a web on the underside of the leaf, near the petiole. The duration of the pupal stage also depends on the temperature. It ranges from 14 days at 20 ° to 3.6 days at 35 °. However, such a high temperature is not the optimum, since only 25 percent of the adult butterflies hatch under these conditions. The optimum seems to be between 27 ° and 30 °, which enables 95 percent of the animals to hatch within 5 days.
The adult butterflies feed on the honeydew of the aphids (Aphidina). The food supply is decisive for the lifespan of the leaf miners. Without food, the small butterflies only survive five to six days, with sufficient nutrition for around 14 days.
Harmful effect
A single L. coffeella caterpillar damages only 1 cm² - 1.36 cm² of the leaf depending on the type of coffee, but the large amount of infestation can mean considerable harvest losses. The palisade parenchyma, which is used to feed the caterpillar, is used by the plant for assimilation due to its rich number of chloplasts. Due to the lack of parenchyma, the plant also loses water and minerals, the metabolic cycle is interrupted, and ethylene is formed . The leaves turn yellow to brown and eventually fall off. The caterpillars prefer to feed on the leaves of the third and fourth internodes of the shrub, which is particularly detrimental to the growth of the plant because this is where the greatest photosynthetic activity takes place.
The fall of leaves due to the damage to the leaves in July hinders flower formation in September and October, so that fewer coffee fruits can develop. Later leaf fall not only hampers the formation of flower buds, but also the development of fruits when flowers have already formed. A leaf drop of 50% means a crop loss of 24%, a drop of 75% of the leaves even a loss of 67%. The failure of the leaf metabolism also weakens the entire plant and inhibits its development.
Biological control
These leaf miners have a variety of natural enemies, including brackish wasps (family Braconidae), particularly the species Mirax insularis , which attack the caterpillars and pupae of L. coffeella and lay their eggs in the larvae. There are also predatory fringed wings and mites . These natural antagonists have been decimated by the excessive use of pesticides , so that there can be massive occurrences of the coffee leaf leaf miners. It has not yet been possible to find and breed a sufficiently efficient antagonist of the leaf miner within the framework of biological pest control .
The massive occurrence of L. coffeella is also dependent on the cultivation conditions within the coffee plantations. Under balanced climatic conditions, where it is not too dry, there will not be any major problems with the leaf miners, even without the excessive use of pesticides. L. coffeella has the best conditions for spreading under dry conditions with low humidity and high temperatures. A culture under shady, humid conditions can therefore prevent the pests from spreading, and a good supply of nutrients for the coffee plants also leads to less damage after being infested by the leaf miner.
An insecticide can carbamates , pyrethroids and organophosphates are used when the infection has become too large. The observation of the infestation is accomplished by attractant traps with the use of pheromones .
It is also intended to breed resistant or genetically modified varieties.
Individual evidence
- ↑ Oliveiro Guerreiro Filho: Coffe leaf miner resistance . In: Braz. J. Plant Physiol., 18 (1): 109-117, 2006 online edition (accessed July 23, 2007)
- ^ Anna-Elisabeth Jansen: Plant Protection in Coffee. Recommendations for the Common Code for the Coffee Community Initiative . German Society for Technical Cooperation GmbH, July 2005, page 46 Online version ( Memento of the original from September 27, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (Accessed July 23, 2007)
