Asterolecanium coffeae
| Asterolecanium coffeae | ||||||||||||
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| Asterolecanium coffeae | ||||||||||||
| Newstead , 1911 |
Asterolecanium coffeae is a scale insect fromthe Asterolecaniidae family . It is one of the most important pests of coffee plants and in some cases causes considerable crop losses.
features
In the first larval stage, the animals are approx. 0.3 to 0.4 millimeters long, yellow in color and have a teardrop-shaped and flattened body. The head and the thorax are fused together. You can see seven abdominal segments. In front there are two inconspicuous, colorless eye spots. Your two antennae are easily recognizable and probably consist of eight segments. Although they have six fully developed legs, their movements are very slow. In the second larval stage, the animals grow to 0.5 to 0.8 millimeters. You can no longer see any segmentation, the legs and eyes are completely reduced, the antennae are only recognizable as small stubs. After the second molt, the adult reach imagines about 1.5 millimeters in length.
Occurrence
The species is found in Angola , the Democratic Republic of the Congo , Kenya and West Africa .
Way of life
In addition to Arabica coffee ( coffea arabica ), the animals also infest Japanese medlars ( Eriobotrya japonica ) and plants of the Jacaranda genus .
They prefer to stay at the base of the leaf stalks on young, one and two year old shoots. From there they can tap into the pathways of the leaves. This causes them to die off quickly and turn black, which then typically remain on the shrub and do not fall off. In the places where the lice sit, the still green branches are always deformed towards the lice's sitting position. They also cause the growth of long, whip-like shoots. The lice are occasionally found on the fruits, only rarely on the leaves of the plants. The damage is particularly serious towards the end of the two dry periods between March and October. Although the plants recover in the subsequent rainy season, as the number of lice decreases as a result, a heavily infested plant will be more severely damaged in the next dry season than it can recover in the rainy season. Especially since the growing larvae then have more food available because the plants are more concentrated in the sap.
development
The females hatch their yellow, approx. 0.3 millimeter large eggs in their bodies and die as a result after a while. The inside of the chitin shell dries up and offers the eggs enough space and protects them until they hatch. The larvae can free themselves from the shell through an opening after hatching. Then they look for a suitable position to suck up plant sap. The fertility of Asterolecanium coffeae is low compared to other representatives of the scale insects, a female produces an average of 50 offspring. Most of them are females, which is why mating rarely occurs due to the lack of suitable partners.
After about 7 to 12 days, the larvae molt for the first time, the second and last time after another 18 to 25 days. The females develop their eggs in about a month. Their entire lifespan is therefore approx. 60 to 70 days.
Natural enemies
The main enemy of Asterolecanium Coffeae is Metaphycus lounsburyi , a parasitic living wasp from the family of Encyrtidae . An important documented predator of the larvae is Chilocorus angolensis . In addition to him, other ladybirds such as the black scale insect ladybird and Chilocorus dicoideus are suspected to be predators, but this has not yet been documented. In contrast to the wasps, the beetles are only insignificantly involved in the decimation of the lice.
Combat
Fighting a heavy infestation is very difficult. The most effective control measure against Asterolecanium coffeae is to severely prune the plants. This must be done before the plants are about to emerge. In addition, the remaining trunks must be scrubbed (not sprayed) with suitable means in order to kill the remaining lice, which are very resistant to spray due to their body shape. The cut branches must be burned. Even with less severe infestations, a more or less radical pruning and treatment with sprays is the only effective method to ward off major damage to the plants.
literature
- James, HC (1933): The biology and control of Asterolecanium coffeae , Newst., The fringed scale of coffee, in Kenya colony. In: Bulletin of Entomological Research 24 (3) : 421-427. doi : 10.1017 / S0007485300031746