THE AGROMYZID LEAF MINER, LIRIOMYZA TRIFOLII (BURGESS), A NEW PEST OF POTATOES AND OTHER VEGETABLE CROPS IN MAURITIUS

Liriomyza trifolii appeared in Mauritius in 1979, increased rapidly and became a major pest of potatoes in 1980. Blighting and premature defoliation caused serious losses in tuber production.
The outbreak was short and the insect population decreased during the second half of the season, to stabilize thereafter at a much lower level.
The insect was also observed on 25 other vegetable crops but damage to these was not comparable to that caused to potato crops.
Two distinct types of injury are caused: mining by the larvae and feeding punctures of the adult females.
At the peak of the out-break the number of larval mines per leaf averaged 51 in an untreated observation potato plot 7 weeks old.
Damage due to feeding punctures was not negligible, the proportion of leaf tissue destroyed reaching 7%. Leaf mining always begins on the lower leaves and works upward, suggesting that infestation is associated with leaf age.
This was reflected in the field by more rapid infestation late in the crop and in cultivars having a shorter growth cycle.
Insecticidal tests indicated that methamidophos, omethoate and decamethrin gave effective control.
Four hymenopterous parasites which already existed in Mauritius were reared on L. trifolii.
It is believed that their combined action has been an important factor in stabilizing the pest’s population.

IX African Symposium on Horticultural Crops

J.H. Dove

https://doi.org/10.17660/ActaHortic.1985.153.28