1. What are the “basics” ?
Medfly is one of the world’s most destructive agricultural pests. The female fly (and not the male) attacks ripening fruit so that she can lay her eggs. The female fly can infest more than 300 commercial as well as wild hosts and can produce approximately 400+ eggs in her lifetime.
2. What is the life cycle?
a. The mature female lays her eggs just under the skin of the fruit;
b. The eggs develop into larva;
c. The larva feed inside the fruit and fall to the ground when they are mature (this occurs after the 3rd instar);
d. Larva tunnel into the ground and change to pupae;
e. The fly develops inside the pupa which it leaves when it matures;
f. Depending on the climate (temperature is the most important) the mature fly can complete its life cycle within 30 days, however in cold and unfavourable conditions it can take up to 2 months and longer.
3. What is the history of this pest?
The Medfly comes out of Africa and has spread right through the Mediterranean countries, Southern Europe, the Middle-East, Western Australia, Southern and Central America and Hawaii.
4. How can we control or eradicate it?
a. The proven method is by practicing the principles of Integrated Pest Management (IPM):
i. Monitoring of the target area is done to establish the population fluctuation of the pest and where the “hot spots” are in the area;
ii. Regular air- and coordinated ground releases are carried out over the entire target area (area wide control) to decrease the wild fly population numbers;
iii. Alternative hosts are eradicated or at least managed better;
iv. Effective orchard/vineyard sanitation is implemented by producers; and
v. Sterile Medfly males are released in the target areas.
5. What detrimental consequences can the presence of the Medfly hold in SA?
The South African export deciduous fruit industry is of huge economical interest for the country. It is estimated that crop losses and control costs as a result of fruit flies in the Western Cape alone amount to more than R20 million per year. Furthermore, the impact of a quarantine ban on the export of South African fruit due to the presence of fruit flies can be devastating to the economical welfare of our local communities and businesses which are dependent on a profitable and viable fruit sector. The creation of low-prevalence or fruitflyfree areas is therefore an urgent necessity.
6. Why does it appear that the GF-120 and/or Malathion and Hynlure are not really effective against fruitflies?
a. The spray equipment is not calibrated to deliver the correct amount of active component per ha;
b. The use of incorrect nozzles which do not deliver the required droplet size (1-4 mm in diameter);
c. Control strategies start too late in the season,i.e. all the stages of the Medfly namely eggs, larva, pupae and mature flies are found in large numbers in orchards and vineyards.
7. Why is a winter programme against fruitflies so very important?
a. When orchards/vineyards lose their leaves, fruitflies migrate to home gardens, river courses and any other place where there is adequate shelter and food.
b. Plant and/or scale insects in home gardens release honeydew which is a good source of food, whereas bird guano which is high in proteien, is an excellent source of food.
c. During the winter and early spring fruitfly bait must be placed in home gardens, on farmyards and at farm buildings at least every 14 days on warm, sunny days.
8. For how long must I apply bait?
Bait application against fruitflies must be done throughout the year with shorter intervals (every 7 days) during summer months when monitor traps i) indicate an increase in population, and ii) at least one month before fruit start to ripen. Make intervals longer (every 14 days) only when the fruitfly numbers remain low over an extended period (less than a total of 2 flies per trap over 3 – 4 weeks). Post-harvest release treatments of clean-picked orchards must be continued for 4-6 weeks or for as long as fruitflies are caught in one or more traps.
9. How many traps must I have on my farm?
The recommendation is that one “Yellow Delta” trap per 2 ha must be hung out.