Trichogrammatoidea cryptophlebiae referred to as Trichogramma are minute parasitoid wasps. Originally from Southern Africa these indigenous parasitoids are considered to be one of the most important parasitic wasps for controlling False codling moth (FCM) (Thaumatotibia leucotreta). Trichogramma are egg parasitoids, which means that they lay their eggs in FCM eggs. This ensures that the developing larvae within the FCM egg are destroyed before fruit injury can occur.
Appearance and Biology
Trichogramma wasps are small (0.2-1.5mm) with a yellow/brown body colour. Their wings are translucent and males are generally smaller in size than females (Figure 1).
Trichogramma females use chemical and visual clues to locate FCM eggs. Once a suitable egg has been found the female drills a hole into the FCM egg and oviposits 1 to 2 eggs (Figure 2). Trichogramma eggs hatch within 24 hours after being deposited in the FCM egg. Trichogramma larvae develop through 3 instars and will feed on the content of the FCM egg for 3-5 days. After 4-6 days the Trichogramma larvae will pupate turning the FCM egg black in colour (Figure 3). 8-11 days after being parasitised an adult Trichogramma will emerge from the egg. Mating between adult males and females occurs within minutes of emergence and a few hours after emerging, females will begin parasitising FCM eggs. A Trichogramma female will parasitise up to 10 FCM eggs per day and can live from 3 to 10 days depending on availability of food. The life cycle from egg to adult is on average 10 days, however, this will vary depending on temperature and humidity.
How to make use of Trichogramma as a control agent of FCM
In order for Trichogramma to be most effective, early season releases are recommended. Trichogramma release programmes must be carefully planned. Parasitoids cannot be released in conjunction with harsh insecticide sprays (check with your IPM consultant).
4 releases of 25 000 parasitised eggs/ ha should be made from October to May (100,000 parasitoids per season). During October/November, FCM populations generally increase. Thus, the first release of Trichogramma should be made during this period. Timing will obviously depend on the type of spray programme being followed. Three further releases should be made 4 weeks apart from each other.
Du Roi IPM has developed a means of ensuring all FCM eggs on the egg-sheets are sterile which ensures that no FCM larvae will emerge from the few non-parasitised eggs on the sheet.
Trichogramma parasitoids are produced in egg form. Adult FCM females lay their eggs onto eggs sheets. There are about 1000 eggs per sheet which are parasitised by Trichogramma. These parasitised egg sheets are then prepared for sale.
Once the egg sheets are received, tear the sheets apart along the perforation and attach them to a leaf as close to the middle of the tree as possible using a stapler or a pin. It is important that the egg sheets are not exposed to direct sunlight.
Trichogramma should be released as soon as possible after they have been received.
To ensure that Trichogramma has established after 10 days regularly inspect fruit for parasitised FCM eggs (black in colour). Use Trichogramma in conjunction with other suitable FCM control products for most effective results.
NB Orchard sanitation is the most effective method of FCM control. Fruit should be destroyed or buried immediately after collection.