Du Roi Integrated Pest Management - perm

By: Du Roi Integrated Pest Management  11-11-2011
Keywords: Wasps

C. perminutus (often referred to as Cocci’s), are small wasps which originate from Hawaii and now occur widely throughout the world. They are extremely effective parasites of Citrus and Vine mealybug, providing control of low and high-density infestations. C. perminutus are black in colour with noticeable translucent wings, have relatively long antennae and are approximately 3mm long. They can be seen with the naked eye. Females lay their eggs into the first 3 instars of Citrus mealybug and are able to lay between 60 to 90 eggs each. The eggs develop into pupae within the mealybug insect slowly feeding off the host. Parasitised mealybug continue to develop, but are eventually killed by the growing pupa. About 16 days after egg laying adult C. perminutus wasps emerge from pupae and are immediately ready to mate and continue the cycle. The speed of the lifecycle is dependent on temperature and humidity. Generally, C. perminutus adults are active for about 7 days and are most effective at temperatures of between 20 to 30º C and humidity of between 50 to 90%.

How to Make Use of C. perminutus Augmentative Releases
C. perminutus are best released in spring and early summer, before mealybug populations build up to unacceptable levels. It is important to determine the type of mealybug present before considering the use of C. perminutus since the parasite is not very effective against species other than Citrus and Vine mealybug. In Citrus orchards, releases should be considered if, after the spring complex sprays are complete, an infestation level of 5 - 10% is recorded. Placing of C. perminutus in orchards will serve to supplement the naturally occurring enemies of mealybug (Lacewing, Anagyrus sp., etc.) and speed up control so that economic damage is not caused and corrective chemical treatments can be avoided. Winter releases are not recommended due to low temperature and the consequent reduction in mealybug populations. Do not release C. perminutus too soon after applying toxic chemicals and avoid harsh chemical applications after insects are released
C. perminutus are sold in pupal form and supplied in matchboxes with a small hook attached. Each matchbox contains 3000+ pupae (1500+ in the case of vineyards), which will begin to hatch on the hatching date (approximate) indicated on the box. Remove the sticker from the box exposing the exit hole. Place the sticker on the tree so that you can locate the release site at a later date. Position the matchbox inside the tree at head height and if possible, in close proximity to mealybug. Once the parasites begin to hatch, they will be attracted to the exit hole by sunlight and emerge. The pupae can be stored prior to release if necessary but not for longer than 3 days. Take care not to expose the stored insects to excessive temperatures. The ideal storage temperature is between 20 to 26º C.

Recommended Release Rates: 60 000 wasps per hectare. For the best results make 4 releases spaced 2 weeks apart. High populations of mealybug will require at least 90 000 parasites per ha with the possibility of booster releases in problematic areas. After release, one should ensure that the C. perminutus have become established. The parasite is difficult to detect in the early stages of release. However, one should search for adults as well as pupal cases (containing the parasite) in the clusters of mealybug. Pupal cases are about 3 mm long and appear yellow to brownish in colour with a leathery texture. The presence of adults or pupae will confirm C. perminutus activity.

Practices Assisting the Establishment of C. perminutus
1. Reduced wind velocity, increases in humidity and dust reduction within orchards will assist
C. perminutus establishment. Windbreaks are helpful in this regard.
2. High ant populations will interfere with parasite activity reducing their performance. Ants should be controlled by selective spraying, treatment of ant nests or the application of ant barriers.
3. Insecticides to be applied should be carefully selected to ensure low impact on the parasite population.

Keywords: Wasps

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