Why Monitor Citrus

> Why Monitor Citrus

Why Monitor Citrus

Monitoring in Citrus is voluntary in New Zealand

Training for monitoring citrus was rolled out in the Bay of Plenty in the mid 20000’s, taught by Dr Keith Pyle. There were only three staff from Fruitfed’s Katikati branch trained initially, Cathy Harris being one of them.

The ten years that the voluntary programme was running allowed the industry to develop the most effective programme. The monitoring frequency started at weekly, changed to monthly, then back to fortnightly, where the best practice recommendation remains, having proved to be the most cost effective and best for control of pests on the orchard.

The original intent of monitoring was to reduce pest damage to fruit, therefore achieving a higher packout with better quality fruit, Now, AvoGreen© is also used as the major tool to gain access to overseas markets, with the AvoGreen© programme being the point of difference.

Q:  Are there any thresholds for pests found on Citrus?

A: No thresholds have been set, which leaves the decision up to the grower as to whether to take action or not, and when any action needs to be taken. We can advise on the insect lifecyle, but not the sprays that should be applied. There are other more qualified advisers available to give that advice, for example Farmlands or advisers through Citrus New Zealand  https://www.citrus.co.nz/.

Q: How often should I monitor my citrus?

A: There is no IPM programme in place for citrus at this stage. However monitoring is good when done regularly, to avoid pest and disease damage to the fruit and trees. From October to April, it is advisable to monitor 2 weekly, with 4 weekly monitoring from May till September. The major insects we are looking for that cause most damage, are:

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Kelly’s citrus thrip

This insect does most of the damage at the end of flowering, mostly November/December. It is important to find the KCT just before petal drop, so the spray can be ready to go when full petal drop has occurred. Damage occurs possibly as early as when the flowers are starting to drop. Monitoring is recommended 2 weekly till spraying occurs.


Black citrus aphid

Black citrus aphid cause the new shoots on the trees to deform and can also be a minor cause of sooty mould. The BCA attract ants that love to ‘farm’ and ‘milk’ the aphid.


Citrus white fly

CWF was first seen in New Zealand in 2006 and has now become widely established in our citrus, causing severe sooty mould on both the fruit and the leaves. A predator ladybird, the Serangium maculigerum, was found by an entomologist in Auckland in 2005 and is now spreading throughout the northern areas of New Zealand. This ladybird predates on the Australian Citrus white fly, which is the variety that is established here. The time to monitor for CWF is from August to December,  though they can be found most of the year.


Flower moth

Flower moth are usually found towards the end of flowering. A sign flower moth are present is the webbing in the flowers which is created by the caterpillar. The moths lay eggs in the flowers and on the tiny fruit, where the hatching larvae feed on the surface of the fruitlet, causing scarring which we call Rind Spot.



There are a number of varieties of Scale found on Citrus, some  are more damaging than others, such as the Californian Red Scale, which can be found in high numbers on the fruit, causing indentation and high reject rates. These scale are tiny, so very hard to detect at the crawler stage. Scale hatch twice a year in New Zealand – August/September and January to March.


Greenhouse thrip

Greenhouse thrip are present between February and April/May, feeding on the surface of touching fruit, causing scarring on the fruit.