Monitoring for insects is an important part of any Biological Fruit Production (BFP) or Integrated Fruit Production (IFP) programme. The main purpose of monitoring is to obtain action thresholds for pests. These thresholds will determine when control measures for pests need to be applied so that pesticides, or other controls, are only used when absolutely necessary. Pest monitoring can also help understand the pest life cycles, for example the timing of generations.

As well as investigating the reactions of the different pests to IFP and BFP programmes, scientists have been evaluating the different methods of monitoring pests and predators. Some of these methods are suitable for routine orchard monitoring, although some are time-consuming and are probably only useful for research purposes.

Here are the main monitoring methods evaluated to date. They have been evaluated in all districts as part of an experimental IFP programme, although these comments are mostly from the work done in Central Otago and Canterbury.

Pheromone traps

Most growers are familiar with the pheromone sticky traps which are readily available for monitoring of codling moth and leafroller. Now commercial pheromones are available for the noctuid moth, Graphania mutans, and San Jose scale. Pheromone traps are usually hung in trees 1.5 to 2 metres off the ground, around the edge of a block and/or within the block, at about 1 - 2 per hectare (depending on the species you are monitoring). Pheromone caps need to be replaced every six weeks and the bases every three weeks. Bases are checked every week and the different insects are recorded.

• Very useful for codling moth. Can measure timing of generations as well as thresholds for spraying.
• Useful for leafrollers at present. Can measure the timing of generations. Eventually, timing of leafroller spraying may be based on life-stage models and possibly a regional trapping system. Not useful for thresholds.
• Used for the noctuid moth, Graphania mutans. It is difficult to get a relationship between trap catches and economic damage and further evaluation is needed.
• Traps for monitoring San Jose scale have been available since the 1970s. The number of insects caught in the trap indicates the timing of generations. Information on the timing of male emergence/ flight could be used to guide the application of selective scalicides in the spring. SJS pheromone traps are also useful for catching and determining the presence of scale insect parasites.

Bait traps

• Little use to growers - time consuming and not good attractants to male moths.
• Used in experimental trials for checking codling moth and leafroller.

STP (Pane) traps

These traps comprise of a clear perspex plate (30 cm x 30 cm) coated on both sides with a thin layer of STP oil treatment. The traps are suspended vertically in the trees, usually on a supporting wire, at 1.5 - 2 metres above the ground. The traps intercept insects in flight and the STP provides a greasy and slightly sticky surface able to catch small insects. Traps are checked once per week from the beginning of December.

• Useful for monitoring Froggatt’s apple leafhopper and some predators
• Time consuming - a smaller, simpler trap is needed, especially as Froggatt’s apple leafhopper is only a minor pest.

Timed shoots and cluster sampling

This method has been trialled for leafroller and apple leafcurling midge larvae, egg and damage sampling. Trees are randomly selected and are ‘searched’ for one hour per cultivar. Leaf clusters are classified as terminal shoots, side shoots, and spur clusters. A record is kept of the damage (or no damage) to each one so that the number of clusters (also including fruit clusters) examined is known and the association of damage with cluster type and tree number can be analysed. The timed searches are carried out fortnightly throughout the season.

• This research is providing the data needed for the development of the leafroller monitoring methods in the IFP programme ie. 1 larva or fresh damage in 200 shoots/fruits per cultivar block.
• Difficult to locate live leafroller larvae - observation of fresh leaf roller damage is an essential part of IFP monitoring.

Beating technique

• Used for predator sampling.
• Simple to use but difficult to interpret - more research needed on the benefits for monitoring predator populations. Not intended for grower use at this stage.

Using a beating tray for sampling

(See also, "Comparison of suction and beating tray sampling for apple pests and their natural enemies" Suckling et al, Proc 49th Plant Protec Conf 1996 : 41 - 47).

Leaf sampling and brushing

Used for mites and mite predators. In the research programme, 50 leaves/ cultivar are collected from each block on a monthly basis. The mites are brushed onto a glass plate using a mite brushing machine (Leedom Engineering, California, USA) and counted. Growers can make use of commercial/ HortResearch mite monitoring services, where available, at critical times during the season.

Terminal and water shoot sampling

Used for woolly apple aphid and the associated predators and parasites. In the research programme (Central Otago), a series of ten five-minute random time searches was carried out on each cultivar for woolly apple aphid colonies on water shoots, non-bearing side shoots and terminal shoots. Water shoots were preferred but were rare in some cultivars, particularly in the younger trees. Records were kept of the numbers of shoots examined, those infested by woolly apple aphid, and the numbers of colonies on each infested shoot.

• This level of monitoring is probably unnecessary on individual orchards but the IFP method is based on this research.

Acknowledgments

HortResearch acknowledges ENZA New Zealand (International) and the Foundation for Research, Science and Technology for funding.