1. The trials ...
2. 1995/96 Spray programme details
3. Success of the pest control programme
4. How the different pests were affected
   • Codling moth
   • Leafrollers
   • Noctuid moth
   • Apple leafcurling midge
   • Woolly aphid
   • Froggatt’s apple leafhopper
   • Oystershell and San Jose scale insects
   • Mites
5. In summary

Many pipfruit growers would like to reduce the number of insecticides for health, cost and environmental reasons. Yet many perceive the risks of cutting down on insecticides, and certainly cutting them out altogether and growing organically, as too high.

Growers have three options :

1. To use a conventional spray programme which includes organophosphate insecticides (chlorpyrifos, azinphos-methyl).
2. To use an integrated fruit production (IFP) programme where "soft" chemicals are only used if necessary. Pest and disease monitoring and alternative methods of control are key components of this programme.
3. To use a biological fruit production (BFP) programme. Sometimes called "organic" production, BFP uses only natural products, biological processes and practices.

The conventional spray programme may appear to be the least risk option, however, with increasing resistance to certain pesticides and stringent market access demands, it may not be an option for much longer. BFP may seem an extreme option, however, many of the techniques which have been developed in this programme now form part of the more moderate IFP programme. Pest monitoring reduces the risk of pest control failure.

Dr Howard Wearing and his team at HortResearch are comparing the three options on pipfruit grown at the Clyde Research Orchard. In the first year of the trials (1994/95), there was no difference in overall fruit damage from fruit grown under each of the three regimes. In the 1995/96 season, there was, once again, little difference in the overall percentage of fruit free of insect damage or infestation. Slightly higher damage occurred in the 4 year old BFP block, although this was mainly due to codling moth (for which no controls were used). Mating disruption will be used to control codling moth in the 1996/97 season.

The purpose of this article is not to report whether one system is better than another, but to describe the interactions between the pest species and natural enemies and their response to controls (or lack of control). Understanding the pest interactions will help you if you are considering reducing the insecticide levels on your orchard. It is also important for pipfruit growers who are switching to an IFP programme to see how a "real-life" orchard converted to IFP operated in the first two years of the programme.

The trials ...

At the Clyde Research Orchard there are :

• 1.2 hectares of apple trees managed under an IFP programme. One hectare of Pacific Rose, Southern Snap and mixed GS series have been managed under IFP since 1994. The 0.2 hectare, which also contains Braeburn, Fuji, and Royal Gala, has been managed under IFP since 1995. Before the IFP programme, these blocks had a conventional organophosphate spray programme.
• One hectare of apple trees (Braeburn, Fuji and Royal Gala) sprayed with a conventional organophosphate programme.
• Three hectares of apple trees managed under a BFP programme. This 3 hectare block consists of conventional varieties (Braeburn, Fiesta, Fuji, Royal Gala) and disease resistant varieties (Dayton, Jonafree, Liberty, Prima, Redfree)

Initially the aim was to establish pest and disease control programmes under the three systems. However, don’t forget that IFP and BFP include other biological management practices for weed control, soil structure and water quality which will not be discussed here. Further details of the disease control results can be found under Organic alternatives to black spot and powdery mildew sprays.

Please click on the heading below to see the trial spray programme. This was the spray programme used in the second year of the trial. Remember the BFP and IFP programmes are still experimental and will need further refining.

Table 1: Spray programme for conventional production (OP), and preliminary spray programmes for integrated (IFP) and biological fruit production (BFP) - 1995/96 season.

For further details of the monitoring methods used, see Pest monitoring in an IFP programme.

Success of the pest control programme

The best way to gauge the effectiveness of the different programmes in the first two seasons was to measure the pest populations and levels of infestation and damage.

First year - 1994/95 season

At harvest, fruit from the conventional (OP), IFP and BFP programmes all had the same overall percentage of fruit free of insect damage or infestation (no significant difference). However, different insects were responsible for the damage in each programme - damage or infestation from one pest in one system was compensated by freedom from another pest. For example, leafroller damage in the BFP programme was compensated by lack of mite infestation, while the opposite occurred in the OP programme. See Table 2 for further details of overall damage.

Table 2. Percentage of harvested fruit clean of all insect damage, and percentage of fruits infected by black spot, from different cultivars within the IFP, OP and BFP production blocks.

Second year - 1995/96 season

The new IFP block was infested with oystershell scale which originated from a nearby shelter-belt of alder (Alnus incana). This shelter belt has now been removed. Apart from this pest infestation on a small area of the IFP block, there was no difference between the IFP and OP programmes in the overall percentage of harvested fruit free of insect damage or infestation. Higher damage occurred in the BFP programme, but this was mainly as a result of an increase in codling moth damage which has recently colonised the block. Mating disruption will be used in the BFP block in 1996-97 to combat this pest. See Table 3 for overall damage in the second season.

Table 3. Percentage of harvested fruit clean of all insect damage, and percentage of fruits infected by black spot, from different cultivars within the IFP, OP, and BFP production blocks.

How the different pests were affected

Codling moth

Pheromone and bait traps were used to monitor codling moth.
When the populations in the traps reach a set threshold (approximately 2 moths per trap per week), sprays are applied to the OP and IFP blocks, provided leafroller insecticides are not already giving protection.

No control was used in the BFP block as pheromone trap catches have been low (equivalent to less than one moth per tree). In year one, only 0.9% damage was recorded at harvest. By year 2, trap catches were still low on this block. However, damage at harvest averaged 3% over all varieties, with codling moth damage reaching 10.9 % for Dayton (this variety had a very light crop). As the trap catches did not predict the final damage levels, it is possible that the threshold level for IFP may need to be lowered. The threshold levels were originally based on sprayed blocks which didn’t have any existing populations of codling moth. The BFP block in this trial already had codling moth present which explains why the traps didn’t indicate the final level of damage. Next season, mating disruption will be used to control codling moth in the BFP block.

In the first year, 1994/95, there was no codling moth damage in the IFP block at harvest. In 1995/96 only one Mimic was used (so as to test the threshold levels). Total damage at harvest was 0.4% on the new IFP block and 0.1% on the rest. No live codling moth larvae were found. Therefore, no specific sprays are needed to supplement Mimic in the insecticide programme, but Mimic needs to be applied once the threshold is reached

Only minimal damage was found on the OP block : 0.2% in both years, plus 0.03% live larvae in year 2.

Leafrollers

Leafrollers were monitored with pheromone and bait traps. High levels of light brown apple moth were found in the BFP block, probably due to insects breeding in the ground cover and lack of insecticides in this block.

No live leafroller larvae were found in the IFP or OP blocks, and only low numbers were found in the BFP block from sampling clusters on apple trees. Overall the OP programme provided excellent control with less than 0.1% damage in all three cultivars in both years.

Less than 1% damage was found in the IFP block in 1994/95 and less than 0.1% damage in 1995/96. This indicates that Mimic, along with other management practices (eg. mowing), can successfully control leafroller.

Leafroller damage in the BFP block ranged from 0.8 to 3.4% in year 2. Damage to each of the three resistant cultivars was greater than to the conventional cultivars, although this difference was only slight in 1996. Leafroller damage to leaf clusters increased from mid January onwards, rising from 1% in January to 5.5% in May in the 1995/96 season. This fresh damage is more easy to detect than larvae and is used as part of the IFP sampling programme to indicate the presence of leafroller.

Leaf damage by leafroller

Noctuid moth

Noctuid moths (eg. Graphania mutans) can cause damage to harvested fruit, particularly on unsprayed trees with light crops. In the first year, moth damage was unusually high with up to 16% on individual cultivars of the BFP programme. Some cultivars had more moth damage than others, but at harvest the three programmes showed no significance difference in the overall level of damage (3 - 6 %).

To determine the cause of this level of damage, moths were monitored in the second year using pheromone traps. Noctuid larvae, eggs and damage were monitored at the same time as checks were made for leafroller larvae. The Mimic and OP insecticides, used for leafroller and codling moth in the IFP and OP blocks, were toxic to noctuid caterpillars - trap catches of noctuid moth were lower after these sprays had been applied. It was actually difficult to find any larvae in the IFP and OP blocks, although small numbers of larvae were found on the BFP block. Damage in the 1995/96 season was lower than in the previous year, (0.2 % to 4.4 % damage) and once again there was no difference between any of the programmes.

OP and Mimic sprays provided the main control of these pests. In addition, hand thinning appears to be a useful in removing any fruit damaged in the spring before the insecticides were used.

Apple leafcurling midge

Apple leafcurling midge (ALCM) damage has been higher in the IFP block than the OP or BFP blocks so far. Populations of the predatory bugs, Orius vicinus and Sejanus albisignata, are still building up on the IFP block and have not yet provided sufficient natural control. Despite the high levels of ALCM found during the season (up to 35% of leaf and fruit clusters infested), the actual level of ALCM on the fruit at harvest was very low (0.1%). It will be interesting to see whether the predator populations can increase enough to control ALCM on this block.

On the BFP block where these predatory bugs were well established, there was minimal ALCM on the fruit at harvest. Sejanus, in particular, appears to be an important natural enemy of ALCM. There was no ALCM infestation on fruit from the OP block.

Curled leaves due to apple leafcurling midge

Woolly aphid

This pest has not been a problem so far, with very low levels of infestation recorded at harvest. The only exception is Southern Snap in the IFP block which had up to 3% of the fruit with woolly aphid at harvest. Biological control from parasites and predators appears to control woolly aphid in the BFP programme, especially on the young trees. These natural enemies should control woolly aphid in the IFP programme as well, provided the parasites can establish before the aphid population grows too large. To encourage the build-up of the parasite population, orchardists must avoid applying any organophosphate sprays to IFP blocks.

Froggatt’s apple leafhopper

High numbers of Froggatt’s apple leafhopper (FAL) were caught in sticky pane traps in the BFP block, and foliage damage was high in this block.

In contrast, very low numbers were caught in the traps of the IFP and OP blocks, although the levels may still build up on the IFP blocks as the effects of previous insecticides decline. This is being monitored.

There are two distinct generations of this pest in Central Otago which peak in adult numbers in December and early March.

San Jose pheromone "tent traps" can also be used to monitor FAL. These traps also pick up Anagrus sp., a natural parasite of FAL.

Oystershell and San Jose scale insects

Scale insects can be difficult to control, even when specific insecticides are applied. All three programmes included pre-bloom oil for scale control, although in the OP block the oil was combined with chlorpyrifos for both scale and woolly aphid control. This programme also included chlorpyrifos mid-season for the same purpose.

Despite the use of oil and OP sprays, a small percentage of Braeburn and Fuji fruit were infested in the OP programme in the first year. For better scale control, total spray coverage with both oil and insecticides is essential.

Fruit infestation by scale insects was unacceptable (1-10%) in the IFP block in year one. No specific scalicide was applied and the level of natural enemies was not high enough to provide biological control. In the second season, a high volume oil spray + Applaud was applied and this reduced the level of fruit infestation. There was a major outbreak of oystershell scale in IFP blocks next to a shelter belt of Alnus incana. The only practical solution was to remove this shelter belt.

In a normal year, and in the absence of scale-infested shelter, green-tip oil or oil + Applaud should be able to control scale insects in an IFP programme in Otago.

Few fruit from the BFP block were infested with scale insects. This was expected because the trees are still young and the scale populations have not yet established. The next few years will show whether a satisfactory balance can be maintained between the scale insects and their natural enemies.

Mites

Mites can certainly be controlled by natural enemies. In year 1, no mites at all were found on fruit at harvest that had come from the BFP block. In the second year small levels of infestation were confined to 3 of the cultivars used in the fungicide trial. Less than 0.2% of fruit from the IFP block had mite infestation.

Yet, in the OP block where predators were killed from fungicides and insecticides, a total of 0.1% fruit were infested with European red mite and the Fuji block had 12% two-spotted mite

(Tetranychus urticae) damage at harvest in the first season. In year 2, the mites exceeded the spray threshold in the Braeburn block in January and a miticide was applied to all cultivars. This miticide also controlled two spotted mites and the mite populations remained low for the rest of the season.

Twospotted spider mite adult and egg

A whole range of predatory mites and other species of predators were found in the BFP block. In addition to the predatory mites, T. pyri and G. occidentalis, other predator species included the following : Stethorus, Haplothrips, Orius, Sejanus and Agistemus.

T pyri feeding on European red mite

In summary

Without fungicides and insecticides, a wide range of pest natural enemies exist in an orchard. However, it can take time for natural enemies to build up if a conventional spray programme has been previously used on the orchard and natural predators are not present. This was evident in the IFP orchard where control of some of the pests was more difficult because of low levels of natural enemies.

Once populations of natural enemies have been able to increase, excellent control of pests such as mites, woolly apple aphid and apple leafcurling midge can be expected. Control of certain species on a biological orchard must be weighed up with the lack of control of other pests such as leafroller. This is where techniques such as mating disruption have a role. Insect pests which are only a minor problem on conventionally sprayed orchards, can become important pests on an IFP or BFP block.

The challenge with a newly-converted IFP orchard is for the number of pest natural enemies to build up before a pest population grows to such a level that natural enemies will be unable to control it.

In the two year of trials in Central Otago, the overall levels of damage or infestation on the fruit at harvest were not very different between the three programmes. Although some damage was caused in the second year by oystershell scale (within the IFP block) and codling moth (within the BFP block), these pests can be controlled in future years.

The IFP programme for pipfruit appears to be successful. Mimic provides high level of control of the major insect pests, leafroller and codling moth, provided it is applied once the thresholds are exceeded. Scale control by the use of high volume pre-bloom oil + Applaud, assisted by natural enemies, was adequate on the main IFP block in 1995/96. Woolly apple aphid and Froggatt’s apple leafhopper occurred at acceptable levels in the second season of IFP use, but will require continued monitoring. Similarly, the occurrence of ALCM in the Pacific Rose, Southern Snap and mixed GS trees of the IFP programme does not require specific control action at this stage, because promising numbers of predatory bugs were recorded in association with ALCM. This will also require continued montioring. Mite control under IFP was satisfactory through the actions of a range of natural enemies.

Finally, it is important to look at the interactions as a whole rather than looking at one species in isolation - this holistic approach will form the basis of a biological or integrated fruit production system.

Acknowledgments

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