Effective and sustainable pear sucker control using Siltac SF: the Dutch experience – The Fruit Grower

Siltac SF is a very effective novel physically-acting product for the control of pear sucker (Cacopsylla pyri) and other soft-bodied insects. It has become the go-to product for pear growers in the Netherlands and Belgium, with regular low doses applied from mid-May. This effectively controls pear sucker, while protecting natural beneficials in a truly sustainable approach.

Pear growers Chris Beerepoot from Zwaagdijk (North Netherlands) and Jeroen Peters in Ingen (Betuwe, East Netherlands) add Siltac SF to every pear scab spray. Using this approach, pear sucker larvae are cleaned up almost every week in the critical early summer period and populations cannot build up.

Chris and Jeroen both chose to focus on Siltac SF for their pest control because of decreasing availability of chemical options and their limited efficacy and application windows. “The disadvantage of chemical controls is that you have to be there at exactly the right time, or you have to repeat applications. It did not work satisfactorily and the costs were rising” said Chris.

Siltac SF does not work like conventional chemical crop protection products: rather it has a purely mechanical effect which means it is not required to be registered as a plant protection product. It contains a patented blend of silicone polymers that forms a net over target pests when sprayed which quickly contracts as the product dries, crushing them to death.

Repeatedly spraying a low dose (0.1%) of Siltac SF provides constant pressure on the young, harmful pear sucker – helping to prevent populations building up. This also applies to other pests like spider mite, rust mites and aphids. Natural enemies are spared because they are typically larger, stronger, move faster and are often hidden within the canopy when spraying.

Jeroen Peters tried Sitac SF for a number of years in trials before using it as standard in 2023. “You have to start applying from an early stage of the season, but make sure it is not too humid. If the leaf is wet, and the product is unable to dry quickly, it can lead to some leaf burn. This may be a deterrent, but I am convinced that pear growers will use Siltac SF more”.

According to the growers, optimizing the agronomic strategy is a learning process. Chris has now been using Siltac SF for 8 years. “We went from lots to no sooty mould and greater customer satisfaction. At the same time, we observed more parasitic wasps, predatory bugs and earwigs”. If he still sees earwigs feeding in the autumn, he considers. this a good sign because young earwigs consume the pear sucker larvae.

In previous years before widespread Siltac SF use, during winter pruning in January and February, he saw many adult pear sucker “jumpers” which then lay millions of eggs. This spring in May, following programmed use during 2023, the pressure was extremely low. However, he remained alert because he did not expect so much from the earwigs which overwintered in the soil this spring. “This spring, the predation effect may be disappointing; it was a wet winter, and I don’t know how long those creatures can hold their breath”.

Wet areas in the orchards are often the highest pressure for pear sucker. “That’s where we first see problems. We managed to solve this last year by blowing a high dose of Siltac SF through the row with extra ventilation. On top of that, we placed a reflection screen on the single-row sprayer to increase the effectiveness of spraying”.

Jeroen agrees, saying he saw many natural enemies last year and admits it can be exciting. “Sometimes you know that you are at the tipping point and then nature takes over. But if the pest pressure is high, it can be stressful.”

To prevent sooty mould in high pressure situations, he sprinkled water and sprayed with soap solution, but he also added a high dose of Siltac SF and a lactic acid bacteria to break down honeydew.

It is important to start on time with a strategy using Siltac SF, since it works best on juvenile stages and small insects.

“Don’t wait until all the stages are already present. Then you don’t take out everything and you never get rid of it” Chris Beerepoot explains. The most susceptible stage is the first larval stage of the pear sucker, which occurs when the eggs turn orange. “During warm weather, pest pressure can increase explosively, which is why we are careful to use Siltac SF as a preventative measure to stop the population building up”

Growers would prefer to start in April, but the risk is that the crop is not often dry enough at this time for good effects and crop safety. Chris says “The practice is that we start in mid-to-late May, otherwise the leaf can be too sensitive”.

Jeroen adds that a follow-up spray should be done in the autumn, after picking and before leaf fall “Otherwise, they will feed on the buds”.

Integrating other insecticides in the programme is important too. Typically, the first aphid spray is carried out at the beginning of April with flonicamid, which is selective and with a good profile on beneficials. Peters also uses spirotetramat in May, which has a strong systemic effect. Caterpillars and leaf rollers are chemically controlled fourteen days after full bloom in Zwaagdijk, while they build confidence in biological control options. In Betuwe region, Peters has good experience using chlorantraniliprole for these pests.

Both growers agree that the sprayer equipment is vital to get good leaf cover and to get sprays into hiding places. Chris Beerepoot has been very happy with his single-row cross-flow sprayer for the last 8 years, but has invested this year in a Wanner 2-row sprayer with reflection screens. Jeroen Peters has good experience with the Wanner sprayer, but in high pressure situations last year he used the traditional single-row cross-flow sprayer which he believes can provide better coverage in tricky areas. “We then drive at slow speed, lots of ventilation and good water volume so that the leaves both above and below get wetted”

The standard dose of Siltac SF is 1 litre in 1000 litres water (0.1%). At driving speeds of 6.5km/hr, Beerepoot sprays 250 litres per hectare. Peters says he goes up to 300 litres per hectare. These relatively low water rates are perfect to get optimum control and crop safety from Siltac SF. Where higher doses are needed, both growers have gone as high as 0.15%.

For efficiency of spraying, Siltac SF is frequently mixed with fungicides, so saves a lot of additional work by removing a separate spray pass – but care should be taken to establish crop safety first.

In total, the growers used around 2.25 litres of Siltac SF over the whole season, giving them complete control of pear suckers, aphids, spider mites and rust mites with no other chemical controls during the main summer period. This has given a significant cost saving to the growers, with much improved sustainable control.

Siltac SF is marketed by ISA CropCare and distributed in the UK exclusively through Hutchinsons. It is designed to combat numerous pests such as pear sucker, spider mites, aphids and whiteflies.

According to both European and UK (CRD) Regulations, Siltac SF does not require approval as a crop protection product because of its physical mode of action. It is completely degradable and has no MRL. Moreover, it is difficult for pests to build resistance due to its physical mode of action.

Applications should take place in good drying weather to maximise efficacy and crop safety. The silicon polymers in Siltac SF then form a net that shrinks quickly around the pest, killing it in less than a minute. After this, the net can be degraded by water into harmless components.

Siltac SF is suitable for a wide range of crops including top and soft fruit, greenhouse vegetables and ornamental plants.