Pest Control for free
Does it matter to farming that a UK study recorded a 37% decline in all types of insects with a 67% decline in predators i.e. those that can help control crop pests? The statistics are alarming:
- 23 species of bee and flower-visiting wasp have gone extinct since 1850
- Geographic ranges of many bumblebee species more than halved (1960 – 2012).
- Numbers of butterflies fell by 46% between 1976 and 2017,
- The abundance of larger moths such as the Garden Tiger dwindled by 28% between 1968 and 2007, with Southern England experiencing a 40% drop in numbers.
Apart from farming getting the blame for some of the decline in insects (both species type and abundance) there is a knock effect for agriculture. The loss of beneficial insects is bad news for farms that would otherwise benefit from the natural control of pest species. Whilst some farms have ceased to use insecticides altogether, those that continue have access to a declining range of products and resistance inevitably continues at pace. As the variety of insects decline farming will be losing some of its allies- those that prey on pests. Insects such as bumblebees, hoverflies, solitary bees are of course also important as pollinators of oilseed rape and field beans.
If farming wishes to reduce spending on insecticides and practice ‘Integrated Pest Management’ how and why should beneficial insects be supported?
Some of the key species that can work for free on your farm to control pests:
- Parasitic wasps that sting and lays its eggs inside aphids which carry plant viruses such as Barley Yellow Dwarf Virus. These are effective hunters flying through the crop to find aphids with females able to parasitise 300 aphids in her lifetime.
- Larvae of green lacewing also voracious predators of aphids etc. The adults hunt down aphid colonies and lay eggs nearby so that on hatching the larvae have access to their prey
- Ladybirds which prey upon aphids and the eggs and larvae of cereal leaf beetles.
- Ground beetles – Of the 350 different species in the UK, 30 are typically found in farmland and they predate flea beetles, weevils, aphids, and newly hatched slugs. They can also consume 4,000 weed seeds per sq. M daily. They lay their eggs in soil so cultivation will adversely impact upon eggs that will hatch and become larvae before becoming adult beetles.
- Rove beetles – These prey upon aphids, fly eggs and larvae.
The key to having these predators work effectively on farmland pests is to ensure they are able to react quickly when an outbreak first emerges. Pest species typically reproduce quickly and in large numbers so they have be dealt with speedily. Predators must be near to, or present within the farm, and close to the crop. Those that have the ability to survive overwinter need to be provided with a suitable habitat and this need nothing more than areas of tussocky grassland either in a field margin or within a ‘beetle bank’ located through the crop itself. Insects also need sources of pollen and nectar to sustain them, hence flower-rich margins containing plants such as knapweed, Birds-foot-trefoil, Red Clover, Yellow Rattle and Ox-eye daisy are an important habitat to be provided. Ground beetles are thought to travel not much further than 50 m through a crop so some farmers have sown flower-rich ‘highways’ at 100m intervals to give the predators easy access to their prey.
Creating a diverse landscape with a range of habitats including trees, woodland and scrub will provide a home or food source for insects. Their exact needs may not be fully understood so a range of habitats with many different plants should be the aim to maintain a farmland well stocked with predators. This will also provide for many other forms of wildlife. Plants provide seeds for birds such as grey partridge and small mammals with those in turn being fed upon by animals further up the food chain- barn owls preying upon mice and voles for example.
There are many other practices that will sustain beneficial insects. Reducing the frequency and degree of soil disturbance will ensure all those species at the bottom of the food chain can thrive. It will also help to be tolerant of some ‘weed’ species within the crop that are beneficial for predators such as annual meadow grass, chickweed or knotgrass but not the likes of black grass. Cover crops will help insects to overwinter and under-sowing provides a habitat that will support predatory insects within the crop itself. Low-input grassland can be used by insects and mob grazing means there are areas of very lightly grazed swards which can be allowed to remain taller and with more structure for longer.
Minimising the use of all and any pesticide type will help sustain more beneficial insects. Even some co-formulates within Azoxystrobin fungicides may have an adverse upon insects such as bees. The timing of any pesticide treatment is critical to assess as is to ensure sprays are only applied when pest thresholds have been accurately assessed. Being careful to avoid spray drift is of course an obvious requirement to keep insects alive within their adjacent field edge wildlife habitats.
There is financial support for those who wish to follow integrated pest management (IPM) practices. The Stewardship scheme can a provide annual payments on various insect friendly options including:
- Beetle Banks at £667/ha
- Nectar flower mix at £614/ha
- Flower-rich margins & plots at £673/ha
- Autumn sown bumblebird mix at £637/ha
- Taking small areas out of management at £331/ha
- Low input Permanent grassland at £151/ha
- Buffer strips (4m- 6m) at £451-£325/ha
- Watercourse buffer strips on cultivated land (12m- 24m) at £612/ha
- Undersown cereal at £306/ha
Contact Mark Simmons, Catchment Sensitive Farming Adviser ([email protected]) for further advice and support.