What do you think are the main adavantages of these approaches? Think about the advantages to the farmer, to the environment and over chemical control.

An alternative approach to biological control.

Rather than introducing novel organisms an alternative approach would be to encourage natural predators. Reasons for the current interest are:-

* In southern England there are over 400 potentially beneficial predators and parasites may live in cereal crops.

* ALSO as the price of cereal crops falls expensive pesticides seem less attractive.

The are two main approaches.

A. To help overwintering survival rates.

Hedge banks are warmer than the open field in winter. Furthermore tussock forming grasses (Dactylis glomerata and Holcus lanata) provide the best micro-climate for ground and rove beetles to over winter (by providing a slightly warmer micro-climate). Experiments have included creating new 'hedge banks' across the middle of fields by mounding up soil and sowing a suitable grass seed mixture. This did two things;

* increased the number of predators

* put those predators closer to the prey populations (i.e. the dispersal distances for the beetles were shorter)

This idea of 'artificial' hedge banks has been catching on, it's fairly cheap!

B. To augment food sources in early spring.

The work has concentrated on hoverflies, the larvae can be voracious predators of aphids. Part of the reason for their effectiveness is that the adults will lay eggs were the prey densities are low, the larvae may even outnumber the number of aphids, hence they can stop aphid outbreaks early on. BUT females require protein (from pollen) for their eggs to mature. Keeping the field margins herbicide free or by sowing wild flower seed mixtures around the seed mixtures along the margins will increase the sources of pollen. The sowing of artificial hedge banks with non-native flowers (e.g. Phacelia tanacetifolia, imported from the USA) that have long flowering periods, out compete many farmland weeds and attracts many hoverfly species is being tried. This can cause a large increase in hoverfly abundance.