Crop protection is one aspect of gardening that has changed significantly in recent years.

It is not only us who find our crops good eating; there are many pests interested in them as well.

Some pests such as cabbage white butterflies and cabbage root fly are specific to particular vegetables, whilst others such as slugs and pigeons target a wide range of crops.

For many centuries’ gardeners have known the benefits of protection against the weather and pests.  Years ago, walled gardens, wattle wind barriers, greenhouses, cold frames, cloches, hot beds and fruit netting were common in providing protection and good growing environments. Damage by insect pests was often controlled by chemical insecticides and quite a few would perish in the harsher winters we once experienced. Troublesome birds also recognised the sound of gunshot and pigeon pie meant a pest could actually be put to good use. Times have changed.

Allotment sites have always been havens for pests and by various means more are being imported each year. Many are annual occurrences often causing low level damage however each year some occur in far greater numbers, unfortunately we get no advance warning of which pests will be particularly problematic. On the plus side due to greater research, increased knowledge and better communications we are now far better informed and with modern methods and materials stand a very good chance of outwitting them.

Having arrived many of the pests at Ashbrook are with us for keeps, overwintering as eggs, pupae or adults they reappear during the spring. The damage of pests such as carrot fly, cabbage root fly, and leek moth is a consequence of eggs laid some weeks or months previously so some understanding of their life cycle will help us outwit them, early protection can result in minimal later damage.

Allotment sites and particularly Ashbrook can be very harsh places and tender plants can suffer frost damage however with a bit of thought this can be avoided. Wind can be very damaging in that it causes plants physical harm, plants rock, root grip loosens, leaves transpire, and the ground dries out just at the point where our plants are most in need of moisture. Weather protection particularly for early spring and autumn plantings can make a big difference.

Some gardeners are prepared to accept pest and weather damage, others prefer to see their crops developing without any covering, however it can be disheartening for crops to be lost or severely damaged. Ultimately it is for the individual to decide how much and what protection is used.

Many pests and particularly their pupae spend part of their life, normally the winter, buried in the soil. This is one of the reasons many gardeners favour winter digging so as to expose them to severe weather or predating birds, this will partly reduce the problem. It is also noticeable that tidy plots where the surrounding grass paths are mowed regularly seem to have less pest problem, probably because shorter grass offers less cover and more opportunity for predating birds. Some pests and diseases can be avoided by adjusting sowing and planting dates or by growing resistant varieties.

There are great advantages in starting crops off under cover in a greenhouse to allow several weeks of growth and a strong root system to develop away from marauding pests so that when transplanted into the open plot they grow away quickly and stand more chance of survival. The bulk of my vegetable plants are started off this way.

Nematodes can work well in the confined environment of a greenhouse however on an open allotment most do not seem so effective. The exception is perhaps those used against slugs however for an allotment they are not cheap and to be effective require the right conditions.

These days physical barriers are the most common form of protection and there is a huge range of different materials available, the choice of what to use is normally determined by what we are trying to keep out e.g., pests and what we need to let in e.g., pollinating insects.

Each year more crops need protection. Jackdaws and magpies have learnt that by pulling up garlic, shallot and onion sets also seedlings of broad and French beans any insects buried in the soil below can be exposed.  Below are a few notes on some of the materials in use today: –

Glass, for many years horticultural glass has been used for cloches and cold frames but is prone to wind damage, can be dangerous and is not suitable on exposed allotment sites. If available toughened or laminated glass is far preferable.

Chicken wire is a very useful material to provide bird protection over seedlings and allium sets.

A four-foot square of small mesh chicken wire with the corners folded in to resemble a large threepenny piece and laid on the ground under a dalek type compost bin should keep the rats out.

Clear plastic/polycarbonate sheet isvery useful for cold frames and cloches.

Bubble Insulation, very useful for lining the inside of greenhouses to provide frost protection also for temporary covering of cold frames containing susceptible plants.

Fleece, very good as frost protection either in the greenhouse and cold frames. To be effective it needs to be dry and clear of foliage. If severe frost is forecast it can be doubled or trebled for extra protection. Fleece can be used on open plots as short-term protection but if left on for any length of time is likely to be shredded by birds, particularly jackdaws seeking nesting material.

Plastic/monofilament netting, is available in green or black colour, mesh size about 25mm, ideal for keeping birds off soft fruit and vegetables. If used over brassicas it needs to be supported so it is well above the plants. It allows pollinator access to blossom therefore useful over soft fruit such as strawberries but does not keep out small pests such as carrot fly, butterflies, moths, aphids and whitefly etc. In winter if used for the top of fruit cages it is advisable to remove the top to eliminate possible snow weight damage and to allow predating birds in, over brassicas cages the top can be replaced with a larger mesh net to keep pigeons out but again to prevent snow damage. Unfortunately, garden centres tend to only stock this material in widths up to two metres which is often inadequate for allotment use, for greater widths try local trading huts such as the one at Dagnall and online companies.

Plastic/monofilament anti butterfly netting, similar to above but with a smaller mesh size usually between 6 and 9mm.  Keeps birds and cabbage white butterflies off brassicas providing it is suspended above the plants so eggs can’t be laid through, does not keep out smaller insect pests such as cabbage root fly, aphids, flea beetle, whitefly and moths. Again, garden centres tend to only stock this material in widths up to two metres, for greater widths try local trading huts and online companies.

Rokalene and scaffold debris netting. Rokalene is intended as shading or wind protection netting, scaffold debris netting is a good alternative, both provide about 40% shading, generally green although debris netting is now often blue or red. Useful as bird and butterfly protection although can cause leggy growth due to loss of light. Very useful as wind protection particularly around young plants when first transplanted out. Not suitable for keeping out small insect pests.

Both can be used internally or externally to keep greenhouses cool during the summer however a far better shading product is aluminium strip shading also known as thermal screen, this material is used externally on greenhouse slopes that face the sun and is available online from companies such as Simply Control.

Environmesh and similar insect mesh.  Normally white in colour, various sized meshes are available ranging from about .6mm up to about 1.6mm. Used extensively commercially and is currently probably the best physical means of protection against most pests. For aphid, flea beetle and white fly protection the finer, insect meshes are necessary as these pests will pass straight through meshes of 1.6mm.  This material allows rain to pass straight through and also filters the wind therefore the ground below dries out more slowly. It provides about 15% shade however the white colour seems to reflect more light within the growing area and it generally creates a first class growing environment, plants develop particularly well under this material.

A few points to bear in mind when using this material: –

a) Use a mesh size suitable for what you are trying to keep out.

b) Ensure plants particularly brassicas are clean of pests and eggs before covering them.

c)  Allow plenty of spare material around the perimeter so that it can be well weighted down to      accommodate any irregular soil contours and prevent ingress by pests crawling in underneath. Any gaps along the bottom edge will allow pests free access to your crops.

d) Allow sufficient material for the full height growth potential of the crops below, plants grown under this material are likely to grow taller due to the better growing environment.

e) Cover plants immediately they are put out and leave on all the time, if weeding or harvesting only expose the plants below for the shortest possible period preferably during windy or damp conditions when insect pests are less likely to be on the wing. If crops are exposed on windless, dry, sunny days the pests will be very grateful for the easy access you have allowed.

f)  Avoid using mesh over crops whose blossom needs pollinators e.g., strawberries.

This material can be supported using plastic hoops, canes, posts and ropes or timber framework.

Alternatively, it can also be loose laid directly onto the crops which then push it up as they develop. If growing this way use a large enough piece of material to allow the crop to grow to its mature height and enough slack around the edges to prevent ingress by pests.  It can be anchored to the ground with wire pegs, lengths of timber or iron or bricks. Brassicas and salad crops perform very well when grown under loose laid insect mesh; much cleaner crops, particularly of lettuce are produced as soil splashes during heavy rain are prevented.  Garden centres often only stock this material in narrow widths for greater widths try the trading hut at Dagnall and online companies such as Wondermesh.

To prevent snow weight damaging winter brassicas it might be worth changing the mesh for bird netting during November, by this time insect pests will be hibernating and pigeons then become the main nuisance. Bird netting will keep pigeons off your crops and should prevent the plants being damaged due to snow weight.

Support.  There are many ways protection can be supported. Blue plastic water main tubing, in lengths between six and eight feet forming a hoop and with splay cut ends pushed into the ground is very effective, this tubing is generally available from builder’s merchants and stores such as Wickes. Plastic water bottles on bamboo canes support netting quite well. Other materials such as posts and rope and timber framework can be used.  A walk around the allotment site will reveal various other ingenious ways of providing support.

Fencing. This might seem extreme however in recent years, muntjac, foxes, rats and badgers have all found the sweet corn on our site very attractive, they tend to wait until the cobs are almost ripe before attempting to take them. Muntjac, deer and rats tend to nibble the cobs leaving them on the plant whereas badgers flatten the whole crop making it resemble the work of a steam roller. You can take a chance and leave your sweet corn unprotected however surrounding your plants with a simple enclosure about 3’ high of rokalene, chicken wire or whatever other material might be available supported with timber or steel posts, road pins or whatever can mean the difference between a saved and lost crop.

Slugs.

None of the above materials will deter slugs, Ashbrook has several varieties however the keel slug seems to be the most common and although small is the most destructive. This slug spends much of the year below ground and can be a nuisance at any time however from about the end of May and in June they come to the surface to breed and are particularly troublesome. It is at this time of year when gardeners are sowing seed outdoors and transplanting bedding and vegetable plants all of which are particularly vulnerable until established. With a bit of thought damage can be minimal.

1. If transplanting aim to produce strong growing pot grown plants that have been properly hardened off, are therefore a bit tougher and establish quickly. Retain a few spare plants in case of losses.
2. Slugs tend to be nocturnal so water transplants in the morning so the foliage and surrounding soil is dry by nightfall, they should then be less prone to slug attack.
3. Simple temporary wind protection will encourage young plants to establish quicker.
4. Weeds provide slugs with damp cover, keeping the soil surface around your crops well hoed and weed free should help.
5.  Use an effective slug deterrent of your choice until plants are growing strongly.

As mentioned at the start of this piece crop protection is an aspect of gardening that has changed significantly in recent years, in the future we can expect more pests to be imported and our methods of combating them are therefore likely to be constantly developing.