Organic Crop Covers Fruits

Tunnels

In the last ten to fourteen days before harvest, cherries gain an extra 10-15 per cent in weight and change color to deep red or purple (depending on the cultivar). The fruits are at their most prone to splitting from excess moisture at this stage, so rainproof covers or tunnels are normally put up as soon as the fruits start to color. They may, however, be positioned much earlier in the year to help reduce wind, hail and frost damage to the trees, especially if trees are covered at night during the vulnerable blossom period. Plastic sheeting or closely woven plastic fabrics are normally used. Covers must be both easily removable and replaceable in order to help ventilation and assist pollination by insects. Some crop protection firms now offer covering systems specifically for cherries. Many different sizes and combinations are possible, for covering single- or multi-row bed systems using French or Spanish tunnels. Some tunnel systems come with added vertical extensions to give extra tunnel height to accommodate the trees' profile. This has the advantage of being able to be used for other crops after the fruits have been picked.

The main drawback to using tunnels is the difficulty in keeping birds nut whilst ventilating the tunnels. Most growers therefore use a combination of crop covers and bird netting. If adequate ventilation is not given, lime introduction of covers can have the disadvantage of creating high temperatures and a humid atmosphere around the trees, favourable to fruit 'moulds such as grey mould (botrytis), brown rot (Monilinia) and pests each as spider mite. Some growers decide not to use rain covers or tunnels for this reason, although they are usually considered essential for regions.

Where there is a high risk of rain during the stages of late fruit swelling and ripening and where crop quality is essential (for example, growing for supermarkets). Crop covers (and netting) also have the disadvantage of reducing light interception by the trees by 25 per cent. Some growers claim that fruit grown naturally, without covers, tastes so much better, possibly because it gets slightly more light and sun, leading to increased levels of soluble solids (mostly in the form of sugars). Conversely, growers using covers can afford to be more relaxed in the knowledge that their crop is protected from adverse weather during ripening and has the potential to improve in color and size the longer it is left on the tree.

Bird Netting

The use of bird netting is the most effective way of protecting vulnerable cherry and plum crops from birds, although other forms of bird deterrent such as bird scares and scarecrows may have some effect. Protective bird netting is best erected before flowering to protect the flowers, buds and developing soft leaves from pigeons, bullfinches and other birds that are partial to the crop. Much damage can also be done by pigeons at fruit stoning, therefore it is worth putting up nets early to avoid crop losses. Other bird species such as blackbirds and starlings are very partial to the fruit as it ripens. Many growers use a simple netting system supported by a series of poles and wires above the rows of trees. Snagging of the nets can be prevented by covering the tops of the posts with smooth polythene, or plastic pots such as old yoghurt cartons or flower pots. Netting can be erected over individual rows, multiple rows or even over a whole orchard, but should have the capacity to be easily hoisted out of the way of harvesting operations, or removed altogether. Depending on whether tunnels are used and at what time of year they are erected, the netting can either be placed on the outside of a tunnel structure or inside it. Some tunnel structures have a built-in facility to accommodate netting easily.