Anna Pavord's A to Z of pests and problems: B is for bindweed, black spot and boasting

Back

Our backs were designed to cope with much heavier work than we usually find in our gardens. But we have become a sedentary lot, so the back gets a shock when it is suddenly involved in the destiny of a 75-litre bag of compost, or a day's digging on a draughty allotment. Pictures of The Correct Way to Dig show unnaturally rigid figures with a foot on a spade that enters the earth almost at the vertical. I bend over my spade, which you are not supposed to do. When weeding though, it's better to kneel than bend from the waist. Occasional backache is inevitable. Jo Malone's Lime, Basil and Mandarin Bath Oil in a very long bath is my favourite remedy.

Bindweed

"Neither blasphemy, hoeing, nor selective weedkillers have yet destroyed it," writes Geoffrey Grigson in his Englishman's Flora. The vast number of common names for bindweed – bellbind, cornbine, Devil's guts, withywind – shows that it is an ancient enemy. The thick, fleshy roots lurk underground till quite late in spring. By August it is fully on the rampage, garrotting raspberries, swamping blackcurrant bushes, fighting buddleias and roses. It can cover 250sq ft in a single growing season. Glyphosate (the active ingredient in Roundup) will knock it back, if you spray in July, but it won't get rid of it permanently. Remember that this weedkiller kills whatever it touches, which means you can't use it where bindweed is inextricably tangled with other plants, as it usually is. Glyphosate kills top growth relatively slowly – you don't seef the results for about a month – but it is a translocated herbicide. It works through the leaves of a plant down to its roots and it is most effective when there is the maximum leaf area to take it in. But the best remedy against bindweed is vigilance, pulling out the growths at ground level before they have a chance to start climbing.

Biological control

There is a ghastly fascination in peering through a magnifying glass at a purposeful ladybird cramming mealybugs into its mouth with the delight of a five-year-old at a birthday tea. This is biological control in action.

This particular ladybird (Cryptolaemus montrouzieri), a black and brown beast about 4mm long, is one of a whole series of exotic predators which you can let loose in your garden or greenhouse to attack troublesome garden pests.

One of the biggest problems associated with biological controls is timing. The parasitic wasp Encarsia formosa (which controls whitefly) works best, for instance, if it is introduced three times at two weekly intervals as temperatures warm up in spring. Hatching at regular intervals, the wasps are then brilliantly poised to take on the whitefly right in the middle of their reproductive cycle. Creating the optimum environment is another problem. The wasp will not work while night temperatures are below 10C/50F and is most energetic in day temperatures of 18C/64F and above. If the temperature's too low, the wasp doesn't breed as fast as the whitefly and so can't keep its end up in the battle.

Black spot

Black spot is a pernicious fungus that attacks the leaves of roses, leaving irregular black blotches over the surface. The leaves eventually fall off and this relentless defoliation severely weakens the bush. It's spread by rain and can be carried from rose to rose on the blades of secateurs. Spores of the fungus overwinter in the soil from leaves that have dropped and reinfect bushes the following year. The disease spreads most rapidly in warm, moist summers.

Clear up and burn affected leaves to minimise the amount of reinfection. Mulch plants thickly in spring to prevent spores splashing up from the surface of the soil. But above all, avoid planting roses, such as 'Grandmere Jenny' or the yolk-yellow climber 'Alchemist' which are particularly susceptible to black spot. Choose, instead, blue-mauve 'Veilchenblau', or pink 'New Dawn' climbing roses which have inbred resistance to the disease. By refusing to buy disease-prone roses, we can force breeders to give us something better.

Blight

Germaine Greer, when she wrote a gardening column for Private Eye, used the pseudonym Rose Blight. What could be better? As a word, it is saturated with gloom. It describes how my garden feels on certain days in winter: rotting stems of Brussels sprouts, melting piles of poppy leaves, slimy trails of mollusc. Cosmic blight.

In the more specific sense, blight can be potato blight or tomato blight. They are both fungal infections, discolouring leaf tips and edges, particularly when the weather is warm and moist. Plant potatoes with inbuilt resistance, such as the second earlies 'Baillie', and 'Estima', maincrop 'Diamant' and late maincrop 'Cara'. Avoid varieties known to be prone to attack such as 'Arran Comet', 'King Edward' and 'Ulster Chieftain'. Forget seedling blight and chrysanthemum petal blight. They may never happen.

Boasting

You, yourself, will never do it of course but you may have to put up with it going on round you. "Oh! I never realised how lucky I'd been with my lapageria until I saw yours." Yours, of course, has never bloomed and now looks as though it is going to throw the towel in altogether. What can you do except grit your teeth and wait for your reward in heaven?