Recognizing problems We’ve had a year relatively free from pest and disease damage so far. I add that last rider because the voles are doubtless hatching their plans of action, but thus far the beetroots and most of the pumpkins have had no bites taken out of them. A few years back voles worked their way along the rows of beets and took several bites out of each one. I took preventive action last year and sprayed with a chilli mixture which wasn’t to their taste.We didn’t realize they had moved across the path and found richer pickings. The pumpkin patch had been well fed which meant the initial uptake of nutrients went to the leaves and stems, resulting in wonderful growth of big and healthy leaves. But that meant the setting of fruits was delayed, causing a few weeks of panic concern until finally we counted at least 7 starting to swell. We love pumpkins both from the aesthetic of having big orange fruits sitting on the early winter hearth and because we are discovering more ways of cooking them each year.The voles, not to be outdone, hollowed out three big beautiful (‘Atlantic Giant’) pumpkins in such a way that it wasn’t visible until we waded into the patch to harvest. To their credit, they made a good job of it and there was only a shell left. There was no waste.This spring one of the pumpkin plants lost its label and ended up in the courgette bed, which was well away from the main pumpkin patch. While having both in the same bed is logical, there just wasn’t room this year the way the rotation worked out. Both are in the Cucurbitaceae family, along with squashes, gherkins and cucumbers. They have similar requirements apart from cucumbers who need warmth and shelter to do well.Anyway, this single ‘Uchiki Kuri’ pumpkin was attacked a few weeks back—three bites! My solution was to find a net bag big enough in hopes that might deter the vole, and a green organic onion bag seems to be the right size. So far so good. These pumpkins don’t grow large.I have also grown three plants up vertically and then trained them onto horizontal wires. The fruits need extra support. I’ll report later on about this method.Vigilance is the key to keeping pests and diseases from spreading. First, be sure to revel in the beauty of healthy plants, soak up that sense of colour and scent and radiated health. In so doing, we store up a mental database of what that plant looks like at its best. This gives us a basis for comparison when wondering if a plant is well, training intuition.There are various clues we can pick up from both changes in plant appearance and the type of damage we are seeing. If there is a problem, it is important to diagnose it (or get help in diagnosing) properly so as to find the most effective treatment. And the faster a plant returns to good health, the more we benefit cropwise.There is a subtle change in the green colour of many plants which indicates they are getting short of water. This occurs before they wilt. The sooner they are watered, the less they are set back in their development. But don’t rush to conclude it is dry, check the growing medium. There are other potential causes, involving root or stem damage (internal or external), or insect attack. Check for insect attack. Aphids are small bugs, many green and not always easy to spot. The black or white woolly aphids stand out more readily. You may see large clusters of them, and they will distort the growth and possibly transmit viruses if left unchecked.Aphids suck sap which carries nutrients in water throughout the plant, and they multiply at an alarming rate. They thus weaken plants which wilt or may even be killed. There is good advice online for dealing with them. Be sure you don’t spray open flowers, as it can affect bees. Blackfly (black aphids) on the tops of broad beans are easily prevented by pruning out the tops in late June before the aphids attack. This can also be done afterwards but in my experience they are more difficult to get on top of. Root damage or too much intense sun can also cause wilting. In both instances the plant is limiting its water loss by wilting. Vine weevil grubs will eat roots, especially of potted plants, and a light tug may bring the whole plant up in your hand. The adults eat holes around the outside of evergreen leaves, which can be very unsightly but not life threatening.Stem damage has been a problem this year in my polytunnel. Botrytis (grey mould) can girdle the stem of a plant, killing the cells all the way around which stops the water flow, and the leaves above that point wilt and die. It can spread quickly in moist, unventilated areas so correct these conditions. Remove any diseased material. I have rigorously pruned off affected leaves and stems, removing some plants altogether, which has kept it at bay (just). Other diseases rot stems as well.Fungal diseases often present as leaf spots. Powdery mildew (pictured) causes white spots or a fine overall white dust to develop, and while it doesn’t often kill a plant it is debilitating and can look unsightly. It occurs when conditions are too dry. Downy mildew also affects leaves, causing darkening and distortion. Water regularly, keep a good air flow, mulch.Fungal diseases are more common during warm wet summers. On tatties the large round black spots of potato blight appear on the leaves. Once a plant is infected, cut the shaws off immediately down to ground level. Don’t put them on the compost. Try to do a good job of clearing up as this will reduce any spores left on the surface, which could infect the tubers as they are lifted. Infected tubers won’t keep.Leave the tubers that are destined for storage in the ground for a few weeks before lifting. You can eat tatties right away after cutting them down but throw away any tubers showing signs of disease. Lift the crop after a few weeks. If you leave them in the ground for too long, slugs, eelworms and others will feast on them. You will see holes, tunnels or surface damage. Damaged potatoes won’t store well, so eat those ones first.Remove any volunteers in the spring—these are from tatties that may have been missed when the crop was lifted. They may harbour disease.When choosing roses or tatties try to find varieties with resistance to black spot. Clear away any infected leaves that fall, prune out infected branches especially those with lesions. Mulch well in late winter to bury any spores. There are various sprays available to help prevent or treat black spot, but these are best used as a last resort after good cultural care, including treating aphids and other pests. Many pests and diseases can be controlled by simply pruning off the affected part of the plant and disposing of the prunings. If pruning doesn’t work, dig out the plant especially if it is the only one out of your crop that is affected. No infected material should go into the compost though, as our home heaps don’t normally heat up well enough. They can go into the council’s green waste bin as commercial compost heats up well in the making.Fungal diseases also turn leaves yellow or brown or black. Clear away these leaves and any debris below to prevent reinfection next year. Don’t take cuttings or propagate from diseased plants.Some changes are based on nutrition, seasons or weather. More anon!