This is a time of hope. The veg garden is planted up and all we need to do is sit back and look forward to the fruits of our labours. If only it were that simple.

With an army of pests and diseases attracted to our gardens, vigilance is essential and this is a pivotal time of year. A fresh batch of headaches is on the way.

Against all the odds, I can confirm that most slugs become less menacing as the summer wears on. They are lethal for emerging seedlings and small transplants: the row of freshly sown carrots you never see, or a broccoli’s tasty and tender growing shoot devoured. But now our plants are larger, they tolerate some predation. So keep trapping molluscs without panicking.

But bitter experience tells me that keel slugs start devastating the potato crop from early August onwards. I foil them by growing early maturing varieties that are large enough to lift by the end of July.

Other groups of pests work the same way, with species attacking their own hosts at different times.

The larvae of the first generation of cabbage rootfly are still devouring the roots of unprotected transplants leaving wilted young brassicas to be taken to the compost heap. But by the time the second generation of rootfly emerges next month, the main crop brassica root systems will be large enough to withstand attack. Only summer sowings such as spring cabbage will be threatened.

But carrot rootfly is now coming into its own. The first generation of Psila rosae is working on unprotected crops, and this will be followed by 2 more batches in August and September. The larvae will keep munching into winter. So don’t remove protective fleece before November.

Cabbage white butterfly attack becomes more severe as the summer develops. But, as with rootfly, different species inflict the damage. First up is the small white, Pieris rapae. It lays 2 or 3 eggs on its host and the small velvety green larvae do little damage though they do make a mess.

The large white, Pieris brassicae, is altogether different. It lays several hundred eggs, in batches of 20-30. From late July onwards these hairy green and black thugs strip down every brassica in sight. And last year produced the largest plague I’ve ever seen. A fleece or insect net protective cover is utterly essential as it stops the insects laying eggs on plants.

Blight, the fungus-like disease that attacks potatoes and tomatoes, is another disaster waiting to pounce. A healthy, tasty crop is turned to stinking mush.

Some of you may already have seen the first blight-like symptoms on foliage, dark brown/black circular blotches followed by withering leaves. Relax. This is only early blight, Alternaria solanii. The unsightly pathogen causes disfiguring foliage but little or no damage to the crop. You certainly don’t need to cut down the offending shaws as a friend of mine once proudly did.

The very early symptoms of late blight, Phytophthora infestans, are similar. But dark blotches, especially at tips of leaves are quickly followed by white fungal growth underneath. The whole stem soon collapses. The disease thrives during a typical Scottish summer. The optimum temperature is a cool 15-20C and our damp atmosphere readily provides the required 2 consecutive days of 75-80% humidity.

Timing varies throughout the country, from mid July onwards. So look out for it, especially during a muggy summer. Cut the shaws to ground level and compost, but only if you have a lidded bin. Otherwise, dispose of them. Leave potatoes in the ground for 14 days and lift. Check the harvest frequently and remove any blighty tatties.

Plant of the week

Sweet Pea ‘Anniversary’. Highly scented. The edges of the petals are ruffled and flushed with a delicate pink. Perfect for summer.