Blackfly On Broad Beans

Blackfly can completely devastate a crop of broad beans at this time of year. They are the great enemy of broads. At flowering time masses of these irritating sap-sucking pests can descend on a crop and extract the life out of the beans as they form. It does not happen every year, but Dirty Nails has suffered such heartbreak, and tries a number of ways to avoid this problem.

In years when blackfly is rife, he pinches out the growing tips of his plants and burns them. This removes the most tender bit which the blackfly like best. For other affected areas, he makes up a weak washing-up liquid and water dilution and dispenses this with a hand-held mist sprayer. He does this on a daily basis, but it is not always satisfactory. The most successful tactic Dirty Nails has used to beat blackfly is to sow broad beans direct into the ground during November. This way a variety such as Aquadulce will grow on slowly throughout the winter months and produce pods for picking a fortnight or so earlier than a spring-sown crop. The important thing is that autumn-sown broads are usually productive before blackfly are a problem. If they do clash, the advanced state of growth renders these broads more able to withstand attack.

In some years Dirty Nails has had to write off his spring-sown Witkiem. All is not lost however, as elsewhere on the veg plot Aquadulce is already feeding the family and there is hardly a blackfly in sight.

Natural History In The Garden: Cuckoo Spit

Dripping globs of frothy spittle appear on grasses and plant stems all over the garden in June. Known as cuckoo spit, it is actually the work of an insect called the common froghopper. These sapsucking bugs are mottled in their adult form, but the cuckoo spit hides and protects their tiny green larvae. The mass of bubbly goo is exuded from the anus of the juvenile froghopper.

Vegetable Snippets: The Fascinating World Of Aphids

Aphids are true bugs, also known as blackfly. They are a major pest of both farmers’ field and kitchen garden, but are also amazing creatures in their own right. They provide a major source of sustenance for useful species such as ladybirds, lacewings and hoverflies, which can be encouraged onto the veg patch with the allied provision of suitable flowering plants and habitat. Insect eating birds like blue tits may depend on them in hard times during winter, when they flock to the hedgerows and shrub borders, acrobatically eking out a meagre ration. Ants ‘farm’ them, protecting vast herds on the stems and underside of leaves. Using their antennae to stroke their charges, the ants receive a sugar-loaded drink of honeydew direct from the aphid’s anus.

Honeydew is the sap which constantly flows around a plant. It is accessed by the aphid via its needle-like mouthpart, a hollow tube that is thrust into the tender host. Viruses are often transmitted from plant to plant by dirty ‘needles’. Honeydew is rich in sugar and low in protein. In order to achieve satisfaction, enormous amounts must be consumed. Happily for the insects, it circulates at such a rapid rate that it is constantly dripping out of the feeding hordes. This is why plant foliage is often sticky in the summer, especially on trees like sycamore, and can be the cause of mouldy fungal growth later on. Weakened by these mass gatherings, infested plants often appear weakened, twisted and gnarled.

In mild winters aphids may pass the coldest months as adults feeding amongst plot-side weeds. More usually, however, they over-winter as eggs. Spindle is a favourite host plant, but ornamental lilacs and Vibernum species are also popular. In spring aphid nymphs are born as already-pregnant females. This is called parthenogenesis (virgin birth). A fortnight or so later, winged youngsters are being brought forth too. These take to the air and find other host plants for a summer of feasting.

Aphids can be found in profusion on spinach, wild flowers such as thistles, poppies, dock, cultivated domestic roses and many other herbaceous plants. As the season turns towards autumn the bugs respond to decreasing daylight hours and temperatures by bearing winged males and females. They fly off, mate, and deposit eggs on a suitable host, whereby the cycle of life, death and rebirth continues for another year.