Cut Worms

                              BEWARE OF CUT WORMS!

 

 Many a keen gardener when sowing seeds of their favourite vegetables, dream of harvesting a bumper crop, then imagine their despair when they find their beloved seedling transplants toppled over, severed from the infant root: then you have probably fallen foul of the dreaded “Cutworm”!

  If you are now imagining a chainsaw–crazed earthworm, you would be wrong; the culprits are nothing more than the larval stages of some of our most common moths.

   The name cutworm is given to these caterpillars because they frequently feed on plants at ground level severing them from their taproot. They generally spend the day in the surface layers of the soil, or hidden under leaves or stones and come out to feed at night, sometimes on the foliage, but more often on stems above and below soil level. Cutworms often work along a row of plants cutting them off one after another – hence their name. Larger roots such as turnips and potatoes are also attacked, the larvae burrowing into the root or tuber to hollow out the interior in a similar way to garden slugs.

  It is now time to name and shame. All the offenders belong to the family Noctuidae and are mostly rather drab moths. The four most serious species are the Turnip Moth, Heart and Dart, Garden Dart and the Large Yellow Underwing. Their caterpillars are also rather drab in colour making them very difficult to see in the soil, but can sometimes be found by day just beneath the soil surface near the attacked plant. Being nocturnal, detection of the caterpillars may be easier after dark if searched for with the aid of a torch.

  The adult moths start to emerge in late may and some may produce a second brood in September, but in both cases over-winter as caterpillars which feed when mild weather permits. The Garden Dart has a single brood and over-winters as an egg, and on hatching feeds from spring to early summer.

  It gets worse!! Just when you think you have survived the Cutworms and the plants are well established and leafy, then in comes the foliage champers. This time the villain is a micro moth, the Diamond Backed Moth, only about 6 mm long, brown grey in colour with long white marks along the inner margins of each forewing forming a diamond pattern. Appearing in May and June, sometimes augmented in great numbers by moths arriving from the continent, they lay their eggs on cultivated and native plants of the cabbage family, and on hatching the larvae feed on the underside of the leaf rejecting the upper surface and main veins. 

 Then there’s the Butterflies known as the ‘Cabbage Whites’, which need no description--- it seems that you can’t win! But don’t despair, with a bit   (a lot) of luck, there will always be enough to harvest.

When it comes to controlling these ‘Pests’ don’t bother serving ‘ASBOS’, they don’t work and don’t consider inflicting pain for fear of being arrested for assault. After all, these insects are essential in the environment and if you don’t want these crawlers on your plot then gather them up and relocate them on native wild plants where they can take there chances in the natural world.

 

John Petyt

          The Butterfly Bush

When it comes to providing a source of nectar in the garden for visiting Butterflies and Moths, many will agree that by far the best choice is the Butterfly Bush or Buddleia.

 

Belonging to the family BUDDLEJACEAE  (LOGANIACEAE) the genus Buddleia consists of about 100 species occurring in Africa, Asia and both American continents.

 

Buddleia davidii was discovered in 1876 growing in river gravel beds in southern China, by the French naturalist and missionary, Father Pierre David, after whom the species was named.  The generic name originates from the 17^th century naturalist, the Reverend Adam Buddle, vicar of Farnsbridge in Essex who had no connection with the plant at all, but some kind person thought it would be rather nice to attribute the plant to him.  Today the accepted spelling of “Buddleja” is the one used by Linnaeus.

 

It was first grown in Kew Gardens in 1896 and the first reported ‘Garden escape’ noted in the wild was in Harlech, North Wales c 1921 and many would agree that this plant is a welcome alien in our countryside.

 

The species davidii is the best for attracting Lepidoptera.  It is a hardy shrub with ribbed stems and long lanceolate leaves capable of growing to five metres, but when pruned correctly, usually only half this height.  The flowers are small, orange eyed in the original form, very nectar rich and borne in clusters grouped in long tapering fragrant spikes or ‘Panicles’.

 

Buddlejas are easily grown in any light soils, including chalk – though not having a preference for this mineral – in full sun.  Seeds are produced in large numbers which are sometimes carried to derelict sites and unlikely places such as old walls and neglected guttering where they grow into stunted plants.

 

Vegetative propagation couldn’t be easier.  Simply cut the current season’s growth into lengths of about 30 to 45 cm and pushed into light soil to about two thirds of their length they will root readily the following spring.  I find that pruning to within 15 cm of the previous season’s growth is best done in mid April as this induces flowering when the bulk of summer butterflies are on the wing.  Removal of dead flower spikes can prolong the flowering season.

 

The colour range of Buddlejas is quite wide, including mauves, crimson-purple, violet blue, white and pink.  Variegated varieties are also available.

 

Buddleja globosa is a tall species from South America producing orange yellow globular flowers about 20 mm in diameter and of little attraction to butterflies.  However this species has been crossed with B. davidii x B. weyeriana and the varieties Golden Glow and Sunglow are very similar to B. davidii, but are a rich golden yellow and very attractive to butterflies.  Another virtue is that it will continue to flower well into late autumn producing nectar for late flying species such as Comma, Painted Lady, Red Admiral and Peacock.

 

As well as attracting butterflies, Buddlejas are much loved by both day and night flying moths and to see a Hummingbird Hawk moth taking nectar on a sunny day is a delight.

 

The flowers are not the only part of the plant attractive to Lepidoptera as it is claimed that 23 species of moth larvae feed on the foliage, ignoring their native foodplant in preference for this alien plant.

 

The only species I am aware of feeding in this manner is the Mullein moth, feeding naturally on Mulleins and Figworts, both of which are members of the family Scrophulariaceae.  Interestingly these plants contain the chemical compound Catalposide which was first discovered in the American plant Catalpa bignonioides also known as the Indian Bean Tree and is also present in the leaves of Buddleja. Catalposide  seems to stimulate the larvae to feed and it is said that an extract of Catalpa applied to the foliage of other species will render them palatable to these species of moth.

 

The Holly Blue butterfly larva has also been reported feeding on Buddleja – but in this case on the flower head, and may account for the increase in Holly Blue numbers as the plant has become more popular in gardens.

 

          Scarce Vapourer

The SSSI status of the Messingham Sand Quarry Nature Reserve was awarded, in part, due to the presence of a rare and fascinating day flying moth; the Scarce Vapourer, Orgyia recens.  Not the largest of moths - the males have a wingspan of about 15 mm – orange brown in colour with white marks near the tips of the forewings.  The female is very nearly wingless, with a swollen abdomen when holding four to five hundred eggs which are deposited on emergence on the exterior of the pupal cocoon.

 

Being wingless the female is unable to disperse her eggs.  This is achieved by the tiny larvae being carried on the wind on a thread of silk, or by crawling, resulting in small and vulnerable colonies.

 

The larvae feed from July, resting for winter hibernation, and recommence feeding in the spring.  The adults emerge in June with a second brood of adults occasionally in August.

 

The main foodplants are Hawthorn, Oak, Sallow and Bramble, but it is also found on other species of trees and shrubs as well as on herbaceous plants such as Meadowsweet and Water Dock.

 

The adults may not be the most striking of moths, but the fully grown larva is superb!

The body is black, up to 35 mm in length, covered with tufts of whitish hairs arising from small warts in a double row along the back.  Tufts of greyish hairs decorate the sides.  It has a pair of long forward pointing black tufts on the first segment with a smaller single tuft at the rear.  A double row of orange-red spots extend along the back with a broad red line along each side.  The head is black.  The most striking features however are the orange-brown “shaving brushes” on segments four to seven.

 

This is a Red Data book species in steep decline and has been lost from its sites in the southern counties, and is now restricted to few sites in South Yorkshire, North and South Lincolnshire, Nottinghamshire and Norfolk.  Once plentiful in the Scunthorpe area, even occurring in gardens on ornamental shrubs it is now, sadly, very rare indeed, and the last record for feeding larvae at Messingham was on the 22^nd May 1998.

 

Fortunately this rare British species ranges through Europe and as far as the Far East and Japan, but on the reserve at Messingham may now be extinct, a fate suffered at many other sites in Britain.

 

John Petyt.

          Apples or Marbles?

Our two native Oak trees, the Sessile and the Pedunculate play host to many species of insects providing nutrient and shelter.  Two of these are tiny gall-wasps resembling small ants and cause the host tree to produce abnormal growths known as galls.

 

The first of these, the Oak Apple or King Charles’ Apple is a growth, spongy in texture, often rose pink and up to 4 cm in diameter.  It can be found in June-July singly or in clusters and contain an average 150 larval chambers with each apple containing, usually, a single sex.  The life cycles of these galls are complicated having sexual and asexual alternative generations.

 

The Oak Apple starts its life with a wingless female gall-wasp laying in mid winter, unfertilized eggs in terminal or auxillary buds.  The gall appears in April, produced by the host tree in response to the stimuli secreted by the digestive glands of the feeding larvae.  The adult gall-wasps emerge from the mature Oak Apples in July, males a day or so before females, and after mating the females of this sexual generation fly to oak tree roots exposed or just beneath the soil surface and deposit eggs into the surface tissues.

 

The resulting galls appear towards the end of August and are brownish in colour and about 10 mm in diameter, sometimes merging into a single mass.  Each gall contains a single larva developing after some 16 months into wingless females which ascend the trunks of oaks in mid winter to deposit their eggs thereby completing their bizarre life-cycle.

 

Other species of insects inhabit the galls. Some are parasites, others simply lodgers, making the gall a complex community.

 

May 29^th is Oak Apple day, commemorating the restoration of Charles the second to the throne and coincides with the colourful development on the summer gall.

 

The Marble Gall - Bullet Gall – Oak Nut or Devonshire Gall (Take yer Pick) is quite unlike the soft fleshy Oak Apple, being round, quite hard and woody, about 1.5 cm in diameter.

 

Like the Apple Gall the Marble Gall has alternating sexual and asexual generations.  The familiar summer gall develops from eggs laid by a sexual female in the developing buds of our two native oaks in May or June; the host trees usually being immature or retarded specimens. The developing spherical galls are green at first, brown later, and mature in August.

 

Each gall contains a central chamber, with a single female wasp larva of the asexual generation, which emerges as an adult winged gall-wasp in September.  These asexual females lay unfertilized eggs between the embryonic bud leaves of the Turkey Oak, with galls slowly developing during winter, and are visible in March and April as small oval structures between the bud scales.  The emerging adult gall-wasps in spring are the asexual generation, producing both males and females, which fly to the Common Oaks to initiate the formation of the summer Marble Gall.

 

The Marble Gall-wasp is not native to this country, being introduced about 1830 when galls, which are rich in tannic acid, were imported from the Middle East into Devon for dying cloth and ink making.

 

John Petyt