Not Virus Infection On Dahlias

It doesn't look as if the dahlia leaf problem was caused by a virus (see 'Mottled Dahlia Leaf?'. New leaves are now looking quite healthy after feeding, and the leaf discolouration does not seem to have spread.

GIVEN FEED WITH TRACE ELEMENTS
Dahlias are often short of trace elements at this stage of growth, and applying these usually significantly brightens flower colour. Seaweed feeds are very good. But I used good old 'Phostrogen' because its analysis shows it not only contains trace elements but is also rich in potassium, which is also beneficial for flower production.

ALSO SPRAYED FOR THRIPS
I also sprayed with thiacloprid to control thrips. This should also control aphids (which spread viruses) and other pests till the end of the season. Pity it doesn't also control snails!

Notches In Leaves

Beetles and weevils damage leaves by biting chunks (notches) out of them. Vine weevils - and sometimes chafer beetles - are a particular nuisance at this time of year.

Vine weevils love to lay eggs in pots of favourite plants. These eggs hatch into white maggot-like grubs with brown heads, which devour fresh white roots and subsequently kill the plants. Although vine weevils have a seasonal life cycle, in practice they can are usually present in some stage of development at all times of year.

CONTROL MEASURES
The adult weevils can get almost anywhere, and can even climb polished glass. So this somewhat limits control measures to surrounding pots with water (weevils can't swim!), greasing sides of pots, trapping adults with upturned seed trays or similar dark vessels (they shelter in them overnight), or chemical control.

Chemical Control
I treat all pots and susceptible plants with thiacloprid. I know it's a carcinogen, but it gives good long-lasting control (several months) and also controls many other pests such as aphids and whitefly. But, most important - it kills vine weevil and chafer grubs.

Mottled Dahlia Leaf?

Wonder what's caused this yellowing on this dahlia leaf? Haven't seen it before.

MAGNESIUM DEFICIENCY?
Yellowing between the leaf veins is often a sign of magnesium deficiency, so could be this in an early stage. Doesn't seem likely, but given a dose of trace elements just in case.

VIRUS?
Mottling is often associated with virus disease. But this is also unlikely, as I haven't seen it before, and haven't brought any new plants in. But could have been there all along and is now showing up because of recent stress (plants have never been watered, apart from rainwater)

THRIPS?
Seems strange that it is only now noticeable after much rain and thundery hot weather. Might be thrips (thunder flies) damage, though haven't seen any. Another mystery. Will have to wait see what develops.

Weeding Reduces Both Water Loss And Slug Movement

We talked last year about the virtues Dutch hoeing.

SEALS IN WATER
Now, after the recent rains, when the weed seeds in the soil have germinated but not yet seeded, is a perfect time to use a Dutch hoe. Loosening the top half inch (2.5cm) or so of soil will not only kill weeds, but will also break the wicking (capillarity) link between the soil surface and lower layers, thus creating an effective mulch which will both insulate the soil and greatly reduce water loss - it effectively seals the water in.

REDUCES SOIL TEMPERATURE
Loose, airy soil dries very quickly and lightens in colour. Thus, more of the sun's heat is reflected; and what is not reflected cannot conduct down through the loose soil as easily. Hence, the roots can work more effectively.

CONTROLS SLUG MOVEMENT
Slugs do not like moving over loose, dusty surfaces which stick to them, preferring wet conditions. You will notice the difference immediately - they seem to completely disappear. However, they soon return once the surface is wetted again . . . more's the pity.

Slug Eggs

Found this group of presumably over-wintered slug eggs in a container. Slug eggs resemble little dark yellow pills about 3mm diameter. Although laid in groups in a damp spot just beneath the soil/compost surface, they are also laid amongst the roots and tubers of over-wintering plants and are a particular problem with dahlia tubers because the slugs hatch out just as the tender young shoots are emerging from the tuber. Slugs can do massive damage to young plants in a very short space of time - they need watching, especially in damp, warm conditions.

If buying plants from a nursery, do not confuse slow-release fertilizer granules with slug eggs. They are about the same size, but slug eggs are definitely dark yellow.

Troubleshooting Holes In Rose Leaves

Never ever seen holes in my rose leaves before. Leaf cutter bees bite large chunks out of leaf edges. But this? A complete mystery. The way some of the leaves have holes chewed in their centres upto the veins (these have been left intact), resembles slug, snail, chafer beetle, or sawfly damage (see last year's sawfly problems on euonymus).

Rose slugworms are the yellow-green larvae of a sawfly. But they only usually feed on the lower leaf surface and cause light brown patches to develop. There is no such evidence. It really is a mystery.

Anyway, whatever the cause, healed edges of holes indicate pests have gone - at least for now. Sprayed with thiacloprid 'Provado', anyhow - a systemic (travels around plant within sap) insecticide which gives protection against most rose pests for upto two months. Situation needs watching closely.

Advantages Of Storing Begonia Tubers As Root Balls

Many begonia growers brush their tubers off before storage. I have never had much luck with this method. I always store mine as a root ball complete with soil or compost, and find it has advantages.

ADVANTAGES FOR STORING
Although I stop watering my begonias in pots around the start of October, I still find they do not really dry out. Consequently, it is for me almost impossible to clean them without breaking the tubers or damaging them in some way. So I just place them in an airy spot to dry them as much as possible before storage, then don't cover until the really severe weather comes. They seem to store well this way with little or no disease problems. We covered lifting begonias last year.

ADVANTAGES FOR PLANTING
Once it becomes clear in early spring that tubers are showing signs of growth, root balls can be watered lightly and placed in a light frost-free place. This helps them along and avoids the need to pot up the larger tubers which are almost impossible to fit into almost any pot.

BEWARE OF VINE WEEVIL GRUBS
The tuber above has been treated as described and can now be planted as it is. However, it will need some treatment for vine weevil grubs which will almost certainly have overwintered with the tubers and will be hiding in the roots somewhere. I use 'Provado Vine Weevil Killer', a stronger dose of thiacloprid.

Blackfly On Dahlia Bud

It doesn't pay to let aphids - such as the blackfly seen here on a dahlia bud - get out of control; they multiply incredibly quickly, as you can see from the infestation (right) of a black bean aphids on an elderberry branch. Is it any wonder a plant has difficulty coping? And that's aside from the fact that aphids also bring virus and other diseases.

CONTROL
Only certain varieties of dahlia seem to be affected by blackfly. Control as per greenfly and all other aphids, by organic or inorganic methods (see 'Troubleshooting Aphids On Rose Bud').

Pinching out the tip will remove most of the aphids and induce bushiness in this single-stemmed plant. The downside is that it delays flowering. Flowering in dahlias takes about 8 weeks from stopping (pinching out).

Troubleshooting Aphids On Rose Buds

Aphids, especially greenfly, are a real pest on juicy rose buds during a hot spell at this time of year (roses open around the time of the summer solstice). Although there is one adult here (bottom right), we have mostly young greenfly, which are born live (viviparous) and develop through several stages, often shedding cuticles or skins which fall down to leaves below (see 'Old Cuticles Are Sure Sign Of Pest Trouble')


Young blackfly are also present

Aphids need controlling because they spread viral diseases and cause structural damage to flowers and leaves. They also excrete honeydew as they feed (you have probably experienced this when walking beneath the canopy of summer trees) which drops onto the lower leaves and attracts black sooty mould (this is not in fact harmful, just disfiguring).


Also in other colours:

Aphids also come in many other shades and colours


CONTROL
Control with 'Provado' (thiacloprid) for long-lasting systemic action, or organic fatty acid sprays, or soap and water, or water, or remove by hand or . . . there are many treatments.

See also 'Lonesome Greenfly'; 'Blackfly On Dahlia Bud'

Old Cuticles Are Sure Sign Of Pest Trouble

If you find discarded cuticles lying around on your plant's leaves (this is a geranium leaf), it's a sure sign of pest trouble. These look like aphid cuticles, and aphids reproduce very quickly. So check the plant immediately and take appropriate action.

I use thiacloprid spray (eg 'Provado Ultimate Bug Killer', which is a long-lasting systemic (enters plant and moves to where needed) pesticide. But you can use an organic spray, or even soapy water (some growers even wash them off with plain water). The only downside with contact pesticide sprays is that, because they work by contact, you must apply to the whole plant.

Troubleshooting Mystery Holes On A Spring Lawn

If mystery holes like these suddenly appear on your spring lawn, suspect bird damage, particularly starlings. These will be searching for grubs (usually leatherjackets or chafer grubs) in the turf. We dealt with leatherjackets and how to remove them, last year. But if damage is serious (i.e. there has been considerable root and/or young shoot damage), you will see dead patches suddenly appear (around where the holes are) during dry spells. If you pull the grass, it can be removed easily. If you really suspect grub damage, best to remove a divet of turf with a trowel and search in the turf for them. You can also water the lawn, then cover with a light-proof sheet overnight. Leatherjackets will be seen in the morning if they are there, and can be picked off. You'll need to be early, though. Otherwise, it's chemicals. TREATMENT FOR LAWN GRUBS 'Provado Lawn Grub Killer' is very effective. See last year's posts (first link). However, one or two grubs will not do much harm. So I would not recommend using this treatment unless absolutely necessary. You can also use nematode worms as a non-chemical approach. But they're expensive, not always effective, and need specific temperature and moisture conditions.

Conifer Hedge - Does Potassium Feed Prevent Die-Back?

Normally, at this time, the conifer hedge has several dead patches from the previous year, plus occasional winter damage. Not this year. Although there is slight frost damage, it's still completely free from die-back. Why?

I'm not sure. But I think feeding last year with 'Phostrogen Plant Food', a highish potassium feed (14-10-27), has much to do with it. I think the potassium has hardened the foliage, making it less attractive to insects and fungal disease.

I am still not really sure what causes die-back, even after much research. There seem to be several theories, ranging from suffocation through to disease and aphid attack. The trouble is that by the time the symptoms appear the causal agent is long gone. I currently think it's aphids, since the birds start feeding on the hedge around this time.

I applied the feed with a hosepipe applicator.

TREATING THE DIE-BACK
If you're wondering what the holes are for, they're where I dug out the last lot of die back. I have found that after cutting out the dead tissue back to the stems, re-growth occurs and the holes fill in. However, it's very important not to cut TOO far back. You want to be able to see at least a glimmer of green life.

Vine Weevil Grubs On Fuchsia Roots?

This fuchsia was cut back almost to surface level last autumn and kept in its original compost. It seemed to be doing quite well until a week or two ago, when the bloom disappeared and it didn't look so healthy. At this time of year, the root damage caused by over-wintering vine weevil grubs in the compost becomes noticeable on plants. I would not expect to see vine weevil, since the compost and roots were treated with 'Provado Vine Weevil Killer' (9g/litre thiacloprid) in August; this should protect for six months so is probably about spent. Nevertheless, we cannot take a chance. Time to examine the roots.

Removed plant from pot and gently brushed away compost from around roots, trying not to damage them. No vine weevil grubs. So washed off rest of compost, just to make sure. Still no grubs.
There is very little new root growth. And what there is is not yet of the fine fibrous kind (this develops later) which fuchsias use for feeding. I don't know why this should be, unless it is a late developer (I haven't grown it before).

As to the loss of bloom, I could have damaged them in some way, though I can't think how. Although I might have recently given the plant a bit of dilute feed to help it along. This could have burned the infant root hairs. Seems the most likely cause. Will I ever learn?


Just out of interest, here is a different variety of fuchsia treated in an identical fashion. Look at how many fine white feeding roots there are. Note that they are growing from the old, thicker, brown root material which seems to be attached (I'm 99% certain) to the old, thicker, tapered, brown 'tap*' root on the right.


*A tap root system develops from the radicle, the first primary root to emerge from a seed.

Stem cuttings produce several primary adventitious roots around the stem, each of which produces lateral offshoots. When young, these roots are white, but as they get older, secondary thickening occurs (we haven't covered this yet) and cork material is laid down producing a darker brown root behind the area of the root hairs.

Plants do not take in water and nutrients through older wood, but through the root hairs, as seen elsewhere. These are very short-lived and exist only at the tips of new roots. It is worth bearing this in mind when growing plants, because it is this area which needs special nurturing; the older wood doesn't matter.

Glyphosate Safe On Moss On Flags

Glyphosate is normally used as a safe systemic weedkiller which is inactivated on contact with the soil. It is supposed to be very safe to all animals (including us) and can, apparently, be used around fish ponds without damaging the fish.

What I didn't know, however, is that it also works on moss - Moss on the flags that is, NOT ON THE LAWN.

Of course, it will work on the lawn, but because it is non-selective it would also kill the grass - and we don't want that (not after all the years I've spend keeping it alive!).

I always have a problem with moss growing on some shady flags, because the birds use it for nesting. And by the time they have finished, the season is nearly over. Consequently, moss builds up year by year.

WHAT ABOUT TEMPERATURE
As outlined elsewhere, glyphosate is extremely good on all sorts of weeds. However, it works best in warm weather, usually in late April or early May when the weeds are growing actively. Of course, the moss is growing now; so I have treated a small patch to see how it goes. About 8 hours of dry weather is needed so that it doesn't get washed off before it can be absorbed.

BEGINNERS NOTE:
'Tumbleweed' and 'Roundup' are trade names for glyphosate in the U.K. But you needn't use a brand name; you can use a cheaper generic brand. Look at the label, usually the front one. Glyphosate will be stated as the ACTIVE INGREDIENT, along with its strength. The cheapest way is to buy the concentrate, make it up yourself and apply with a hand sprayer (e.g. old kitchen cleaner spray).

ALWAYS USE RUBBER GLOVES WHEN USING WEEDKILLERS AND PESTICIDES, no matter how safe they are supposed to be - they can be absorbed through the skin!

Slugs Love My Delphiniums

It's that time again. That time when the weather wakes up, along with the slugs. Problem is, the delphiniums are also awake, producing tender new roots - the ideal breakfast for hungry slugs. Yes. There's no doubt about it. Slugs love my delphiniums.

Treating the roots with aluminium sulphate (pellets dissolved in water) at 2 oz per gallon, given at about 1 litre per plant last year, seems to have been successful. This was outlined last year in 'Slugging It Out - Part I'

Not all slugs attack plant roots, but the ones that do - such as the Garden Slug (Arion hortensis Agg) and the Keele Slug (Tandonia budapestensis) - cause devastation.

Aluminium sulphate is a contact poison. This means that it is not ingested (as are stomach poisons, such as methiocarb), but is absorbed through the skin when contacted. So the slugs need to be active, as they probably now are. And if they're not, no matter - aluminium sulphate destroys the eggs.

To help avoid damaging the beetles, which also eat eggs, I poured the solution close to the old stems. Sorry beetles. But I just can't take a chance.

Note that aluminium sulphate only works on small slugs.

Pests Have Favourites - Usually Mine!

Most garden pests can be tolerated, at least to a large degree. And, if left to its own devices Nature has its own methods of dealing with most of them.

I am absolutely fascinated by the ways in which plants can not only resist attack by pests, but also communicate with both insect predators and with other plants, in the process. There has been much research of late, most of which has already been outlined, for example in this review by Sophie Wilkinson.

PESTS HAVE FAVOURITES - USUALLY MINE
If you were with us last year, you will recall the problems I had with snails on a hosta and on some dahlias. But it was only on certain plants, not them all.

This is typical of pest attack. They usually tend to attack just certain varieties and leave others. And these seem to remain attack-free, year after year. So the obvious way would be to keep the ones which survive without protection and discard the rest. This, I do - and given the problems I had with snails on one of the hostas last year, I am also thinking of doing the same here. Problems arise when favourites are attacked. What then?

As you know, I don't like using chemicals for pest control. I know I recommend them, but this is to show that pests can be controlled this way, and also that it's not a closed shop - although I would prefer natural control, I am open to any means possible to control them, especially to preserve my favourites.

But, more than this: There are certain pests and certain types of attack which I am not confident can be left alone. I am thinking of slugs, snails and vine weevils, which attack the roots. I have lost endless plants this way.

I know there are nematodes (these look like tiny worms and enter the pest to destroy it from the inside) which will work in the soil. But these are expensive and will only work in warmer conditions - not now when the slugs are doing the worst of their damage on the tender young delphinium roots, and vine weevil grubs are attacking azaleas, primulas and pansies the same way.

Mice-Damaged Crocus

This is almost certainly mice damage on the remains of these sprouted crocus corms. Pity. They were just about to break through the soil surface. The mice must have smelled them.

Put some bait under an upturned plant saucer to protect the birds. A bit late now, though - nearly all crocus are gone. First year this has happened.

Strip Geraniums Almost Bare

Shortly after bringing the troubled geranium indoors, it became obvious that, even after spraying with fungicide, the leaves did not look healthy. So, because new leaves and buds were developing, I stripped plant almost bare of leaves and flowers, and re-treated with fungicide and insecticide ('Provado': thiacloprid, a systemic). Should really have done this earlier, but afraid of creating too much stress. Shall re-treat with fungicide ('Systhane') in a couple of weeks.

LAYERS OF QUARANTINE
I ought to have made it clear I do not recommend bringing plants from the garden indoors, at least not without placing them in quarantine for a few days (preferably weeks) first. And I ought to have told you I have areas in my house kept for these purposes so I can strictly observe plants for a while.

If you remember, we took cuttings in August. These were for indoors. They're not only cleaner (because they have come from new growth), they don't need as much room either.

In a few weeks, we can take the shoot tips off this plant for cuttings. Removal of the apical (terminal) buds will encourage plant to branch, ready for next year. This way we 'kill two birds with one stone'. That's the theory, anyhow.

Insect Pests on Over-Wintering Dahlia Tubers

Slugs, earwigs (pictured) and wireworms are all serious pests which can over-winter with stored dahlia tubers. Of these, I have found wireworms to cause the worst damage, since they attack the necks and render the tubers useless; the other two attack the young plants during the next growing season.

Although I have never stored tubers individually, complete removal of soil and a thorough washing is obviously ideal for removing pests, along with their eggs. If the pest problem is severe, this might justify the increased risk of loss of tubers through disease (especially if tubers were dusted with sulphur powder).

So far, this has not proved necessary. I have found a dusting with "Derris" dust ('0.2% w/w rotenone') effective against wireworms. The others are removed with the soil just prior to planting. Though, to be honest, I haven't really had a problem with earwigs before. It might be worth spraying tubers with 'Provado Vine Weevil Killer' (9g/l 'thiacloprid') at some stage.

Sterilizing Soil in a Microwave Oven

Due to cool spots, I find it best to spread very damp soil out evenly on a plate before heating in a microwave. About 8 to 10 minutes per litre should be sufficient to kill most creepy-crawlies and soil fungi.

Place kitchen towel over soil before starting, then heat until soil is just beginning to dry out amid much steam.

Leave it all to cool naturally, watching for any sign of life.