Chrysanthemums in Aberdeen

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Common Pests:
- Thrips
- Leafminer
- Earwigs
- Slugs 
- Whitefly
- Capsid Bug
- Caterpillars
- Red Spider Mite
- Vine Weevil
- Sciarid Fly
- Stool Miner

Common diseases: 
- White Rust
- Verticillium Wilt
- Powdery Mildew
- Crown Gall
- Chrysanthemum Rust
- Botrytis

Common disorders:
- Nitrogen 
- Phosporus
- Potassium 
- Magnesium
- Manganese
- Copper
- Iron
- High Salt levels

Suggested settings:
- Monitor

- contact me

Date last updated: 
10 July 2008


Ivor's notes 

Note 1 - Use of Imidacloprid
We are going to find that Imidacloprid is going to be the best control presently for many  pests including leaf miner. 

Some growers advise using Admire as a spray and not a drench to the roots. I have used it as a spray myself to plants in smaller pots, mainly because I don't want to handle the compost during potting on. However I do support the idea of using Admire as a soil drench because it is then active for a very long period. Three months for aphids and at least a month for the heavier insects like leaf miner and whitefly, which is enough to break the cycle. Hardly anyone gets leaf miner any more because if they give a soil drench it usually eliminates it. 

The main disadvantage I find with a drench to the roots on Earlies is that it would kill earth worms etc because its so indiscriminate. The other disadvantage is that when you rely on it to cure all ailments it will not,  e.g. it has no effect on caterpillars including tortrix as a soil drench. Likewise for thrips. 

Note 2 - Bifenthrin for caterpillars
I have found that a spray with Bifenthrin before the main caterpillar period (July August) discourages most of the moths from laying their eggs. My pal on his allotment observed that even though there is only a few days harvest interval on Bifenthrin which suggests it is pretty short lived. He found that when he sprayed his Brussels sprouts the cabbage white butterfly never visited those plants again to lay eggs for well over a month. They came and turned away.

Note 3 - Apply dry fertiliser evenly
One other point I would like to make, I use dry fertiliser on my pots of late flowering chrysanthemums, and I water it into the compost. Or the rain washes it into the compost. It is important to apply this fertiliser evenly over the surface of the compost. This is because the roots take up ions along with water. If there is a very strong concentration of ions in one part of the pot the roots on that side of the plant will be hampered from taking up water, the xylem tissue from those roots go directly up the stem to the leaves and petals on that part of the stem. You may find petal scorch in just one segment of a bloom. Likewise iron deficiency symptoms on half the plant, perhaps due to poor roots on one side or high pH in one spot.

Note 4 - Other nutrients needed in smaller quantities than N-P-K. 
Magnesium (Mg) & Calcium (Ca)
Both are positively charged and stick more strongly than Ammonium nitrogen or Potassium. They only release after considerable watering, thankfully neither are required in large quantities. 

Magnesium is a constituent of chlorophyll and has an important role in photosynthesis, once used it is transported to other parts of the plant usually to the new growth when magnesium is deficient. The result is, a deficiency shows up as darker leaf veins because the inter-vein tissue is more easily depleted of Mg and appears paler, where as the Mg remains in the leaf veins, so they show up darker. This shows in the older leaves because magnesium is transported from these older leaves into the younger leaves. Mg can become deficient when potassium levels are high and are a common problem in tomato growing. An ounce of Magnesium sulphate (Epsom Salts) in 2 gallons of water, watered over the plant by watering can and rose will help correct a deficiency. Mg acts much quicker as a foliar feed, it raises soil conductivity dramatically when applied to the soil, therefore a foliar feed is probably the best course of action to correct a deficiency. 

Calcium is used in the building of cell walls and has a very important role in plant growth. A deficiency will show up in young developing cells at the shoot tip and root tip. 

Iron (Fe) 
Is an important constituent of chlorophyll. A deficiency can be distinguished from Mg deficiency because it always occurs at the top of the plant. It cannot be transported from the lower leaves like Mg. The leaves appear more evenly pale than the inter-veinal yellowing associated with Mg. iron deficiency often occurs when the pH is high. And because ferrous sulphate can often be unavailable to plants because it reacts to oxygen and forms rusts, therefore chelated iron in the form of sequestrated iron is the best way to correct a deficiency. Poor oxygen content after prolonged periods of rain often result in iron deficiency, although if the soil dries out this often rectifies itself, however weak rooted varieties are often more problematic. 

Sulphur (S) 
Sulphur is negatively charged and leaves the soil unless calcium is present. It is readily available as sulphate and has a role with amino acids.

(last updated 10 July 2008 )

Other information 

Ivor Mace
Ivor Mace



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