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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.
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