# Use of systemic insecticides and fungicides



## papheteer (Sep 2, 2013)

I read somewhere that the use of these systemics eventually retards the growth of plants. It says the chemicals remain in the plants very long after use. What's your experiences on this?


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## TyroneGenade (Sep 2, 2013)

A while ago I used malathion to kill scale, mealy bugs etc... Didn't seem to hurt plant growth one bit. And it was taken up by the plants. The adjacent lemon tree got some around the base and over the next few days the bugs infesting it were all dead. The lemons, that ripened some weeks later, were delicious as always.

I think there can be an issues with chronic application... But some are definitely longer lasting than others. Most will come with a warning label advising how long you have to wait before you could eat any fruit/leaves of the plants after dosing. The shorter the time frame the faster it is cleared.


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## orcoholic (Sep 2, 2013)

Been using systemics for years and never noticed any problems. Most of them are only effective for a limited time - about 6 weeks is the longest I've heard of.

If you're referring to systemics that certified applicators can apply, then disregard the above. Have no idea about them.


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## DavidCampen (Sep 2, 2013)

A number of fungicides and some insecticides are known to be phytotoxic. It seems that fungicides are more likely to exhibit phytotoxicity than insecticides. 

The fungicides propiconazle, mefenoxam and the strobilurins exhibit phytotoxicity. The degree of the phytotoxicity varies widely according to the specific plant. The label of the strobilurin fungicide Heritage DF says that it is highly toxic to certain types of apples but I have used it a number of times on my orchids without any apparent ill effects. The label for mefenoxam says that it exhibits some phytotoxicity and, since it is a systemic, suggests that the frequency of application should be limited; I have used mefenoxan once on my orchids with no apparent ill efffects. The fungicide propiconazole is known to function as a plant growth regulator and to exhibit phytotoxicity; I have never used it on my orchids and would be wary of doing so.

The label of the miticide Kontos states that it is not recommended for use on orchids. I have seen one claim that the insecticide imidacloprid can be toxic to orchids but many people use it on orchids and do not report any ill effects.


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## Ray (Sep 3, 2013)

Forgive me for this hijack, but is there any knowledge out there concerning the effectiveness and longevity of systemics in orchids as compared to other plants?

If I recall correctly, it is the metabolites of the applied chemials that provide the systemic protection, and while I would expect the metabolic functioning to be similar enough, there could be rate-, and concentration differences that could affect things. 

Just speculating, and looking for more science.


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## NYEric (Sep 3, 2013)

Don't worry. systematics taste great and are less filling!


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## mango (Sep 4, 2013)

Systemic insecticides and fungicides should be used only during active infection, the preventive use could lead to pest resistance.

In my experience, the two week lasting effect insecticide, is effective with only one application, so, a chronic exposure to the chemical should be rare.

To avoid that, there are preventive specialized chemicals.


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## likespaphs (Sep 4, 2013)

papheteer said:


> I read somewhere that the use of these systemics eventually retards the growth of plants. It says the chemicals remain in the plants very long after use. What's your experiences on this?



this is the whole point of systemics, the fact that they are distributed throughout the plant and remain there for a time to kill any pests that come along (or a new generation that hatches)
i have not seen them retard growth except it can sometimes delay flowering in Arabidopsis for a week or two


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## ALToronto (Sep 6, 2013)

likespaphs said:


> this is the whole point of systemics, the fact that they are distributed throughout the plant and remain there for a time to kill any pests that come along (or a new generation that hatches)
> i have not seen them retard growth except it can sometimes delay flowering in Arabidopsis for a week or two



I don't think that systemics remain active for the 7-10 days before you have to reapply them. They kill the insects during the first application, then you have to wait for any eggs to hatch before the next application kills them. Then one more time 7-10 days later, and you should be insect-free until you bring the next buggy plant into your collection.

I've been battling fungus gnats - window screens don't seem to keep them out. So I can spray them and kill the larvae (adult gnats are not affected), but then more adults come through the windows.


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## likespaphs (Sep 6, 2013)

how long the pesticide lasts in the plant is dependent upon the water solubility of the pesticide as well as other factors
the label of Marathon 1% G (imidacloprid) says it is active for 11 weeks and recommends not applying it twice to the same crop. it also says that it takes up to two weeks to become effective in woody plants and that those in a bark mix may not confer protection for as long a period
then again, TriStar (another neonicotinoid) is only effective for about a week


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## NYEric (Sep 6, 2013)

I don't read labels, that's why I don't use them.


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## Trithor (Sep 6, 2013)

TyroneGenade said:


> A while ago I used malathion to kill scale, mealy bugs etc... Didn't seem to hurt plant growth one bit. And it was taken up by the plants. The adjacent lemon tree got some around the base and over the next few days the bugs infesting it were all dead. The lemons, that ripened some weeks later, were delicious as always.
> 
> I think there can be an issues with chronic application... But some are definitely longer lasting than others. Most will come with a warning label advising how long you have to wait before you could eat any fruit/leaves of the plants after dosing. The shorter the time frame the faster it is cleared.



Most important when you plan to use your paphs as a salad starter. Gordon Ramsay advises finely sliced vine tomatoes with shaved parmesan over a shredded tossed salad of philippinense new leaves. Blooms can be used as decorative addition and balsamic should be avoided with all systemic insecticides!


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