# Merit for scale?



## Orchidnut57 (Aug 7, 2011)

I was hoping some of the growers were familiar with using the systemic
insecticide Merit? I have seen it used as a top dressing and I have read of using it as a flush. Reviews on the product anyone? Many thanks Jim


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## NYEric (Aug 7, 2011)

I use Merit 75 in combination with Neem and other natural soaps. Seems to work but must be followed up after a couple of weeks.


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## Orchidnut57 (Aug 7, 2011)

NYEric said:


> I use Merit 75 in combination with Neem and other natural soaps. Seems to work but must be followed up after a couple of weeks.



Eric, at what ratio do you use it?


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## likespaphs (Aug 7, 2011)

which merit is it? (following are 'click-able' links)
federal law requires the product be used as per the label
also, if you use it at off label rates, there is a greater possibility of phytotoxicity (damage to the plant caused by the pesticide) or ground water contamination issues

*Merit® 0.5 G *

● Product MSDS
● Product Label


*Merit® 2F *

● Product MSDS
● Product Label


*Merit® 2.5 G *

● Product MSDS
● Product Label


*Merit® 75 WP *

● Product MSDS
● Product Label


*Merit® 75 WSP *

● Product MSDS
● Product Label


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## Orchidnut57 (Aug 7, 2011)

*Merit*

Yes, I have not acquired it as of yet. I am a little afraid of it...I have heard of deformed flowers. With my small collection I seem to have a handle on the rare scale breakouts...was more curious than serious. Thanks to all. Jim


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## T. migratoris (Aug 7, 2011)

I use Merit 75 WP periodically for mealybug - it's extremely effective and much better on mealies than Orthene, for example. I use it as a foliar spray and I've never had any negative vegetative effects. 

Never used it for scale.


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## NYEric (Aug 7, 2011)

Merit is good against mealies. For small collection to combat scale I'd just clean with 91% alcohol.


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## Roth (Aug 8, 2011)

I got some phytotoxicity once, could not explain why, but others time it did not make any trouble.

This said, I strongly advise against using imidacloprid/merit if you do not check before all of your plants for mites, because if you have mites, they will breed like crazy and proliferate everywhere. Plus, the imidacloprid-treated mites are resistant to most miticides ( including dicofol, kelthane. pentac, avermectin) for at least 6 months.


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## tim (Aug 8, 2011)

i might suggest you contact a local arborist and try to get some safari (20 sg - dinetofuran) - worked great on scale (and everything else) for me - 1/2 tsp per gal. - it's pretty expensive though


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## likespaphs (Aug 8, 2011)

both merit and safari are neonicotinoids and should not be used in the same rotation program (pesticide class rotation is necessary to delay insect resistance to the pesticide)
safari is exponentially stronger than merit
here is a {possibly outdated} chart of chemical classes
http://www.ohp.com/Labels_MSDS/PDF/CCC_XI.pdf
(merit is not on this chart but has the same active ingredient {imidacloprid} as marathon)


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## Rick (Aug 8, 2011)

I use it in the ready to use dilute product from Bayer (Rose and bloom) spray.

I think it works fine with some of the follow ups as mentioned.

I heard from an Ag extension agent that the product does not migrate (systemically) into spike and flower tissue, so only works topically on those parts of the plant.


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## bullsie (Aug 9, 2011)

I use Merit 75 WP for scale and mealies. At 1/8 tsp to a gallon of water as a drench, I get it in the plants and not everywhere. I do it once a week for three weeks - four for mealies. 

But do have to watch for those critters who are not affected by it. If you have them they will increase drastically - they have the whole plant to themselves!


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## surachais Thai (Oct 4, 2011)

*Merit for scale*

Neonicotinoid insecticide (control thrips, mealy bug, scale, aphid, jassid, leaf hopper, plant hopper, white fly, leaf miner, bug)
All chemicals in this class are systemic action,in the past classify by chemical group,after many years of use and study about resistant,now it classify by pharmacophor (resistant site in chemical chain) as follow :

N-nitroguanidines
-imidacloprid, thiamethoxam, dinotefuran, clothianidine, imidaclothiz

Nitromethylene(nitroenamides)
-nitenpyram

N-cyanoamidines
-acetamiprid, thiacloprid 

For more information : www.irac-online.org (resources-document library-presentation-neonicotinoid resistances)


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## Ray (Oct 5, 2011)

NYEric said:


> I use Merit 75 in combination with Neem and other natural soaps. Seems to work but must be followed up after a couple of weeks.


Most insecticides need to be repeated because they only are effective on adults, allowing the "younger generations" to mature, untouched. Waiting two weeks is probably too long, as many of the critters we deal with have a shorter life cycle. Three repetitions at one-week intervals is my norm.

I will add that if you add an IGR (I like Enstar II) to your spraying program, it's a lot more effective, as it stops the maturation of the youngsters, which means they cannot breed.


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## Roth (Oct 5, 2011)

I have been one of the first to use imidacloprid/Confidor on orchids, about 15 years ago. It is efficient for a few weeks after application, providing there are no resistant bugs. It proved to be ineffective from nearly the beginning against thrips palmii ( the crap that eats the crown of the plants and makes nice marks, but usually is never seen outside).

A few notes :
- Against thrips, you need a drench, as the larvae are very damaging, usually around the roots, the new shoots ( ever seen strange orangish cast to very tiny new shoots), and the crowns ( leaf pleating can be a symptoms, especially if the emerging leaves look 'dirty'). 
- For all the remaining insects ( not the mites), drenches are usually very effective, Merit can be eventually used, with some precautions.

Imidacloprid can induce a burst in reproduction and growth of mites, especially brevipalpus. The treated mites are much more resistant as well to common miticides. I got the problem, and I have unfortunately not been alone. It requires then very harsh miticides ( bromopropylate + clofentezine) to get rid of the problem.

I prefer to use carbamate insecticides, namely aldicarb and carbofuran. 

Though they are deadly and their LD50 is very low, they are not likely to be carcinogenic. I do not trust many of the growth regulators/metabolism disruptor insecticides regarding the risk of getting a cancer. To my mind, even many fungicides are way more dangerous than insecticides regarding mutagenicity/teratogenicity. 

When I used imidacloprid, I got rid of the scales, got plenty of mites on the other side, and did not control the thrips palmi at all ( so I went back to Curater and Parathion...).

I must report that twice, as a tech advisor of two phalaenopsis nurseries, I got report of chlorosis or long term plant stunting when azoxystrobin was used shortly after an imidacloprid treatment. It is anecdotal though.


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## likespaphs (Oct 5, 2011)

imidacloprid has never been too effective for me against thrips.
i have had some success with tristar (Acetamiprid)
what about an avid/azatin tank mix? 
i have success with that against thrips, but on Arabidopsis, haven't tried it on Paphs or other orchids


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