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PitcherCrab
Crescent Fresh



Registered: 12/02/06
Posts: 2,446
Loc: The bottom of the sea.
Last seen: 1 year, 2 months
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White Dots on bridgesii
#13031308 - 08/10/10 11:48 AM (13 years, 6 months ago) |
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On one of my bridgsii's there are quite a few white dots that rub off when I rub my finger over them... are there any cactus pests that this might be? I'll post some pics when I have some more time.
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PoC
Relax



Registered: 03/10/04
Posts: 2,142
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Re: White Dots on bridgesii [Re: PitcherCrab]
#13031329 - 08/10/10 11:55 AM (13 years, 6 months ago) |
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Sounds like mealybugs. Are there some white fuzzy tufts around and also maybe some soft-shelled insects that resemble small pill bugs? If so they aren't too difficult to treat on Trichs - the common method of removal is cotton swabs or paper towel + alcohol.
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theMallacht
Clandestine Hero

Registered: 04/25/09
Posts: 3,428
Last seen: 1 year, 1 month
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Re: White Dots on bridgesii [Re: PoC]
#13032524 - 08/10/10 04:06 PM (13 years, 6 months ago) |
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Quote:
PoC said: Sounds like mealybugs. Are there some white fuzzy tufts around and also maybe some soft-shelled insects that resemble small pill bugs? If so they aren't too difficult to treat on Trichs - the common method of removal is cotton swabs or paper towel + alcohol.

Yeah, they're no big deal... Sometimes I treat, sometimes I don't.... They don't really spread IME and the scarring seems to be about the same whether you treat it or not.
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Agarico
arrrf 3 8 7



Registered: 09/23/02
Posts: 838
Loc: The Netherlands
Last seen: 6 years, 9 months
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Re: White Dots on bridgesii [Re: theMallacht]
#13033870 - 08/10/10 09:06 PM (13 years, 6 months ago) |
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Do they show up in a particular time of the season or is the risk to get them all year round?
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karode13
Tāne Mahuta




Registered: 05/19/05
Posts: 15,290
Loc: LV-426
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Re: White Dots on bridgesii [Re: Agarico]
#13033938 - 08/10/10 09:20 PM (13 years, 6 months ago) |
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They can be a year round problem due to the way they reproduce.
Quote:
Life Cycle
Most mealybugs (especially pest species) have numerous, often overlapping, generations per year. Like all insects, their development is dependant on temperature: there is a threshold temperature for each particular species of mealybug, below which development either ceases totally (dormancy) or is slowed to a greater or lesser degree (quiescence). Just as there is a minimum threshold temperature, there is also a maximum threshold temperature, beyond which development is slowed or ceases all together.
If temperatures remain elevated for prolonged periods, insect mortality increases rapidly with a consequent crash in population size. Mild to warm conditions are therefore favourable for insect development, and mealybugs are no exception to this rule. Temperatures of about 25°C and a high relative humidity are optimum for mealybugs in Australia, and their populations reach peaks in spring and autumn.
Eggs can be laid singly or in clusters, and female Long-tailed Mealybugs have been recorded as laying as many as 200 eggs in a lifetime. Egg clusters are usually embedded in a cocoon of waxy filaments, with the structure varying between species, from tightly packed to loose.
On hatching, the juveniles, known as ‘crawlers’, move away from the cocoon and search for suitable feeding sites in sheltered areas. The juveniles progress through five moults before reaching adulthood. In the case of the males, the last juvenile instar pupates in a silk cocoon, and emerges as a winged adult. Adult males do not feed, having no mouthparts - their sole purpose is to mate with females and pass on their genes to their many offspring. Control
Because mealybugs have high reproductive capacities and multiple generations in a year, they have the potential to become resistant to pesticides very quickly. The use of stronger and stronger pesticides breeds more and more resistant mealybugs, until the stage is reached where efficient and practical chemical control of the pest is no longer possible. Fortunately mealybugs can be controlled using ‘soft’ methods including biological agents and low-toxicity pesticides, most of which are readily available to the horticultural industry and the home gardener.
Quoted from here.
In the past I have had them on my cactus and I found a product which had the active ingredient Potassium salts of fatty acids, this did a good job of controlling them. I would try manual removal first before stepping up to chemical applications and I will advise against the use of alcohol on the epidermis of your cactus as it can burn and scar the plant.
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PoC
Relax



Registered: 03/10/04
Posts: 2,142
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Re: White Dots on bridgesii [Re: karode13]
#13033990 - 08/10/10 09:32 PM (13 years, 6 months ago) |
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Yeah they do tend to be more active in the growing season but I find some in the winter from time to time too. I haven't seen any long-term ill-effects from alcohol, which I have used both sparingly and liberally on cacti. I have even squirted down whole cacti with a spray of undiluted 99% isopropyl alcohol (though I wouldn't recommend it and usually wouldn't do this). It does dry their skin out but it's a matter of judging how bad the infestation is and what the risks/benefits are. I haven't seen any damage caused by applying alcohol yet though, just dry skin immediately after application which makes me nervous and is probably not great for the plant.
I recently received a Lophocereus schottii monstrose that was so covered with mealies that I hand-wiped many off then spritzed the whole plant with alcohol at my friend's house before I would even bring it back home. It's doing a lot better though tonight I should do some more hunting for any that might be lingering.
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World Seed Supply
Seed Man


Registered: 11/12/09
Posts: 2,154
Loc: New York, USA
Last seen: 30 days, 22 hours
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Re: White Dots on bridgesii [Re: PoC]
#13034023 - 08/10/10 09:37 PM (13 years, 6 months ago) |
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They're probably one of the easiest pests to deal with in my opinion.
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karode13
Tāne Mahuta




Registered: 05/19/05
Posts: 15,290
Loc: LV-426
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Re: White Dots on bridgesii [Re: PoC]
#13038567 - 08/11/10 08:36 PM (13 years, 6 months ago) |
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I tried using Methylated spirits(ethanol) to clean off some mealies on my Copiapoa hypogeae and it burnt the shit out of it. I will never use it again on my plants as there are better and less toxic alternatives available IMO. I hear it does work for some people but I tried it and I don't like it.
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