Monday, August 09, 2010

Killing Waxy Scale (Diaspididae) on a Gerbera Daisy

Valued entomological engineer Tim suggested in the comments of my previous post on Momma Daisy's large-scale scale infestation, that I examine predatory insects or environmental controls as a way of dealing with my waxy enemy.

Predatory insects are my favorite means of control and I typically kill aphids with a small container of ladybugs and a bag over the plant. The ladybugs can't fly away and greedily annihilate the aphid infestation. Unfortunately, waxy scale (Diaspididae) has few predators. There's a parasitic wasp that can be used, but obtaining them as a homeowner rather than a grove manager is difficult. There's not much else to choose from.

As Tim notes in his comment, Diaspididae is very resistant to pesticides. The females' waxy covering protects them from contact poisons and I've yet to have much success with systemics. Diaspididae crawlers can be killed by contact poisons, but the females produce so many offspring for so long that wiping out an infestation completely requires total concentration. I've never been successful at that, probably because I've never been able to completely coat the plant in poison. One little spot on a leaf left untouched and some set of crawlers will survive to the next generation.

A thorough examination is required.

I've had the most success with a combination of crushing them with my fingers and a contact poison such as rubbing alcohol. That's known to be incomplete because, again, you just never seem to get every scale and every surface on a large plant.

We have deep concern for the health of Momma Daisy.

This leaves environmental controls. Here's what we know about our two combatants - Diaspididae and Gerbera.

Chrysomphalus aonidum has a preference for humid environments and cannot tolerate freezing temperatures.
Can tolerate some frost but freezing temperatures will kill plant to the roots.
Hmmm. The freezer may well be my friend. It looks like we need to do some experimentation with freezing infested plant cuttings to see how long it takes to kill the little brutes.

Here is our plant sample with scale, as approved by our Maximum Leader. Now, on to the freezer!


Foxfier said...

Do you have a room with a dehumidifier? Maybe that, some AC and a spray bottle with rubbing alcohol?

K T Cat said...

Good idea, Foxie. Controlling humidity would be another tool.

Jedi Knight Ivyan said...

Wait until the end of monsoon and loan it to a friend in the Mojave or send it to me, lol. Living in AZ might have it's advantages after all.

Unknown said...

Was that "Cat scan" approved under the new Obamacare option.....?

Sorry KT. I just couldn't resist the obvious. lol