What makes some strains more susceptible to pests?

[jokerlola]

I just harvested my Harlequin plants. I noticed few aphids on the biggest plant a few days ago but didn't see any on the other plants. Right before putting them into 36 hours of darkness prior to harvest, I noticed a few aphids on the other Harlequin plants. Once I chopped and hung the whole plants I noticed a few more on the underside of leaves at the bottom of the plants. It looks like a very late stage aphid infestation just prior to harvest. I fully examined my other 4 plants (2 Super Lemon Haze and 2 Silver Mountain) and I can't find any signs of aphids or other pests. Descriptions online of the Harlequin strain state that it's susceptible to pests and disease. What makes certain strains like that and others are less so?

2 years ago I grew 3 Gorilla Glue #4 plants and 2 Blue Dream plants. The Blue Dream plants got a late stage Spider mite infestation while the Gorilla Glue plants weren't touched by mites.

 

[bobrown14]

Genetics is the short answer.

Also plants get pests and they send out pheramones to the neighbor plants that signals pests and the other plants react with defense mechanisms like crappy taste and smell (for the pests).

If you had aphids you still have them. Get something to spray to get rid of them before they take hold.

Trust me on this one. They are hard to get rid of. Not hemp mite hard but hard non-the-less. You gotta get on it.

In green house conditions they reproduce asexually. The nymph stage only takes a few days and they are adults reproducing asexually.

Look on fan leaves for shiny spots (thats the honey dew) and also look for white looking small exoskeletons on the leaves thats the nymph molting its skin and turninging into an adult. They get going REAL FAST indoors without pests.

Safers Soap
Neem oil
Spinosad

These are your friends. I've had them since the end of the summer. Not totally gone yet.