I am thinking of using milky spore or nematodes in my yard and garden, but I don't want to hurt my earthworms. Will either of these affect earthworms?
Neither milky spore or nematodes affect earthworms. They are also safe for humans and pets. So go ahead and use them without any worries.
Which poison do you normally use / recommend in your gardens? We have had discussions with the leading pest control agencies in our country and every poison they recommend gets turned down on "environmental" grounds. Meanwhile the problem is just exacerbating. I am not sure whether this is, technically, a gardening question, but would greatly appreciate your suggestions. Rat traps would, of course, be used. I don't think anyone here does an ultrasound method, so that just leaves us with poison used in a very controlled manner under the supervision and control of a responsible company/agency.
I am not an expert, but I have heard that mixing equal parts of flour, sugar and either baking soda or boric acid (Borax laundry detergent) is an organic, environmentally friendly and effective rat killer. Place it in areas that the rats go and they will eat it. The baking soda one is supposedly also safe for domestic animals as it kills the rats by swelling their stomach, and domestic animals like cats and dogs are able to relieve the swelling by belching and, therefore, are not hurt by the poison.
Are spider mites and mealy bugs the same? The same substance comes under the leaf and looks white, sticky and powdery.
No, they are not the same. They are two different types of bugs. That being said, their treatment is very similar. Here are some articles to help you with dealing with them:
Stickiness is a tell-tale sign of mealybugs, but not spider mites. Treat the mealybugs with a solution of 5 part water, 1 part alcohol and a squirt of liquid soap. The key to success is less what you use to spray and more how thorough you are in spraying the entire plant, including all leaf and stem surface.If you miss even a few, they will reproduce and come back later.
Which vegetable oil is the best to use when making spraying oil (for plants)?
While basically any type of vegetable or cooking oil may work (by suffocating the bugs), I would recommend the use of neem oil instead. It is very effective and safe for beneficial bugs as well as for humans and pets. Here is some information that may help:
They strip all the green from the garden plants and some other plants
This article has some suggestions:
A systemic solution was recommended by another extension service, but they did not name a product. A systemic product I like is neem oil. It gets into the plants and will kill off anything that eats the plants, so I would add that to the TAMU recommendations.
I have a customer that has moderate scale on about 20 shrubs we recently installed. They don't appear to be active, leading me to believe the nursery I bought them from has done their job by keeping them sprayed. My question is this: Are scale active in winter time? Does cold weather minimize or kill scale?
They are less active in cold, but cold is not a guarantee that they will be eliminated. Consider spraying the plants with neem oil. We have found it to be very effective on killing scale. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
How do you pretreat your garden to minimize bugs and other insects that destroy your produce?
We are HUGE fans on neem oil for that. It is safe for humans and animals and beneficial bugs but is very good for keeping away damaging bugs. It is as effective as a pre-treatment as it is as a post treatment. Here is more information on it: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm