Flea-eating nematodes are tiny organisms that attack flea larvae and eggs and other harmful bugs (gypsy moths and white grubs, for example). You apply nematodes by mixing them with water and spraying this mixture on your lawn or garden at least once every year. Garden supply stores online and offline sell nematodes in containers ready to use. Ordering these is as easy as ordering any other gardening or flea control product, and many places online provide free shipping.
Measure your yard with a yardstick or measuring tape (the latter is the fastest way). You'll need to know how large of an area you have in order to buy the proper amount of nematodes.
Purchase nematodes directly from the manufacturer (if you are unable to purchase them locally), when possible, via mail-order catalogue or online. The reason for this, according to mastergardeners.org, is that these organisms must be stored and handled properly before they are applied to your lawn. In other words, you want to make certain you are receiving live nematodes.
Order them in time for applying when the soil warms in the spring. Shipping won't take long---and you can usually pay extra to have them rushed to you---however, you should allow for a week or two total for processing and shipping.
Have your credit card ready if ordering these online. Most online sellers will accept only a major credit card---no C.O.D.s or checks. You will also need to supply your name, full shipping address and phone number. If you wish to pay by check, you can mail in an order from a gardening supply catalogue instead.
Prices do vary for these, so it may pay to shop around before placing your order.
If the weather is still cold, wait until it warms before ordering and applying flea-eating nematodes---they won't be active unless the soil temperature is significantly above freezing (in the 50s or 60s Fahrenheit).