These plants have been certified to be free of virus by NY State Division of Agriculture and Markets. It is only feasible to thoroughly virus-test the relatively small number of nuclear plants, and subsequently spot check a few plants at later stages of the production cycle. The hard part is to keep the stock virus-free while it is multiplied to the numbers required for sale. The nuclear block is covered with fine-mesh netting in summer to exclude aphids and leaf hoppers which are virus vectors. In this picture the netting has been taken down because of possible snowfall.
Aphid season is past.
These plants correspond to the tissue cultured plantlets which are produced by the thousands over the winter. Foundation stock differs from nuclear stock in that it is not screened, but both are grown in fumigated soil. They will multiply about 10x over the 18 months before harvest. This sucker division and replanting may be repeated several times to increase numbers before the field is finally harvested for sale. These multiplication fields are not protected with netting, but are sprayed heavily with systemic insecticides to control aphids.