The smell of plant material may be the guide to detecting diseased plants or to determining the species of a plant. Temperature may be the clue to the presence of diseased plants. Plunging his hands into the peat moss in which plant material may be packed, the inspector may encounter a warm spot an almost certain sign of rotting plants, often caused by lack of ventilation.

The plant pathologists of the inspection station must also be concerned with the determination of fungi and bacteria. That often involves culturing. Agar, a gelatinous substance from seaweed, is made sterile, combined with a sterile nutrient, and used as a transplanting "garden," in which material infected with the organism is placed. The growth pattern of the organism in the culture medium enables the pathologist to determine the identity of the organism or at least to assign it to a group whose general habits are known in relation to plant growth.

It is not unusual to find insects among plants quite unrelated to the plants with which they arrive. Orchids from South American jungles are taken from the tops of trees and transported to the United States for growing in greenhouses. Some of them may be many years old. Among the roots accompanying the plants one finds an accumulation of trash and bits of tree bark in which many species of insects are likely to be found. Forest litter also contains many hibernating insects. As many as 40 species have been intercepted in such material that accompanied one case of plants.

Insects at the windows of the Hoboken inspection house, killed by the spray that is applied periodically, show that pests repeatedly enter with plants they are not known to attack. Insects are also collected that were known to have come with certain shipments although inspection of the shipments failed to show their presence. For example, serious pests of cabbage and related plants, a pest of strawberries, and other insects have been collected at the windows when they were not found in shipments with which they must have arrived. A pest of cabbage was found on the stem of a vine related to grape. Even insect vectors of human diseases have been intercepted in orchid plants from the South American jungles. We must therefore regard every insect that attacks plant life as a potential plant pest. We also must regard all plant material as potential carriers of such pests.

NEGATIVE INSPECTION FINDINGS are no guarantee that the material is free of pests; treatment also is needed.

The small size of some insects, the smaller size of their eggs, the fact that insects may be under leaf sheaths or buds or be embedded in plant tissues are some of the reasons why we cannot depend entirely on inspection. While foreign certification as to freedom of plant material from plant pests is a requirement, the purpose of the requirement is to see that obviously infested material is not sent, thereby at least eliminating a known pest risk.

Treatment is required as a condition of entry for practically all plant material, most of which is fumigated with methyl bromide as a condition of release. To do that, the inspection house has six fumigation tanks. The dosages vary with the temperature, the pests,the material, and the fumigation process under atmospheric pressure or vacuum. Material packed in peat moss requires fumigation under vacuum so the gas can penetrate to the plant material. All dosages have been determined by research to kill effectively the various types of pests and yet be within the range of tolerances the plants will stand.

Plants that will not stand fumigation are treated by some other method. Hot water, at 110 to 120 F. for various periods, is an alternative method. The inspection house has a room equipped for various types of heat treatment. There are tanks for hot-water treatments, an electric oven for dry-heat treatments, and chambers for vapor-heat treatments. The latter may also be used as driers by circulating heated dry air instead of vapor. Occasionally material other than living plant material is given a dry-heat treatment in an electric oven.

Liquid insecticides, in the form of dips or sprays, may also be used. Seeds of certain kinds, especially of corn and related plants, may be treated with a special device for coating them with a mercurial dust as a protection against the invasion of germinating disease spores that might be present.

Packing material arriving with diseased or contaminated plants is destroyed, fumigated, or sterilized under steam pressure. There are two autoclaves in the heat-treatment room for steam sterilization. Some of the vacuum fumigation tanks also are so arranged that steam may be injected for giving steam-sterilization treatment under pressure. The tanks are occasionally used to sterilize soil imported for religious or sentimental purposes.

COMPLAINTS OF FUMIGATION INJURY, usually unfounded, occasionally come in. When a permit holder receives an importation of plant material in poor condition, he is inclined to lay the blame on fumigation, not knowing what else to attribute it to. In years past, when fumigation was resorted to only when plants were actually found infested, we got complaints of such injury even when the material had not been fumigated.

Plant material shipped by air has repeatedly reached the inspection house, even in summer, with severe injury caused apparently by low temperatures. Presumably the plane flew at high altitudes and the material was stowed without adequate protection.

TO GET THE BEST RESULTS from imported material the importer should :

(1) Be sure to get a permit in advance of importation by applying to the Import and Permit Section, Bureau of Entomology and Plant Quarantine, 209 River Street, Hoboken, N. J.

(2) Send complete instructions to the shipper as to certification, freedom from soil, and other requirements. ( Information on these matters will be given when the permit is applied for.)

(3) Ask the Import and Permit Section for suggestions as to methods of packing perishable plant material if the shipper is not familiar with them.

(4) Make arrangements in advance for using the proper medium of transportation. That will vary with the perishable nature of the material, and if the material is not to be brought in by mail, advance arrangements should be made for a customs broker to attend to getting it promptly to the inspection house, to getting plant quarantine and customs clearance, and to forwarding the material to the destination. Many heavy losses of material have resulted because of failure to provide for customs clearance.

GEORGE G. BECKER, a graduate of the University of Maryland and Cornell University, is in charge of the import and permit section of the division of plant quarantines, bureau of Entomology and Plant Quarantine. Before he joined the Department in 1926, he was professor of entomology in the University of Arkansas, state entomologist of Arkansas, and chief inspector of the Plant Board of Arkansas.