Agricultural Experiment Station.
to be harvested, the disease could be materially checked by the judicious use of sulphur.
It was not Bottytis but the typical drop, Sclerotina libertina (Fckl), which caused the damage to the crop in the second house. Here the plants were not planted in benches but were set in a solid bed. Originally the greenhouse was used as a garden house for demonstrations in garden craft and the soil had become mixed with chemicals injurious to plant growth. Many of the plants made a poor growth on this account. Those plants then which were held back first by these soil conditions were the first to succumb to the disease. The plants would all be in a healthy condition " or apparently so " at night, while perhaps in the morning several would be found nearly or wholly collapsed, the leaves having become limp and flabby with a loss of their normal ooloi* and turgor. In a short time the leaves would be covered with a growth of hyphae giving them a whitish appearance, but upon examining the surface of the leaves no spor^ could be found. In a few cases leaves which had been killed by the typical drop were afterwards infested w^th the Botrytis, but this was of but secondary imix)rtance as the Botrytis in this case was saprophytic in character. When attaf*ked by the drop whole plants would collapse at once as if the stem had been severed from the roots, thus cutting off the transference of food. Upon examination, the stem, roots, and basal portions of the leaves were found to be completely infested with hyphae, seemingly those of Botrytis cinerea, however the infection took place here from the roots and stems, and the leaves decayed after the injury to the stem and roots. The fungus is a very rapid grower and very active as shown by the little time required to entirely collapse the plant. It soems too as if the nourishment is cut off and the plant succumbs as a result. Upon examining the soil, hyphae were also found abundantly in it. ThU shows that it can live as a saprophite as well as a parasite. Sclerotia were found in the soil as well as at the bases of the leaves, but in no case were spores found. These sclerotia ai^ but dense wefts of hyphae aggregated to b")tter withstand the dry and variable conditions. Numerous cultures were miado ot the mvceliumi found in soil on both the stem' and the leaves, but in no case did these produce conidia though sclerotia were quite readily produced.
Twenty-First Annual Report of the
It thus seems so far a^^ our present knowledpje goes tbat th*^ fungus continues its existence without fonriing spores and lives froml year to year in the soil, usually in the form of sclerotia. Thus in a greenhouse it is a very easy matter for the fungus to continue its purely vegetative existence and, being in the soil, it will attack lettuce whenever it is planted in that soil. The niycdliumi is very similar to that of Botrytis and is indistinguishable from; it. It is only by their different characteristics in attacking lettuce that they can be distinguished without making cultures of them, when they can readily be told from each other. Botrytis cinei*ea, as has already been described, has a watery decay stage followed by the gTay mold or spores on the surface of the leaves while the latter forms no spores, but can usually be distinguished by the sudden collapsing of the whole plant. The former reproduces itself by means of spores while the latter continues its existence in a vegetative state. Several experiments were made in infecting healthy lettuce from soil which was known to contain drop fungus, and in nearly every instance the plants would suddenly collapse when nearly matured. A good deal of work has been carried on by the Massachusetts Experiment Station especially in reference to remedies for the drop. It was there found that one of the most efficient methods of prevention was the complete sterilization of the soil or at least of a layer three inches deep.
It is probable that tlie two are entirely different fungi, as in no case have we been able to produce one from the other and, if they once were the same, each one has now become so fixed in its habit that it is impossible to produce one from the other. But a brief description of the miethods of attack by the two different fungi has been given, for as yet not many experiments have bei^n carried on by this Station with reference to controlling the disease. When lettuce is again grown in the house the next season the work will be primarily along the line of prevention of the disease.
The growing of head lettuce would probably be as profitable near some of our larger cities in. the West as it is in the East if some means of prevention could be found to guarantee against the ravages of these two fungi.