CO885-(19-20) — Page 339

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C.O. 885

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98

There were orchards in which the fungus had come in without any assistance or interference; others where the spores had been sprayed in with one spraying with two sprayings, and with three sprayings. Others, where the fungus had bee sprayed in after the orchards had been sprayed with whale oil soap, and still others where, after the trees had been twice sprayed with whale oil soap, the fungus had come in and assumed control. All these orchards looked about the same to me---a very large percentage of the fly being killed. There was a little black blight to be seen in every grove, but probably not enough to make any difference to the growth of the plant. Probably all the fruit would have to be washed, and, in fact, it seems part of the regular practice to wash all oranges and grape fruit in Florida.

I was much struck by the scarcity of scale insects in the groves visited. In nearly every instance the purple scale was to be made out only by the red headed fungus which had already killed it. Very rarely did I see any scales unattacked. The orange snow scale, I am informed, does not occur in Florida, nor the green scale (Lecanium viride). In most parts of Florida the climatic conditions during 1910 have been very favourable for the development of beneficial fungi.

In Gainesville, Professor Fawcett and I visited the nurseries of Mr. S. C. Graves. In Deland we spent the afternoon visiting orchards accompanied by Mr. H. B. Stevens. At Orlando we drove to Winter Park and saw several groves on the way. We also visited the grove of Mr. Palmer and the nurseries of Mr. Boone, who sells fungus. We also went to the estate of Mr. Stewart at Zellwood. On our drive to Winter Park we came across a small number of trees which evidently had not been cultivated for several years, and here we saw all the scale insects and the white fly These trees had a considerable amount of well-established and well-controlled. dead wood among the branches, and the foliage was rather yellow, but the pests were not specially abundant, and as already stated, they seemed to be well con- trolled. I was told that at St. Petersburg, on the West Coast of the State, near Tampa, the red fungus, on account of dry weather, had failed to take possession after it had been artificially introduced.

The absence of signs of hymenopterous parasites of scale insects was a very noticeable feature. Even in those instances where I found purple scale not attacked by fungus there were none of the holes in the scales indicating the emergence of insect parasites which is so common in the West Indies.

The fungoid parasites of white fly and scale insects occur naturally in the groves of Florida, and under strictly natural conditions accomplish much in the control of these pests. It is estimated that in one year in three the control of white fly by fungi will be complete under the conditions in most of the orange-growing sections of the State, without any artificial aid in their spread and introduction. It is, how- ever, only when natural conditions are supplemented by intelligent artificial measures that the greatest amount of good is done.

Fungi may be introduced into white fly-infested groves by spraying in the spores, tying in leaves, or introducing into the groves trees bearing a good supply In many of fungi. The spore-spraying method is best, and is in most general use. citrus-growing districts there are those who make a business of maintaining a supply of fungi of different species for sale, and in one or two places there are men who undertake the spraying of trees for the introduction of fungi as a regular business venture. Mr. Frank Stirling, of Deland, sprayed as many as 38,000 trees in one season. (Florida Agricultural Experiment Station Report, 1908-9.)

The following is copied from the Florida Agricultural Experiment Station Annual Report, 1909, and is of interest in connection with this report as showing on how large à scale the use of fungus enemies of the white fly has been carried on in some parts of Florida :-

spray-

Mr. Frank Stirling reported that he sprayed between 8,000 and 9,000 trees in Deland and other places. Mr. Stirling is making a business of ing fungus for others, following the method developed and described by the entomologist in Bulletin 97. This spring (1909) Mr. Stirling was again spraying fungus at Deland and other places, and it is a gratification to know that the fungi (principally the red and brown) will be given a trial on such an extensive scale. A letter has just been received from Mr. Stirling in regard to his work up to July, and as this is of great interest, it is here in part submitted:-

"

In answer to your enquiry regarding the fungi,

I will say that I have had varied success in starting them up to June 15.

I

97

From that time on I have had good success, almost three or four times the amount from a spraying that I did up to that time. I have, so far, with one, and sometimes two, men helping me, sprayed 38,000 trees. Of course, some of these trees have been sprayed several times, but as I have kept a strict record of each grove

I have no trouble in giving account.

I sprayed the entire community at Seville, at Spring Garden, and at Pierson, where I found as much A. nubifera as A. citri. Now I want to say that, although I made my solution half of brown and half of red, the red is far ahead of the brown. I might say 100 to 1. This has been the case all spring and summer. Now it may be that the brown is somewhat sporeless or something of that sort, and I have about made up my mind that the red is the only one to do anything carly in the season.'

Now, in regard to spraying in the dry periods; the fungus takes all right, but does not spread so well as when wet."

It has been found that by spraying in the spores, the fungus can be assisted to take control of an orchard some 6-8 weeks sooner than when left to the natural method of spread. This means a great deal in checking the abundance of black blight.

Fumigating with hydrocyanic acid gas does not injure the fungi so far as obser-. vations have indicated up to the present. One or two sprayings with whale oil soap do not seem to be detrimental to the growth of the fungi, since in favourable seasons the fungus is found to establish itself in such groves very shortly after the white fly makes its reappearance.

The growth of weeds and cover crops is found to promote the development of the fungi. This is believed to be due to the more moist conditions of the soil, and of the air near the ground level, which is induced by such growths. The plant that I saw most used for cover crops was beggar-weed (Desmodium tortuosum). This does not make a very dense cover, but seems to be very useful. In many groves where the trees are well grown and in good bearing, grass has been allowed to come in, and in certain places it forms a strong turf.

The natural conditions in Florida make it much easier to carry out processes of tillage, spraying, and fumigating than is usually the case in citrus cultivations in the West Indies. The climate is sub-tropical, with cold weather and even frosts in certain years, down towards the middle of the State. The rainfall is about 54 inches, and the climate is moist. The soils suitable for citrus culture are mostly open and permeable, being thus well drained and well ærated. The surface is very flat, and there are, so far as I saw, no rocks, ledges, or deep ravines. The water table is high, and the soil moisture is abundant, as shown by the number of rivers and lakes. It is probable that the large area of water surface in the State helps to preserve a higher moisture content of the atmosphere than would generally be be found where the rainfall is the same as that of Florida.

There are several diseases of oranges and grape fruit in Florida which I do not think we have in these islands, one of which, die-back, seems to be associated with excess of nitrogenous manures: one aspect of this disease is the production of worthless fruits known as ammoniated fruits. Root disease, which occurs in the

West Indies, does not seem to be known in Florida.

In applying fertilizers to citrus cultivations, potash and phosphates are mostly used, nitrogenous manures being used sparingly. The leguminous cover crops already mentioned supply a fair proportion of the nitrogen necessary.

When land is prepared for planting oranges or grape fruit, it is thoroughly ploughed and harrowed, and during the first few years it may be lightly ploughed or deeply harrowed. After the plants are well grown, and the roots have taken possession of the soil, no deep tillage is given. Weed growths or other covers are harrowed in in the early part of the year, and either the weeds allowed to grow, or another crop of beggar-weed is sown.

Before closing this report, I wish to express my appreciation of the kindness of l'rofessor P. H. Rolfs and of Professor H. S. Fawcett. Professor Rolfs took a great interest in my visit, and very kindly detailed Professor Fawcett to accompany me on the trip to Deland and Orlando. Professor Fawcett was most kind, and his knowledge of the field conditions, of the railways and time tables, and his personal acquaintance with orange growers and the managers of large properties, made it possible to accomplish a great deal more than I could have done otherwise.

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