eradication could be effected within a few years, but the migratory habits of the fly were not known at that time. It was soon found that there was no Spider Mites, Insects, way of preventing flies from moving into Texas citrus groves from north- and DDT eastern Mexico and that eradication was impossible. Research efforts were Howard Baker then directed toward developing ways and means of treating Texas fruit which would permit it to be shipped As recently as 1944, apple growers safely to other fruit areas. throughout the United States feared One method of sterilization consists that the codling moth would put them of lowering the inside temperature of out of business. Other insects and mites the fruit to 32^-33° F. and holding it were of comparatively little concern. there for 18 days, or keeping the tem- Today the situation is reversed. The perature at 33°-34° for 22 days. Either codling moth has been reduced to a will kill any larvae in the fruit. pest of minor importance and a num- The second method is more eco- ber of other insects and mites have nomical and more widely used in become problems. DDT is primarily Texas. Known as the vapor-heat proc- responsible for this reversal : It brought ess, it involves raising the inside tem- the codling moth under control, but perature of the fruit. Larvae can be factors associated with its use have killed much more quickly with high been responsible for some measure of temperatures than with low tempera- the resurgence of other pests. tures. In order to treat large quantities Others had had similar experiences. of fruit properly, specially designed Cotton growers saw the cotton aphid rooms are necessary; the rooms also increase following applications of cal- can be used during the regular pack- cium arsenate to control the boll wee- ing-house procedure for the coloring vil. Pecan growers have seen the black of fruit. Treatment consists of forcing pecan aphid increase following appli- a large volume of air, saturated water cation of bordeaux mixture to control vapor, and water in the form of a fine pecan scab. Citrus growers found more mist through the load of fruit, at a scale insects and mites after the use of temperature of not less than 110°. sprays to control diseases or to correct After the inside temperature of the nutritional deficiencies. fruit has been raised to that point, it is Never before, however, have so maintained there for the duration of many pests with such a wide range of the holding period. The process is then habits and characteristics increased to reversed and a large quantity of dry injurious levels following application air is forced through the load of fruit of any one material as has occurred in order to reduce the temperature as following the use of DDT in apple rapidly as possible and permit the fruit spray programs. to be packed for shipping. Losses due to the codling moth reached alarming proportions during P. A. HoiDALE began his career in the 1930's and early 1940's. Fortunate the Department of Agriculture with indeed was the grower who could hold the Bureau of Plant Industry in April them down to 10 or 20 percent of his 1915. In igiy he transferred to the crop. Much larger losses were not un- Federal Horticultural Board in the usual. Despite the use of stronger spray control of the pink hollworm. When mixtures and more frequent and the Mexican fruit fly w-as first found heavier applications, control became in the Rio Grande Valley, he was more and more difficult. The harder placed in charge of the cojitrol project. the orchardists fought the codling 562 Spider Mites^ Insects^ and DDT 563 moth, the harder it was to control and reasons most commonly advanced to the greater the injury it caused. The explain the situation. codling moth was so all-important that Many orchard pests are normally other pests received but scant attention. greatly reduced in numbers and held That was the situation when DDT was in check by natural enemies, particu- introduced to a discouraged industry. larly parasitic and predacious insects First tested by a few growers on a and predacious mites and spiders, that large scale in 1945, DDT became gen- feed on and destroy them. DDT is erally available to the industry in 1946. highly toxic to many of these natural It promptly proved its worth in check- enemies. It kills them off at a much ing the codling moth and soon dis- higher rate than it does some of the placed lead arsenate or other materials injurious species on which they prey. in most apple-insect spray programs. That is one reason why such pests as Timely, thorough applications of i or orchard spider mites, red-banded leaf 2 pounds of a 50 percent DDT wet- roller, and woolly apple aphid are apt table powder per 100 gallons of spray to develop in injurious numbers when in an average of three to six cover DDT is used in the spray program. Not sprays, depending on the region, all outbreaks of these and other species brought the codling moth under con- are associated with the use of DDT— trol. Growers who had become accus- other factors are involved, factors that tomed to losses of 15 percent or more we do not fully know or understand yet. of their crop are now dissatisfied with DDT is less effective against some losses of more than i or 2 percent. insects than materials it has displaced Many have losses of less than i percent. in apple spray schedules—materials DDT also controls other insect pests such as lead arsenate and mineral-oil on apples. It is effective against most emulsions, or their substitutes, that had leaf-feeding insects that attack apples a wider range of usefulness than to con- and pears, such as tent caterpillars, fall trol only the codling moth. This has wcbworms, Japanese beetles, casebear- led to increases in importance of some ers, leafhoppers, and, to some extent, of the insects that were controlled aphids. Some pests it does not control, through their use. It accounts some- at least not when used in ordinary, what for the increase in injury caused practical amounts. Some other pests by such insects as the plum curculio, seem to be even more serious follow- red-banded leaf roller, and San Jose ing the use of DDT than when it is not and Forbes scales. used. Various species of orchard spider mites, the red-banded leaf roller, and DDT AND THE changes in the com- some scale insects, pests formerly seri- parative importance of the insects and ous only occasionally or in restricted mites infesting apples that have oc- areas, have threatened to cause or have curred following its use have pro- caused serious injury more often than foundly affected apple spray schedules formerly and on a more general scale. and the trend of research to develop Additional insects, for instance the the simplest possible spray program. woolly apple aphid, plum curculio, and Attention used to be focused on finding yellow-necked caterpillar, have also in- and developing a material that would creased in numbers in some places. control the codling moth better than Why is this? lead arsenate. Now it is directed toward Several reasons have been advanced. working out a complete spray program Research might uncover others. The that will take care of all pests that may effect of DDT on the natural enemies be present. This means finding and de- of injurious species and the tendency veloping materials that can be used to omit materials, such as lead arsenate with DDT or substituted for it to con- and mineral-oil emulsions, from stand- trol such pests as mites, leaf rollers, cur- ard DDT spray programs are the two culios, aphids, and scales, as well as 564 Yearbook of Agriculture 1952 the codling moth. A great deal of prog- more likely to injure the trees than ress has been made. oil if used carelessly and not strictly according to directions. VARIOUS SPECIES OF MITES^ former- Another material that has given ly serious pests only occasionally or in good, early-season control of the spe- restricted areas^ came into the lime- cies of mites overwintering in the egg light along with DDT and have since stage is parathion. One pound of a 25 caused, or threatened to cause, serious percent wettable powder per 100 gal- injury each season in all important or- lons of spray in the calyx application chard areas. The most important are has given as good control of these the European red mite, two-spotted species as a 3 percent dormant oil. spider mite, and Pacific mite. The Parathion cannot be used safely on all clover or brown mite has increased in varieties so early in the season: it may Colorado and other western fruit- cause serious injury to Mclntosh and producing areas, and several new or related apples and increase russeting little-known species of Tetr any chus of other varieties, such as Golden De- and other spider mites have become licious and Jonathan. more important. For example, at least Dormant sprays are of little value 11 species of mites in 1952 were known against the two-spotted spider mite. to infest orchards in the Yakima Val- Pacific mite, and other species winter- ley of Washington; three of them were ing as adults. With some of these spe- recognized in that area for the first cies, this is partly because they feed on time in 1950. other hosts before moving into the Orchard spider mites may be di- apple trees. vided roughly into two groups for con- Recent research has aimed to de- trol purposes—those that overwinter velop safer, more effective materials in the ^gg stage on the trees and those for use in summer applications. Such that overwinter as adults in trash, un- materials have been badly needed to der bark scales, and in other protected combat the mite species against which places, mostly on the ground. The Eu- dormant sprays are ineffective as well ropean red mite and clover mite are as to control midseason or later out- in the first group. Most of the others, breaks of the species against which if not all, are in the second group. dormant sprays are used. Summer-oil Dormant sprays are quite effective emulsions, i to i .5 percent, and various against the overwintering eggs of forms of sulfur were formerly com- mites. They delay or obviate the need monly employed for the purpose but for summer sprays to control the sometimes caused injury and were not species that overwinter in this stage, always as effective as desired. depending on the timeliness and thor- The first promising substitute that oughness of their application and came into wide use against mites was whether weather conditions during the the dicyclohexylamine salt of dinitro-o- growing season are favorable for mite cyclohexylphenol (DN-i 11). Its tend- activity and development. Mineral-oil ency to cause injury when high tem- emulsions diluted to provide 3 or oc- peratures prevail and its failure to be casionally 4 percent oil in the dilute fully effective against the European spray are most commonly employed in red mite at safe strengths limit its dormant sprays applied to control usefulness. mites. Lime-sulfur is occasionally used; Many materials have been tested in it has some value but is less effective summer sprays against mites. A few than oil and is not generally recom- have proved their worth in enough mended unless needed for some other tests to justify recommending them. purpose. Some dinitro insecticides also The most promising ones include have shown promise for use in dormant parathion, tetraethyl pyrophosphate sprays against mite eggs, but they are (TEPP), 2-{p'tert-hutylphenoxy)'i- Spider Mites^ Insects, and DDT 565 methylethyl 2-chlorocthyl sulfite (Ara- in apple orchards following the use of mite), O-ethyl 0-jf?-nitrophenyl ben- DDT. It has long been widely distrib- zcnethiophosphonate (EPN), and 1,1- uted on many hosts, but is ordinarily bis ( /^-chlorophenyl ) ethanol ( DMC ). heavily parasitized. Rare indeed was Some growers prefer to include these the orchardist who knowingly had to materials in one or more of the regular contend with it until a few years ago. cover sprays applied to control the cod- Now it is a problem pest throughout ling moth in order to prevent the de- the Midwest and East, where in 1947 velopment of mite infestations. Other and 1948 particularly it caused severe growers prefer to withhold their use, damage in many orchards. A study of unless needed for other purposes, until the problem showed that including lead mites show up in sufficient numbers to arsenate in the first two or three cover require control. In the latter case, two sprays usually takes care of this leaf applications about 7 to 10 days apart roller for the season. Later studies re- may be required. Both systems have vealed the value of TDE, parathion, many advocates and both have advan- and EPN in controlling it. TDE is par- tages and disadvantages. Only further ticularly effective and valuable to com- research will prove which is superior. bat infestations during the summer Just when marked progress was be- whenever outbreaks threaten. Now the ing made in developing effective treat- red-banded leaf roller is a pest growers ments for mite control the problem of need no longer fear but one they must resistance attracted attention. Early in plan to take care of. 1951 recommended quantities of par- athion did not control the European THE WOOLLY APPLE APHID^ a pest red mite in Washington. Later in the widely distributed throughout all ap- season other species of mites, including ple-growing areas in the United States, some not previously suspected of being has been held in check by the parasite present, were not controlled satisfac- Aphelinus mail. This aphid is the insect torily and other promising new mate- that lives in the little cottonlike masses rials were not as cfTective as they had that are often seen around pruning been earlier. Still later reports indi- wounds and other scars on the trees cated that mites were becoming harder and in the axils of leaves on new to control in other areas—West Vir- growth, particularly on water sprouts. ginia and New Jersey. Possibly the or- It may also occur on the roots of the chard mites were developing resistance trees. A particularly important pest in to insecticides. That is not altogether the Pacific Northwest because of its surprising, because a resistant strain of connection with spread of the peren- the two-spotted spider mite has been nial canker disease, it is only in that reported by greenhouse workers. It is area that it has increased to serious apparent that the problem of orchard proportions following the use of DDT. mites is far from solved: We have to Presumably because of the effect of reexamine spray schedules ; find insecti- DDT on the Aphelinus parasite, the cides that do not lead to increases in woolly apple aphid is once again a pest mite populations to replace materials to be reckoned with in that area. whose use seems to favor such in- Formerly controlled with nicotine creases; determine the factors that sulfate when the parasite did not take affect the development of mites; and care of it, it can now^ be checked by put forth further efforts to find mate- including materials such as benzene rials that will hold in check all species hexachloride, parathion, or TEPP in of mites. an early cover spray, or controlled later with either of the latter two materials. THE RED-BANDED LEAF ROLLER is per- Benzene hexachloride may impart an haps second only to mites among the off-flavor to the fruit if used after the pests that have increased in importance early part of the season. 566 Yearbook of Agriculture 1952

THE PLUM GURGULIO, an important fruit pest east of the Rocky Mountains, is most commonly associated with stone fruits, particularly peaches and plums. On apples it seldom caused serious injury when the regular spray program included lead arsenate to con- trol the codling moth. Ordinary dos- ages of DDT do not control it effec- tively. Its jump in importance to apple growers dates from the time they changed their spray programs from lead arsenate to DDT. The best answer has been to include lead arsenate in the early-season part of the spray program, especially in the calyx and first-cover spray. For heavy infestations a spe- cial application between the calyx and first-cover spray is often desirable. Other materials show promise, but none seems to be superior to lead arse- nate for use against plum curculio on apples. Pacific mite.

APPLE GROWERS have known the applications have given complete pro- San Jose scale for many years, but few tection in tests in Indiana. A single were familiar with Forbes scale, which summer application of one-half pound is like it in appearance and habits. of 25 percent parathion per 100 gallons Many growers in the Midwest now are has given partial control of Forbes concerned with both species. Long scale on apples. held under control by the use of dor- mant- and summer-oil emulsions, the I HAVE DISCUSSED Only the pests that scales are growing in importance as the have created serious problems for years use of oil in the regular spray program and in important producing areas fol- steadily declines. lowing the use of DDT. Others, such Dormant-oil emulsions at ordinary as the yellow-necked caterpillar in strengths, usually 3 percent oil in the West Virginia, Virginia, and Mary- dilute spray, are highly effective land and mealybugs elsewhere, have against the San Jose scale but do not appeared for a season or two in limited seem to be so effective against Forbes sections, presumably (but not neces- scale. It appears that former wide use sarily) because of a direct or indirect of oil in summer cover sprays may have effect of the use of DDT. In general, had more effect in scale control than effective treatments have been devel- was generally recognized. oped promptly or adjustments made in Our experimental work has shown the spray program to control such out- that dormant sprays may not be neces- breaks, and they have not proved too sary to control either one of the scales serious. Other ordinarily minor pests if a material such as parathion is in- no doubt will appear in outbreak pro- cluded in the regular spray schedule. portions from time to time and require The minimum effective dosage of temporary or continuing adjustments parathion has not been determined, but to take care of them. But the apple one-fourth pound or more of 25 per- grower must be ever on the alert and cent parathion per 100 gallons in six his spray program must be a flexible applications or one-half pound in three one. The reader should not conclude that increases in importance of previously minor pests following the use of DDT have been confined to apples or that The Japanese Beede DDT is the only one of the newer in- secticides whose use has led to such de- velopments. For example, the use of Charles H. Hadley DDT has been associated with in- Walter E. Fleming, creases of mites on peaches, grapes, pe- cans, shade trees, and cotton; mealy- bugs on grapes; aphids on cotton; the Harry B. Weiss, who since became red-banded leaf roller on peaches and director of the New Jersey Division of grapes; and cottony-cushion scale on Plant Industry, found a few shiny, me- citrus. On the other hand, the use of tallic green beetles in a nursery near materials such as methoxychlor has Riverton, N. J., in 1916. He did not been followed by more mites on apples recognize them at first, nor did anyone and peaches and aphids on cotton. The else, but they were finally identified as use of parathion has been followed by Japanese beetles, Popillia japónica. increases of the soft scale on citrus. That was the first record of their occur- But all in all DDT on apple trees has rence in the United States. Entomolog- been more to blame than the others for ical literature contained little informa- outbreaks of pests that used to be of tion about them other than that they little importance. Despite the problems were common on the main islands of its use has created, DDT has been a Japan and were not considered a seri- great benefit to apple growers ; advan- ous pest. We knew httle about their tages resulting from its use far out- habits in Japan and nothing to indicate weigh its disadvantages. whether they would become serious in the United States. We did know that HOWARD BAKER is assistant division related beetles had caused considerable leader of the division.of fruit insect in- trouble in the Old World and in the vestigations. Bureau of Entomology other Pacific islands that they had and Plant Quarantine. He was gradu- invaded. ated from the University of Massachu- Apparently the beetle had come to setts in ig2S and joined the Depart- the United States with plants before ment immediately thereafter. After restrictions w^ere established by the various field assignments having to do Plant Pest Act of 1912. with apple and pecan insects in the The adult Japanese beetle is plump, East, Middle West, and South, he was shiny brown and green with 12 white transferred to Washington in 1944. spots, and about one-half inch long. It is seen only in the summer and may feed on 275 kinds of plants. Its white grub stage is in the ground, where it feeds on the roots of plants. The beetle does damage estimated at 10 million dollars a year to farm and orchard crops, residential and public ornamental plantings, lawns, and golf courses. Men in the Department of Agricul- ture began an investigation in 1917 to get information about its development and habits in its new home. By the end of that year it was obvious that the Japanese beetle. beetle had found ideal conditions for 567