350 Table 5.-Summary indicated. of greenbug field tests showing percentage TEsT 1 TREATMENT Dosage1 Per Cent Control 48 Hours Mter Treatment .81 66.6 .8il .5ft 89.8 90.4 l' Benzene l' Benzene Hexachloride Spray Hexachloride Dust Parathion Spray Parathion Dust Tetraethyl Pyrophosp~ate Spray Tetraethyl Pyrophosphate Spray2 Pounds active ingredients per acre. Spray applied when temperature was lower than when other "knockout." Parathion and tetraethyl pyrophosphate probably did give sufficient control to enable predators and parasites with favorable conditions to restore the natural balance and prevent another damaging increase of the pest. One field test indicated that parathion had greater residual toxicity than tetraethyl pyrophosphate but observations indicated that tetraethyl pyrophosphate was less toxic to ladybird beetles, important predators of greenbugs, than parathion. The degree of control obtained TESTil Dosage Per Cent Control 48 Hours Mter Treatment .38 .44 81.6 75.6 .11 .85 86.8 97.4 applications TEST 3 Pcr Cent Control IIours After Treatment Dosage 48 168 .'l8 6't.6 77.8 .19 76.0 tl9.4 .'l7 .5't 87.6 94.4 85.8 tl8.4 .'l6 61.3 58.5 were made in same experiment. with insecticidal applications seemed to depend to a large extent on the loeatioIl of the aphids on the plants when the material was applied. This was espeeially true when there was a mat of dead leaves at the base of the plants to shelter them. Low temperature seemed to be the most important factor in causing these insects to seek shelter. Sprays were mueh more practical than dusts for greenbug control because they could be applied effectively when the wind was relatively high. LITERATURE J. control following treatments CITED C. and H. A. Dean. 1950. Effect of climatic factors on the toxicity of certain insecticides. ECON. ENT. 43: 60il. JOUR. The Seasonal Behavior of Meadow Spittlebug and Its Relation to a Control Method C. R. WEAVER, Ohio Agricultural Experiment Station, Wooster The control of nymphs of the meadow spittlebug, Philaenus leucophthalmu8 (L.), by springtime applications of insecticides has some undesirable features that under some conditions prevent the legume grower from applying measures to reduce the damage done by these insects. Forage crop legumes grown for silage and for dehydration into meal are often cut early so that the harvest date comes too soon after the most timely date for effective applications of insecticides. Under any conditions in which the application of insecticides is unacceptable because of the residue hazard, present control meth- ods should not be applied. Late April and early May are usually busy times for the general farmer and weather conditions often limit the use of ground spraying or dusting equipment in legume fields at that time. With these facts in mind the author presents the following biological observations as being of interest to those concerned with alternate methods of control of the meadow spittlebug. The spittlebug apparently does not lay its eggs indiscriminately in fields of forage legume crops of different ages. Observations by the writer have revealed that Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016 1 2 Gaines, Vol. 4.4, No.3 JOURNAL OF ECONOMIC ENTOMOLOGY June 1951 351 WEAVER: CONTROL OF l\IEADOW SPITTLEBUG . Table I.-Mean number of well formed eggs dissected from each of 10 female spittlebugs. NUMDEU OF EGGS DATE PER FEMALE August 24 September 1 September 11 September 13 October 2 October 19 November 2 3.2 10.5 ~O.6 ~O.6 17.7 20.2 21.1 within a few days so that the check and treated populations soon equalized. It must be remembered, however that such applications have been made t~ seed fields and not to the newly seeded meadows which will receive the major infestation the following year. During June and July, the n~w meadow is covered with a grain crop which is not removed until July and ~ometimes early August. Except for tranSIent hordes of newly emerged adults in June, migrating away from the newly cut first year fields, the grain fields have few adult insects present until the ne.w legume seeding starts to produce a faIr!y abundant foliage. Figure 1 shows typIcal adult populations in a first year meadow and in a new seeding. During late July and August the adults will be found in largest numbers in meadows wher~ the vegetation is flourishing. The data m the figure were taken from a field left for a seed crop where there is a natural decline of green succulent foliage as the season progresses. Plants in the new seedings recover from the grain harvest sometime during August, depending upon whether or not the grain stubble is clipped and removed. As the foliage becomes more luxuriant, the adult numbers gradually increase until about the first of September, when there is a tremendous increase suggesting that large numbers of adults are migrating into the newly seeded fields. The author's experience with spraying for adult spittlebug control has paralieled that reported by other workers. Sprays applied in June, July, and August m~y result in large initial reductions, but in te!l days ~otwo weeks an almost complete rcmfestatlOn rcsults. New secdings with sprays applied in early August show tIle same tendency to reinfestation as do old I First, second, and third ~'ear designations cate the year or harvest. arc applied to indi- Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016 in northl.'rn Ohio thl.' insect usually does not appear in I.'conomically important numbprs in sl.'cond and third year meadows..1 The important damage is usually done m thl.'first year fields. This indicates that thl.' bulk of thl.' I.'ggs must be deposited in tht' nt'w st'e-dings. To obtain data on the comparative populations in the first, second and third ye-ar fidds, sWl.'epsamples ~ere taken from such fields on June 12 when a large perce-ntage of the adult insects had ellll.'rge-dfrom the spittle masses and migration frOl~l the field had not yet startl.'d. In .thls case, the plots sampled were a pOl'tlOnof a field rotation eJ\:periment and were locatt'd side by side in blocks so that during the previous year tl~(' adults would havt' had an opportuIllty to lay I.'ggsthroughout the block uniformly. The adult populations as measured by the swe-e-psshould be indicative of thc rdativc number of eggs placed the-re the ye-ar bdore-. Adult spittlebugs pe-r swe-e-pof a 15 inch net for the three type-s of ml.'admv wl.'rl.':first year, 18.1, sl'eond ye-ar,2.9, and third year, 0.9. This indicate-d an owrwhelming tendency for lhe populations to occur in the first year meadow. l\Iundingl.'r (1946) states that on grass Philaenllsleucophthalmus commonly places the I.'~gmass in the axil betwecn leaf and st(,Ill and C('lll('nts the leaf over it. The tl.'lllklley to lay t'~gs in crevices between plant portions makes wheat and oat stubble an ideal egg laying medium. The author has obse-rved that eggs are most readily found on grain stubble and only oeeasiollally on legume stubble and gree;" plant parts. The eggs are inserted between the dead leaf sheath and the stem. If the grain stubble serves as a more attractive oviposition site, then the first y:ar meadows, seeded to grain the prenous Yl.'ar,would be most likely to recpive the majority of the eggs. Reduction of the succeeding year's nymphs by control of the adults has not prt'sented a promising approach to the eoutr?l problem bl.'causeof the rapid reinf('statIon ?f treat.ed fields. Wilson (1949) reported httle resillual effect of DDT upon adults four wel.'ks aIte-r treatment applied on July 12. l>ielou (1950) showed immediate reductions of adults bv DDT applications in .Junc and Julv 'but in ncarly every case reinfestatiOI~'occurred 352 U) z .. AVGusr 1<'IG. J '0/. 44, Xo, :1 JOURNAL OF ECONOl\IIC ENTOMOLOGY I.-Spittlebug SEPT£MSER OCT()8ER populations in two Iegullle fields. ~ .8 ::: a. .6 It 4 :;J... .2 .. ... 1949 TReATED 8.19 9-2 TREATED 12 ., 24 • 12 ·Ie 24 , IE II Z => o ...• ~ ...• 1.0 8 := .6 ~ 4 ~ 2. 1950 Q! Ie 'I AUGUST FIG. 14 • It II t4 SEPTEMBER • It II OCTOBER ~.-Time of treatment and recovery of spittlebug populations. Ratios from three sprayed populations in 1950 and two in 1949 arc shown. In 1950, the population in the plots treated August 9 soon recovered to equal that of the check. Populations of plots treatel[ on September 2 and 13 never recovered. In 1949, the data from figure 2 show that adult spittlebug populations in plots treated on August 19 reeovcred to :some extent but never equalled the eheek while those treated on September 2 neVl'r recovered. Because of the distributional nature of the ratios involved, ordinary statistical tests of the recovery rates arc not applicable. Mr. Paul ::\loranda, Statistical Laboratory, Ohio State University,l suggested and applied a non parametric test described by Mann (1945). Two uses arc made of this test. The first is for detecting whether or not the ratios of tl'eatell and untreated populations associated with a fixed interval of time after the spray date (e.g. 1-10, 11-20 ... 61-70 days after the spray date) decrease as the date of spraying becomes later. The second usc of the test is for detecting whet.her or not for It given field the ratios tend to increasl' with time following treatment. According to Mr. l\foranda's computation and interpretation there was evidence of a downward tn'nd in ratios associated with a fixed inten'al of time afte!' the spray date as the date of spraying Theassistance ofDonald R. Whitneytheslutiulie.llr"ulmentisgratefully aeknowledged. 1 ill Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016 and the field will not become reinfested. The adults apparently move over large areas during the period prior to September. After their migration into new seedings where the eggs are to be laid they do not move about enough to cause serious reinfestations of plots from which th('y have b('('n eliminat('d. Data to support the belief that spittlebugs readily infest fields treated in August and do not reinfest fields treated during September were collected from three fi('lds in each of the years 1949 and 1950. All tests were replicated in randomized blocks with plot sizes of 100 by 100, 200 by no, 70 by 90, 90 by 90, and 50 by 100 feet. Treatment dates in 1949 were August 8, 19,30 and September 2 and 19. Treatment dates in 1950 were July 27, August 10, 12, and September 2, 3, 13, and 20. The effectiyc insecticides used were DDT and methoxychlor at concentrations varying from 1 to 2 pounds of the technical material per acre. Both materials gave good initial reductions of the adult populations. Sweep samples were obtained from both treated and untreated plots at varying int('rvals of time aft('r treatment. Most plots were swept weekly through October, although the time interval varied due to the weather and other factors. At least 50 and usually 100 sweeps were made in each treatment at ('ach sampling. The ratio of populations in the treated plots to those in the untreated plots ,vas then computed and the increase in this ratio used as a measure of reinfestation. To conserve space, only a typical portion of the data is pres('nted. In the graph (Fig. 2) the ratios of treated to untreated populations are plotted against time. I ~ II: o will reduce the population CHECK. .... I- lll('adows. Data collected in 1949 and 19.50 at 'Vooster, Ohio, show, however, that an application of insecticide during the last week in August or in September 1.0 June 1951 "rEAVER: CONTROL OF l\fEADOW SPITTLEBUG 353 to August 24. On August 24 a total of 32 well formed eggs were found within 4 of 10 females dissected. Table 1 shows the numbers of ('ggs found on seven different dates. Apparently maximum egg development is reached during the first 10 days in September and is maintained until cold weather kills the insects. Probably no oviposition occurs prior to the development of filature eggs, therefore it seems reasonable to assume that adult female spittlebugs do not lay substantial numbers of eggs until September under Northern Ohio conditions. Since the development of eggs of the spittlebug is coincident with the lessening nomadic activity of the insect, one insecticide application, timed to take advantage of these events, should result in good control of the species by reducing the number of eggs laid and the subsequent nymphal infestation the following spring. The efficacy of such treatments will be reported in another paper. SUMMARY.-cndernorthern Ohio conditions, heavy populations of adult spittlebugs build up in newly seeded legume fields during the last of August and the first of September. The majority of eggs are laid in the newly seeded fields which have a residue of straw and stubble from the grain harvest. Control measures applied to fields prior to the September build-up are ineffectual because of reinNew York. The author has never observed spittle- festation from surrounding untreated bug eggs in the field prior to September. areas. Little or no reinfestation occurs if The fact that none w{'reobserved docs not insecticides are applied after the last of ('onstitute proof that they are not present August. The development of eggs within in the field before that time. Dissections the female is simultaneous with the adult of adult females were made by the author migration into the new seedings. These during th{' summrr and fall of 1950 to facts should be useful in timing the treat(lrtermine when the eggs developed within ment of fields containing egg laying adults the female. No welI formed eggs were as a means of reducing the resulting found within any dissected females prior nymphal populations. LITERATURE CITED Mann, H. B. 19·'5. l'\on parametric tpsts against trend. Econometrica 13(8): 245-59. Mundinger, F. G. 1946. The control of spittle insects in strawberry plantings. JOUR. EeON. ENT. 39(S): ~99-S05. Osborn, Herbert. 1916. Studies of life histories of frog hoppers in Maine. :Maine Agr. Expt. Sta. Bul. 254. Pielou, D. P. 1950. The effect of insecticide applications on the insect fauna and seed yield of alsike e1oVl'r in southern Ontario. Can. Ent. 82(7): 141-60. Wilson, M. C. 1949. Orglmic insecticides to controlllifalfa insects. JOUR. EeRN. ENT. 42~8): 496-8. Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016 brcoJlles later. An exception to this occurr{'d. No downward tr{'nd was noted in the interval of tinw 1 to 10 days following treatn1f'nt. This indicat{'d that all the treatments probably reduced the populations to about the same level and that this level is maintained for a short time after treatnwnt. The second usc of the test showed an upward tr{'nd in the ratios, indicating that reinfestation occurred, in the fields sprayed August 19 or before. Fields trcatrd August 30 or later showed no such tr{'ud. lJolh applications of the test support the ('oujeeture that the later the spray date thc less reinfestation of the plols. The fact that adult spittlebug populations can be reduced and maintained at a low levrl by one application of insecticide in late August or early September would b{' of no practical value if substantialnumbers of the eggs of the insect were laid prior to that time. Osborn (1916) did not observe any spittlebug eggs being laid through the month of August in Maine. lie stated that well developed eggs \wre not found in dissected specimens before August and that by the middle of August only occasionally are eggs with well formed shells to be found within the females. Mundinger (1946) reported that oviposition began in July but was most int{'nsivc in 5f'pt{'mber and October in