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Plants deficient in nitrogen and phosphorus were less favorable than normal plants for the two-spotted spider mite, Tetranychus urticae (Koch), but were more severaly damaged by the mite increases. Added amounts of nitrogen, phosphorus, and potassium in the soil, and various foliar nutrients did not appreciably affect the mites. Also, various fungicidal sprays and heavy residues of insecticide and fungicides in the soil had no marked effects on egg laying or mortality of the mites on peach seedlings. Egg laying was greatly suppressed by the antibiotic fungicide cyclohexamide. Carbaryl and DDT did not stimulate egg laying; therefore such applications do not account for increases in mite populations observed to follow orchard treatments with these materials. Carbaryl had no appreciable effect on mortality of the two-spotted spider mite, but was very toxic to its important predator, Typhlodromus sp.

In laboratory tests, single-plant outdoor tests, and field tests with artificially infested lettuce plants, dusts containing toxaphene-DDT, DDT, TDE, dieldrin, endrin, and toxaphene were usually more effective against the corn ear worm ( Heliothis zea (Boddie)) than the other materials tested. The toxicity of toxaphene-DDT dust decreased with increase in size of the larvae.

Egg laying of the two-spotted spider mite, Tetranychus telarius (L.), was found to be inhibited by fairly low concentrations of a number of antibiotics. Although data are not given, similar results were achieved with the European red mite, Panonychus ulmi (Koch). Listed in the apparent order of their effectiveness, these antibiotics were: cycloheximide, streptovitacin A, antimycin A, hygromycin B, and amphotericin B. Amphotericin A and several derivatives of cycloheximide were also fairly effective in suppressing egg laying of both species. Cytovirin was as effective against the European red mite as previously reported against the two-spotted spider mite. At the higher concentrations, especially with antimycin A, the antibiotics also caused some mortality of the adult mites. The antibiotics seem to interfere with some process in the division and growth of the egg cells. The more active materials were phytotoxic and especially injurious to apple and pear trees. Cycloheximide at 50 and 100 p.p.m. gave good control of the two-spotted spider mite in field tests on mature peach trees without appreciable injury to the foliage. The more active antibiotics were obviously systemic in the leaves. Cycloheximide was not systemic in soil treatments and in spray oil or ethylene glycol was not appreciably translocated to the leaves when painted on the trunks and basal limbs. Several antibiotics, including cycloheximide, moved to the leaves when injected into the trunks of peach seedlings in the greenhouse. Cyelohximide, when used with different surfactants or added to some of the more common insecticide sprays, was also active in suppressing egg laying of both species of mite.

Studies of the effect of temperature have shown that insect oviposition is limited by definite temperature extremes within which the rate of egg laying is accelerated to a maximum and then is retarded by increasingly higher temperatures. Other work has shown that the acceleration of different biological processes may vary in proportion to the temperature or according to more complex relationships. For this reason a quantitative analysis of the relative effect of different temperatures is generally essential in the proper measurement and interpretation of temperature as an environmental factor and also has an important relation to different theories on the nature of the effect of temperature on physiological processes. Since the effect of the same number of degrees difference in temperature may vary in different portions of the temperature gradient, the relations must ordinarily be determined by experimental studies of the relative influence of different intensities or controlled degrees of temperature. The fact that different temperatures may exercise a disproportionate effect shows that serious limitations may be involved in the analysis of variable temperature data in terms of mean temperatures. Curvilinear relations may be obscured and a spurious appearance of linearity may be produced, since in the use of mean temperatures in correlation there is a tacit assumption that temperatures above and below the mean are proportional in effect, as would be expressed by a straight-line graph.

Various antibiotics and some other compounds were tested as insecticides and chemosterilants on adult female codling moths, Carpocapsa pomonella (L.). These were applied topically to the ventral abdomen or by injection with a microsyringe. Novobiocin was extremely toxic in several tests, killing all the moths treated with dilutions as low as 150 ppm. Egg laying was reduced significantly by a few antibiotics, but most of them had no effect on egg laying or on moth mortality.

The historical development of studies of insect growth has been well reviewed by Calvert (1929). Bodenheimer (1927, 1932, 1933) and Ludwig (1934) have discussed many of the available data in relation to the Dyar rule and the principle of Przibram. The present discussion is concerned chiefly with measurements of several species of Cicadellidae and an analysis of these and other data from various sources in relation to these theories.

In greenhouse tests with the two-spotted spider mite, Tetranychus telarius (L.), the antibiotics cytovirin, cycloheximide, and streptovitacin A were effective when injected into peach seedling stems and sprayed on leaves. Cyclohcximidc was not effective when sprayed on trunks and limbs of peach seedlings or applied in bands of paste on limbs of mature apple trees. Trunk injections and foliar sprays of cycloheximide were effective also against peach silver mite, Aculus cornutus (Banks). Solutions of such water-soluble compounds as trichlorfon and methyl demeton moved rapidly to leaves of pear and cherry trees and gave good control of two-spotted spider mite. Water-insoluble compounds moved to leaves of cherry trees when injected in trunks in emulsions and in solution in dimethyl sulfoxide and some other solvents. Many solvents and solutions were phytotoxic at dosages used and caused considerable streaking or uneven distribution in different tree limbs owing to a much more rapid longitudinal than cross movement of materials from the injection site. Distribution was not improved when solutions were injected into a large tree root. Good control of pear psylla, Psylla pyricola Forster, was obtained in biotests of adults on pear leaves 2 weeks after trees were injected with Bidrin® (3-hydroxy-N,N-dimethyl- cis -croton-arnide dimethyl phosphate) and Bayer 47043 (O,O-dimethyl-S- (N,N'-dimethylmalonicamide) thiophosphate). Trunk injections of dimethoate emulsions and some water solutions of other compounds gave control of the green peach aphid, Myzus persicae (Sulzer), the apple aphid, Aphis pomi DeGeer, and the woolly apple aphid, Eriosoma lanigerum (Hausmann).

Egg laying of the two-spotted spider mite, Tetranychus urticae (Koch), was effectively inhibited by the antibiotic actinomycin D, especially in the first 3 days after treatment, when there was no significant effect on mortality of the adults. After 7 days, the material was significantly acaricidal. Other antibiotics such as pactamycin, novobiocin, ampicillin, anthelmycin D. sarkomycin, humulon, puromycin, Carzinophilin® (from Streptomyces sahachiroi ), and mitomycin C were significantly toxic to adult females (mortalities of 76–100% in 7 days). Most of these antibiotics evidently caused some suppression of egg laying at lower dilutions that were sublethal to some adults. Some purine and pyrimidine derivatives and some dye compounds had no marked effects on the mites.

In tests of several antibiotics on the green peach aphid, Myzus persicae (Sulzer), reproduction (viviparous) was significantly inhibited in various degrees by cytovirin, cycloheximide, antimycin A, actinomycin D, pactamycin, hygromycin B, ampicillin trihydrate, vancomycin, fungichromin, and some other chemicals. In tests of a group of synthetic materials, 2-thiouracil and apholate caused some inhibition. Of these materials, the autibiotics novobiocin and anthelmycin werc notably toxic to the aphids.

Egg laying by the two-spotted spider mite ( Tetranychus telarius (L.)) was strongly inhibited by cycloheximide (3-[2-(3,5-dimethyl-2-oxyeyclohexyl)-2-hydroxyethyl] glutarimide), an antibiotic useful against powdery mildew and some other fungous diseases. This inhibition occurred on peach, pear, apple, and rose leaves. The mites were also suppressed on apple leaves when cycloheximide was combined with Sevin® (1-naphthyl methylcarbamate). This antibiotic is systemic, and mites on potted peach trees were controlled by 25 to 200 p.p.m. for 2 to 6 weeks, the period of protection increasing with the concentration. Another antibiotic, cytovirin, a material extremely hazardous to handle, was about equal to cycloheximide in suppressing egg laying, but several other antibiotics, including derivatives of cycloheximide, showed much less or no activity. Both cycloheximide and cytovirin are phytotoxic at low concentrations. Pear seedlings were much more susceptible than apple and peach plants which were not injured in greenhouse tests by levels effective for the control of mites.

A number of antibiotics, including some known to be toxic to and to suppress egg laying in orchard mites, were tested as sprays at different concentrations for toxicity and sterilizing effects on the green peach aphid, Myzus persicae (Sulzer), the apple aphid, Aphis pomi DeGeer, and the pea aphid, Macrosiphum pisi (Harris). In tests on the green peach aphid, cytovirin (from Streptomyces sp.), cycloheximide (3-[2-(3,5-dimethyl-2-oxycyclohexyl)-2-hydroxyethyl]glutarimide), streptovitacin A (3-[2-hydroxy-2-(5-hydroxy-3,5-dimethyl-2-oxocyclohexyl) ethyl] glutarimide), antimycin A (7-hexyl-3-(2-hydroxy-3-foramidobenzamido)-4,9-dimethyl-1,5-dioxa-2,6-dioxo-8-(iso-valeroyloxy) cyclononane), and hygromycin B (from Streptomyces hygroscopicus (Jansen) Waksman & Henrici) were definitely insecticidal. The other compounds were only slightly toxic or had no effect. Plssible sterilant effects of the more active antibiotics were not shown because of their toxicity and those with lower or no toxicity did not show any marked sterilant effects although the number of progeny was generally less than in the untreated control. Similar effects of some of these antibiotics were shown in tests on the apple aphid and the pea aphid.

During the first years after appearance of the pear psylla, Psylla pyricola Forster, in the State of Washington (between 1939 and 1947), nicotine as the best available material was generally used in summer sprays for control. Subsequently, new organic insecticides, as they were found superior to nicotine, were recommended and widely used. As the psylla developed resistance to one after another of the insecticides in use, these were superseded by still newer insecticides. Parathion and related materials were highly effective for control from 1947 until about 1955 to 1957. Dieldrin came into wide use against psylla in 1957, but resistance to it and related materials developed rapidly (Harries and Burts 1959). In 1959, Guthion® ( O,O -dimethyl 5-(4-oxo-1,2,3-benzotriazin-3(4H)-ylmethyl) phosphorodithioate) was recommended and remained highly effective for about 2 years. In 1961, 3 applications failed to effect control in an orchard at Gleed, Wash. When adult psyllids from this orchard were tested in the laboratory, their LD50 was 6.47 lb of 25% Guthion wettable powder per 100 gal of spray, as compared with an LD50 of 0.02 lb for adult psyllids from an unsprayed orchard. In August 1961, randomized field plot tests with Guthion in this orchard also failed to show satisfactory control.