Unsprayed Trees Research Articles

Resurgence of the Scale, Fiorinia externa (Homoptera: Diaspididae), on Hemlock Following Insecticide Application

When thoroughly applied to the entire crown, dimethoate 2E insecticide can provide excellent control of Fiorinia externa Ferris (Homoptera: Diaspididae), a destructive scale insect of Eastern hemlock, Tsuga canadensis (L.) Carr., in the northeast (U.S.). However, incomplete application of this insecticide, a likely occurrence when treating forest hemlock, favors the resurgence of scale populations. On sprayed trees, F. externa had a faster rate of development and was more fecund than on unsprayed trees. Also, application of the insecticide, even on trees where only one side of the crown was treated, virtually eliminated the parasite, Aspidiotiphagus citrinus Craw., and 3 species of predators from the entire lower crown. Increased rate of growth and fecundity of F. externa and reduced mortality from natural enemies following insecticide treatment will facilitate the resurgence of populations of the scale on hemlock. The relationship between nutritive quality of the host plant and resurgence of post-spray populations of F. externa is discussed.

An Ecological Study of Phytoseiid and Tetranychid Mites on Walnut in Tulare County, California

Mite populations were monitored for a 3-yr period in an 8 ha walnut orchard which, except for a 2 ha corner, was sprayed once annually with azinphosmethyl for codling moth, Laspeyresia pomonella (L.). European red mite, Panonychus ulmi (Koch), reached maximum densities in July each season and was generally highest in the unsprayed block. Twospotted spider mite, Tetranychus urticae Koch, was never abundant. Typhlodromus occidentalis Nesbitt was the prevalent phytoseiid mite species on the unsprayed trees, and showed the greatest numerical response to increases in spider mite populations. Typhlodromus citri Garman and McGregor was generally the most abundant phytoseiid on the sprayed trees. Neither of these 2 species was severely reduced by the azinphosmethyl sprays. Typhlodromus caudiglans Schuster and Amblyseius hibisci (Chant) generally comprised a small proportion of the phytoseiid population, and both were adversely affected by azinphosmethyl sprays. Hanging walnut husks and coverings of dead scale insects were major overwintering sites for T. citri and T. occidentalis , respectively. In another unsprayed orchard surveyed in 1974, twospotted spider mite populations increased to more than 30 mites/leaflet. Here, European red mite and phytoseiids were scarce, and the sixspotted thrips, Scolothrips sexmaculatus (Perg.), was considered the major predator of twospotted spider mite.

Virginia Polytechnic Institute & State University Shenandoah Valley Research Station Steeles Tavern, Virginia 24476 European Red Mite Control on Peach, 1976

Abstract The commercial planting at Lovingston, Virginia, in which the tests were conducted, was planted in 1963 and set 15 feet between trees and 22 feet between rows. Due to complete freeze out of buds in March there was no crop and no commercial spraying was done in this orchard in 1976. All treatments were applied randomly in each of three rows. Unsprayed guard trees were left between each treatment tree and an unsprayed guard row was left between each treatment row. All applications were applied with an adjustable hand gun at 250 psi to the point of run off. Sprays were applied on May 12, 1976 and May 20 to single tree plots replicatec 3 times. Mites and eggs from 25 randomly selected leaves/tree were counted microscopically on the dates indicated after brushing from the leaves according to the Henderson-MacBurnie method. Data on the abundance of rust mite, Eriophyidae spp on the treatment trees was collected and analyzed for the August 3 sampling date. Data were tabulated as mites per leaf, or eggs per leaf, and subjected to analysis of variance.

Effects of Dissemination of Low Dosage Levels of a Granulosis Virus in Populations of the Codling Moth1

Relatively low dosages of a granulosis virus of Laspeyresia pomonella (L.) were disseminated in an Ohio apple orchard in 1974. Dosages of 107 (1/500 larval equivalent (L.E.), 108 (1/50 L.E.), and 109 (1/5 L.E.) capsules/tree sprayed during the 2nd generation reduced population levels by 0, 42, and 34%, respectively. Infestations also were reduced by 28% with a dosage of 109 capsules/tree. Larval populations were affected before entry, soon after entry, and after deep entry into apples. From 15–30% of the larvae in apples harvested from unsprayed trees were infected with granulosis. Apparently, virus increased and spread in the orchard after dissemination.

The control of apple canker (Nectria galligena) in a young orchard with established infections

SUMMARYIn a factorial experiment on canker control the efficiency of phenylmercurie nitrate (PMN) applied at leaf fall, before bud burst or both was compared with the application of dodine, dithianon, triforine, thiabendazole, benomyl or carbendazim in May and June. Of the total number of cankers which developed in unsprayed trees 76–78% resulted from infections in April to August of each year of the experiment. Infection was reduced significantly by all of the fungicides applied in summer. Of these carbendazim was outstanding, controlling both summer and autumn infections. Sporulation throughout the summer was suppressed by carbendazim and to a lesser extent benomyl, but whereas the suppressant effect of carbendazim persisted until long after leaf fall that of benomyl was evident only until August. Dodine, dithianon, triforine and thiabendazole had no significant effect on spore production. Dithianon and dodine showed highest toxicity to the germination of Nectria galligena spores of all fungicides used in summer. All of the fungicides controlled apple scab (Venturia inaequalis) although thiabendazole was the least effective.Autumn applications of PMN reduced canker incidence but their value alone was not as great as carbendazim, dithianon, benomyl or dodine applied in summer. PMN applied in spring reduced the number of cankers in trees receiving no other fungicides but tended to increase the incidence of infections, particularly in autumn, when used in conjunction with fungicides applied in May and June. PMN applied before bud burst reduced sporulation of N. galligena for a few weeks, after which production resumed and in late summer and autumn actually exceeded the controls. None of the fungicides had any direct effect on leaf fall.Infection of the crotch and basal leaf scars was more common in summer than in autumn whereas infection of leaf scars above the basal region was more common in autumn than in summer. The rootstocks of many of the trees became infected via callus tissue associated with adventitious root development and this was controlled by the carbendazim treatment.

Release of Carbaryl-resistant Predatory Mites in Apple Orchards

Carbaryl-resistant Neoseiulus fallacis (Garman) were released into apple trees sprayed with carbaryl and also into unsprayed trees. Both laboratory and field tests confirmed that the resistant predatory mites became established in one season in carbaryl-sprayed trees while resistance was greatly decreased in populations where the trees were not sprayed with carbaryl.

Effects of Some Fungicide Treatments on Earthworm Populations and Leaf Removal in Apple Orchards

SummaryThe persistence of leaf litter in apple orchards sprayed with benomyl prompted surveys to examine the effect of fungicide programmes on earthworm populations and leaf removal. Earthworm populations were unaffected by captan with bina- pacryl sprays, but under trees sprayed with benomyl they were significantly lower than under unsprayed trees. The effect of benomyl increased with the number of sprays.Populations recovered when benomyl sprays were discontinued but some residual effects were apparent after three years. Thiophanate-methyl was also found to reduce earthworm populations.Thiophanate-methyl and carbendazim retarded leaf removal and there was a similar but less marked effect with ditalimfos and captan with binapacryl sprays. Leaves sprayed with carbendazim were slow to disappear when over wintered on untreated soils. This result, and those with captan with binapacryl, suggest that fungicides may influence the rate of leaf removal independently of any effects they may have on earthworm populations.

Laboratory and Field Tests of Insecticides against Douglas Fir Seed Wasp (Megastigmus spermotrophus Wachtl)

SUMMARYTests were made to select insecticides which would kill adult seed wasps in crowns of cone‐bearing Douglas ftr trees. In the laboratory, gamma BHC, malathion and diazinon were found to be active against females. In further tests, on males and females, gamma BHC and malathion were active when the insects were allowed contact with treated surfaces; fenitrothion was less active. The effectiveness of gamma BHC was partly due to fumigant action whereas malathion and fenitrothion had no fumigant effect. In separate field experiments between 1962 and 1966 in Kent and Herefordshire, gamma BHC and fenitrothion gave no control but malathion gave good control. In 1968, trees in Kent to which malathion was apphed three times at 10‐day intervals during June had about 13 per cent infestation of potentially sound seed, when assessed in September, compared with about 45 per cent infestation on unsprayed trees. Malathion plus gamma BHC did not further reduce infestation.

Phenology and Host Relations of the Codling Moth in a Three-Generation Climate12

Seasonal population movement of Laspeyresia pomonella (L.) on unsprayed apple and pear trees were traced with the help of band traps, emergence cages, and a BL trap. The 1st generation was well synchronised with pear and early local apple, but not with introduced commercial apple varieties. Pears were harvested before the main onset of diapause at the end of July. The mean percent of infested fruit per tree was 69.5 and 57.0 for ‘Golden Delicious’ and ‘Orleans’ apple varieties, respectively, and the difference was highly significant. The coefficient of association for percent infested fruit on numbers of fruit per tree was 0.350 and 0.187 for Golden Delicious and Orleans, respectively. The mean relation of donor fruits to mature larvae trapped per tree was 0.5 and 0.6, and the coefficient of association between numbers of donor fruits and percent larvae trapped per tree was −0.11 and 0.29 for Golden Delicious and Orleans, respectively.

Contributions to the Bionomics of Climbing Cutworms: The life History and Seasonal Development of Eupsilia morrisoni12

The seasonal and geographical distribution and developmental biology of Eupsilia morrisoni (Grote) are described. This species overwinters as an adult and has one generation each year. Head-capsule measurements indicate 6 larval stages. This common noctuid ranges from Nova Scotia west to North Dakota, north to southern Quebec, and south to southern Ohio. Moths are active shortly after sundown when temperatures arc above 52°F in the autumn, winter, and spring. Although larvae are sometimes common on unsprayed deciduous fruit trees at bloom, they apparently do not cause economic injury.

CONTACT AND RESIDUAL EFFECT OF LOW-VOLUME DOSAGES OF PHOSPHAMIDON TO CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE) ON TWO SPECIES OF CONIFERS

AbstractA series of low-volume spray treatments were conducted to study the contact and residual effect of two concentrations of the insecticide phosphamidon to fourth instar spruce budworm, Choristoneura fumiferana (Clem.), on balsam fir, Abies balsamea (L.) Mill, and red spruce, Picea rubens Sarg. Treatment of sprayed larvae on sprayed trees, unsprayed larvae on sprayed trees, and sprayed larvae on unsprayed trees, resulted in two principal conclusions: (a) Higher concentrations of phosphamidon (1% versus 0.5% active) accelerated mortality in all instances and (b) no statistical difference (P = 0.1%) was found in the final mortalities between treatments in which only the foliage was treated and where both larvae and foliage were treated with phosphamidon.

An insecticide and a defoliant evaluated for use in a program of integrated control designed to suppress the green peach aphid on peach trees.

Endosulfan or Shed-A-Leaf® (sodium chlorate) sprayed on peach trees in autumn significantly reduced the number of overwintering eggs of Myzus persicae (Sulzer), compared with unsprayed trees. However, the effects of the 2 treatments were not significantly different. From inspection of tree bands and leaves, endosulfan was not toxic to phytoseiid mites but was toxic to syrphid larvae. Shed-A-Leaf was not toxic to syrphid larvae, but fewer phytoseiid mites were found under the bands of trees sprayed with the defoliants. These chemical agents could therefore be fitted harmoniously into an integrated program that involves use of these natural enemies in a specific type of orchard of peach trees to suppress the population of green peach aphids.

Effects of fungicides on the populations of Colletotrichum and other fungi in bark of coffee*

SUMMARYThe effects of copper, captafol and Tuzet, applied to coffee in early season (January to April) and in other programmes continuing through the long rains (January to July), on the bark populations of Colletotrichum cofleanum Noack. (the pathogenic CBD strain and the saprophytic ccm, cca and ccp strains), Phoma spp., Fusarium stilboides Wollenw. and a Phomopsis sp. were investigated on branch material from field experiments in Kenya in 1968 and 1969 by a plating technique which estimated sporulating capacity (s.c.)Fungicide application initially caused a non‐specific reduction in s.c., Tuzet being the most effective. With the onset of the long rains this general reduction was not maintained, although during the period between the long and short rains the levels of many fungi in sprayed plots were still below those in the unsprayed control. In contrast, the s.c. of Phoma in plots sprayed with copper and of Phomopsis in those sprayed with Tuzet were higher than on unsprayed plots. The S.C. of the CBD strain was below that in the control only in plots sprayed with captafol.Effects were still evident after the short rains. Some early‐season programmes of all three fungicides increased the s.c. of the CBD strain while continuing programmes of copper and captafol reduced its S.C. relative to that on unsprayed trees. Differences in S.C. at this time were related to infection in the early crop a few weeks later.The initial antisporulent effect of a fungicide appears less important than its persistence and its effect on bark colonization by the different fungi. Early‐season sprays of copper, formerly used to control CBD, may have contributed to an increase in disease hazards by affecting the primary level of the pathogen.

The Effects of Simulated Rain and Dew on Fluoride Accumulation by Citrus Foliage

Abstract ‘Valencia’ orange trees subjected to a drenching shower twice a week or sprinkled daily with a fine water spray until their leaf surfaces were thoroughly wet were found to accumulate less fluoride than unsprayed trees when exposed to low concentrations of HF gas. In the early stages of leaf development the drenching shower and light sprinkling treatments were equally effective in reducing fluoride uptake. After the foliage was 3 or 4 months old, however, the daily sprinklings had little effect on fluoride uptake whereas the twice weekly 1 hr drenchings effectively prevented fluoride accumulation. Growth responses were inversely proportional to fluoride uptake with maximum growth suppression associated with maximum fluoride uptake. After 9 months of treatment, the drenchings had reduced fluoride uptake by 85% and growth suppression by approximately 87%. In the same period the daily sprinkling treatment had reduced fluoride uptake by 37% and growth suppression by 45%.

Effects of captan on the non-parasitic microflora of apple leaves

The microflora of leaves from Worcester Pearmain apple trees sprayed with captan according to normal orchard practice, and from unsprayed trees, was examined by shaking, macerating and spore-fall techniques. Serial dilutions of macerates or wash liquids were incubated on selective media and the major groups of micro-organisms enumerated. Bacteria and yeasts were more numerous than moulds. Total numbers of yeasts and moulds were greatly reduced by captan but this effect was not long-lasting so that by the end of the season the numbers, and proportions of the major groups, on leaves from sprayed and unsprayed trees, were similar. The effect of captan sprayed in one season was not carried over to the next season. No conclusive data were obtained on the toxicity of captan to leaf bacteria. The implications of fungicide usage in relation to the balance of saprophytic and parasitic micro-organisms of the phylloplane are discussed.

Use of Chemical Defoliants on Peach Trees in Integrated Program to Suppress Populations of Green Peach Aphids123

When peach trees were sprayed with chemical defoliants to control green peach aphids, Myzus persicae (Sulzer), the number of aphids per leaf was higher on leaves remaining on the sprayed trees, but the number of aphids per tree was higher on the unsprayed trees. The high density of aphids per leaf in the foliage still present on sprayed trees was associated with an increase in deposition of syrphid eggs per leaf. Also, the number of aphid eggs was significantly fewer on the sprayed trees than on the unsprayed trees. The decrease in deposition of aphid eggs in 1966 compared with 1965 was correlated with the differences in trends of aphid population, temperatures, and syrphid activities.

Low‐volume spraying to control coffee leaf rust in Kenya

SUMMARYIn a 2‐year trial on arabica coffee in Kenya, a cuprous oxide fungicide (50% Cu) at a range of 0–5% (w/w) was applied by mist‐blower five times a year at approximately 10 gal./acre.The results demonstrated: (i) a positive linear relationship between log. spray concentration and the amount of copper (expressed as log10 mg. Cu/m.2+1) retained by the foliage; (ii) a significant negative linear relationship between spray concentration and the incidence of leaf rust (caused by Hemileia vastatrix Berk. & Br.); (iii) a positive linear relationship between concentration of fungicide applied and yield of coffee.An additional spray in May increased the mean annual yield by 2 cwt. coffee per acre and reduced a heavy rust attack.Trees receiving the highest spray concentration retained the most leaves; at lower concentrations there was considerable leaf fall but this was offset by new leaf production; unsprayed trees suffered severe leaf loss and were unable to produce as much new foliage.

Studies on manganese deficiency in citrus. II.

The investigations on manganese deficiency and its control were carried out from 1955 to 1957 on different kinds of citrus growing in Kanagawa Prefecture.The manganese deficiency symtoms were clear in June when the spring-flush leaves had reached the full size. The interveinal tissues of the leaves turned yellow, leaving a band of green tissues on both sides of the main veins and the mid rib. The contrast in the color of the main veins and adjacent tissues with the interveinal chlorotic portion was not so clear as in zinc deficient leaves. Such leaves were observed throughout the tree, irrespective of the directions in which the orchards were sloping.The severity of manganese deficiency seems to vary from variety to variety, i.e., Naruto (C. medioglobosa Hort.) and Natsudaidai (C. natsudaidai HAYATA) showed the severest symptoms, Unshiu (C. unshiu MARCOV.) showed them moderately, while early Unshiu and sweet oranges were slightly affected.Manganese content in spring-flush leaves increased till August, and thereafter remained fairly constant. Leaf analyses were done in order to find out the manganese content of leaves in 150 Unshiu orchards located in Kanagawa Prefecture. Close relationship between the severity of deficiency symptoms and the manganese content of leaves was recorded. All orchards with leaf manganese less than 15ppm on dry weight basis showed the deficiency symptoms, and 77 per cent of the orchards with leaf manganese less than 20ppm also showed these symptoms.Manganese content in citrus leaves of Kanagawa Prefecture were comparatively lower than those of the other districts, i.e., 71 per cent or more of the orchards in this Prefecture had manganese content lower than 25ppm on dry wight basis. Manganese deficiency symptoms were found in 67 per cent orchards on volcanic ash soils, where average leaf manganese content was 16.01ppm; in 27.3 per cent of the orchards on volcanic gravelly sandy soils the average leaf manganese content was 20.91ppm; and in 36.8 per cent of the orchards on gravelly clay soils it was 21.5ppm.Contents of different elements in leaves collected from 100 orchards in 1956 ranged as follows; nitrogen, 2.88-4.14 per cent; phosphorus, 0.14-0.24 per cent; potassium, 0.762-44 per cent; iron, 95-375ppm. A positive correlation was noted between manganese and phosphorus contents in the leaves and it was statistically significant at 1 per cent level.To contral manganese deficiency, one or two sprayings of 0.4 per cent solution of manganese sulfate before the leaves of spring-flush reached the full size were found effective. Mixture of lime and the above solution appears to be less effective in controlling the manganese deficiency.The soil applications of manganese fertilizers showed no favourable effect on the plants. Foliar applications of manganese to the deficient trees increased manganese content in young spring flush leaves sampled a year after spraying as compared with leaves of the same age from unsprayed trees.

The epidemiology of apple scab (Venturia inaequalis (Cke.) Wint.)

SUMMARYThe prevalence of Venturia inaequalis ascospores in orchards was compared both in terms of the number of spores per volume of air (dose) and the number produced per area of dead leaf (productivity). The two parameters often gave divergent estimates, probably because dose depends on total leaf per unit area of ground whereas productivity does not. Differences in the amount of dead leaf surviving until bud‐burst in different orchards or years were enough to explain the anomalies and suggested that because earthworms often removed over 90% of the fallen leaves by spring, they exercised an important control of ascospore number.Assessments of fruit surface scabbed, an accepted way of judging scab control, were not related to ascospore productivity the following spring, but estimates on the percentage of all leaves infected at leaf‐fall were. Other natural variables, like the dates when leaves were formed or fell, seemed of minor importance, especially when compared with effects of earthworms or chemicals. Applying dinitro‐ortho‐cresol to dead leaves in spring decreased the number of ascospores liberated by at least 90% and there is evidence of a similar effect from broadcast ammonium sulphate. The spring and summer spray programmes were also important. Measurements in several orchards during an 8‐year period showed that dose and productivity both declined to less than a hundredth of the highest levels, but in a single wet year productivity in sprayed orchards increased several times and by 40‐fold on unsprayed trees. Ways to prevent high ascospore doses occurring are discussed, together with possible causes of past severe attacks of apple scab at Wisbech.

Studies on manganese deficiency in Citrus. I.

The investigations on manganese deficiency and its control were carried out from 1955 to 1957 on different kinds of citrus growing in Kanagawa Prefecture.The manganese deficiency symtoms were clear in June when the spring-flush leaves had reached the full size. The interveinal tissues of the leaves turned yellow, leaving a band of green tissues on both sides of the main veins and the mid rib. The contrast in the color of the main veins and adjacent tissues with the interveinal chlorotic portion was not so clear as in zinc deficient leaves. Such leaves were observed throughout the tree, irrespective of the directions in which the orchards were sloping.The severity of manganese deficiency seems to vary from variety to variety, i.e., Naruto (C. medioglobosa Hort.) and Natsudaidai (C. natsudaidai HAYATA) showed the severest symptoms, Unshiu (C. unshiu MARCOV.) showed them moderately, while early Unshiu and sweet oranges were slightly affected.Manganese content in spring-flush leaves increased till August, and thereafter remained fairly constant. Leaf analyses were done in order to find out the manganese content of leaves in 150 Unshiu orchards located in Kanagawa Prefecture. Close relationship between the severity of deficiency symptoms and the manganese content of leaves was recorded. All orchards with leaf manganese less than 15ppm on dry weight basis showed the deficiency symptoms, and 77 per cent of the orchards with leaf manganese less than 20ppm also showed these symptoms.Manganese content in citrus leaves of Kanagawa Prefecture were comparatively lower than those of the other districts, i.e., 71 per cent or more of the orchards in this Prefecture had manganese content lower than 25ppm on dry wight basis. Manganese deficiency symptoms were found in 67 per cent orchards on volcanic ash soils, where average leaf manganese content was 16.01ppm; in 27.3 per cent of the orchards on volcanic gravelly sandy soils the average leaf manganese content was 20.91ppm; and in 36.8 per cent of the orchards on gravelly clay soils it was 21.5ppm.Contents of different elements in leaves collected from 100 orchards in 1956 ranged as follows; nitrogen, 2.88-4.14 per cent; phosphorus, 0.14-0.24 per cent; potassium, 0.762-44 per cent; iron, 95-375ppm. A positive correlation was noted between manganese and phosphorus contents in the leaves and it was statistically significant at 1 per cent level.To contral manganese deficiency, one or two sprayings of 0.4 per cent solution of manganese sulfate before the leaves of spring-flush reached the full size were found effective. Mixture of lime and the above solution appears to be less effective in controlling the manganese deficiency.The soil applications of manganese fertilizers showed no favourable effect on the plants. Foliar applications of manganese to the deficient trees increased manganese content in young spring flush leaves sampled a year after spraying as compared with leaves of the same age from unsprayed trees.