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Masters Theses 1911 - February 2014
1955
The biology of the clover mite, Bryobia praetiosa Koch, with preliminary investigations on its control.
Roger Weston Kelley University of Massachusetts Amherst
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Kelley, Roger Weston, "The biology of the clover mite, Bryobia praetiosa Koch, with preliminary investigations on its control." (1955). Masters Theses 1911 - February 2014. 2914. Retrieved from https://scholarworks.umass.edu/theses/2914
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THE BIOLOGY OF THE CLOVER MITE, BRTOBIA PRAETIOSA KOCH
WITH PRELIMINARY INVESTIGATIONS ON ITS CONTROL*
by
R* Weston Kelley, Jr*
Thesis submitted in partial fulfillment of the requirements
for the degree of Master of Science*
University of Massachusetts August 20, 1955* ACKNOWLEDGMENT S
The author wishes to take this opportunity to extend his most sincere appreciation to the members of his Thesis
Committee, Profs. Walter M. Banfield and Robert C. Perriello, and the Thesis Committee Chairman, Prof. Harvey L. Sweetman.
Prof. Sweetman has, for several years, been a highly respected source of inspiration to the author. As a result of this, coupled with the contributions of all faculty of this depart¬ ment under the inspiring supervision of Prof. Charles P.
Alexander, the author feels highly indebted.
Other contributors include Dr. Edward W. Baker of the United States National Museum, and Dr. Philip J • Spear,
Technical Director of the National Pest Control Association. TABLE OF CONTENTS
Page
INTRODUCTION ...... 1
ANALYSIS OF LITERATURE...... 2
Food Plants and Economic Importance of the
Clover Mite .. 2
Taxonomy and Synonymy .. 5
Distribution .. 8
Biology... 10
Control. Hi
Chemical lU
Biological. . 18
DESCRIPTION OF METHODS AND PROCEDURES. 19
DESCRIPTION OF STAGES. 2li
Egg. 21*
Larva ....•••••••••.. 2ii
Nymph .. 25
Adult. 25
LABORATORY BIOLOGICAL STUDIES. 25
Oviposition .. 25
Larval and Nymphal Development .. 28
Incubation .. 29
Activity Responses . 29
Heat. 29 Heat and Light .. 31 Page
FIELD BIOLOGICAL STUDIES.33
The Clover Mite on Its Host Plants ...... 33
Grasses .. 33
Apple .. 35
Deutzia .. 36
The Clover Mite in Households •.«••..••••••••• 38
General .. 38
Population Distribution. k3
CHEMICAL CONTROL OF THE CLOVER MITE.hi
SUMfoiAHT.U5
CONCLUSIONS. U6
LITERATURE. 1*8 Older than the modern science of entomology, as we regard it today, is the history of the economic inportance of the clover mite, Bryobia praetiosa Koch. Records of the early 1800*s reveal the fact that this pest has, for many years, been of economic importance primarily in the orchards of the northern, especially northeastern, latitudes of the
United States. Due to the numerous and varied insecticidal and fungicidal applications normally applied by commercial growers, this mite seldom attracted the attention of entom¬ ologists. It was seemingly being held in check by the ar- chardists* spraying schedules. However, because of its close association and often confusion with such spider mites as
Tetranychus telarius (Linnaeus), it gained frequent mention in the literature, due to the latter*s importance (Peairs
19U1).
In addition to the clover mite gaining mention and recognition in this respect, a considerable number of isolated cases of this mite infesting private dwellings were noticed and recorded. Reports date back as far as the middle and late 1800*s reflecting the economic importance of the clover mite as a household pest (Howard 1899). Increasing importance - 2 -
of this mite with relation to its occurrence in private dwellings, coupled with the fact that comparatively little work has been done in the past, indicated that a detailed study of the biology, ecology and control of B. praetiosa was necessary*
It is the purpose of these investigations to provide data which may serve as a basis for better understanding and control of the clover mite in environmental conditions as they prevail in the Commonwealth of Massachusetts.
Dr. Philip Spear, Technical Director of the National
Pest Control Association, has expressed the grave concern of the Association and many of its members regarding household control of this pest. The National Pest Control Association has summarized the current important knowledge of the clover mite (N.P.C.A. TR 5-53, U-55).
ANALYSIS OF LITERATURE
Food Plants and Economic Importance of the Cover Mite
Although it is closely related to the comron two- spotted mite or so-called Hred spider” mite common in orchards and greenhouses, the clover mite lives almost exclusively out- of-doors on trees, shrubs and grasses. Throughout Canada and the northern half of the United States, especially during the drier seasons, the clover mite often may be seen swarm¬ ing over the foliage of peach, prune, apple, pear, cherry, almond, raspberry and other fruits, and many forest trees and shrubs as well. These mites have mouth parts well-adapted for piercing the plant tissues; heavily infested foliage assumes a blanched, yellowish, sickly appearance*
As previously stated, the clover mite on its host plants has never been considered of sufficient importance to warrant extensive investigation and research* Probably the primary reason for this is that this mite is generally ef¬ fectively controlled in orchards by insecticidal and acarici- dal applications aimed at pests associated with the clover mite* B* praetiosa has been found in abundance on certain shade trees, especially the quaking aspen, Populus tremuloides however not to such an extent as to be of any economic import¬ ance (Howard 1899)*
The tendency of this mite to migrate from lawn areas into private dwellings reportedly has been steadily increas¬ ing over the years, so that today the clover mite is a primary problem and concern of many commercial pest control operators of the northern United States and Canada* In this - k -
sense, the clover mite seems to be a nuisance during the early spring and late fall in this area.- Its presence on various grasses, shrubs and trees in the immediate vicinity of the dwellings concerned can generally be detected throughout the summer months; however, during this time, its role as a house¬ hold pest is seldom, if ever, in evidence*
The primary objection to this pest from the house¬ holder’s point-of-view is purely a psychological or aesthetic one* Its mere presence, especially in the great numbers in which it is so often seen, is objectionable* It is commonly seen on windows, especially on sills and areas contiguous to same, and walls, especially on the warmer or sunny-sides of infested homss* Serious infestations may display the presence of the mite in nearly all rooms of a house, including multi¬ story apartment houses and office buildings* This mite does not feed on or cause damage to materials or people in private homes* Reports of this mite biting children, adults and pets are probably false (Riley 1899, Hartnack 19ll3)• The National
Pest Control Association (l955) describes a serious mite in¬ festation as follows? "In a typical house in New Jersey, sufficient counts were made to give reliability to the estimate of more than a quarter of a million mites on the floor of a - 5 -
single average-size bedroom* When mites occur in a home in these numbers, they are sufficient to cause a sound like the grating of fine sand as one walks across the floor, and to cause little red streaks to occur on all types of surfaces where the mites* bodies are crushed.H
Taxonomy and Synonymy
The position of B. praetiosa in the animal kingdom may be summarized as follows (Pritchard and Baker 1955)*
Clas s-Arachni da
Family-Tetranychidae
Subfamily—Bryobiinae
Tribe-Bryobiini
Genus-—Bryobia
Species——praetiosa
It is comparatively easy to differentiate the clover mite from its allies in that it possesses an unusually long pair of forelegs and twenty-eight dorsal spatulate setae.
It is a minute, spider-like, reddish-brown to green mite about
3/100 of an inch in length (fig* 1)* Pritchard and Baker
(1955) distinguish the clover mite as follows:
wBryobia praetiosa, as here identified, may be Subfamily Hryobiinae Uerlese
Figure X* Bryobia praetiosa: dorsal aspect of female, Los Alamos, New Mexico. Spider Hites
Figure 1A* Petrobia latent: dorsal aspect of female - 6 -
differentiated from other members of the genus by having strong propodosomal projections and by having empodium I of the adult female consisting of a single pair of tenent hairs (a short empodial pad with several pairs of ventrally directed tenent hairs is present on this segment in the nymphs)*
Bmpodia II and IV are pad-like, about as long as the claws, and with two rows of ventrally directed tenent hairs* Dorsal setae of the body are short and broadly spatulate* Males are unknown.”
The taxonomic status of the clover mite, B. praetiosa, has been rather confused. The synonymy as given by Pritchard and Baker (1955) is as follows*
Scientific Name Locality Host Upon and Authority Date Prom Which Which First Described Observed
Acarus garaminum Schrank 1781 Germany Grass
Bryobia brevicomis Ewing 1921 Arizona Alfalfa
Bryobia denticulate Tragardh 1901* — —
Bryobia glacialis Berlese 1913 Florence, ..- Italy
T AAQf^ jmRnrmW jUUJ.4* a gXauioJLAO«r1 ar>,t al 4 * APa^VaTcl auaai u
Bryobia gloriosa Koch 1836 Germany Fields
Bryobia grandnum Oudemans 1929 Germany Grass - 7 -
Bryobia haustor Oudemans 1937 Karguelen Land, Under Stones Indian Ocean
Bryobia hiune rails Halbert 1923 Ireland Garden walls and moss
Bryobia longicomis Ewing 1921 Ashland, Dutchman's Nebraska Breeches
Bryobia nobilis Koch 1838 Germany
Bryobia pallida Garman 1885 Illinois Grass
Bryobia praetiosa Koch 1836 Germany Shrubbery
Bryobia pratensls Oarmn 1885 Illinois Grass
Bryobia ribis Thomas 1896 Germany Grossularia sp
Bryobia speciosa Koch 1838 Germany Woods
Bryobia weyerensis Packard 1889 Weyer's Cave, Virginia
Rhyncholophus haustor Hardy 1850 England Grasses and fruit trees
Schiniedleinia tiliae Oudemans 1930 Berlin Dahlem, Tilia sp* Germany
Although B* praetiosa is commonly referred to as the
"clover ndte,M there is little evidence to support any claim that clover is a preferred, or even a common host of “this mite*
Baker has suggested that the common name be changed to the
Bryobia mite, since it is so rarely found on clover (N.P*C,A* TR U-55). - 8 -
Distribution
B. practiosa has been recorded in nearly all parts of Canada, in Australia, New Zealand, South Africa, Tasmania and parts of Asia. It occurs quite commonly in the northern and central sections of the United States from Massachusetts to California on a wide variety of hosts (fig. 2). In moun¬ tain ranges of the Pacific coast of the United States, its eggs have been found in enormous numbers on the bark of various forest trees. These eggs may often be in a mass two or three layers deep, and their reddish color may entirely obscure the natural color of the bark. Howard (1899) has stated that bark areas of at least fifty square feet on the south sides of the trunks of some cottonwoods at an elevation of 6,000 to 8,000 feet were covered with eggs. In the eastern and central states, the eggs are found similarly placed in the crotches of orchard and shade trees, and frequently may be in sufficient numbers to give a reddish hue to some areas*
The literature here considered of distribution of
5* Praetiosa is general and does not consider the mite as a household pest. In this respect, the areas of serious infest¬ ation are more or less concentrated in a band running across the
United States, roughly from New England to Washington and across Figure, 2 Oartcirraft LV»k Outline Map, North Amrrira No. I MOO S
Distribution of Dryobia ; nraetlosa "och in Ho. Anerica. (1391-1955)
• Areas of heavy infestation. (Webster 1912) dCSB General area of infestatioinfostatio:jl
HU Onconfiraed isolated claiatT of infested areas.
o* a-m L ■ | i ■ .—i-* —' o rx> «oo wo j
Published by DENOYER’GEPPERT CO.. Ch.crfR.. 1 i
- 9 -
to Chicago, Illinois and St. Louis, Missouri. Other important infestations have been observed in such high western areas as
Denver, Colorado and Los Alamos, New Mexico. Hubbard and
Schwarz (Hartnack 19i*3) reported that in Utah at 10,000 feet, the adte was in such thick layers between snovrfields, that it could easily be collected by the quart. Currently the eastern portion of this band is of most importance from the household pest point-of-view (N.P.C.A. TR During the fall and spring months in many parts of the United States and
Canada, it can be seen crawling on the sidings of houses while the ground is still covered with snow (Hartnack 19^3)• They have been observed crawling across snow, migrating in the general direction of houses (Venables 19^3)• In Canada, its current economic importance is due to its ability to function as a household pest. Currently, the province of British Colom¬ bia is experiencing the most trouble.
Papers by Riley and Marlatt (1891), Evans (l91i|),
Crosby (l9lU)> Garman (l9i*0), Venables (19U3)> Jenkins (I9it3) and Baker (195>U) present, en masse, a rather detailed and complete picture of its distribution in North America since the late 1800*s to date.
Several European countries have experienced heavy 10
infestations and damage caused by the clover mite* Among these,
Germany, England, Eire, Belgium, Italy and France seem to be most troubled (Kramer 1936, Hartnack 1939, Pritchard and Baker
1955)* In those countries, the import.nee of B. praetiosa is determined primarily by the damage which it causes in orchards and vineyards; it does function as a household pest in some areas (Riley and Marlatt 1891)•
Biology
The literature on the biology of B* praetiosa offers little in the way of reliable information. The vast majority of the information appears to be based on casual field obser¬ vations, with considerable contradiction.
Orchards, Forests and Woodlands. Throughout the northern half of the United States and Canada, especially during the drier seasons, the clover mite may be seen swarming over the foliage of peach, prune, apple, pear, plum, cherry, almond, raspberry and other fruits, and many forest trees as well. Slingerland and Crosby (191U) believe that it prefers these drier seasons of the year*
In wanner localities, many of the mites may be found in hibernation on the bark or in other sheltered localities; - 11 -
but in more northern regions, the winter is passed in the egg stage. Oftenti es, the bark of fruit trees, especially in the crotches, is covered in winter by many thousands of tiny, round,
reddish eggs. The conspicuous, rusty, reddish appearance given
to the bark by masses of these eggs may often serve as the
source of discovery of the pest. The eggs hatch early in the spring and breeding continues through several generations dur¬ ing a growing season (U.S. Bur. Ent. 1912). Upon hatching, the mites pass through a larval and two nymphal stages, each of which entails a resting stage. Influenced by the particular environment, these stages last from three to six days. The larvae generally feed upon the younger leaves at the end of the twigs. The new adults emerge in early June (Andre* 19hl).
In the New England area, it is believed that the mite has three to five generations per year. In other parts of the United
States, an average of from two to four generations are exper¬ ienced each year. In the British Conmonwealth, the average number of generations per year varies from two to three (Evans
1953).
Households. B. praetiosa, in the role of a household pest, presents a seemingly more complicated and confused biological 12 -
picture than as an orchard pest. Probably one of the primary questions that has arisen in the minds of investigators is,
"Why does this mite remain close to and enter households ?"
Many varied opinions have been offered by authors who have taken an interest in the problem. Three such opinions seem to predominate in the literature* Venables (19U3) is of the opinion that these mites migrate to homes, initially attracted by a light or heat reflection from the house siding, and migrate to the interior in order to find a more dry and pos¬ sibly warm environment in which to spend the quiescent period supposedly prior to each molt. He, in addition to this, re¬ ports that in British Colombia, cast nymphal skins and some eggs were found in an occupied college campus building. This opinion is opposed by Barnes (195&) and others who conclude that the migration is primarily due to the mite seeking a more moist environment due to the drying of vegetation surrounding the building in question. The third, and perhaps the most frequently mentioned opinion appearing in the literature, con¬ sists of the migration of clover mites into homes as a result of their seeking a more favorable host plant or shelter from the elements (Riley and Marlatt 1891)* Authors entertaining this latter opinion seem to imply that the migration to homes is more - 13 -
a result of chance than being due to any specific attractive¬ ness of the building in question.
There appears to be only one record of eggs in build¬ ings. Venables (19i;3) found eggs and cast nymphal skins in a college campus building, representing a probable accumula¬ tion of several years. The mites first may be noticed feeding upon various types of vegetation, primarily grasses, surrounding homes during the months of March and April, depending upon location and environment. The subsequent migration into homes soon follows, often reaching serious proportions by the middle of March in many areas. Many interesting reports have re¬ flected that the clover mite may be found migrating under very unusual conditions. Zappe (19^1) in Connecticut reports that a clover mite building infestation occurred during the very early spring while snow was still on the ground. Reports seem to present little variation regarding the activity of mites within an infested building. Generally the mites seem to be most prevalent on the house exterior and interior on the warm¬ est side of same, generally this being the south or east side.
The mites seem to show little, if any, preference to any par¬ ticular type of house or content thereof. The number may vary greatly, depending upon the seriousness of the infestation of - lU -
surrounding foliage. An infestation of an Eastern home was reported in which an estimate of nearly one quarter of a million mites were on the floor of a single room (N.P.C.A.
TR o No variation in the opinions of previous workers was noted by the author with regard to the belief that the clover mite experiences but a single, or possibly two,
generations per year as a household pest.
Control of the Clover Mite
Chemical. The clover mite has seldom, if ever, been a ser¬ ious problem in orchards since the recommended spray schedules prescribed for more important pests presumably controls them.
Occasionally, B. praetiosa has become a serious pest in or¬ chards, but for the most part, growers seem to have had little difficulty in eliminating this threat. Householders during
the late 1800* s used such ineffective preparations as carbolic
acid, corrosive sublimate dissolved in benzene, insect powder
(pyrethrum), tobacco, salt, gasoline, coal-oil, onion Juice, oil and grease (Riley and Howard 1890). Good formulations of nicotine and pyrethrum are effective. However, acaricides utilizing an oil base are still deemed to be among the most effective, especially in attempts to control the mites in the egg stage. - is -
Extensive research has been conducted in California
(195>1) to evaluate chemicals of possible acaricidal value for control of B. praetiosa in apple and pear orchards (tables 1,
2, and 3)«
Prom these data, it appears that parathion is less effective as a corrective spray than as a preventive spray for clover mite, the three corrective trials with parathion,
(tables 1 and 2), averaging 63 per cent reduction. EPN pro¬ vided corrective control, proving superior to parathion. In a preventive program, however, it was deemed less effective.
Compound 923 was shown to provide excellent over-all control.
IM) provided excellent control of clover mites following a preventive schedule of two U-ounce sprays derived from the emulsifiable solution. K-3926 provided only intermediate or fair control. Dicyclohexylamine dinitro-o-cyclohexylphenate, as reflected in the first tabular summary, provided excellent control.
In summary, for the control of the clover mite, as a result of this very extensive work, dicyclohexylamine dinitro- o-cyclohexylphenate-parathion*l,l-bis-(p-chlorophenyl)-methyl- carbinol>p-chloro-benzenesulfonate»2,U-dichlorophenylbenzene- sulfonate>2-(p-tert-butylphenoxy) isopropyl 2-chloroethyl ♦ ♦ #"4
CO CO CM r-4 A r-f co Os n VS < < < < < < < < C- so p- N P- p- IV p- N N < < < < < < < < vO'O'OvOvO'CUX vO 'O o so sO SO vO SO 0 • n • £ £3 • •••••• • • • o o V\ o *« p- US §§00000 o 8 ■& a* S O CA r- HHW CM 04 CD HI H -9 CO O o CM 3 SB i 1 f 11 n n f * 5 5i 3 £? i *? 3 CO US us I»«»»»«VJ s s^9 Os « Y> P- p- 8 4 rrn$«$«*i •E’3a,g'3C,3C ^ggggggg §5515555 « «1 W < a )?i H I I sljfjijifeiiii 5 « oooo**e*e ri Os oo <1 to ASsO r— r-f o VS o o O O © TO 'Onos Os CM f— VS V\ VS VS P < a CM < a a CO 3 & © O bDO Os TO rH h , © U OO co MD s> $ c ^CVOvO CM OO o CO CM xj © XACM^ * CM t*\ CM CO O m, H 0\ b -G & S XJ rH r-t -St s • • CM CM ncONOOO CM CO CM P*5 g i—I rH CM i -P M b C o O G © «H a |so O © rH w 8 *h o o o (0 1 x> 4fU CM > © aJ b t © h s 3 XJ 01 b •«* ©_ bO’p G •rC G •H ■31 rH o 00 o-H-P n xf 4» © g. rH r- XJ rH O cfl %%%OOP © © © •H tao '-’jS x* & isUS © © >» jC .g o o as ■4&3 s I n333 ft ft rH rH •H * &h a 3 ° T 7 b O o ss a o '■*' H Pi A <) rl b b O O g g -g Xi I I 43 4-( O O H H O O rH ^4-PHH I rH rH r-t Q Q rl rl O o cj s >» a g SS I i SS S Jg S5 5'T ”T woo -G-G o o o O (X, M M N CM ft ft CM CM ft ftQ • • • • • • • • • • • • • •a rH CM c^^xa MD C-OO On o rH CM CA &■« cm -^vr\ rH rH rH - 16 - sulfite*p-chlor ophenyl phenylsulfone>ethyl-p-nitrophenyl thionobenzene-phosphonate• In addition to, and repeating some of the above, many pest control schedules pertaining to apples, prescribe the use of organic phosphate compounds such as TEPP, parathion, EPN, demeton and malathion, and the less hazardous, non-phosphate materials such as Aramite and Ovex. These compounds have been classed as Bmiticides" by the publications and are not necessarily specific to clover mite control* Thomas and Raphael (1933) reported on the efficiency of oils against various life stages of B. praetiosa. Apple twigs infested with winter eggs of the clover mite were dipped into emulsions of twenty petroleum oils, which varied mainly in their viscosity and the type of emulsifier used. The re¬ sults indicated that of two emulsions containing oils with the same viscosity, the oil with the lower volatility gave better control* The types of emulsifier used seemed to greatly in¬ fluence the effectiveness of the oil* Quick-breaking emul¬ sions seemed to be more satisfactory than the slow-breaking ones* With reference to the foregoing, literature reveals that sprays applied to the other economic hosts of B* praetiosa - 17 - such as pear, plum, cherry, almond, grape, etc*, are essen¬ tially the same excepting a few instances where alterations are made in order to avoid possible phytotoxicity or violation of the newly-enforced agricultural chemical tolerances estab¬ lished by the United States Department of Agriculture, etc* The control of the clover mite as a structural pest requires precaution against phytotoxicity to lawns, shrubbery, trees and other ornamental plants, toxicity to pets and man, damage to paints, wall paper, clothing and other cloth items, furniture and woodwork, etc* Thus the use of agricultural acaricides calls for modifications of formulations and methods of application in and about residences. Interior household control of B. praetiosa has not presented the problem that has its control outside the homes* Interior control may be quite successfully accomplished by the use of emulsions containing pyrethrins (aerosols recom¬ mended), Dimite, di(p-chloroethyl) methyl carbinol and Aramite, 2-(p-tertbutylphenoxy) isopropyl 2-chloroethyl sul¬ fite* Emulsions seem to be preferred in that greater residual effectiveness seems to be achieved (Mallls 195>1*, N*P*C.A* TR Nos* S>-£3, U-£5>)* Both success and failure have been recorded with a number of materials under yard conditions* Exterior 18 spray applications in currant use consist primarily of Araadte (in emulsifl&ble solution or as a wettable powder containing 15 per emit of the active ingredient), CMC (or Disite, as an emulsive solution containing 25 per cent of the active ingredient) and malathion (as an emulsive solu¬ tion, two quarts of a 50 per cent solution per 100 gallons is suggested) « For outside dust applications, good results have been reported in New Mexico and California with the use of a 3 per cent Aranite dust® Appliestions of dusting sulfur when the temperatures are rel tively high, have boon successful (Barnes 1955)® Methods of application naturally vary with the degree of infestation concerned, and other highly variable factors as surrounding vegetation, type of building concerned, etc® In general, exterior spray and dust applications are made very heavily to the lawn area, with most emphasis placed upon the area contiguous to the building foundation! this is cost only the area supporting the highest site population, and said area generally extends out about 10-15 feet from the foundation base® Further surfaces treated include the out¬ side walls of the bouse and the foun ation, emphasising areas surrounding openings to the building® Biological® Literature reveals that there are only two insects - 19 V of sufficient importance warranting mention with regard to biological control of the clover mite. Neither of these in¬ sects is reported as having exerted effective control from an economic standpoint. One of these predators is a Coccin- ellid, Scymnus vagans (Blkb), and the other is a thrips, Leptothrips mali (Fitch). S. vagans was described in this capacity in Tasmania by Hobart (19^2). L. mali is discussed in detail by Bailey (19U0) with respect to its activities in California. Both of these insects restrict their predatory activities on B. prae- tiosa to the eggs. DESCRIPTION OF 1&TH0DS AND PROCEDURES Exclusive of general field observations, certain methods were used to determine population conditions and treatment ef¬ fectiveness, etc. The Berlese funnel utilizes the principal concerning the negative response of most forms of life to an exceedingly hot and dry environment. Within the funnel is a sieve-bottomed pan to hold the soil sample. Below this are two finer sieves for catching falling debris. The three sieves are 16, 12 and 8 inches in diameter and screened with kf 6 and 16 inch mesh respectively. The collected samples were - 20 heated by means of three electric lamps located just above the sample. Samples were collected by digging one square foot samples of topsoil, £^-6 inches deep, at various locations* The heat from the lamps gradually desiccates the soil sample, thus driving the mites down¬ ward into a small container positioned at the basal open¬ ing of the funnel* Petroleum jelly was smeared around all openings to prevent escape of the mites. Collections of mites for laboratory studies from infested lawns were made by collecting infested grass in a fruit jar covered with a fine wire mesh screen to prevent escape of the mites* Mites were transferred either by means of an aspirator or a pipette, using a second container for pure collection and subsequent trans¬ fer* Attempts to rear clover mites for experimental use were made on transplanted grass contained within a glass sleeve 10 inches in diameter open at the top (fig* 2)* A plastic sealing compound was used to seat the base of this sleeve to prevent escape of the mites* Petroleum jelly smeared around the cylinder 8 inches above the grass pre¬ vented escape* 21 - The cage devised by Ubertalli (193>3) was used for life cycle observations. In his method, four U-inch square sections of glass were used. The two inner plates had two 1-inch holes drilled in each of them. A plant section, leaf in this case, was placed between the top and bottom couples of glass plates. A blotter section was used as a backing and absorbing material to keep the leaf moist being located in the middle of the apparatus. Two heavy- clamps were used to keep all parts close together. A common one quart Mason jar equipped with wire screen top, was used as a supporting container for a branch of apple. This container was kept about one-quarter full of water at all tiii.es. This method was used in attempts to determine the effect of low temperatures on B. praetiosa while on one of its primary host plants. Petri dishes were used as containers for folded sections of a common blotter in incubation and oviposition experiments. These dishes were kept covered at all times during the course of the experiments, with dishes of larger size. In one case, the blotter section was moistened to an estimated point of one-half saturation; in the second case. the blotters were not moistened. 22 - A gradient chamber, U inches in diameter and 3 feet long was used in testing the response of clover mites to variations of heat and light (fig* 3)* The wooden chamber was lined with a gray-colored cardboard to facilitate observation through the glass face* Holes at 5-inch intervals in the top of this chamber for in¬ sertion of thermometera, etc., were available. Heat was provided at one end of this chamber with an electric lamp or hot water coils. The temperature came to equilibrium in about four hours. This procedure was improvised slightly by putting a coil of copper tubing in place of the light source to procure a source of heat without light* This tubing was connected to a hot water outlet by means of a length of rubber tubing* Chemical applications were made as follows: wet- table powders were dispersed on all vegetation at a rate of about lj pounds for every 30 linear feet of foundation. These applications extended from the base of the founda¬ tion to about 12 feet out into the lawn. Generally, heaviest lawn growth close to the foundation required heaviest appli¬ cations* Areas treated in this manner were then wet down thoroughly with the fine spray of a common garden hose - 23 - equipped with nozzle. This technique left a greater concentration of insecticide at the soil surface where mites were most active and abundant. Wettable powders were applied to foundations and walls after being dissolved in water, atomized by a compressed air garden sprayer. Exclusive of wettable powders, all other chemicals were applied by use of a compressed air garden sprayer or gasoline engine-powered sprayer. Areas treated with spray solutions included lawns, foundations, walls, and other vegetation found within the infested area. Determination of the effectiveness of these control attempts was accomplished by making actual counts, pre-treatment and post-treatment, of the surviv¬ ing mites. These counts were made from two surfaces, the window sill and the window sill ledge face. The window sill is the top surface of the window sill, inside the house. The window sill ledge face is the horizontal cross-sectional face of same, outside the house. Op-r „ 0 (10-J in. diam. ) Ring of Vaseline Cylindrical glass sleeve Old grass (lyr. old) New grass (2{rmos. old) Flower pot , (3 in. inside mouth diam.) Plastic Sealing compound Solid glass base Apparatus for Clover Mite Rearing Electric Thermometers Glass face light bulb Gradient Temperature Chamber Figure 3# - 2U - DESCRIPTION OF STAGES la The shiny eggs of B. praetiosa are about 0.19 mm. in diameter, spherical, slightly flattened at their base and generally of a uniform red color. They are laid singly or, more comonly, in masses covering various sections of the bark of trees from one to three layers in depth* Larva The larvae are approximately 0.20 mm. in diameter and nearly circular. They are red (vermilion) and the surface is irregularly striate. They have three pairs of five-jointed legs, not exceeding the body length, with the second and last segments being the longest. The first pair of legs slightly exceeds the other two pairs in length. The tarsi are surrounded by six knobbed hairs, two at the tip and four at the base. They have two eyes, situated on a purplish triangular spot slightly posterior to the center and near the edge of the cephalothorax. The ceph- alothorax is approximately two-thirds the size of the abdomen. The scale-like appendages on the dorsum of the larva occur in the same number and position as on the adult. - 25 - but are more elongate, being more in the nature of ser¬ rate spines (fig* 1). Nymph The nymphs of B. praetiosa very closely resemble the adult with the exception of size and color* The nymphs are smaller and paler in color* Adult The adults vary in color from brown to almost black, often with a greenish tinge* The color is uniform throughout* This color disappears in alcohol* The dorsum is depressed and appears coarsely wrinkled* The tarsi are long with six tenent hairs on leg I, and a conspicuous setose empodium between the claws of the running legs. The palp tarsus has four heavy and three slender setae on the terminal segment, with the hook of the tibia strong and sharply curved, extending to the tip of the palpus* The adult female is between 0*80 and 0*95> nsa. in length and about 0*60 ran. in width. No males are known. LABORATORY BIOLOGICAL STUDIES Oviposit!on Twenty-five adult clover mites were introduced in - 26 - each of two Petri dishes containing two U-inch pieces of blotter. The blotter in one dish was moistened slightly* Both dishes were covered and kept at room temperature. After 1*8 hours, four eggs were found in the folds of the dry blotter (table h)• At the end of five days, eleven eggs, laid singly, were counted on the dry blotter* none could be found on the moistened blotters. At the end of seven days, all of the mites in the Petri dish containing the moistened blotters were dead. Only five mites were alive in the second dish containing the dry blotters. Thirteen eggs were found at this time on the dry blotters and all had been laid singly in the folds of the blotters. Table 2u Oviposition of B. praetiosa in various environments. Temperature Approximate Egg Counts Number living °C Relative Days after 7 days Humidity 2 5> 7 27-28 32-33 U 7 2 5 26-27 fili-89 0 0 0 0 Fifty adult clover mites were taken from an in¬ festation on apple. A branch, bearing five leaves, each supporting 10 mites, was placed in the Mason Jar container - 27 - previously described. The jar and its contents were then placed in cold storage at a constant temperature of 0°C. Oviposit!on and other mite activity was very slight up to the time of their death, prior to the end of the second day. This experiment was repeated, the temperature hav¬ ing been raised to *>°C. Activity, especially oviposition, was noticeably greater than in the previous test. In ad¬ dition, it was noted that the mites were not readily killed in this comparatively slight increase over the 0°C. lethal temperature (table 5). The author concludes from these tests that the minimum temperature required for the survival of the clover fidte, while living on one of its primary hosts, apple, is between 0°C. and 5°C. The mites were obviously induced, probably by the low temperature conditions, to lay a seasonably abnormal number of eggs. An additional result of this experiment worthy of mention, is that the mites kept at 5>°C. readily became active upon exposure to room temperatures. - 28 - Table 5>. Effects of unseasonably low temperatures upon the activites of adult clover mites. T-Trace, X—-Inactive, A—Active Temperature Activity Total Eggs/Leaf Number Dead-Missing °C. Days Days Days _1 2 10 21 3g 1 2 10 21 yj 1 2 10 21 35 0 T I I I I - 50 - - - 5 A T T I I U 26 29 29 29 0 0 17 10 23 Larval and Nymphal Development Utilizing the glass observation cells previously described, eggs of B. praetiosa were placed on an apple leaf and observed over a two-week period of time at room temperatures. The eggs were of unknown age. These tests were initiated during June when suraer eggs were plentiful. Thirty eggs were used, of which 76% hatched. Table 6 sum¬ marizes the results of these observations. Table 6. Hie development of immature stages of the clover mite, at an estimated average temperature of 27°C. and probable high moisture conditions. Days to Develop Larval Stage 1st Nymph. Stage 2nd Nymph. Stage number number number 2 2 0 1 3 12 h U 7 10 8 5 1 3 2 Percentage of Survivors De¬ veloped 73 91 7$ Average Days to Develop 3*3 3*8 3.8 - 29 - Incubation Apart from the foregoing tests, the incubation period was studied with 22 newly-deposited eggs# These eggs were found and maintained on apple under laboratory conditions# Sixty-eight per cent of the eggs hatched in an average of 2k»h days# The percentage of hatch was somewhat lower than in the preceding environment# Table 7 summarizes the results# Table 7# The incubation of eggs of the clover mite at 27°C# and an estimated relative humidity of 50*. Days to Hatch Wo# of Eggs m-i6 i 19-22 2 23-26 8 27-28 2 29-31 1 32-33 1 Activity Responses Heat 1A# In June, 1955, several thousand mites were collected from a house infestation at lestover Air Force Base, iSassachusetts • Three hundred of these mites were introduced to a plot of grass contained within a glass - 30 - sleeve previously described. The grass was laboratory- reared from seed procured from >Vestover Air Base, and was of the same varieties and mixture as was the original infested grass. In the center of this eight inch in diameter plot was placed a smaller plot of grass, three inches in diameter, taken directly from the infested lawn. The introduced mites were very active and soon were dispersed throughout the old and new grass. 11A. This experiment was repeated, this time using 300 mites taken from an infested apple tree. The results were essentially the same as those found in U. IB. The foregoing test 1A was repeated, this time placing the plots of grass containing introduced mites in a cooler room. HB. Test 1IA was repeated, again with cooler conditions prevailing. Table 8 summarizes the results of these tests. - 31 - Table 8* The responses of lots of 300 adult mites of various ages when exposed in a glass sleeve with food under laboratory and greenhouse conditions* ♦-many +♦-majority Test Ave* Temp* Moisture No* Mites No* Feed- Bst. Length/ °C* Sat* Def• on Glass Life Day Night Day Night (Hours) (Hours) (Hours) 6 18 30 30 72 1A 31 2k 9 1*5 ♦ +♦ 220 0 0 6k HA 31 2k 9 1.5 ♦ +♦ 230 0 3 8k IB 25 21 9 3.5 ♦ 90 200 6 12 108 11B 25 21 9 3.5 + + 200 8 9 108 By transferring the infested plots of grass to a cooler environment, the activity of the mites was notice¬ ably increased, and they seemed a little more induced to feed upon the grass* Their feeding activities, however, were negligible as compared with the original lawn infest ation from which they were taken* The author considers the possibility that prevailing moisture conditions were too high to be favorable for normal activities* Heat and Light Tests were conducted to determine, if possible, the reactions of B* praetiosa and P* latens to alterations - 32 - in physical environment. These tests utilized the gradient temperature described under "Methods and Pro¬ cedures •" The mites, when liberated in the gradient cham¬ ber, reacted promptly, the great majority migrating toward the heat and light source except when liberated at a lethal temperature (fig. h)» When electric lamps were used to produce the heat, the response may have been to both or either source of energy. When liberated at 26°C., the mites migrated to and congregated at the warm end of the chamber. When liberated at 36°C. and 1*7°C., migra¬ tion to and away from the heat source occurred, but the vast majority showed a positive reaction. However, with electric lamps (EL, B2) they congreated at U7°C., while in the absence of the light (Cl, C2) they assembled at U0° and U2°C., thus indicating the influence of light. A few of the mites migrated to lower temperatures. The mites liberated at 60°C. were killed without observable response. The slight difference in response shown between D1 and D2 may have been produced by the difference in sources of the mites or a species difference. The rela- CV • ra © P •H • • a 01 ra © © © P P 43 •H •H P p E a •H • Ah tive humidity in all the tests ranged from 33 to 39 per cent. This low moisture condition may have influ¬ enced the results. The mites maintained a position in the lower half of the chamber during migration and assemblages. They displayed little activity after 6 hours. The aver¬ age length of life was between 36 and h8 hours, indicat¬ ing that one or more environmental factors were unfavor¬ able for survival. FIELD BIOLOGICAL STUDIES The Clover Mite on Its Host Plants Grasses. Observations were conducted over a one-year period, from September, 19$h to September, 195# in¬ clusive. During the first week of April, 1955* a number of inquiries came to the attention of the author re¬ garding Hclover mite” infestations of private homes in Massachusetts, principally in the Springfield area. Upon examination, it was found that the mites were feeding principally upon lawn grasses. The main varieties are Colonial Bent, Chewings Fescue, and Domestic Rye (table 9) • The vast majority of infestations were in and on homes and lawns averaging no more than two years old; lawn weeds and other superfluous vegetation were at a minimum. The mites exhibited little, if any, prefer¬ ence for various lawn clovers* Fields of cultivated clover in the Amherst area were also free of clover mites, despite the fact that nearby apple trees supported heavy infestations. This parallels the findings of Dr. Edward Baker of the D. S. National Museum. The mites infesting homes and lawns in this area were identified by Dr. Baker as Bryobia praetlosa 0Coch) and Petrobia latens (Muller) in an estimated 5>0/5>0 ratio. Both of these mites i^mained in their respective areas of lawn infestations until about the first of July, at which time a very noticeable decrease in population was noted. These observations were on control areas where no acaricidal treatments were made. By the middle of July, none of the more than twenty control areas supported heavy infesta¬ tions of "clover mites•n Occasional mites could be found during the suBmer months in these areas after this time, but close inspection was necessary to reveal their presence. Between the first of July and late August, - 3$ - householders were generally unaware of the presence of the mites in their lawns, as the few remaining were relatively inactive, as opposed to their mass migra¬ tions of the early summer months* The prevalence of this mite in fairly great migrating abundance was noted in some control areas during early September, 1955* Reports of 19f>U fall infestations were also confirmed by the author. These infestations were generally negli¬ gible, compared with the spring observations* It is concluded that B* praetiosa, in close association with P. latensj experiences one to two generations annually in and about households in this area* Apple* On apple in this area, heavy infestations of B. Praetiosa developed shortly after foliage appeared. Within three weeks after the initial infestations were noticed, spring eggs were in abundance, having been laid singly on both upper and lower sides of the leaves, gen¬ erally along the midrib or primary lateral veins* Infes¬ tations fluctuated in population, but in general, remained quite constant throughout the summer, until about the middle of September, at which time the mites migrated - 36 - downward after oviposit ion. Oviposit! on at this tie varied from their summer habits in that the eggs were laid in much greater numbers, not on leaves, but on small branches and branchlets, often in clusters in small crevices of the bark. The author concludes that the clover mite on apple experiences between three and five generations per year in this area. Deutzia. An additional primary host of the clover mite in this area is the so-called "berry bush,” known com¬ monly by its generic name, Deutzia (table 9). In the early summer, as soon as the foliage was becoming abun¬ dant on Deutzia, a favored food plant, clover mites could be found. At this time, many unhatched clover mite eggs were in clusters in small crevices of the bark. As in the case of infestations on apple, few, if any, mites were feeding on other plants in the immediate vicinity. Infestations on Deutzia were generally heavy and infested bushes displayed obvious symptoms of clover mite attack. Infestations were on every Deutzia bushj an estimated 100 widely scattered bushes were examined. The populations on these plants remained quite constant and heavy until 37 - late June or early July, at which time the mites dis¬ appeared, leaving heavy deposits of eggs behind as they had prior to this generation* These eggs did not hatch during the summer of 195# • The author concludes from these observations that the clover mite experiences only one generation per year on Deutzia in this area. The choice of food plants in this area follows (table 9)* The food plants listed include only those which were found in the immediate vicinity (10 to 2$ feet) of a clover mite infestation. Deutzia was found to be a choice food plant* It was selected by the mite over all plants in the last column except the ornamental evergreens, white birch, spearmint, rose, and lilac, which were not found in the immediate vicinity of Deutzia. The ornamental evergreens, white birch, spearmint and lilac were surrounded by in¬ fested grass; the rose was in the immediate vicinity of infested apple and cherry trees. Clover, in the column headed "Less Favored, " was supporting actively feeding mites in several lawn areas, but to a much lesser extent than the surrounding grass. A single case of clover Table 9* The response of the clover mite to plants in the immediate vicinity of infestations. Favored Less Favored Non-infested Plants Deutzia scabra - Deutzia Clover Ornamental evergreens Malus sp. - apple Ulmus american - Acer rubrum - red maple Pyrus sp. - pear Am. elm A. saccharinum - sugar maple Primus sp. - cheriy Aesculus hippocastanum - Domestic rye grass horse-chestnut Festuca sp. - chewings Agvilegia sp. - columbine fescue grass Betula alba - white birch B. papyrifera - paper birch Cornus florida - dogwood Helianthus decapetalus - sunflower Forsythia sp. - golden bell Lonicera sp. - honeysuckle Mentha spicata - spearmint Osmunda spp. - ferns Spiraea opulifolia - nine bark Philadelphia coronarius - mock orange Quercus alba - white oak Rosa sp. - rose &alix sp. - willow Solidago rlgida - golden- rod Syringa - lilac Sembucus sp. - elderberry Juglans cinerea - butter¬ nut J. nigra - black walnut - 38 - mites feeding on American elm was observed in the vicin¬ ity of a clover mite infestation on lawn grasses. All host plants listed under the "Favored” heading in the table* had serious infestations of B. praetiosa. The host plants included under this heading are arranged* according to the author*s opinion* in descending order of preference. The Clover Mite in Households General. The clover mite, when observed in households was seen behaving in conjunction with its close associ- ate, Petrobia latens (Muller) (fig. 1A) in an approximate 50/^0 ratio. Near homogeneous results were attained in the comparative laboratory tests involving pure and mixed cultures of B. praetiosa. Most observations made under the above heading regarding the activity of "clover mites” concerns primarily, perhaps entirely* mixed infestations. All observations were made during fair afternoons (clear to partly cloudy). Mites* obviously feeding upon surrounding vegeta¬ tion, primarily grasses, were found in a concentrated - 39 - area, generally only within fifteen feet from the base of the foundation of an infested building, (table 1C). Many mites were nearly always actively engaged in mi¬ gration in the direction of the nearest side of the building in question* Mites could be found crawling on grass, across the soil surface, up the foundation and side of the house, and into cracks and crevices around side shingles, door and window frames* Window sills and window sill ledges seemed to reveal particularly high populations compared to other surfaces examined* Perhaps surfaces such as this, where reflected light and heat tend to be greatest on the sides of the building, were especially attractive to the ndtes* Comparatively speaking, the ndtes* activity over these surfaces was at a low ebb* A further indication of the clover mite*s preference to heated and/or lighted surfaces was displayed by their quite consistent preference for the warmer, sunny-sides of buildings (primarily the south side)* The primary stimulus influencing the migration towards the side of a house may rest in the light and heat re¬ flected and radiating from same* Once entrance has been Table 10. Population distribution counts Adj* — adjacent to foundation* I* — pre-treatment counts. Exp* Berlese Funnel Counts Ledge Counts* Ledge Face Counts* No* Adj. 3 ft. 6 ft. 12 ft. Pre-treatment Pre-treatment 1 79 53 8 56 9 2 66 55 10 32 31 3 82 61 9 22 7 5 52 59 13 32 38 6 92 66 19 1 ltU 29 10 1*2 28 3 19 11 13 77 65 11 2 U9 29 *Days stated refer to "days after treatment." - ho - gained, little or no preference was seemingly shown as the mites may be found in and on practically any con¬ ceivable article contained within an infested building* As any householder who has experienced an infestation of clover mites would readily testify, these mites are very soft-bodied, and in the majority of cases where clean-up or brushing off, etc*, is carried out by the householder, a brownish, tobacco-like stain frequently remains after such an operation, marking the spot where pressure on the mite*s body caused the bursting of the exoskeleton and subsequent release of bocy contents* Householders have found that a most efficient way to combat this problem is in the use of a vacuum cleaner or similar device. In only one case were eggs of B* praetiosa found on the structure itself* In this case, the eggs were under side of shingles that were being removed from the side of the house exterior* The eggs had been laid singly and not in very great abundance* Probably the primary locus of egg-laying occurred in the sandy soil surrounding the buildings* Here, eggs were on several occasions found in relative abundance* again laid singly and adhering to larger particles of sand* The eggs were not found on grass* In the majority of cases examined* little or no vegetation existed in the ifsaed- iate vicinity of Infested horns* with the exception of the grasses upon which the mites were feeding; the author concludes that clover sites infesting houses commonly deposit their eggs on surfaces other than vege¬ tative, pririKirily on the surface of sandy areas in the lawn close to a building* This seeming preference of the clover mite to deposit Its eggs in such a locality is considered a still further indication of the sites* preference for drier* warmer areas in which to experience certain biological processes* The altos seemingly do no actual damage whatsoever once they ha /e gained entry to a household* The sites did not exhibit preference* In these canes* the sites did not attack or feed on any article as furniture* clothing, decoration or utility, etc* Likewise, there was no con¬ firmed report of the clover mite attacking man or other animals* To be sure* these sites were found on humans and - 1*2 - domestic pets of various sorts, but their occurrence was no more than would be expected in view of their comparative occurrence on other articles in the immediate vicinity within the home. Of the twenty-five houses examined, the major¬ ity were of wood shingle siding, seldom dark in color (table 11)# Nearly all of these homes were less than three years old. Topsoil condition was generally fair to poor, supporting vegetation of similar quality. Lawn condition being generally poor was due to malnu¬ trition as well as mite damage. The author concludes that the primary determining factor of the mites1 prevalence in lawns is due to the type and age of the grass, younger grass being preferred. The center of mite abundance and activity was generally the wannest sides, south and east, of the infested buildings and lawn areas. Table 11 summarizes the observations of 2£> cases of mite infestations of private homes and lawn areas, conducted in Massachusetts. These observations have been grouped according to the color of the building concerned. Population Distribution* On the basis of the field observations (table ll) follairing this discussion, certain general statements say be made* To begin with, the author found that the most efficient sampl¬ ing technique for population determination, was in the use of the Berlese funnel* In general, the window sill ledge counts seemed to parallel Berlese funnel results, but the latter served in more accurate de¬ terminations* After an individual has gained famil¬ iarity with these various sampling methods, the author feels that Berlese tests would be less efficient from a time-saving point of view. In the experience of the author, field observations of mite prevalence and re¬ sulting damage to grass were closely correlated (directly proportional) to the results of the Berlese tests « CHEMICAL CONTROL OF THE CLOVER MITE Chemical control experiments consisted in the utilization of seven insecticides, reputed of possible acaricidal value (table 12). The results of these tests indicate that malathion o CO m CM CM 'S i c •0k »S c M 5 W O «P -P m T» CO CO •p ft) -p O rH M o tI m W M CO •«* w CO ft) > ft) o o V. cd «m CO CO CM g 5d ® W o sc CM vO CM o ft) 55 O O c « § SC CM CO SC « CO E vOSC h a £ S " 'O “ S -? f 1 H CM H CM CM ft) CM v_<* ft) CO tb s Q« § t § s § o O, o i ! t*5 25 < ss a s £ sc n ■s«fio as o 3 § CQ ft) ^ C -H I I I |oO «P 2 2 2 o M * a CO ft) CO CM vr\ too U < H A o s «) ■P ^ 4S ►4 fc^oocs^o^o S 6*^ W 5 o 5r •H■ d H o 43 Pi P*< «P W JS*> g Io E-* ft) CO ^ 4 CM CM CM H li! N>>« i • H 3 < H cm o CO K > H rH V. *0 Ov <*> \A •S sJI fr« lit ft) CQ O CM CM CM toD U 44 O TJ •t) *8 ■8 8 5 I £ iBI ISB m 5 6 I s la the most affective of those here considered. Applied at an average rate of about one-half pound per 100 square feet of lawn area, all three formulations seemed to give excellent results. It is concluded that a U-W formula¬ tion is sufficient in concentration of the toxic agent, when applied in this manner, so as not to warrant higher formulations• Chlorobenzolate offered very good to excellent control in all cases. Experiments involving this insect¬ icide were repeated in order that its value could be well substantiated. Of the remaining five chemicals, Systox gave the best results. Dimite offered only fair control, as did Compound iil2U* The single test involving Trionone-20 gave poor results. Due to the fact that the single test involving Aramite was both conducted and reported by the householder in question, the author does not wish to indorse same. In the above tests where the buildings were treated as well as the lawn areas, initial relief of the mite nuisance within the home was accomplished sooner than in tests where one or more surfaces were 3 rH rH «a "§ H fM 1 cd rt o03 $ 6) & •nE §S w * 2 ■p g 4 CNJ H is &4 neglected in the treatment. Ultimate results were seem¬ ingly not affected in cases where foundations and/or walls were not treated; treatment of the lawn alone was sufficient. SUMMARY The clover mite, B. praetiosas was found to be common on several grasses, apple, and Deutzia. The literature analysis, laboratory and field biological observations all seem to indicate that this mite exists as at least two biological races in the Massachusetts area. Oviposition habits and seasonal distribution on various host plants comprise the primary biological differences. The clover mite seems to respond very readily to alterations in physical environment. Laboratory re¬ sponses were determined by the use of various incubation techniques, a gradient temperature chamber and other rearing techniques. Oviposition habits and seasonal distribution on various host plants were determined primarily by extensive field observations. Several laboratory studies were conducted regarding oviposition. Mites invading private homes in the western Massachusetts area were found to be mixed infestations containing B. praetiosa and P. latens* Superficially, these mites look very much alike and their field behaviors are likewise in parallel. Exclusive of lawn infestations, P. latens could not be found living in association with B. praetiosa. It is felt that liter¬ ature of the past in many cases may be inaccurate due to an apparent failure to recognize this possibility. Phases of the life cycle of the clover mite were studied in the laboratory under various physical environ¬ mental conditions. Extensive field observations supple¬ mented these studies. Control experiments were conducted using seven comparatively new insecticides of reputed acaricidal value. Malathion and chlorobenzolate offered excellent results in most cases. Other chemicals were only slightly to moderately effective* CONCLUSIONS Perhaps the primary conclusion which the author has drawn from his observations is that the clover mite in this area probably exists as at least two biological races* It is believed that these two races are most commonly found on 1) grasses and Deutzia, and 2) fruit trees* Although these two races seem to have different habits in several respects, they are essentially both susceptible to the same chemical control measures* There seems to be considerable variation in the habits of each of the respective races; however, the reasons behind these patterns of behavior are not, for the most part, clearly understood* Observations indicate that mite infestations, in part B* praetiosa, of households and lawns are di¬ rectly dependent upon a sandy soil supporting young vegetation for optimum development* Physical factors in the environment enhancing maximum development include low summer temperatures and/or low moisture conditions* It must be emphasized, however, that great variation exists to these general characteristics* LITERATURE Anonymous 19i* *l* Some common pests of fruit trees and vines in Southern Australia* Jour* Bert* Agric* S* Aust* *1*3* 9s633-k6* 1953* The clover mite* Nat* Pest Control Assoc* (New York) Tech* Rel* 5-£3* 1—sli* 195U• The midwest farm handbook* Iowa State College* Ames, Iowa* $k p* 1955* 1955 pest control schedules for apples. Univ* of Mass* Depts. Ent., Bot., and Pomol* p* 1-lU* \ Andre, M* 19lil* Sur le Bryobla praetiosa* Bull* Mus* Nat* Hist* Nat* 2:13* (Abs* in Rev* Appl* Ent. 33*356). Baker, E* • 195U. Pest control technology* Nat* Pest Control Assoc*, New York* p* Barnes, J* 1951* Studies with acaricides for control of mites in apple and pear orchards in Southern California* Jour* Econ* Ent. J4i:672-U, 676-81* -k 9 - Barnes, M. M. 1955* The clover mite problem. Univ. Calif. Cit. Exp. Sta. Hews Ltr. 70: 1—1*. Bailey, S. F. 191*0. The black hunter, Leptothrips mail (Fitch). Jour. Econ. Ent. 29A: 211. Blenton, F. S. and F. A. Harris 19l*2. Insect trans¬ mission of the virus causing narcissus mosaic. Jour. Agric. Res. 6£. 9:1*13- 1*19. Borden, A. 1931*. The tank mixture method for dormant oil spraying of deciduous fruit trees in California* Calif. Agric. Exp. Sta. Bull. £79:1-11. _ 1938* Oil sprays of deciduous fruit trees by the tank mixture method. Calif. Agric. Exp. Sta. Circ. 3l*£sl-3l*. Bourne, A. I. 19l*3. Observations on fruit insects for 19l*2. Mass. Fruit Grow. Assoc. Rept. l*9sl*£-6. Boyce, A. M. 1938. Dinitro-o-cyclohexyphenol in the control of the citrus red mite. Rev. Appl. Ent. 2?A:26l. - 50 - Chapman and Lienk. 1950. Orchard mite control experi¬ ment in western New York. Jour* Econ. £nt. 43*309, 312-13. Cartwright, B. 1933* Notes for 1932 on cereal and forage insects in California. Calif. Dept. Agric. Mon. Bull. 22, 2-3*156- 60. Cockerell, T. D. A. 1895. Insect Life Bryobia praten- sis. 7*210. Cottier, W. 1935* Red mite control by oil sprays. N. Z. Jour. Sci. Tech. 16. 5*261-70. (Abs. in Rev. Appl. Ent. 23A:U37). Crosby, C. R. and M. D. Leonard 1918. Manual of vege¬ table and garden insects. Norwood Press, Norwood, Mass. p. 351-4• Deel, D. P. 1935* Red spider and clover mite. Kans. Hort. Soc. Biem. Rep. 42:50-2. Ellis, L. H. 1890. Abundance of Bryobia pratensis. Insect Life 2*78-9. Essig, E. 0. 1915. Injurious and beneficial insects of California (2nded.)* Mo. Bull. (Suppl.) Calif. State Comm, of Hort. p. 13-14. Evans, J. W. 19li2# Orchard and garden mites and their control# Tasmanian Jour. Agric. 13• >. iis334.C>-J42« (Abs. in Rev. Appl. Ent. 3Us31l). _ 1952. The injurious insects of the British Commonwealth• Commonwealth Institute of Entomology, London, England, p. 201# Fenton, F. A. 19Ul« The brown wheat mite, Petrobia la tens. Jour. Econ. Ent. ijiis 996# Friend, R# B# 19U0# The clover mite. Conn. State Entomol. Rept. 1939, 39th. Qarman, Philip 19^0. Tetramychidae of Connecticut. Conn# Agr. Exp. Sta. Bull. U31 *87• 191*8. Mite species from apple in Connec¬ ticut# Conn. Agr. Exp. Sta. Bull. 520:21. Gnadinger, C. B. 1933 • Selanium insecticide national for controlling red spider. Industr. Engin. Chem. 25s633-7* Hartnack, Hugo 1939* 202 conmon household pests of North America. Hartnack Pub. Co. Chicago, Ill. p. 269-70. -52 - Hartnackp Hugo 19i*3» Unbidden house guests* Hart- nack Pub* Co* Tacoma, Wash* 1k2 p* Herrick, 0. 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