Search

Squash bug, Anasa tristis DeGeer (Hemiptera: Coreidae), is a major pest of squash and pumpkins in the United States. In order to better understand the importance of natural egg parasitism of this species in Virginia, we conducted a 2-yr statewide survey. In total, 1,127 squash bug egg masses (~20,000 total eggs) were sampled from squash and pumpkins from 43 counties in Virginia from 2014 to 2015. Egg masses were brought back to the lab to record levels of squash bug nymphal emergence or adult parasitoid eclosion and identification. Over 50% of the total squash bug eggs collected statewide were parasitized. Gryon pennsylvanicum Ashmead (Hymenoptera: Scelionidae) was the predominant egg parasitoid accounting for over 98% of all parasitoid adults recovered. The only other species emerging from squash bug eggs was Anastatus reduvii Howard (Hymenoptera: Eupelmidae), which is a generalist parasitoid. G. pennsylvanicum was found in 75% of the counties surveyed with the highest levels of parasitism occurring in the Northern, Southwestern Mountain, and Western Piedmont regions of the state and the lowest levels of parasitism occurring in the Tidewater region in the southeastern portion of the state. Based on this 2-yr survey, G. pennsylvanicum was determined to be a major natural enemy of squash bug, significantly reducing the number of nymphs that emerge from deposited eggs. Conservation of this natural enemy should therefore be a priority for integrated pest management programs in cucurbits.

In 1992, sentinel squash plants treated with carbofuran successfully attracted and killed squash bug, Anasa tristis (De Geer), and cucumber beetle, Acalymma vittatum (F.), emerging from overwintering at 5 locations in Atoka County, Oklahoma. In 1993, responses of cucumber beetle and squash bug to carbofuran-treated squash trap plants and to Adios or Adios-AG attracticidal baits were compared in 90% of the estimated squash bug population but were less effective in squash. In all cases, squash trap plants treated with carbofuran killed >90 and 16-37%, respectively, of the cucumber beetles and squash bugs found on the plants. Single applications of attracticidal baits provided up to 70% cucumber beetle mortality for 3-5-d post treatment. Studies conducted in 1994 showed that significantly greater numbers of cucumber beetles, primarily Diabrotica undecimpunctata howardii Barber, were attracted to ‘Blue Hubbard’ than Lemondrop squash trap plants that were treated with systemic insecticides, carbofuran at 0.15 g (AI) or imidacloprid at 0.04 g (AI), and positioned in a field of watermelon. Imidacloprid was as effective as carbofuran, each provided >90% cucumber beetle mortality. In this study, an estimated 46.7% of the total cucumber beetle population was attracted to the squash trap plants. Results from these studies suggest that minimal plantings of systemically treated squash can be used effectively to suppress early season populations of cucumber beetle and squash bug in seedling cantaloupe, squash, and watermelon.

Field releases of the indigenous egg parasitoid Crayon pennsylvanicum (Ashmead) resulted in a 4-fold reduction in squash bug, Anasa tristis (De Geer), densities on ‘Jack-O-Lantern’ pumpkins in 1991. However, pest populations subjected to parasitoids were consistently higher, and fruit yields and quality lower, than on plants that were treated with the insecticide, esfenvalerate, When the squash bug-resistant ‘Green-Striped Cushaw’ was used, the difference in pest densities on parasitoid-released and insecticide-treated plants was only half of that observed on the susceptible cultivar. In 1992, under abnormally wet, cool conditions, squash bug densities were higher on insecticide-treated plants and lower on plants where parasitoids were released than in 1991. Fruit quality for both cultivars was substantially reduced in all treatments in 1992, The wet, cool conditions apparently had less of an effect on pest densities and fruit yields on resistant pumpkins than on susceptible pumpkins. The expected net income for insecticide-treated pumpkins was substantially lower in 1992 than in 1991. Where biological control and host plant resistance were combined, loss in expected net income in 1992 was considerably less than in 1991. Although costs associated with biological control were very high relative to the revenues, integrating biological control with host plant resistance may have some potential as an alternative management strategy.

Adult squash bugs, Anasa tristis (De Geer), were confined on seedling watermelon plants at densities of zero, one, two, and four per plant. Squash bugs were allowed to feed on the plants until plants died or reached 30 cm in height. Number of leaves and length of plant vine were recorded at 2- or 3-d intervals. Seedling foliage, stems, and roots were harvested and dried after plants reached 30 cm in height. Growth of seedlings was regressed on number of squash bugs and results indicated that an increasing density of squash bugs feeding on seedlings resulted in a significant reduction in plant growth. Additionally, increased density of squash bugs resulted in reduced weight of foliage and root dry biomass. Seedling mortality increased as the density of squash bugs increased.

An investigation to delimit the influence of feeding by adult squash bug, Anasa tristis (De Geer), on squash, Cucurbita pepo var. melopepo L. ‘Hyrific’, was done during the summers of 1988 and 1989. When two or more adult squash bugs were allowed to feed on plants at the two-leaf stage for 200 DD (base 15.6°C), yield reductions were caused primarily by seedling mortality. Plants surviving the infestation period were typically unable to make up for growth delays induced by squash bug feeding. The size of the plants at infestation influenced yield, with four-leaf plants producing lower yields at maturity than those with six leaves.

Squash bugs, Anasa tristis (De Geer), were intensively sampled in summer squash plots from three locations in Oklahoma in the spring and summer of 1987 and 1988. Data collected from whole-plant samples for adults, egg masses, and nymphs were fitted to the Poisson, negative binomial, and positive binomial frequency distributions, as well as Taylor’s power function and Iwao’s patchiness regression. None of the three theoretical distributions fit the squash bug populations on all sample occasions. Taylor’s power law provided a better fit to the count data than did Iwao’s patchiness regression. All life stages exhibited aggregated patterns of spatial dispersion; small nymphs exhibited the largest degree of aggregation, followed by large nymphs, adults, and egg masses. Sequential sampling plans for squash bugs were developed using estimated variance-mean relationships derived from Taylor’s power function. Because small nymphs were highly aggregated, greater numbers of plant samples were required to estimate population means of nymphs with specified levels of precision than were needed for adults or egg masses. Validation with Monte Carlo simulations indicated that these procedures may not always estimate mean population density at specified levels of precision.

A laboratory study was conducted to quantify the relationship of adult squash bug, Anasa tristis (DeGeer), density to summer squash ( Cucurbita pepo L. var Hyrific) plant damage. This relationship was investigated at five temperatures (20.0, 22.5, 25.0, 27.5, and 30.O°C) and four adult squash bug densities (none, two, four, and six). Vegetative growth rates and ovulate flower productivity decreased with increasing squash bug density; staminate flower productivity was not significantly affected by squash bug density. Growth rates and ovulate and staminate flower productivity increased with increasing temperatures. Squash bug mortality was highest at 25.0°C and lowest at 22.5°C. Female squash bug mortality was significantly higher when there were only two squash bugs per plant. The number of mean eggs per female increased with temperature and was unaffected by squash bug density.

The effect of summer squash ( Cucurbita pepo L. cv. Hyrific) planting dates on the seasonal abundance of squash bug, Anasa tristis (De Geer), populations and fruit yields was investigated. Colonization by overwintered adult squash bugs was directly influenced by planting date. Significantly higher adult population densities developed on older, larger plants containing higher numbers of leaves than on younger plants with fewer leaves. As a result of adult preference for larger plants, egg mass and nymphal populations were significantly more abundant on early-planted squash. Mean numbers of squash bugs per leaf were correlated ( P < 0.05) with mean number of leaves per plant, suggesting that plant size may influence host plant selection. Regardless of planting date, squash bugs were most abundant on plants during flowering and fruit set. Manipulation of squash plantings may be a means of managing overwintered squash bug populations in spring crops to avoid yield losses.

The occurrence of squash bug, Anasa tristis (DeGeer) on yellow summer squash grown under different cultural systems was studied in one experiment in 1987 and two experiments in 1988. The influence of row covers-black plastic and aluminized mulch-on the occurrence of squash bug was evaluated. Mulch production systems (black plastic or reflective) harbored more squash bugs than bare ground in 1987 studies. No differences in the density of squash bug were detected in plots with aluminum mulch (paper-backed) compared with either white plastic or aluminized black plastic. Early in both 1988 studies, significantly more squash bugs were observed in plots with aluminum mulch compared with those with black plastic. As plant development progressed, differences in squash bug numbers between the two mulch types decreased. However, squash grown in mulched plots, regardless of the type of mulch used, had consistently larger squash bug populations than those grown in bare ground. Row covers delayed squash bug colonization but when the covers were removed to allow plant pollination, squash bug colonized quickly. Mulch covers, regardless of type, provide a harborage for squash bug adults and nymphs. Greater numbers of squash bugs in mulched culture systems may result in increases in squash bug control costs, which could offset any production benefit gained by mulch systems.

Six squash cultivars, Cucurbita spp., were evaluated in the field during 1983 and 1984, and five cucurbit hosts were evaluated during 1985 for ovipositional preference by squash bugs, Anasa Tristis (De Geer). Yellow straightneck ‘Hyrific’ and crookneck squashes were found to be the most preferred in the squash study. In the cucurbit study, two cultivars of C. pepo L., yellow straightneck ‘Hyrific’ squash and ‘Jack o’ Lantern’ pumpkin, were most preferred. Relatively few egg masses were found on watermelon, Citrullus lanatus (Thunberg) Matsumura & Nakai ‘Crimson Sweet’; muskmelon, Cucumis mela L. ‘Hales Best #36’; and cucumber, Cucumis sativus L. ‘Poinsett.’ The abaxial leaf surfaces of all hosts in both studies were the favored ovipositional site of squash bugs. This phenomenon is important in developing squash bug sampling strategies and in insecticide applications.

Adult squash bugs, Anasa tristis (De Geer) (Heteroptera: Coreidae), were confined on watermelon plants at differing phenological stages and at densities of zero to four per plant in one trial and zero to 32 per plant in three additional trials. Squash bugs were allowed to feed on the plants until plants died or fruit matured. Plant foliage, roots, and fruit were harvested and weighed to determine effects on growth and productivity. Growth and fruit production was regressed on number of squash bugs and results indicated that an increasing density of squash bugs feeding on vining and flowering stage plants resulted in significant reductions in plant growth and fruit yield. When plants were infested at the fruit set stage of growth, there was either less effect or no effect on plant growth and fruit production. Plant mortality increased as the density of squash bugs increased regardless of the stage of growth when plants were infested with squash bugs.

The population dynamics of the squash bug, Anasa tristis (DeGeer), and the seasonal development of the squash plant, Cucurmta pepo L. variety ‘Hyrific,’ were monitored during 1984 and 1985. Numbers of squash bugs increased dramatically throughout the season. Overwintered adults and subsequent oviposition occurred soon after plant emergence. The development of first-generation nymphs and adults slowly increased the total number of squash bugs in the field. The development of a second generation caused a pronounced increase in the total numbers present. The numbers of nymphs, adults, and eggs in the field increased at an exponential rate beginning about Julian date 192 (10 July). Late in the season the rate of oviposition decreased. Squash bugs complete two to three generations per year in Oklahoma. Our data suggest that early-season control of squash bugs is essential to prevent high densities of insects from occurring late in the year. Mean plant leaf area and the number of leaves followed a sigmoid-shaped growth curve, increasing slowly early in the season, becoming faster through midseason, and slowing again late in the season. The numbers of flower buds, flowers, and immature and mature fruit also followed a sigmoid-shaped growth curve throughout the season.

Egg and nymphal developmental times of the squash bug, Anasa tristis DeGeer, were measured at five an six constant temperatures, respectively, in the laboratory. A linear equation was used to describe the effect of constant temperature on the mean rate of egg development. A degree-day model derived from the linear equation adequately predicted rates of egg development at two variable temperatures in the laboratory and in the field. A nonlinear equation, the two-parameter form of the enzyme kinetic model of Sharpe & DeMichele (1977), was used to describe the effect of constant temperatures on median nymphal development (egg hatch to adult eclosion). Although the nonlinear model under-estimated developmental rates at two variable temperatures in the laboratory by 12 and 14% and in the field by 25-32%, its predictions were consistent enough to permit accurate predictions of developmental times. Nymphal survivorship, teneral adult weights, and adult mesothoracic femur length decreased with decreasing rearing temperatures.

Greenhouse studies involving interactions of six varieties of Cucurbita spp. and the squash bug, Anasa tristis (De Geer) (Corei dae, Hemiptera), indicate that Butternut is the most resistant and Black Zucchini is the most susceptible of the group. A smaller amount of plant sap was removed from the more resistant plants. Lack of preference appeared to be the major factor involved in resistance. However, the resistant plants produced an antibiotic effect on nymphal development. Nymphs reared on Black Zucchini and Pink Banana attained a significantly later instar and lived longer than those reared on the other four varieties. Tolerance did not seem to be involved in the greenhouse studies. The order of resistance of the six varieties from high to low was Butternut, Royal Acorn, Sweet Cheese, Green Striped Cushaw, Pink Banana and Black Zucchini.

The life-cycle of the squash bug, Anasa tristis, in Massachusetts has been worked out and compared with the records for other parts of the country. An attempt to find an efficient insecticide for the destruction of adult bugs without injuring the vines was unsuccessful. Brief notes on a Tachinid parasite, Trichopoda pennipes are given.

During the summer of 1926 experiments were conducted upon squashes with cyanogan calcium cyanide “A” dust for the control of squash bugs. Over 80% control was obtained with undiluted dust. All dusting was done in the open air. Applications were very heavy, using 1½ ounces of dust per hill. Little or no injury was noted when the dust was properly applied.

To obtain more information on arrestants and feeding stimulants for insects in general, and the boll weevil, Anthonomus grandis Boheman, in particular, tests with water extracts obtained from several plants were conducted at the Boll Weevil Research Laboratory during the summer of 1963. Four species of insects in addition to the boll weevil became numerous enough in the vicinity of the laboratory for such studies. The insects and plants used in the studies were: Monarch butterfly, Danaus plexippus (L.), on milkweed (Asclepias syriaca L.) ; elm leaf beetle, Galerucella xanthomelaena (Schiffermuller), on American elm (Ulmus americanam . L) ; a species of Gastrophysa on dock (Rumex obtusifolius L.) ; the squash bug Anasa tristis (De Geer), on pumpkin (Cucurbita pepo L.); and the boll weevil, on cotton squares (Gossypiuin hirsutum L.).