Development, Survival and Phenology of the Sweetclover Weevil Parasitoid, \u3ci\u3ePygostolus Falcatus\u3c/i\u3e (Hymenoptera: Braconidae)

Biennial sweetclovers were widely used for soil improvement and as for- ages in the first half of the 1900s. The introduction of the sweetclover weevil, Sitona cylindricollis, caused a drastic decline in sweetclover acreage. In North Dakota, yellow sweetclover, Melilotus officinalis, is still the legume of choice on organic farms. In an effort to control the weevil, the thelyotokous parasitoid Pygostolus falcatus was imported. Parasitoids were studied for temperature-dependent development, and adult longevity as influenced by temperature and availability of provisions. Development from egg to adult at 15, 20, 25 and 30°C was 58, 28, 22 and 21 d, respectively. No parasitoids were reared out at 10°C, although diapausing first instars were present. Longevity of adult parasitoids provided honey, water, sweetclover and sweet- clover weevils at 15, 20, 25 and 30°C was 29, 22, 12 and 6 d, respectively. Adults provided the following combinations of provisions at 25°C survived for: nothing-2 d; water-2 d; honey-4 d; honey and water - 6 d; honey, water and sweetclover - 11 d; honey, water, sweetclover and hosts - 12 d. Field cage releases and a degree-day model developed for the parasitoid demonstrated that poor synchrony between P. falcatus and the sweetclover weevil hinders its usefulness as a biological control agent

Host specificity of divergent populations of the leaf beetle \u3ci\u3eDiorhabda elongata\u3c/i\u3e (Coleoptera: Chrysomelidae), a biological control agent of saltcedar (Tamarix spp.)

The leaf beetle, Diorhabda elongata (Brullé) sensu lato, was released in 2001 for the classical biological control of exotic saltcedars, a complex of invasive Tamarix species and hybrids. It did not establish at sites south of 37°N latitude where summer daylengths are below the critical photoperiod of the northern-adapted populations of the beetle that were released. Therefore, we assessed the host specificity of four D. elongata populations collected from more southern latitudes in the Old World (Tunisia, Crete, Uzbekistan, and Turpan, China). All populations were similar to each other and the previously released populations of D. elongata in their host specificity. Larval/pupal survival for all populations was 34–100% on Tamarix test plants, 0–76% on native Frankenia plants (both in the order Tamaricales), and 0% on the remaining 28 species of plants on which all the larvae died as 1st instars. D. elongata laid high numbers of eggs on saltcedar, generally fewer eggs on athel (a moderately valued evergreen species of Tamarix) except for Uzbekistan beetles, and few to no eggs on three species of Frankenia. Few to no adults were found on Frankenia plants which also were poor maintenance hosts. The release of any of the four D. elongata populations in the southern US and northern Mexico should pose no risk to plants outside the order Tamaricales and a low risk to native, non-target Frankenia plants. Athel may be less damaged than saltcedar

Development, Survival and Phenology of the Sweetclover Weevil Parasitoid, \u3ci\u3ePygostolus Falcatus\u3c/i\u3e (Hymenoptera: Braconidae)

Biennial sweetclovers were widely used for soil improvement and as for- ages in the first half of the 1900s. The introduction of the sweetclover weevil, Sitona cylindricollis, caused a drastic decline in sweetclover acreage. In North Dakota, yellow sweetclover, Melilotus officinalis, is still the legume of choice on organic farms. In an effort to control the weevil, the thelyotokous parasitoid Pygostolus falcatus was imported. Parasitoids were studied for temperature-dependent development, and adult longevity as influenced by temperature and availability of provisions. Development from egg to adult at 15, 20, 25 and 30°C was 58, 28, 22 and 21 d, respectively. No parasitoids were reared out at 10°C, although diapausing first instars were present. Longevity of adult parasitoids provided honey, water, sweetclover and sweet- clover weevils at 15, 20, 25 and 30°C was 29, 22, 12 and 6 d, respectively. Adults provided the following combinations of provisions at 25°C survived for: nothing-2 d; water-2 d; honey-4 d; honey and water - 6 d; honey, water and sweetclover - 11 d; honey, water, sweetclover and hosts - 12 d. Field cage releases and a degree-day model developed for the parasitoid demonstrated that poor synchrony between P. falcatus and the sweetclover weevil hinders its usefulness as a biological control agent

Photoperiodic Response of Abrostola asclepiadis (Lepidoptera: Noctuidae), a Candidate Biological Control Agent for Swallow-worts (Vincetoxicum, Apocynaceae)

A biological control program is in development for two swallow-wort species (Vincetoxicum, Apocynaceae), European vines introduced into northeastern North America. One candidate agent is the defoliator Abrostola asclepiadis (Denis and Schiffermüller) (Lepidoptera: Noctuidae). The moth reportedly has up to two generations in parts of its native range. We assessed the potential multivoltinism of Russian and French populations of the moth by rearing them under constant and changing photoperiods, ranging from 13:11 to 16:8 hour (L:D). The French population was also reared outdoors under naturally-changing day lengths at a latitude similar to northern New York State. Less than six adult moths emerged, with one exception, for any photoperiod treatment. We expect A. asclepiadis to be univoltine if it were to be released into North America, limiting its potential impact on swallow-worts. It should therefore be given a lower priority for release

Host speciWcity of diVerent populations of the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae), a biological control agent of saltcedar (Tamarix spp.)

Abstract The leaf beetle, Diorhabda elongata (Brullé) sensu lato, was released in 2001 for the classical biological control of exotic saltcedars, a complex of invasive Tamarix species and hybrids. It did not establish at sites south of 37°N latitude where summer daylengths are below the critical photoperiod of the northern-adapted populations of the beetle that were released. Therefore, we assessed the host speciWcity of four D. elongata populations collected from more southern latitudes in the Old World (Tunisia, Crete, Uzbekistan, and Turpan, China). All populations were similar to each other and the previously released populations of D. elongata in their host speciWcity. Larval/pupal survival for all populations was 34-100% on Tamarix test plants, 0-76% on native Frankenia plants (both in the order Tamaricales), and 0% on the remaining 28 species of plants on which all the larvae died as 1st instars. D. elongata laid high numbers of eggs on saltcedar, generally fewer eggs on athel (a moderately valued evergreen species of Tamarix) except for Uzbekistan beetles, and few to no eggs on three species of Frankenia. Few to no adults were found on Frankenia plants which also were poor maintenance hosts. The release of any of the four D. elongata populations in the southern US and northern Mexico should pose no risk to plants outside the order Tamaricales and a low risk to native, non-target Frankenia plants. Athel may be less damaged than saltcedar. Published by Elsevier Inc

Plant-mediated interactions: considerations for agent selection in weed biological control programs

Plant-mediated indirect interactions among herbivores (arthropods and pathogens) are common and extensively reported in the ecological literature. However, they are not well-documented with respect to weed biological control. Such interactions between biological control agents can have net positive or negative impacts on total weed suppression depending on the strength of the interaction(s), the relative importance of the agent indirectly impacted, and the combined weed suppression that results. A better understanding of plant-mediated interactions may improve decision-making about which agents to introduce in classical biological control programs for greatest impact on invasive weeds. This paper reviews the subject, including examples from the biological control literature; outlines the need for research on indirect effects of herbivores on other herbivores; discusses how such knowledge may strengthen classical biological control programs for invasive weeds; and provides recommendations for the kind of studies that should be done and how information about plant-mediated interactions could be integrated into agent evaluation protocols, to assist in decision-making about agents for importation and release

Establishment of the invasive perennial Vincetoxicum rossicum across a disturbance gradient in

Abstract Vincetoxicum rossicum (pale swallowwort) is a non-native, perennial, herbaceous vine in the Apocynaceae. The species' abundance is steadily increasing in the northeastern United States and southeastern Canada. Little is known about Vincetoxicum species recruitment and growth. Therefore, we conducted a field experiment in New York State to address this knowledge gap. We determined the establishment, survival, and growth of V. rossicum during the first 2 years after sowing in two old fields subjected to four disturbance regimens. We hypothesized that establishment and survival would be higher in treatments with greater disturbance. At the betterdrained location, overall establishment was 15 ± 1% [mean ± standard error] and did not differ among treatments. At the poorly drained location, establishment varied by treatment; mowed and control plots had greater establishment [10 ± 2%] than herbicide ? tillage and herbicide-only plots [1.6 ± 0.5%]. Of those seedlings that emerged, overall survival was high at both locations (70-84%). Similarly, total (above ? belowground) biomass was greater in herbicide ? tillage and herbicide-only plots than in mowed and control plots at both locations. Thus, V. rossicum was successful in establishing and surviving across a range of disturbance regimens particularly relative to other old field species, but growth was greater in more disturbed treatments. The relatively high-establishment rates in old field habitats help explain the invasiveness of this Vincetoxicum species in the northeastern U.S. and southeastern Canada