A binomial sequential sampling plan for Bactericera cockerelli (Hemiptera: Triozidae) in Solanum lycopersicum (Solanales: Solanacea).

The tomato-potato psyllid Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is a pest of many solanaceous plants, including tomato (Solanum lycopersicum L.) and potato (Solanum tuberosum L.). In tomato, feeding by nymphs is associated with "psyllid yellows." B. cockerelli also vectors "Candidatus Liberibacter psyllaurous," an infectious bacterium that causes "vein greening" disease. Decisions about management action are much more effective when guided by robust sampling. However, there are few previous studies of potato psyllid spatial distribution in tomato fields, and no published sequential sampling plans for the pest in tomato. We studied B. cockerelli in various tomato fields in California and used these data to generate a sequential sampling plan. We found that juvenile B. cockerelli in tomato fields exhibit an edge effect, an aggregated distribution, and individuals are primarily located on the bottom of leaves. Psyllids were concentrated in the upper segments of plants, but this changed over time. Finally, we present three binominal sequential sampling plans for managing tomato psyllids in tomato fields. These plans differed from both those for bell pepper (Capsicum annum L.) and potato, indicating that B. cockerelli needs to be sampled using crop-specific sampling plans.

Identification and impact of natural enemies of Bactericera cockerelli (Hemiptera: Triozidae) in Southern California.

Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is a major pest of potato, (Solanum tuberosum L.), tomato (Solanum lycopersicum L.), and peppers (Capsicum spp.). The purpose of our research was to identify and determine the impact of natural enemies on B. cockerelli population dynamics. Through 2 yr of field studies (2009-2010) at four different sites and laboratory feeding tests, we identified minute pirate bug, Orius tristicolor (White) (Hemiptera: Anthocoridae); western bigeyed bug, Geocoris pallens Stål (Hemiptera:Geocoridae), and convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) as key natural enemies of B. cockerelli in southern California potatoes, tomatoes, and bell peppers. In natural enemy exclusion cage experiments in the potato crop and in American nightshade, Solanum americanum Miller, the number of B. cockerelli surviving was significantly greater in the closed cage treatments, thus confirming the affect natural enemies can have on B. cockerelli. We discuss how this information can be used in an integrated pest management program for B. cockerelli.

Effects of insecticides on behavior of adult Bactericera cockerelli (Hemiptera: Triozidae) and transmission of Candidatus Liberibacter psyllaurous.

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is a serious pest of potatoes (Solanum tuberosum L.) that can cause yield loss by direct feeding on crop plants and by vectoring a bacterial pathogen, Candidatus Liberibacer psyllaurous. Current pest management practices rely on the use of insecticides to control the potato psyllid to lower disease incidences and increase yields. Although many studies have focused on the mortality that insecticides can cause on potato psyllid populations, little is known regarding the behavioral responses of the potato psyllid to insecticides or whether insecticides can decrease pathogen transmission. Thus, the objectives of this study were to determine the effects of insecticides on adult potato psyllid behaviors, the residual effects of insecticides on potato psyllid behaviors over time, and effects of these insecticides on Ca. L. psyllaurous transmission. Insecticides tested included imidacloprid, kaolin particle film, horticultural spray oil, abamectin, and pymetrozine. All insecticides significantly reduced probing durations and increased the amount of time adult psyllids spent off the leaflets, suggesting that these chemicals may be deterrents to feeding as well as repellents. Nonfeeding behaviors such as tasting, resting, and cleaning showed variable relationships with the different insecticide treatments over time. The insecticides imidacloprid and abamectin significantly lowered transmission of Ca. L. psyllaurous compared with untreated controls. The implications of our results for the selection of insecticides useful for an integrated pest management program for potato psyllid control are discussed.

Effects of terrestrial pollutants on insect parasitoids.

Parasitoids are important organisms in the regulation of insect herbivores in natural, urban, and agricultural ecosystems. The impact of pollutants acting on parasitoids has not been extensively reviewed. This prompted us to propose a falsifiable null hypothesis (pollutants have no effects on parasitoids) and two alternative hypotheses (pollution negatively or positively affects parasitoids) to assess in the available literature the effects of pollutants acting on parasitoids. We found 26 studies examining 39 biological systems that met our criteria for inclusion. Of these studies, 18 of the 39 biological systems (46.2%) supported the null hypothesis while 18 (46.2%) supported the first alternative hypothesis in which pollutants exhibited negative effects on parasitoids. Only a small percentage of the studies (7.6%, 3 of 39) supported the second alternative hypothesis suggesting that pollutants had positive effects on parasitoids. We provide a synthesis of the available data by pollution type, summarize trends for different pollutants, and suggest future areas of research.

Voracity and prey preference of insidious flower bug (hemiptera: anthocoridae) for immature stages of soybean aphid (hemiptera: aphididae) and soybean thrips (thysanoptera: thripidae).

The generalist predator, Orius insidiosus (Say), is an important natural enemy of the soybean aphid, Aphis glycines Matsumura. Soybean thrips, Neohydatothrips variabilis (Beach), serve as an important prey resource for O. insidiosus in soybeans, sustaining the predator's population before the arrival of the soybean aphid. Although generalist predators can forage on a broad range of prey, they may show distinct preferences for particular prey, attacking prey at levels disproportionate to their relative numbers. To assess the preference of O. insidiosus for soybean aphid and soybean thrips, attack rates of nymphal and adult O. insidiosus were measured in the laboratory. For both adults and nymphs, the number of prey attacked increased as more prey were provided. For nymphs, the total number of prey attacked increased as the predator matured. In general, the number of prey attacked by adult predators was relatively constant as the predator aged. Both O. insidiosus nymphs and adults displayed a preference for soybean thrips, by disproportionately attacking soybean thrips over soybean aphid regardless of the relative densities of the two prey. We discuss implications of this preference on O. insidiosus life history characteristics and the potential impact on O. insidiosus-prey dynamics in the field.

A sequential binomial sampling plan for potato psyllid (Hemiptera: Triozidae) on bell pepper (Capsicum annum).

BACKGROUND: Potato psyllids (Bactericera cockerelli Sulc) are a pest on solanaceous crop plants, including bell peppers. Potato psyllids vector Candidatus Liberibacter psyllaurous, but bell peppers (Capsicum annum L.) do not exhibit symptoms from infection. Potato psyllids show variation in spatial patterns and host choice with cultivar and plant species. Consequently, a study of spatial distribution and sampling plan specific to bell peppers is necessary for management of this insect pest, as those developed for other crops are unlikely to transfer among crops. RESULTS: Potato psyllids were evenly distributed on both sides of leaves but prefer the top two-thirds of pepper plants. Within fields, psyllids demonstrated an aggregated spatial distribution, but the edge effect observed in other crop plants was absent. Eggs and nymphs had similar spatial distributions that differed from adults. A series of nymph-based sampling plans were examined. Sampling plans based on an infestation of less than 41% of plants infested (5 nymphs plant(-1)) were statistically unacceptable, while little difference was found between the 41% infestation plan and 56% (20 nymphs plant(-1)) infestation plan. At 41%, an average of 11 and maximum of 49 samples would be necessary to make a treatment decision. CONCLUSION: The binomial sequential sampling plan presented here offers an important yet simple tool for managing potato psyllids in bell pepper.

Spatial dispersion and binomial sequential sampling for the potato psyllid (Hemiptera: Triozidae) on potato.

BACKGROUND: The potato psyllid is a serious pest of potatoes. Sampling plans on potatoes for the potato psyllid have yet to be developed, thus the authors' objectives were (1) to determine the most efficient within-plant sampling unit, (2) to determine the spatial dispersion of potato psyllids in potato fields and (3) to develop a binomial sequential sampling plan for this pest. RESULTS: Significantly more potato plants were infested with potato psyllids on the edges of the field, and significantly more plants were infested with psyllids on the 'top' and 'middle' of the potato plant. Significantly more psyllids were also found on the undersides of leaves. The potato psyllid has an aggregated distribution in potato fields. Binomial sequential sampling plans were developed for three action thresholds representing 0.5, 1 and 5 psyllids per plant. The average sample numbers for these action thresholds were between 12 and 16 samples, depending on the action thresholds. However, based on the shape of the operating characteristic curve, the 0.5 and 1 sampling plans were more reliable than the 5 psyllids per plant plan. CONCLUSION: The binomial sequential sampling plans are useful for detecting potato psyllids at low levels of infestation, which will be useful for pest management purposes.

Effects of pollutants on bottom-up and top-down processes in insect-plant interactions.

Bottom-up (host plant quality) and top-down (natural enemies) forces both influence the fitness and population dynamics of herbivores. However, the impact of pollutants acting on these forces has not been examined, which prompted us to review the literature to test hypotheses regarding this area of research. A comprehensive literature search found 126 references which examined fitness components and population dynamics of 203 insect herbivores. One hundred and fifty-three of the 203 herbivores (75.4%) had fitness impacted due to bottom-up factors in polluted environments. In contrast, only 20 of the 203 (9.9%) had fitness significantly impacted due to top-down factors in polluted environments. The paucity of results for top-down factors impacting fitness does not necessarily mean that top-down factors are less important, but rather that fewer studies include natural enemies. We provide a synthesis of available data by pollution type and herbivore guild, and suggest future research to address this issue.