Viruses cause many important plant diseases and are responsible for yield and quality losses in crops in all parts of the world. No curative methods are available for infected plants and the main control strategies are cultural practices including prophylactic measures to prevent virus arrival, installation and spread into the crop or use genetic resistance to limit disease damage. Factors driving viral emergence include genetic variability of plant viruses, changes in agricultural practices, exchanges of plant material and new introduction or increase in the population of insect vectors in the environnent of the crops. In this review, we briefly describe the most important viruses emerging in economically important vegetable greenhouse crops including pepper, tomato and cucurbit species.

/pdf/integrated-pest-and-disease-management-in-greenhouse-crops-5dsa245win.pdf

Integrated pest and disease management in greenhouse crops.

Alfalfa, Medicago sativa L., is among the most prized of forages, and is grown worldwide as a feed for all classes of livestock. It is one of man's oldest crops, and its cultivation probably predates recorded history. In addition to its versatility as a feed, alfalfa is well known for its ability to improve soil structure and, as a legume, is an effective source of biological nitrogen. As a perennial crop, alfalfa has a lifespan approaching 5 years, but in some areas of the world fields may remain productive for considerably longer. Such a long stand life affords ample time for the establishment and development of a diverse community structure by an abundance of organisms. In spite of system perturbations caused by frequent harvests and occasional pesticide applications, an alfalfa field provides a temporal stability which is uncommon among field crops. As a result of this stability, alfalfa supports an immense diversity of flora and fauna which, at times, exceeds that of riparian ecosystems. While most of alfalfa's inhabitants have little or no impact on it as a crop, a few are capable of causing extensive damage. Arthropods, plant pathogens, weeds, vertebrates, and plant parasitic nematodes can all cause significant yield and/or quality reductions and frequently contribute to shortening the productive life of the stand. This paper reviews the major strategies which have been developed to manage many of these alfalfa pests including: host plant resistance; cultural controls, such as harvest strategies, irrigation management, sanitation, planting schedules, and crop rotation; mechanical and physical controls; chemical control; and biological controls. Multiple pest interactions, e.g. insect-insect; insect-disease; insect-weed, and their management are discussed. Potential conflicts arising from the use of strategies which may reduce one pest but exacerbate others are also examined. A cross index of management strategies and their role in managing multiple pests is provided. Computer models, both ecological and economic, and their role in alfalfa pest management are discussed. Selected information sources on alfalfa and alfalfa IPM available over the Internet are listed. Alfalfa's role in the agricultural landscape, as it relates to pests, natural enemies, and pest management in other cropping systems as well as its role in crop rotation, is considered.

/pdf/integrated-pest-management-in-forage-alfalfa-466rsycjo7.pdf

Integrated Pest management in Forage Alfalfa

Electrical penetration graphs (DC EPG) were used to monitor the feeding behavior of the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae) exposed to the flavonoids luteolin and genistein in artificial diets. The EPG patterns generated by aphids feeding on plants were used to interpret the patterns generated on the artificial diets. Addition of flavonoids to the diets generally prolonged the period of stylet probing (as indicated by EPG pattern d-C), reduced salivation (as indicated by pattern d-E1) and passive ingestion (as indicated by pattern d-E2), and also delayed the onset of salivation and passive ingestion. At higher concentrations (≥100 μg cm−3 for luteolin, ≥1,000 μg cm−3 for genistein), the flavonoids completely stopped salivation and passive ingestion. In most events associated with active ingestion (EPG pattern d-G), however, differences in feeding behavior did not statistically differ between the control diet and those with flavonoids; luteolin, and genistein only at 10 μg cm−3 prolonged the time until the first d-G pattern was observed. The current findings demonstrate detrimental effects of the isoflavone genistein and the flavone luteolin on the feeding behavior of the pea aphid, A. pisum. This can be employed to create plants which are resistant to aphids and other herbivores.

/pdf/antifeedant-activity-of-luteolin-and-genistein-against-the-11bw1h71ix.pdf

Antifeedant activity of luteolin and genistein against the pea aphid, Acyrthosiphon pisum.

Insects and mites.

Feeding Value (Forage Quality)

Economic injury levels and economic thresholds for pea aphid, Acyrthosiphon pisum (Harris), on alfalfa

Experiments were conducted at Rosemount, Minn., to establish economic injury levels and economic thresholds for the potato leafhopper, Empoasca fabae (Harris), on established of alfalfa, Medicago sativa L. Gradients of potato leafhopper numbers were established in plots of cv. ‘Vernal’ alfalfa by using insecticidal sprays and bordering uncut strips of alfalfa. In 1981, damaging potato leafhopper numbers occurred on third regrowth and showed negative linear relationships with dry-matter yield and U.S. dollar value of yield. In 1981, damaging potato leafhopper numbers occurred on both second and third regrowths. On second regrowth, nymphal numbers were high and had significant negative effects on percent crude protein, plant height, dry-matter yield, and dollar yield as computed from the cost of an equivalent substitute ration of corn and soybean meal. On third regrowth, significant negative relationships were found between potato leafhopper numbers, primarily adults, at 5 and 17 cm of regrowth and dry-matter yield, height at harvest, and dollar yield. Calculated economic injury levels for vacuum and sweep-net sampling were 30.3 potato leafhoppers per 0.48 m2 per sample week and 37.1 potato leafhoppers per 25 180° sweeps per sample week, respectively. The calculated economic threshold in 1979 for 12 cm of regrowth alfalfa was 0.4 potato leafhopper per pendulum sweep. Values in 1981 for 5 and 17 cm of alfalfa were 0.32 and 0.5 potato leafhoppers per pendulum sweep, respectively.

Economic Injury Levels and Economic Thresholds for Potato Leafhopper (Homoptera: Cicadellidae) on Alfalfa in Minnesota

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Economic injury levels and economic thresholds for pea aphid, Acyrthosiphon pisum (Harris), on alfalfa

Economic Injury Levels and Economic Thresholds for Potato Leafhopper (Homoptera: Cicadellidae) on Alfalfa in Minnesota