Adventive Gryon aetherium Talamas (Hymenoptera, Scelionidae) associated with eggs of Bagrada hilaris (Burmeister) (Hemiptera, Pentatomidae) in the USA

Bagrada bug, Bagrada hilaris (Burmeister) (Hemiptera, Pentatomidae), has become a major pest of cole crops (cabbage, broccoli, cauliflower, kale) in California since its arrival in 2008. In this study we documented parasitism of B. hilaris eggs at a highly infested site in northern California by deploying sentinel B. hilaris eggs and collecting naturally-laid B. hilaris eggs in the soil. Two parasitoids, Gryon aetherium Talamas (Hymenoptera, Scelionidae) and Ooencyrtus californicus Girault (Hymenoptera, Encyrtidae), emerged from sentinel eggs, but only G. aetherium was documented attacking eggs in the soil. Gryon aetherium is currently being assessed as a classical biological control agent for B. hilaris in California, and mating experiments showed that crosses between G. aetherium from Pakistan and California yielded viable female offspring. This report marks the first known record of G. aetherium in the USA, and further work should be conducted to assess the potential of this parasitoid for biological control of B. hilaris.

Socio-ecological impacts of water hyacinth, Eichhornia crassipes (MART.) in Lake Tana, Gulf of Gorgora, Ethiopia

Water hyacinth is one of the aggressive alien aquatic macrophyte threatening biodiversity, economic development and human wellbeing. Currently, the macrophyte has invaded Lake Tana and its catchment causing several socio-ecological impacts. So far, there is limited information on socio-ecological impact of water hyacinth in Lake Tana specifically gulf of Gorgora. Therefore, the main aim of this study was to assess socio-ecological impact of water hyacinth in Lake Tana gulf of Gorgora, located in North West of Ethiopia from November 2019 to January 2020. Two sampling sites (infested and non-infested) were identified based on infestation of water hyacinth. A total of 30 water and 12 water hyacinth samples were collected with a survey of 50 individuals. Results revealed that water quality, phytoplankton diversity, fishing, navigation, health condition of local people, recreational and aesthetic value were impacted negatively due to infestation. Conversely, higher accumulation of toxic heavy metals and dissolved metallic ions in the root, stem and leaf of the macrophyte impacted positively. Infestation of the macrophyte significantly affected water quality and species diversity of Lake Tana. In the infested site; DO (3.3 to 4.5), SRP (0.012 to 0.023 mg L-1), TP (0.24 to 0.28 mg L- 1), NO3-N (0.74 to 0.97 mg L-1) and TN (2.1 to 3.2 mg L-1) were significantly (p < 0.01) lower than non-infested site. Generally, infestation of water hyacinth negatively impacted the society and the ecology in Lake Tana catchment. Therefore, continuous monitoring and management of the macrophyte is required.

Influence of sowing and harvest dates on production of two different cultivars of sugar beet

Small-plot trials conducted in 2013–2015 studied the impact of longer vegetation periods (by means of earlier drilling and/or later harvest) on production results of two sugar beet cultivars – one nematode-tolerant cultivar and one cultivar without such tolerance. The trials took place at two sites with different Heterodera schachtii infestation levels. In all trial seasons, root yield was significantly higher in the earlier drilled plots. On average, prolongation of the vegetation period in spring by 13 days increased root yield by 10.9%. Therefore, each day by which drilling is postponed represents a 0.7–0.8% loss of yield. As to sugar content, no statistically significant benefit of vegetation period prolongation by early drilling was found. The spring gain was slightly higher for the non-tolerant cultivar than for the tolerant one on average over all trial seasons. This result confirms the theory that nematodes impact the crop mainly in later stages of vegetation, and early drilling can thus help eliminating, to a certain degree, the risk of nematode damage. In the autumn, root yield increased by 14.3% on average over 39 days. The autumn daily gain was about half of the rate found in the spring. The increase in sugar content was between 0.6% and 1% (abs.) on average. Autumn growth achieved at the non-infested site was much higher than at the infested site.

New strawberry genotypes tested for organic production on a Verticillium-infested site

Nineteen new strawberry breeding clones, bred at the Institute for Breeding Research on Fruit Crops in Dresden-Pillnitz, Germany, were evaluated for their suitability for organic production at a Verticillium-infested site in Vienna, Austria. Soil cover, plant vitality, resistance to leaf spot diseases as well as flower damages by the strawberry blossom weevil (Anthonomus rubi) and by spring frost were recorded. In two consecutive years, marketable yield and fruits infested by Botrytis cinerea were assessed. Three breeding clones, P-7189, P-8043 and P-8071, were considered as suitable for organic strawberry production. P-7189 and P-8043 showed high tolerance to Verticillium wilt. The breeding clones P-8155 and P-8166 performed well under organic management but had very soft fruits that were not acceptable for commercial fruit production. The rest of the breeding clones were low-yielding, however, some of them could be of interest for home gardens due to their good flavour and high plant vitality. &nbsp;

Management of Soilborne Diseases in Strawberry Using Vegetable Rotations

The influence of crop rotation on soilborne diseases and yield of strawberry (Fragaria × ananassa) was determined at a site infested with Verticillium dahliae microsclerotia and at another with no known history of V. dahliae infestation during 1997 to 2000. The rotations studied at the V. dahliae-infested site were (i) broccoli-broccoli-strawberry, (ii) Brussels sprouts-strawberry, and (iii) lettuce-lettuce-strawberry; the treatments at the site with no history of V. dahliae were (i) broccoli-broccoli-strawberry, (ii) cauliflower-cauliflower-strawberry, and (iii) lettuce-lettuce-strawberry. The effects of rotation on V. dahliae and Pythium populations, strawberry vigor, Verticillium wilt severity, and strawberry fruit yield were compared with a standard methyl bromide + chloropicrin fumigated control treatment at both sites. Rotations did not alter total population levels of Pythium spp. at either study site. However, V. dahliae microsclerotia were significantly reduced with br occoli and Brussels sprouts rotations compared with lettuce rotations at the V. dahliae-infested site. Reduced propagules led to lower Verticillium wilt severity on strawberry plants in the broccoli and Brussels sprouts rotations than in lettuce-rotated plots. Strawberry vigor and fruit yield were significantly lower in lettuce-rotated plots than in broccoli- and Brussels sprouts-rotated plots. Despite no detectable microsclerotia at the other site, strawberry vigor and fruit yield were greatest in plots rotated with broccoli, intermediate with cauliflower, and lowest with lettuce. None of the rotation treatments were better than the fumigated control for all variables measured. In the absence of fumigation, rotation with broccoli and Brussels sprouts is an effective cultural practice for managing Verticillium wilt in strawberry production; whereas, in fields with no detectable V. dahliae, broccoli is also a feasible rotational crop that enhances strawberry growth and yield. According to a cost-benefit analysis, the broccoli-strawberry rotation system could be an economically viable option provided growers are able to alternate years for strawberry cultivation.

Suppression of Phytophthora Root Rot in Red Raspberries with Cultural Practices and Soil Amendments

Various soil amendments and cultural practices were examined in both a phytophthora-infested (Phytophthora fragariae var. rubi) (+PFR) and uninfested field (–PFR) planted to `Heritage' red raspberries. Although plants in the +PFR field did not exhibit typical disease symptoms due to unseasonably dry weather, their growth was less than those in the –PFR field. After 2 years, plants in the +PFR site had the highest yields in plots treated with phosphorous acid or amended with gypsum, whereas compost-amended plots had the lowest yields in both +PFR and –PFR sites. A second field study confirmed the positive effect of gypsum on growth and yield of raspberries in an infested site. In a third study, `Titan' raspberries grown under greenhouse conditions in pots containing unamended soil from the infested site, then flooded, exhibited severe disease symptoms; however, pasteurization of the soil, treatment with phosphorous acid and metalaxyl fungicide, or gypsum amendment mostly prevented symptoms from developing. These three studies suggest that a preplant soil amendment containing certain readily available forms of calcium, such as found in gypsum, can help suppress phytophthora root rot and increase survival, growth and yield of raspberries in sites where the pathogen is present.

Effect of Crop Rotation on the Survival of Phytophthora capsici in Michigan

Phytophthora capsici is a limiting factor for some vegetable producers in Michigan despite crop rotation and fungicide applications. Our objective was to assess the effect of crop rotation on the survival of P. capsici at a naturally infested site in Michigan planted to cucumbers in 1998, corn in 1999 and 2000, and tomatoes in 2001. Isolates were characterized for compatibility type (CT), mefenoxam sensitivity, and amplified fragment length polymorphism (AFLP) marker profiles, and compared with isolates recovered from other locations in Michigan during the same time period. The A1:A2 CT ratio was 1:1, and approximately 60% of the isolates recovered in both years were intermediately sensitive or insensitive to mefenoxam. The majority of the isolates (89%) had unique AFLP fingerprints, and no members of the same clonal lineage were recovered among years. Isolates from this location were more similar to each other than to isolates from other locations in Michigan, and it was not possible to distinguish isolates based on the year of isolation. Genetic similarity analyses indicate that isolates from this location are part of a genetically distinct outcrossing population. These data indicate that P. capsici persisted as oospores for the 2 years between cucumbers and tomatoes, and that crop rotation and mefenoxam are not likely to provide economic control.

Calcium Sulfate Soil Amendment Reduces Incidence of Phytophthora Root Rot in Raspberry

Phytophthora is a debilitating root disease of many crops, and limits raspberry production in much of the world. Two fungicides are labeled for use against Phytophthora on raspberries in North America, but they are not effective when disease pressure is severe. We were interested in the effect of preplant soil amendments such as composts, fertilizers, gypsum and limestone on the incidence of Phytophthora in red raspberries. Various amendments were incorporated simultaneously at two sites prior to planting raspberries. Both sites had identical soil, but one had a known history of P. fragariae var. rubi and the other had no history of raspberry production. Differences in survival and plant growth of `Heritage' among fertilizer (ammonium nitrate, phosphorus acid), compost, gypsum and lime (calcitic or dolomitic) treatments were small in the uninfested site, whereas differences were large in the infested site. Gypsum (CaSO4) treated plots had higher yields and greater cane diameter, density, and height compared to control plots after 2 years. Plants in compost amended plots exhibited the most severe disease symptoms; liming had little effect. In a second field experiment, various sources of calcium and sulfate were compared in an infested site. As before, plants in calcium sulfate-amended plots performed better than plants in control plots or in plots amended with sulfur or potassium sulfate. In a greenhouse experiment using infested soil and artificial flooding, calcium sulfate also reduced disease incidence in `Titan' compared to unamended soil. Data from these three experiments suggest that gypsum could be used in an integrated approach to Phytophthora management in raspberries, and perhaps other crops as well.