- (Focus Area) Agriculture
- Author: Jorge Antonio Angeles
- Posted by: Gale Perez
Silverleaf nightshade, Solanum Elaeagnifolium, is perennial weed that is native to South America, Mexico, American Southwest and Southern States. This herbaceous and woody summer weed belongs to Solanaceae just like other weeds such as black nightshade (Solanum nigrum), hairy nightshade (Solanum physalifolium) and horsenettle (Solanum carolinense). It can be found throughout California and in grows in desert and semi-arid areas. Silverleaf nightshade is often found growing in different cropping systems, rangeland, pastures, roadsides, and disturbed areas. Silverleaf nightshade is highly adaptable and can tolerate a wide range of soil and climatic conditions such as high temperatures, low rainfall, saline and drought conditions. The leaves and berries produced by silverleaf nightshade plants have glycoalkaloid compounds that can be toxic to livestock and humans if consumed (UC IPM) (Boyd 1982).
Life Cycle
Impacts
Silverleaf nightshade is becoming a problematic weed in some young pistachio orchards in Tulare, Kings and West Fresno. This perennial weed is mostly found in young orchards that are planted on west Fresno and Kings County by interstate 5 highway (Figure 3). In Tulare County, silverleaf nightshade is found pistachio orchards that were planted in unmanaged fallow land or in fields near roadsides where it's commonly found. One of the major impacts of silverleaf nightshade is that it competes with young pistachio orchard for resources such as water, light and nutrients. If left unmanaged, silverleaf nightshade can also interfere with irrigation operations and potentially reduce crop vigor in young pistachio trees (Figure 2). Since silverleaf nightshade can adapt to alkaline and saline soils, it will also outcompete many of the summer annual weeds and become the dominant weed in the population.
Management
Silverleaf nightshade can be a weed that is difficult to control with the available management methods in orchards. Tillage is not recommended as that is one of the ways that rhizomes can be spread across the orchard (Ensby 2011). Mechanical control methods such mowing can be an effective control method to prevent weeds from setting seed. Flail mowers are often used in orchards and vineyards to mow weeds in between tree rows. It is important to note that, new silverleaf nightshade shoots will potentially sprout from the root system after the tops are mowed (Stanton 2011). Even though mowing can be an effective weed control method during the growing season, most commercial mowers will miss the weeds that grow in between trees that directly compete with young trees. Hand weeding can be used to remove some of the weeds around the trees, but extra precaution needs to be taken. Mature silverleaf nightshade plants are covered in reddish prickles that can be harmful if weeds are handled with bare hands. Weeding tools such as shovels and hula hoes can damage surface drip hoses if the user is not careful.
Herbicides can be an effective weed management method to control silverleaf nightshade in different tree crops. There are a twelve pre-emergent and thirteen post-emergent herbicides with different sites of action that are registered for use in pistachios (Table 1). Pre-emergent herbicides are normally applied during the dormant season and most only control weeds before they germinate. Pendimethalin, rimsulfuron, mesotrione, flumioxazin, isoxaben, and flazasulfuron are herbicides that have great control over black and hairy nightshade. Isoxaben can suppress silverleaf nightshade, but cannot be used in pistachios that have not been established for at least three years. Pre-emergent herbicides will not control silverleaf nightshade that emerges from rhizomes in the summer. Post-emergent herbicides can be used to control silverleaf nightshade that emerges in the summer and early fall before harvest. Glyphosate, glufosinate, pyraflufen, and carfentrazone are post-emergent herbicides with different sites of action that can be used to control different weeds and can be used up to two weeks before harvest. 2, 4-D is another post-emergent herbicide that is registered for use in pistachios, but needs to be applied to trees that have been established for at least one year and has a pre-harvest interval of 60 days. Research work from other researchers has shown that glyphosate and 2, 4-D have excellent control of silverleaf nightshade (DiTomaso 2013) (Gitsopoulos 2017). Glyphosate is a systemic herbicide that can potentially kill the root system of silverleaf nightshade, when applied at the correct timing and rate. Since Silverleaf nightshade has extensive rhizome root systems, the root systems need to be killed to fully control this weed. In the summer months, a combination of mowing and the use of post-emergent herbicides can kill the aboveground tissues of silverleaf nightshade weeds and deplete the root bank in the soil (Heap 2018). Post-emergent herbicides need adjuvants such as nonionic surfactants, crop and seed oils, to increase their efficacy. Furthermore, always consult the herbicide labels on information regarding information on the required adjuvants, pre-harvest intervals, application rates and maximum applications per seasons.
The weed management tools to control silverleaf nightshade in pistachio orchards are limited. Developing and maintaining field records before planting is a great way to determine the history of a field before planting. Conducting weed surveys in the winter and spring can help determine what weed species are present in a field. Silverleaf nightshade populations can be reduced by mowing in between tree rows and applying herbicides to weeds present in between trees. These management practices need to be done before the weeds set seeds to contribute to reduce the seedbank. To avoid introducing silverleaf nightshade to other fields, it is important to sanitize tractor equipment and manage the weeds that grow on the field edges or near irrigation canals (. To have an effective silverleaf nightshade management program, a combination of herbicides with different modes of action are needed decrease the possibility of it developing herbicides resistance. Silverleaf nightshade is difficult to control because of its tolerance to many herbicides (Gitsopoulos 2017). During the summer months, it is best to use a combination of systemic and contact post-emergent herbicides to get higher levels of control for silverleaf nightshade. To enhance the efficacy and herbicide absorption, post-emergent herbicides require adjuvants such as methylated seed oils, non-ionic surfactants, crop-oil concentrates, and nitrogen-based fertilizers.
Cited Literature
Boyd, J.W. and Murray, D.S. 1982. Growth and development of silverleaf nightshade (Solanum elaeagnifolium). Weed Science 30, 238-43.
DiTomaso, J.M., G.B. Kyser et al. 2013. Weed Control in Natural Areas in the Western United States. Weed Research and Information Center, University of California. 544pp.
Ensbey R. 2011. Noxious and environmental weed control handbook – A guide to weed control in non-crop, aquatic and bushland situations. 6th ed. New South Wales: Department of Trade and Investment, Regional Infrastructure and Services.
Gitsopoulos, Thomas & Damalas, Christos & Georgoulas, Ioannis. 2017. Chemical options for the control of silverleaf nightshade (Solanum elaeagnifolium). Planta Daninha. 35. 10.1590/s0100-83582017350100064.
Heap, J. & Wu, H. 2018. Silverleaf Nightshade: Australian best practice management manual. Primary Industries and Regions SA & NSW Department of Primary Industries: Adelaide.
Roberts J., Florentine. 2022. Biology, distribution and management of the globally invasive weed Solanum elaeagnifolium Cav. (silverleaf nightshade): A global review of current and future management challenges. Weed Res. 2022;62:393–403. doi: 10.1111/wre.12556.
Stanton, R. & Wu, Hanwen & Lemerle, D. 2011. Root regenerative ability of silverleaf nightshade (Solanum elaeagnifolium Cav.) in the glasshouse. Plant Protection Quarterly. 26. 54-56.
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- Author: Elizabeth J Fichtner
- Author: Santosh Bhandari
- Author: Jennifer Randall
- Author: Richard Heerema
Walnuts and pecans represent two of the four major nut crops grown in California. The California walnut industry dwarfs the state's pecan industry in acreage, with over 300,000 acres dedicated to commercial walnut production and approximately 3,000 acres to pecan. The relatedness of the two crops has facilitated an overlap of specialization in the grower community, with many long-time walnut growers also managing the state's pecan acreage.
Walnuts and pecans are both in the same plant family (Juglandaceae); consequently, they have similar reproductive habits. They are both monoecious, meaning that male and female flowers are borne on the same tree. Also, both pecan and walnut produce male flowers called ‘catkins' (Figure 1), and the non-showy female flowers are produced at the terminus of a preformed shoot (Figure 2) that emerges from a compound bud. On walnuts, the catkin buds are visible at nodes, sometimes with two catkins occupying a single node as a primary and secondary bud (Figure 1A). Conversely, the catkin buds on pecan are not readily visible before bud break (Figure 1B). During the delayed dormant phase on pecan, the catkins are hidden behind a scale sheath that covers the catkins and compound shoot bud (Figure 1 B and C). As a result, the catkins only emerge as the entire bud assemblage pushes, generally in late March-early April in California. The compound bud, containing the current season's shoot and female flowers, is assembled with catkins that emerge in groups of three (Figure 1C and 2B). As a result, groups of catkins mature at the base of the current season's shoot (Figure 2B).
The compound buds of walnut and pecan are similar in that the bud contains the preformed shoot and preformed leaves as well as the female (pistillate) flowers. The female flowers are located at the apex of the preformed shoot (Figure 3 A and B). Walnuts and pecans both have variable numbers of pistillate flowers in each compound bud. Walnut flowers are readily visible with the naked eye, whereas pecan flowers are smaller, and observation of the stigmatic surface may be enhanced with the aid of a hand lens. The final nut set of each compound bud varies based on the number of initial pistillate flowers and the success of pollination and fertilization processes.
Both walnut and pecan tend to exhibit apical dominance as evidenced by the stronger, and often earlier, growth of the apical bud. In walnut, two buds (primary and secondary) may be present at each node. Usually, one bud will dominate and grow, while the weaker bud will remain static or die off. Occasionally, both primary and secondary buds grow, resulting in branching at acute angles, often referred to as “forking”. In walnut, nut set can be evaluated by early June and buds for the next year's crop may already be visible in May (Figure 4A). In vigorous orchards, in-season growth may be produced beyond the position of the nuts (Figure 4B). In-season (neoform) growth is less common in pecan. Researchers speculate that the neoform growth observed in walnut may be related to the use of vigorous hybrid rootstocks.
Although pecan and walnut are related species hailing from the same plant family, their growth and reproductive habits do have notable differences. Growers with a lifetime of experience with walnuts may be baffled by the lack of visible catkins on pecan during the dormant season. A bit of patience in the spring, however, reveals the reproductive structures upon bud break. The need for patience in pecan cultivation is also notable at harvest time. In California, the pecan harvest generally commences after the walnut harvest is complete and often continues into the successive year as fall rain events may impede orchard access.
- Author: Ben Faber
So rain is great………as long as it doesn't cause problems like increased iron chlorosis, root rot, snails, erosion, too many weeds, etc., etc., etc, And now we are seeing more anthracnose. This disease is not normally much of a problem in dry California. Colletotrichum gloeosporioides, the causal fungus of the disease, is widespread in avocado and citrus groves. We see it frequently on small stems and branches, but It is normally of little importance on fruit because unusually large numbers of spores are required to produce damaging infections.
Disease on stems
Disease on leaves
Low humidity and no rain during much of the growing season limit disease development in California. With extended foggy or rainy conditions and mild winter temperatures, and where many dead leaves and twigs and mummified fruit accumulate in trees, the fungus can produce enough spores to cause a disease problem. Spores spread in splashing water and can cause infection anytime from fruit set to harvest. Once infected fruit starts to ripen, temperatures of 75°F and above will accelerate anthracnose development, while temperatures below 59°F retard disease development.
Disease on fruit - black speckles
Fuerte, Rincon, and Wurtz scion cultivars are more susceptible to anthracnose than Hass. Healthy trees often recover from foliar infections and defoliation once conditions become dry. Anthracnose becomes a postharvest problem after the grove has been excessively wet for extended periods. Poor growing practices and mishandling of fruit during or after harvest greatly increase the potential for significant fruit loss.
Anthracnose is controlled primarily with good cultural practices in the grove and proper preharvest and postharvest fruit handling.
- Prune out dead limbs and twigs where fungi sporulate. If many dead leaves are entwined in the canopy, knock them out of the tree.
- Prune low limbs to at least a foot off the ground to reduce humidity within canopies by improving air circulation.
- Prune and harvest only during dry conditions and minimize fruit contamination and injury.
More at UC IPM
https://ipm.ucanr.edu/agriculture/avocado/anthracnose/#gsc.tab=0
We do like the rain, so keep it up.
- Author: Christine Casey
The Haven was created in 2009: we celebrate our 15th anniversary this year. I joined the garden in 2012 and was tasked with creating an outreach and education program. Tours, social media pages, classes, and this blog soon followed. This will end in June, when my position at the Haven is being eliminated.
I've enjoyed introducing so many of you to bees, providing information about gardens and bees, and answering your questions. Working with our amazing volunteers and donors has been extraordinary.
This blog is a short reflection on what I've learned from this work. Look for additional posts throughout May that will provide more bee gardening information, including resources beyond the Haven.
Some random thoughts:
- Children often arrive at the Haven afraid of bees but leave excited to learn more. If you are an adult with children in your life, take advantage of their curiosity to teach them about the natural world. Events like the UC Davis Biodiversity Museum Day are a great place to start.
- You're probably overwatering your garden. Irrigation information for California gardens is here.
- Go on as many garden tours as you can. There's always more to learn.
- There's a lot of bad gardening information on social media. Stick with reputable sources like universities, government agencies, and good independent garden centers.
- In shared public spaces, please don't litter or use a speakerphone.
- Small public gardens and museums are passionate about what we do but operate with minimal resources. Please give what you can and understand that we can't always meet every need or provide all the programs we'd like to.
- Support local nurseries and plant sales.
- Pick up after your dog and leash them in areas where it's required.
- Leave some bare soil for ground-nesting bees.
- There's always room for one more plant.
- Author: Neil McRoberts
General outlook After a brief spike in temperatures over the last few days, with highs in the low to middle 80s F, a more unsettled and cooler pattern will return for the coming week, including a chance of localized rain showers on Saturday. Highs will likely be in the low 80s F once Saturday's cooler front has passed through. Overall temperatures will be adequate for thrips development and we expect to see populations continue to develop.
Thrips/TSWV situation We are expecting generation 2 adults to peak in the next few days. If temperatures stay on track generation 3 will likely see its peak adult numbers in the first week of June. We have now had confirmed TSWV cases in the southern San Joaquin Valley and the Sacramento Valley, so this seems like a year when targeting generation 3 will give useful benefits. Generation 3 juveniles will be feeding and developing over the rest of May, so treatments applied in the second half of the month will have a chance to prevent infected adults from spreading the virus to new hosts. If you are considering investing in a thrips treatment this season, the second half of May appears to be a good time to make that treatment.