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Friday, December 21, 2018

Aphids Overwinter near the Soil on Many Plants

Q. I have a small crape myrtle tree with leaves that were constantly wet this year. The ground and plants underneath were always wet. Now that the leaves are gone. I can see the branches are also wet. Another tree I have is perfectly dry and normal. What’s causing this and how can I correct it?

A. This “wetness” was caused by one of the leaf sucking insects, most likely aphids. If you inspect this “wetness” I think you’ll find it is shiny and sticky as well as wet. It probably attracts flies, bees and other insects.
Common occurrence in late fall and early winter before leaves drop are "wet leaves" due to aphids feeding.

            Aphids suck plant juices from the leaves and then exude a shiny, sugary liquid that drops on the leaves, limbs and plants below it. There are about 4000 different kinds of aphids and about 10% of them cause problems to our plants.
            In the eastern US they have a special aphid, called the crape myrtle aphid, that causes these problems only on crape myrtle. Several aphids specialize only on certain plants. But there are also aphids which are general feeders and infest a variety of different plants as well.
In the spring, aphids feeding on new leaves cause the leaves to distort from their feeding. Leaves that have fully developed won't demonstrate this when aphids feed on them.

            Aphids are a huge problem because they reproduce rapidly in the spring without the help of male aphids. Later in the season, females can be found with wings and fly from plant to plant giving birth to living young wherever there are succulent young leaves nearby. If you don’t get them under control, they can spread.
            To add to this problem, ants pick them up and distribute them as well because they like the sugary liquid they produce from sucking plant sap. Controlling ants in the spring is one way to reduce their spread in the spring.
Good reason to clean up your garden area of weeds is to prevent aphids from staying the winter on these plants. They will huddle on the lowest leaves or stem in loose soil or mulch at the soil surface.

            There are lots of predatory insects and even fungi that attack them during the growing season, but their reproduction and spread is so rapid that these biological controls can’t keep up with their rapidly increasing numbers.
            I guarantee there are winged females and overwintering eggs hidden at the base of woody plants and tucked into nooks and crannies on the trunk and stems.
            What to do? Spray both trees with dormant oil this winter to suffocate both the eggs and the overwintering females. These dormant oils are made from paraffin or mineral oil. Neem oil, although it might be effective, is not a dormant oil.
            Select a warm day, without wind and the sun shining, for spraying. Mix the dormant oil with water at the rate recommended on the label. The oil is emulsified and can be diluted with water for spraying.
            Spray the trees from top to bottom, covering the trunk and all the limbs. They like to overwinter at the base of plants where it’s out of the weather so spray there as well. Remove weeds where they can hide during the winter.

Reasons for Palo Verde Limb Dieback

Q. The palo verde tree in our daughter’s yard looks like it has damage. The top has some dead branches in it. We have had to remove some limbs because of this problem. Can it be saved?

A. There are several different kinds of Palo Verde used primarily in desert landscaping. All have tender new growth that can be severely damaged when exposed to intense sunlight. It is important these trees are pruned throughout their lives so that the tree’s canopy shades the trunk and limbs.
If desert adapted trees have limbs removed that expose the trunk or large limbs to direct sunlight and sunburn, borers can be a problem in these trees such as Palo Verde and acacia

            Pruning them in a fashion that exposes limbs and the trunk to intense sunlight causes damage that causes limb death that becomes visible a few years later. It’s a progression that usually starts with bad pruning practices. This progression begins when too much is removed from these trees. When too much is removed, the limbs and trunk are exposed to high intensity desert sunlight.
Exposing the trunk and lower limbs to direct sunlight and sunburn can create future problems to trees like the Palo Verde.

            Intense, direct sunlight on young limbs first causes a discoloration due to intense sunlight. As this direct sunlight repeats day after day, exposed areas of limbs and trunk facing the sun die. Water can’t through dead areas of the trunk and limbs.
            Unless this sunburn causes severe damage, the top of the tree probably looks fine. The tree can still move water around the damaged area from roots to tree branches. The damage could be as much is 50% of the limb and trunk area and the tree looks fine.
This is not Palo Verde but when the trunk and limbs are exposed to intense sunlight for a long period of time, year after year, the intense sunlight can damage or even kill the living part of the tree under the sunburned area. The beginning of this damage can be very attractive to some wood boring insects which can make the damage worse.

            This damage from sunburn attracts insects such as borers that feed on living parts of the tree close to the damaged area. This feeding by borers causes even more damage that reduces water movement to the limbs. Perhaps the first year or two, trunk and limb damage goes unnoticed because the canopy looks fine.
The first sign of sunburn is a discoloration or off-color to the trunk, limbs or even fruit on fruit trees.

            But at some point, damage becomes severe enough that water movement from roots to the canopy is reduced.  Limbs start dying back because the tree can’t get enough water past the damage. This usually happens during the heat of the summer when demand for water is highest.
            The homeowner now notices the limb death in the canopy. The homeowner removes dead limbs. This exposes the tree to more intense sunlight and further damage. Tree damage is so severe and unsightly the homeowner considers removing it. This is the tree “death spiral”.
            What to do? Damage to the tree may be already extensive. Decide whether you can live with this damage or not. If not, have the tree removed. If you decide to keep the tree, then encourage it to heal as quickly as possible. Contribute to this healing by giving it enough water on a regular basis and apply fertilizer in early spring.

High Nitrogen, Quick Release of Fertilizers Keep Plants Green during Cold Weather

Q. Our lawn was beautiful during the summer but started turning brown when it got cold here in Mesquite. This is a fescue lawn and we were told it would stay green all winter long.

A. There are several different kinds of fescue, but the fescue used for lawns is technically called “turfgrass type tall fescue”. Tall fescue lawns stay green through the winter in our Mojave Desert climate if they receive an application of nitrogen fertilizer in late Fall and night temperatures don’t drop below about 15° F.
This is a conventional high nitrogen fertilizer called ammonium sulfate. It is used to feed plants only nitrogen for promoting growth of stems and leaves.Where the nitrogen comes from but conventional fertilizers may contain other ingredients in very small quantities. Some followers of organic principles might call these other ingredients, "contaminants" in the fertilizer. Any fast release slow nitrogen fertilizer will keep plants green longer into late fall and early winter then not applying any nitrogen.

            If the lawn is without nitrogen, and nighttime temperatures drop below freezing, fescue lawns will go dormant and turn brown. Apply a high nitrogen fertilizer or compost to the lawn late in the fall before freezing temperatures.
A high nitrogen fertilizer but derived from dried blood. It is also high in nitrogen and releases it fairly quickly but not as fast as ammonium sulfate. This blood meal is not certified organic by the USDA but many would consider it as "organic" nitrogen.
            You can use any fertilizer if the first number is the highest number on the bag. Examples can be 21-0-0, ammonium sulfate, applied 2–3 weeks before freezing weather hits. In our Las Vegas climate, applications would be around Thanksgiving, or possibly even later if nighttime temperatures don’t drop below freezing.
            Nitrogen, the first number on the fertilizer bag, is responsible for a plant’s dark green color and encouraging new leaf and stem growth. It can also keep plants from going dormant during the winter.
            There is a nefarious side to late applications of nitrogen. Nitrogen applications made in late Summer or early Fall can compromise our winter-tender plants such as many types of citrus. Applications of high nitrogen fertilizer to these plants late in the growing season can cause them to be more susceptible to freezing temperatures. Never apply high nitrogen fertilizers during Fall to plants that might freeze during winter the winter.

Best Time and How to Prune Ornamental Shrubs

Q. I have some shrubs in my yard that are getting rather scraggly looking.  I was wondering when and how far back I can prune it back in to shape.
Shrubs improperly pruned with a hedge shears. Unfortunately, most people do not recognize bad pruning when they see it and now unfortunately are asking for this kind of pruning.

A. First decide if now is the best time for pruning them or not. You can prune anytime during the winter months. Some plants look better through the winter if they are pruned now. Other plants look fine now but might not look as good if you were to prune them.
As shrubs are pruned more and more into a gumball, in a few years they developed exposed strong stabs at the base.
            Remember, if you prune now you will have to look at them the rest of the winter. If these are flowering shrubs, prune them soon after they finished flowering. If the shrubs do not have ornamental flowers, prune them anytime during the winter.
            The best pruning methods remove the oldest growth from the bottom of the shrub with a lopper or hand shears. Hedge shears for pruning shrubs are, as the name implies, for hedges, not for shrubs.

Properly pruned shrubs require to – 4 cuts at the very bottom to keep it looking good and juvenile.

Organic vs Conventional Strawberries: Nutrition and Pesticide Residues

Organic and conventional strawberries: nutritional quality, antioxidant characteristics and pesticide residues

H.B. Kobi1, M.C. Martins1, P.I. Silva1, J.L. Souza2, J.C.S. Carneiro1, F.F. Heleno3, M.E.L.R. Queiroz3 and N.M.B. Costa1,a
1 Federal University of Espirito Santo, Center for Agrarian Sciences, Alegre, 29500-000 ES, Brazil
2 INCAPER – Centro Serrano, Venda Nova do Imigrante, 29375-000 ES, Brazil
3 Federal University of Viçosa, Department of Chemistry, Viçosa, 36570-000 MG, Brazil

What is already known on this subject?
Organic farming may affect the food composition and produce healthier foods than the conventional system, characterized by intensive use of chemical products.

What are the new findings?
Organic farming produced pesticide-free fruits but did not imply on substantial changes in the nutritional quality or antioxidant properties of strawberries.

What is the expected impact on horticulture?
It is expected to encourage the organic farming system in order to produce healthy and pesticide-free strawberries.

Introduction – Organic farming system may affect the food composition and produce healthy foods. The aim of this study was to compare the nutritional quality, antioxidant properties and pesticide residues of organic or conventional strawberries.

Materials and methods – In a first experiment, organic and conventional fruits from the cvs. Camarosa and Albion were obtained directly from the farmers. Subsequently, ‘Camarosa’ was produced in organic and conventional systems, under controlled conditions. Pesticide residues were analysed in the second trial and the remaining parameters were evaluated in both experiments.

Results and discussion – In the first experiment, the fruits of organic cv. Albion showed higher moisture (91.8%) and lower total solid (8.2%), and carbohydrate (5.7%) contents. ‘Albion’ fruits also showed higher total solid content than ‘Camarosa’ fruits in conventional farming system. Pesticide residues were not detected. Under controlled conditions, organic ‘Camarosa’ fruits had higher moisture (91.5%) and ash (0.4%) contents, whereas conventional strawberries had higher soluble solids (8.5 °Brix), proteins (0.9%) and anthocyanins (17.7 mg 100 g-1). Residues of azoxystrobin, lambda-cyhalothrin and thiamethoxam were detected at values below the limit of detection (<LOD) in all organic samples, and below the limit of quantification (<LOQ) in conventional strawberries.

Conclusion – Organic and conventional production systems do not promote any expressive difference in the nutritional quality or antioxidant properties of strawberries, although the organic farming produced pesticide-free fruits.

Fraises biologiques et conventionnelles: qualité nutritionnelle, propriétés anti-oxydantes et résidus de pesticides.

Introduction – Le système d’agriculture biologique peut affecter la composition des aliments et produire des aliments sains. Le but de cette étude était de comparer la qualité nutritionnelle, les propriétés anti-oxydantes et les résidus de pesticides des fraises produites en système biologique ou conventionnel.

Matériel et méthodes – Dans une première expérience, les fruits biologiques et conventionnels des cvs. Camarosa et Albion ont été obtenus directement auprès des agriculteurs. Par la suite, les fraises ‘Camarosa’ ont été produites en systèmes de culture biologique et conventionnel, en conditions contrôlées. Les résidus de pesticides ont été analysés dans le deuxième essai et tous les autres paramètres ont été évalués dans les deux expériences.

Résultats et discussion – Dans la première expérience, les fruits biologiques du cv. Albion ont présenté des teneurs en eau (91,8%) plus élevées, et des teneurs en matières solides totales (8,2%) et en hydrates de carbone (5,7%) plus faibles. Les fruits d’‘Albion’ avaient également une teneur en solides totaux plus élevée que ceux de ‘Camarosa’ produits en système de culture conventionnel. Aucun résidu de pesticides n’a été détecté. En conditions contrôlées, les fruits biologiques de ‘Camarosa’ avaient des teneurs en eau (91,5%) et en cendres (0,4%) plus élevées, tandis qu’en conventionnel, les fraises contenaient plus de matières solubles (8,5 °Brix), de protéines (0,9%) et d’anthocyanes (17,7 mg 100 g-1). Des résidus d'azoxystrobine, de lambda-cyhalothrine et de thiaméthoxam ont été détectés, à des valeurs inférieures à la limite de détection (<LOD) dans tous les échantillons biologiques et inférieures à la limite de quantification (<LOQ) dans les fraises conventionnelles.

Conclusion – Les systèmes de production biologiques et conventionnels ne favorisent pas l’expression de différences de qualité nutritionnelle ni de propriétés anti-oxydantes des fraises, même si l’agriculture biologique produit des fruits sans pesticides.

This is a peer reviewed publication appearing in the International Journal for Tropical and Subtropical Hortculture

Fruits 73 (1) 39-47 | DOI: 10.17660/th2018/73.1.5
ISSN 0248-1294 print and 1625-967X online | © ISHS 2018 

Why Cleanup Around Fruit Trees and Vegetable Gardens

Survival of pathogenic Colletotrichum isolates on dormant buds, twigs and fallen leaves of apple trees in commercial orchards

N.A. Hamada1,ª and L.L. May De Mio2
1 IFPR, Paraná Federal Institute of Education, Science and Technology, Palmas, Rodovia PRT, 280, Trevo da Codapar, 85555-000 Palmas, PR, Brazil
2.UFPR, Federal University of Parana, Department of Crop Protection, 80035-050, Curitiba, PR, Brazil

Introduction – Glomerella leaf spot on apple (Malus × domestica Borkh.), due to a complex of Colletotrichum species, causes severe leaf spot symptoms leading to early leaf fall, and eventual symptoms on fruit before and after harvest. Under the Brazilian conditions, it is the main apple disease responsible for severe damage in all production areas. This study aimed 1) to verify the survival of Colletotrichum spp. in dormant organs, fallen leaves and soil samples from fungicide-sprayed commercial orchards during winter; 2) to verify the survival of Colletotrichum spp. on asymptomatic leaves during the vegetative period; and 3) to identify the species complex and to confirm the pathogenicity of the isolates obtained from different parts of the plant (on fruit and leaves).

Materials and methods – The study was conducted in a commercial orchard during the winters of 2010 and 2011, assessing the pathogen survival on buds, twigs, asymptomatic leaves, fallen leaves and soil samples. Fungal isolates from different substrates were inoculated on fruit (with and without wound) and on leaves of apple cv. Gala to prove their pathogenicity.

Results and discussion – This is the first investigation on the survival of the Colletotrichum complex in apple under the conditions of Brazilian commercial orchards. All isolates (16) from dormant twigs and fallen leaves were identified as C. acutatum species complex. Five (5) isolates from dormant buds were identified as C. gloeosporioides species complex and three (3) as C. acutatum species complex. According to the data collected, Colletotrichum spp. are able to survive during winter in dormant buds, on dormant twigs and fallen leaves, but are most frequent on fallen leaves. The isolates obtained from buds, twigs and fallen leaves were pathogenic on leaves and fruit of apple. Copper sprays during the dormant stage did not completely eliminate the inoculum. The pathogen was not recovered from soil or from asymptomatic leaves with the methodology used.

Conclusion – Fallen leaves on the ground can be a source of inoculum from one season to the next, so they must be considered in disease management programs to avoid the spread of primary inoculum.

My Comments. This again points to the importance of sanitation in growing areas. Pick up fallen leaves, old fruit, remove remaining fruit from fruit trees, and do not leave old debris from the orchard or garden in the growing area unless it has been properly composted. Most other types of plant materials left as a surface mulch not related to the garden or fruit trees is fine.

Fertilizer Improves Yield of Cactus Fruit

Effects of nitrogen and phosphorus fertilization on fruit yield and quality of cactus pear Opuntia ficus-indica (L.) Mill.


M. Arba1,a , A. Falisse2,3, R. Choukr-Allah1 and M. Sindic4
1 Department of Horticulture, Hassan II Institute of Agronomy and Veterinary Medicine, Horticultural Complex of Agadir, Morocco
2 Crop Production Unit, Gembloux Agro-Bio Tech, Liège University, Belgium
3 Faculty of Agriculture, University of Agricultural Sciences and Veterinary Medicine, Cluj, Romania
4 Quality and Food Safety Laboratory, Gembloux Agro Bio Tech, Liège University, Belgium

What is already known on this subject?
Studies on mineral fertilization of cactus pear were carried out in some countries where cactus pear is cultivated. Several authors reported that mineral fertilization increased fruit yield, but some of them have indicated that fruit quality could be affected by fertilization.

What are the new findings?
Obtained results showed that nitrogen and phosphorus mineral fertilization improved fruit yield, mainly fruit size (weight and dimensions). Fruit quality was not significantly affected. Mineral fertilization also increased the emission of buds and of shoots.

What is the expected impact on horticulture?
Understanding the effects of nitrogen and phosphorus mineral fertilization on fruit yield and quality of cactus pear. The improvement of cactus pear managing practices, mainly the application of fertilizers, pruning and harvesting. The improvement of the socio-economic life of the farmers and the rural populations in the arid

Introduction – In order to optimise the nitrogen (N) and phosphorus (P) fertilization of cactus pear in arid regions, we decided to determine its effects on the yield and fruit quality as well as on the plant phenology.

Materials and methods – Five N-P dressings were compared on the spineless cv. Moussa in the Agadir area: 0–0, 0–80, 40–40, 60–0, and 60–80 (in kg N ha-1 – kg P2O5 ha-1) over two consecutive growing seasons (2011 and 2012). Yield components and physico-chemical characteristics of the fruit were recorded at harvest.

Results and discussion – Although in 2011 the applications of N and P had no effect on fruit yielding, in 2012 the dressings 60N or 80P alone increased the yield by +3.0 and 6.1 kg plant-1, respectively, compared with the control. Combining both N and P at the same rate resulted in a maximum yield of 14.9 kg plant-1. Fertilization had positive effects on flowering rates, fruit size and fruit number, and did not modify the content of pulp, the juice content, peel thickness, the juice dry matter, the pH, titratable acidity, total sugars and soluble solids. It also did not modify the dates of flowering and of ripening. Nitrogen dressings significantly increased the number of emitted buds and emitted shoots on one-year cladodes by four fold.

Conclusion – Relevant N-P fertilization significantly improved fruit yield, the number of fruits per plant and fruit size in particular. Long term and postharvest effects shall be further studied.

Introduction – La fertilisation azotée (N) et phosphorique (P) du figuier de Barbarie a besoin d’être optimisée en zone aride. Cette étude vise à en évaluer les effets sur le rendement et la qualité des fruits et à en décrire les effets sur la phénologie de la plante.

Matériel et méthodes – Cinq fumures N-P ont été comparées pendant deux années sur la variété inerme ‘Moussa’ dans la région d’Agadir: 0–0, 0–80, 40–40, 60–0, et 60–80 (en kg N ha-1 – kg P2O5 ha-1). Les composantes du rendement et les caractères physico-chimiques des fruits ont été enregistrés à la récolte.

Résultats et discussion – En 2011, les différents niveaux de fertilisation n’ont pas eu d’effet sur le rendement alors qu’en 2012, l’interaction entre N et P était très significative. En comparaison avec le témoin, l’apport de 80P ou de 60N a augmenté le rendement de +3,0 et +6,1 kg plante-1, respectivement, et le traitement 60N + 80P de +14,9 kg plante-1. Les traitements fertilisants ont eu des effets positifs sur le nombre de fleurs et le nombre de fruits formés, ainsi que sur le calibre des fruits; en revanche, ils n’ont pas eu d’effet significatif sur la teneur en pulpe et en jus de fruits, l’épaisseur du tégument, la teneur en matière sèche du jus, le pH, l’acidité titrable, les sucres totaux et matières sèches solubles. Ils n’ont pas nettement modifié les dates de floraison et de maturation des plantes. Cependant, l’apport d’azote a augmenté le nombre de bourgeons émis par cladode et le nombre de pousses sur les cladodes d’un an, jusqu’à le multiplier par 4 environ.

Conclusion – Une fertilisation N-P appropriée permet d’améliorer de façon significative le rendement en fruits des cultures de figuier de Barbarie en condition aride, en particulier le nombre de fruits par plante et le calibre des fruits. Les effets dans la durée et en post-récolte doivent encore être étudiés.

My Comments. This is another study that demonstrates increased yield of cactus pear (aka beavertail cactus) fruits when fertilizer is applied. Water must be applied more carefully because of damage to the plants if watered too often. But this paper also addresses fruit quality to some degree. Sensory evaluation is not considered but fruit quality is measured by laboratory equipment rather than by people tasting it. Sensory evaluation is hard to judge using laboratory equipment.

Using Pheromone Traps to Control Wormy Apples

Q. We have six apple and two pear trees in Ely, Nevada. This year all the fruit had worms in them. The damage started when the apples were only about 1 inch in diameter. Every single fruit had worms in them. I am suspecting a moth but I’m not sure. We sprayed with Neem Oil before they blossomed and after the fruit set. Any ideas?

A. This “worm” is the juvenile or immature form of a moth called the codling moth. They ruin the apples or pears by devouring the inside of the fruit leaving their feces and allowing for the fruit to start rotting. Hence, “wormy apples” which can look disgusting later. In commercial apple and pear production, as many as eight “cover sprays” are applied to the trees every year to prevent wormy apples.
An early sign your apples may be wormy. The codling moth lays an egg on the outside of immature apple or pear fruit. The warm hatches and tunnels inside the apple. Conventionally, insecticides are sprayed on the trees and fruit to kill the warm before it enters the fruit.

Codling moth is the most destructive insect of apples and pears in the world. We see codling moth damage to apples and pears in the Las Vegas area as well. But because we are in the Mojave Desert, this pest is not as damaging as it could be. As more homeowners plant more fruit trees however, we will see more of this pest creating damage to these fruits in the future.
This is a winged sticky trap with a reddish brown rubber lure that was impregnated with a pheromone. This sex hormone is released into the air and one gender of the past is lured to the trap where it is stuck. When the sticky bottom of the trap is full or no longer sticky, it is replaced. In a dusty environment this can be weekly. The lure weakens over time and is replaced to keep the scent at its maximum filling the air.
            As I mentioned in passing, one method of control is using insecticides as a “cover spray”. A cover spray is an insecticide sprayed over the entire tree, not just the fruit. Sprays are applied often enough to create a poisonous barrier for the female codling moth. Neem oil will not work in this way against this pest.
This is a Delta trap used mostly for monitoring when the moth is flying. It does a great job telling you when sprays are needed. I like the trap better when relying only on disrupting the mating of insects for control.
            If you choose to use an insecticide, it must be something other than Neem oil and it must be sprayed frequently over the entire tree. There are insecticides you can purchase from the store but the secret is to apply it often beginning when the fruit first begins to develop.
            Another option, pheromone traps, can either reduce the number of times the tree is sprayed or even eliminate spraying altogether. Pheromone traps are cardboard traps which contain a sex hormone released into the open air. This pheromone prevents the male codling moth from finding a female and, instead, gets stuck in a sticky mess inside the trap.
            Under some circumstances, these pheromone traps may catch enough males to prevent female moths from laying their eggs. This interruption in mating can prevent wormy apples from occurring.