Commercial Horticulture > Comm Hort Blog

Growers make many decisions every year about what chemicals to use for pest prevention and/or control. These are very important and, often, expensive decisions to make. Unfortunately, sometimes we get less than desirable results from chemical applications.

Many factors influence the efficacy of chemicals. One simple factor we often overlook is coverage. We assume we are getting adequate coverage when we really are not. It is important for growers to pay close attention to their spray equipment. When spraying fungicides it is imperative to get thorough coverage.  Vegetables crops typically have dense foliage which can be difficult for spray droplets to penetrate. Most fungicides recommend using at least 20-30 gallons of water per acre on vegetable crops.  In order to achieve higher spray rates without run-off you must also adjust sprayer pressures accordingly. Increasing sprayer pressure will create finer droplets resulting in better coverage; however, smaller droplet sizes will increase the risk of off-target drift issues.  Therefore, growers need to pay close attention to environmental conditions when spraying.  It is also a good idea to add anti-drift aid products to your spray solutions.

There are many types of sprayers to choose from, I feel one of the best sprayers for vegetable production is an Air Blast Sprayer. Air blast sprayers use a large fan to create a powerful column of air that blows the spray solution onto the crop. Air blast sprayers come in many different configurations. In general, they typically put out a large volume of spray solution, and can easily handle rates of 50 + gallons of solution per acre.  The column of high velocity air produced by this type of sprayer not only creates very fine spray particles it also causes the spray to penetrate deep into the crop canopy, resulting in excellent spray coverage. 

Obviously not all growers have access to air blast equipment; however, I have seen many homemade sprayers that do an adequate job as well. By utilizing different types of sprayer tips and playing with spray pressures growers can increase the performance of their existing sprayers.  Just keep in mind that it is imperative to accurately calibrate your sprayer before applying any chemicals.

Regardless which type of sprayer is used growers must pay close attention to sprayer tip selection, pressure and calibration to ensure proper coverage. By eliminating just a few of these potential problems, growers can help ensure they will get the most out of their chemical applications.        

 


Neil Kelly

Regional Extension Agent 



Stink bugs in vegetables.jpgIn general, vegetable insect pests have chewing or piercing-sucking mouthparts. Caterpillars, beetles, and grasshoppers are good examples of insect pests with chewing mouthparts. Large stink bugs and leaffooted bugs are some "macro bugs" with piercing-sucking mouthparts. On the contrary, various species of aphids, thrips, and whiteflies are "micro bugs" that have been discussed earlier in separate articles.    

  • Unlike moths and caterpillars that are very common in rural areas and may take several years for population buildup, macro bugs like stink bugs and leaffooted bugs are active in both rural and urban farms. Leaffooted bugs belonging to the genus Leptoglossus have now become the dominant sucking insect pests in vegetable fields and fruit orchards.
  • Stink bugs and leaffooted bugs are highly migratory and breed rapidly initially on the field edges. Thereafter, the bugs may become more prolific throughout the field as overlapping generations and various life stages feed together.  
  • While the adults are distinct looking and typically found in small numbers feeding or mating on host plants (except leaffooted bugs that may form large aggregations), nymphs stay together in the early stages and scatter out at later stages. Nymphs (pest species) are easiest to recognize when they are in masses under plant parts.
  • Stomach insecticides, specially the organic ones, are usually ineffective against the macro bugs since they do not consume toxic doses of those insecticides. Therefore, sucking insect pest management generally involves heavy use of broad-spectrum contact insecticides that can also kill beneficial insects. This is the reason organic producers should have alternative landscape-level IPM tactics for pest management. Keep records of all IPM successes and failures as research data is lacking for many organic insecticides.
  • How would you tell a nymph whether it is pest or beneficial species? Nymphs of beneficial species disperse rapidly upon hatching from eggs (e.g., assassin bugs) in search of prey that include small caterpillars, leafhoppers, and other smaller insects. Beneficial insects generally hunt singly while perched on top of leaves or branches.  Pest species stay together in masses usually hidden under plant parts. They tend to scatter when disturbed. Identify bugs from anatomical details as well as their behavior before making any treatment applications. Use the image on top as a field guide for identifying some of the major adults and nymphs.

Management

  • Use prevention tactics first –
  • Conventional insecticides – many synthetic pyrethroids (Mustang Max, Karate, Brigade) are effective, neonic insecticides like Venom or Scorpion also work well although there can be use restrictions on the labels that must be followed.
  • Organic insecticides – kaolin clay can act as a deterrent; natural pyrethrin and spinosad products are effective against nymphs infesting the main crops or trap crops.

New Organic Vegetable IPM Toolkit Slide Charts Available for Farmersorganic IPM toolkit2.jpg

A brand new Organic Vegetable IPM Toolkit is now available for natural and organic farmers. This rectangular slide chart has sustainable IPM recommendations for over 20 major vegetable insect pest species and is a good starting point for beginning farmers to learn about the three levels of pest management. For your free copy, please email bugdoctor@auburn.edu, contact a commercial horticulture regional extension agent in Alabama, or attend a beginning farmer IPM workshop. Funding for this IPM toolkit has been provided by the USDA SARE, BFRD, and Specialty Crops Block Grant Programs. 

Ayanava Majumdar

Extension Entomologist and State SARE Program Coordinator

Neil Kelly

Regional Extension Agent


A few cucurbit diseases were found in a few commercial fields in south Alabama along with the cucurbit downy mildew sentinel plots in Fairhope and Brewton. Gummy stem blight was fairly common on watermelon; downy mildew was found on cucumbers and butternut squash, and powdery mildew was observed mainly on yellow squash.  


One disease surprising to see was Plectosporium blight on yellow squash. Interesting disease in that it produces white spindle-shaped lesions on the stems and petioles, but typically does not effect the leaves or fruit. We most often see this disease on pumpkins in the fall in wet years, but to see it on yellow squash in July was unusual. 

The crops scouted were mature and near the end of their production cycle, but all the diseases found will pose a risk to late summer and fall Cucurbits plantings. 

Extension Plant Pathologist

 


2018 has been a wet year so far for most of us. The excess moisture is allowing for an abundance of mushrooms to emerge. At the Auburn University Plant Diagnostic Lab, we have received many mushroom identification requests, specifically for Chanterelles. We cannot identify mushrooms for human consumption at the diagnostic lab, especially based on pictures. There are look-a-like mushrooms that can be difficult to distinguish without fresh specimens (Jack O'Lanterns and false chanterelle). You should never eat a mushroom you have identified based on pictures. And never eat anything you can't positively identify!

Chanterelles grow from summer through early fall. They are usually found associated with hardwood tree roots. They form a symbiotic (beneficial) relationship with the tree. They are usually found growing solitary or in a small bunch and have a sweet smell. They are usually orange-yellow in color with a convex or vase shaped cap. They have false gills that appear as forked folds or wrinkles on the underside of the mushroom. The false gills are decurrent, meaning they run down the stalk.chanterelle.png

Jack O'Lantern mushrooms are also orange in color, but are found growing in large clusters and not necessarily associated with tree roots. When you cut a Jack O'Lantern stalk open, it will be orange through the whole stalk. Chanterelles are usually white inside their stalk. Jack O'Lanterns also have true gills, meaning they are non-forked and knife-like. Jack O'Lanterns contain the toxin muscarine. If eaten, they can cause severe cramps and diarrhea. The Jack O'Lantern mushroom is named such because it has the ability to bioluminesce (glow in the dark), although difficult to see. The picture on the right is Chanterelle by Chris Schnepf, University of Idaho, Bugwood.org.

jackolantern1.png

The false chanterelle is also orange in color and vase shaped, but has true gills. The gills are forked on the edges, but still appear as close blades rather than folds or wrinkles. The orange color is also graded, meaning they're darker at the center of the cap rather than one uniform color. There are reports that this mushroom is poisonous, causing upset stomach and digestive problems. The picture on the left is Jack O'Lantern by Chris Evans, University of Illinois, Bugwood.org.

Picture below is False chanterelle by Kuo, M. (2015, March). Hygrophoropsis aurantiaca. Retrieved from the MushroomExpert.Com.


flasechanterelle.png


Kassie Conner 

caterpillar complex1.jpgIt is time to scout crops again and prevent insect outbreaks with timely intervention! Excessive rain in much of May have slowed moth activity, but we have detected a sudden increase in armyworm activity across the state. Beet armyworm moths appear to be the most active in vegetable and peanut fields followed by other species like the fall armyworm, southern and the yellowstriped armyworms (the average moth counts is 5 moths per trap). Armyworms typically start out in hay and pasture fields, or feed on weedy hosts before making a move to the specialty crops. Armyworms typically lay a large number of eggs in several masses on leaf terminals or stems and flowers covered with body scales making them look fuzzy. Colors of these egg masses may vary from grayish to green – eggs seem to darken as they get closer to hatching. Caterpillars hatch and stay clumped together for several days before dispersing – the best control of armyworms is when the caterpillars are small and aggregated.

egg masses1.jpgCorn earworm, cabbage looper and soybean looper moths have also started to show some activity in vegetable fields (1 moth average per trap); those moths lay round eggs singly on tender leaves and fruits. Caterpillars typically feed on the leaves of vegetable crops first before moving on to fruits where the damage can be irreversible. On fruits, most caterpillar feeding damage causes fine round holes that may or may not close depending on the development stage of the fruit. Most moths mentioned are night-flying pests when they are most active for mating and egg laying; however, there are other insects like squash vine borers and cabbage butterflies that are major vegetable pests active during the day.  

organic IPM toolkit2.jpgAlways start out with moth or caterpillar prevention strategies for your farm or garden. Having healthy plants, timely planting, and using pest exclusion systems are helpful pest preventions strategies. Several insecticides are also available for caterpillar control – they broadly range from general nerve toxins (like synthetic pyrethroids belonging to Group 3 insecticides), feeding inhibitors (Group 22 and 25 insecticides), and growth regulators (selective insecticides in Groups 15 and 18). Remember that selective insecticides belonging to the newer generation of insecticides do minimal environmental harm. One of the major concerns with insecticide misapplications is the rise in spider mite infestations due to reduction in the number of beneficial mites. Insecticides also destroy immature lady beetles and lacewings that may result in outbreak of other pest species like aphids and whiteflies. Protection of natural enemies is thus a very critical aspect of the farming system. Consult extension agent for correct insect identification and for developing an IPM plan that is suitable to your farm. For more details about individual IRAC Insecticide Groups, visit www.irac-online.org. For IPM training videos and toolkits, please visit Alabama Vegetable IPM.

 If you wish to see statewide moth numbers from Alabama, then please download Moth Activity Updates 6-25-18

Ayanava Majumdar, Extension Entomologist and

State SARE Program Coordinator, Auburn University


squash bug1.JPGThere have been many recent calls about squash bugs (Anasa tristis) and how to get rid of them in farms and gardens. We wish for a magical solution to the squash bug problem, but unfortunately we don't have a silver bullet against this pest. Squash bugs have piercing and sucking mouthparts that like to feed on cucurbits like squash or pumpkins, and make the plants sick through feeding and disease transmission. Squash bugs take a long time to mature (~8 weeks) during which time the immature stages (nymphs) and adults feed alongside one another causing much of the crop loss.

Squash bugs produce shiny red eggs in clusters on various plant parts; the nymphs hatch in about seven days in hot weather and remain young for about a month.

Nymphs tend to stay in clusters for protection (see the picture below of a large aggregation of squash bug nymphs and adults on Hubbard squash). Nymphs are grayish and look like adult bugs, but nymphs lack wings. Adult squash bugs are large, somewhat flattened insects that hide well under debris, plant leaves, soil cracks, or under the plastic mulch. Under extreme dry conditions, adults often hide under the plastic or soil debris remaining close to the drip lines for moisture. In other words, good scouting practice for squash bugs include looking for egg masses and nymphs under the small or large leaves and around the plant base.

SB on hubbard2.JPG

Crop damage happens when the bugs inject a toxic saliva into the plant; large aggregations can cause plants to wilt gradually. Under drought conditions, this wilting becomes more intense and can even kill the mature plants reducing yields. Squash bugs also vector a bacterial disease called Cucurbit yellow vine decline (CYVD) which has become a major issue in the southeastern US over the past decade.

Squash bugs carry the bacteria inside the body throughout life and cause rapid increase in disease incidence during migration from plant-to-plant or field-to-field. Once the CYVD bacterium is inside the plants, there is no cure for the disease. 


IPM recommendations:  Squash bugs are difficult insects to manage in organic or low-input production systems. Squash bugs have natural enemies like tachnid fly (Trichopoda), but these flies are generally slow to kill the pest during which time the squash bugs continue to feed on plants. Selecting good, fast-growing hybrids can help reduce the effect of stressful environmental conditions and feeding injury.

A pest exclusion system using spun-bounded polyester fabric such as Super Light Insect Barrier (Gardens Alive) or AgroFabric Pro fabric (Seven Springs Farm) immediately after seeding or transplanting and continuing through flower initiation can deter squash bug infestation and allow plants to grow under protection. Take the fabric off during flowering to allow insect pollinators to do their job. The practicality of using pest exclusion on a large-scale can be cost prohibitive. High tunnel producers can use a permanent exclusion system with 55 percent or higher shade cloth to slow down or deter adult squash bugs

For medium-sized organic operations, using a Hubbard Squash trap crop with mixed stands of 'Baby Blue' and 'New England' Hubbard squash can be distracting to squash bugs.  This distraction can protect the main crop from feeding damage. Nymphs can be killed in the trap crop with organic insecticides as discussed below. Several trap crop videos summarizing results from trap crop studies for cucurbit production are available on the Alabama Vegetable IPM website.

Organic insecticides for killing squash bugs include only a few products with spinosad and pyrethrin as their active ingredients. The major issues with contact insecticides is the problem of getting the product where the insects are hiding. Nymphs are more susceptible to insecticides compared to the adults.

Synthetic pyrethroid insecticides can be effective, but often supply a short-term solution and require multiple applications. Many Group 4A neonicotinoid and some Group 3 synthetic pyrethroid insecticides (bifenthrin, zeta-cypermethrin and lambda-cyhalothrin among others) are effective against squash bugs but have many use restrictions on the insecticide label. Group 4A insecticides have contact and translaminar action (e.g., dinotefuran) whereas synthetic pyrethroids provide excellent short-term contact action against the pests. Please refer to the Southeastern U.S. Vegetable Crop Handbook for complete insecticide recommendations. Consult a regional extension agent for proper insect identification, learn proper scouting practices, and develop an IPM plan appropriate for your farm or garden.

For further reading:

Article authors:

 Dr. Ayanava Majumdar, Extension Entomologist,

Dr. Edward Sikora, Extension Plant Pathologist,

and Dr. Joseph Kemble, Extension Vegetable Specialist


Pierce's Disease (PD) is a serious threat to the cultivation of grapes in the United States, especially in the warmer southern regions. Recently the UC Davis grape breeding program has developed new European (Vitis vinifera) grape selections with resistance to PD that are expected to produce high quality yield in regions with PD pressure where the Vitis vinifera production was previously not a viable option. On-going research in my lab focuses on investigations to determine the development and production potential of three PD resistant 87.5% V. vinifera selections from the UC Davis program that were planted at the Chilton Research and Extension Center in Clanton in 2010.  Our results are very promising and indicate the newly developed PD resistant European grape hybrids have the potential to greatly impact the fruit industry in Alabama and the Southeast by providing new specialty fruit crop to the market and broaden the window of economic opportunities especially for small- and medium-size family farms. Actually, based on the promising results of our research, two commercial vineyards in Alabama were granted the license to grow these experimental vines. Building on our previous experience cultivating European grapes in Alabama, we established a new research plot in December 2016 to evaluate a PD resistant 94% European grapevine (Fig. 1, A).

Figure 1. PD resistant 94% Vitis vinifera selection trained to a Watson system (A) and cluster development (B) at the CREC, on June 6, 2018.

Vines are planted at 6', 7', and 8' in-row distance and trained to a highly efficient Watson trellis system. Observations are on-going to determine vine phenology, cropping potential and fruit quality.


 


Bacterial wilt has been detected in five samples submitted to the Plant Diagnostic Lab in the past week.  This includes samples collected from both commercial fields as well as backyard gardens.  Bacterial wilt is caused by a soil-borne bacterium (Ralstonia solanacearum). A characteristic of this disease, which sets it apart from other wilt diseases, is that plants wilt and die rapidly without the presence of yellowing or spotting of the foliage. The disease can occur in newly cleared land as well as in areas where susceptible crops have not been grown previously. The bacterium often enters a field on infested transplants, equipment or through drainage water. The pathogen can overwinter in soil.

Bacteria infect plants through the roots or stem, most often where tissue has been injured by cultivating, or by some other physical means such as nematodes. Bacteria invade the vascular tissue, apparently causing wilt by a gradual blocking of the water conducting vessels. The disease is most commonly found in low, wet areas of fields and is most active at temperatures above 75 degrees F.

To identify bacterial wilt, cut and peal back a section of the epidermis and cortical tissue just above the soil line. The center of the stem (pith) will, in early stages, appear water soaked; later, the pith will turn brown and sometimes become hollow (Figure 1). The discoloration of the pith distinguishes this disease from the fungal disease Fusarium wilt which can also be common in home gardens.

Bacterial wilt attacks members of the Solanaceous plant family, which includes peppers, potatoes, and eggplant, making crop rotation an effective method of control. Growing susceptible crops in the same area no more than once every 4 years will reduce inoculum in the soil. Removing wilted plants and the soil surrounding their roots can reduce spread of the disease and may be a viable control alternative in home garden situations. Soil solarization is another alternative for control of bacterial wilt. See more articles on this disease here.


Figure 1.  Discoloration of pith of plant infected with bacterial wilt.  


Edward Sikora and Kassie Conner

Extension Specialist, Plant Pathologist, ACES



I receive many questions every year and teach many classes on plant propagation. Many different aspects of plant propagation can be fascinating, but I probably receive more questions on grafting than any other propagation method. Why would someone graft rather than propagate with other common methods such as division, seeds, cuttings, or layering? The main reason is to propagate plants that can not be readily maintained with those other methods. For example, many trees such as peach, apple, pear, plum, and pecan are grafted in order to maintain the cultivar characteristics that may be lost if seeds of these crops were planted. In addition, these plants do not root well, as do blueberries, blackberries, muscadines, and figs. However, there may be other reasons to graft even when a plant can be easily maintained with a method such as rooting. 

Before grafting can be done, you will need to collect scion wood in advance. Scion wood are the shoots collected from the plant you are trying to propagate. This can be collected after the tree goes dormant from healthy shoots of the previous season's growth. Scion wood can be collected anytime during the dormant season, but make sure you collect it before the buds start swelling in early spring. I usually like to have scion wood collected no later than February 15. Once collected you need to keep them moist and dormant until time for grafting. This is accomplished by putting the scion wood in an air tight container such as a freezer bag along with some damp wood shavings or wrapped in a damp paper towel and placed in a refrigerator. Some people even double bag the scion wood to ensure they will not dry out.

The other thing you will need is a rootstock. There are many nurseries that grow rootstock specifically for grafting purposes, but they can sometimes be hard to get in small quantities. Sometimes the best thing to do would be to plant seeds of some crops such as pecan or persimmon to be used later for grafting. Along with maintaining cultivar characteristics, grafting to different rootstocks can reduce the mature height of plants such as apples and provide nematode resistance in peaches. Tomatoes, roses, dogwood, camellia, and many other plants are grafted for different reasons as well. Make sure the rootstock you are using is providing the benefit you are after. Many hobby gardeners will purchase a plant on the rootstock they want, then they will graft the desired scion onto the rootstock. I will continue with more on grafting in my next article. If you need information on grafting now you can find a publication titled 'Budding and Grafting Fruits and Nuts' on our website at www.aces.edu, or you are always welcome to contact your local Extension Office.

Regional Extension Agent

During the current season some strawberry growers have seen production of leaves and other vegetative organs from fruit tissue around achenes of strawberry fruit. This abnormal development of floral parts into leafy structures has been ascribed to physiological causes due to temperature conditions during transplant cold storage, plant response to changing seasonal conditions at flower initiation time, and to phytoplasma infection. Four distinct phytoplasmas associated with phyllody of strawberry fruit were found while investigating phylloid fruits from different strawberry clones and from different locations and sources. 









Figure 1. Non-infectious phyllody of strawberry fruit. Photo credit Thom Flewell.

Figure 2. Phyllody and other fruit distortions caused by phytoplasma infection (normal on right). Photo courtesy Steven Koike, UCCE. 


This abnormality can affect the flower and flower parts in strawberries which can cause problems for potential growers. There are two main ways that phyllody can occur:

Non-infectious phyllody: Non-infectious phyllody (Fig. 1) seems to be associated with an excess of supplemental chilling of the transplants while in storage. Although these symptoms are as alarming as they are, they will go away after showing up in a spring flush of fruit. Therefore the condition is not persistent.

Infectious phyllody: This category of phyllody occurs due to infection by a phytoplasma (Fig. 2). Phytoplasmas are bacteria-like organisms that are pathogenic to plants and are vectored by leafhoppers. Leafhoppers carry the phytoplasmas in their bodies and inject them while feeding on plants. Strawberry plants infected with phytoplasmas often continue to bear deformed fruit.

When you observe similar symptoms on your strawberry fruit and need to identify the cause, you can collect symptomatic fruit and send the sample to the AU Plant Diagnostic Lab Services.


Elina Coneva

Extension Fruit Crops Specialist




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