Floriculture Greenhouse Update

It is not unusual to discover outbreaks of pests such as spider mites, thrips, whiteflies and aphids in greenhouses full of flowering bedding plants scheduled to be sold in the next week or two. If you discover an insect problem now, we suggest using a safe, effective contact spray that will knock down the infestation to provide good protection for a couple weeks. If infestations are localized, spot treating may be best. Once plants are planted outdoors in a garden, aphids, mites, whiteflies and thrips are not usually a problem. Some good choices for out-the-door treatments are:

• Thrips, aphids, whiteflies: abamectin (Avid), imadacloprid (Marathon II), dinotefuran (Safari), pyridaben (Sanmite), acetamiprid (Tristar), thiamethoxam (Flagship), and bifenthrin (Talstar).
• Aphids and whiteflies: pymetrozine (Endeavor)
• Mites: abamectin (Avid), bifenazate (Floramite), hexythiazox (Hexygon), pyridaben (Sanmite).

You will want to use the safest products available with everything in bloom. None of the products listed above are known to cause a phytotoxicity problem when used at the rate on the label. Usually wettable powder and flowable formulations are the least likely to be phytotoxic. However, wettable powders may cause visible residue. Make sure wettable powders are completely dissolved in the spray tank and the tank is agitated. This will prevent slurry from forming at the bottom of the spray tank, which could be phytotoxic if sprayed on plants. The re-entry time-period following application of the products listed above is 12 hours with the exceptions of Tristar (24 hours). Note that Endeavor works by interfering with the insect’s ability to feed and may take 5 – 10 days or longer to see results.

Tina Smith, University of MassachusettsLeanne Pundt, University of Connecticut

Thrips are active in many greenhouses now. If you use pesticides to manage thrips then plan to treat in the early evening. Thrips have two mass flights per day, so sprays in the early evening may contact more thrips.  Treating before you see a peak in adult numbers on yellow sticky cards is critical. Adult thrips numbers on cards tend to peak every two to three weeks. Apply insecticides before this peak, so adults will be killed before they lay eggs. Small droplets of pesticide sprays are most effective for coverage.

To manage thrips, make two to three pesticide applications about 5 days apart and rotate pesticides with different modes of action. Two materials that some growers are successfully using are pyridalyl (Overture) and chlorfenapyr (Pylon).  It appears that pyridalyl (Overture) is more toxic to second instar nymphs than adults. Also, Overture takes at least seven days to kill a majority of WFT, so don’t expect an immediate reduction in populations when using this insecticide. Read the label for plant safety. Both products have precautions. Both of these products also have translaminar activity. Remember that translaminar insecticides penetrate leaf tissues and form a reservoir of active ingredient within the leaf, providing residual activity. Insecticides with contact or translaminar activity are generally better than pesticides that are systemic because systemic insecticides typically don’t move into flower parts (petals and sepals) where WFT adults normally feed. Azadirachtin (Molt X, Aza-Direct, Azatin, Ornazin, Neemix) is an insect growth regulator (IGR) and "stressor" so may be helpful in some tank mixes. For example, if thrips populations are low and plants are not yet in flower, Beauveria bassiana (Botanigard, Mycotrol) and azadirachtin may be an option. Abamectin (Avid) (translaminar activity) with azadirachtin has also been working well for some growers.

Pesticide rotation options for management suggested by Dr. Raymond Cloyd, Kansas State University are: * Spinosad (Conserve), Chlorfenapyr (Pylon), Abamectin (Avid), Methiocarb (Mesurol) * Novaluron (Pedestal), Pyridalyl (Overture), Chlorfenapyr (Pylon), Spinosad (Conserve) * Beauveria bassiana (BotaniGard/Naturalis), Acephate (Orthene), Spinosad (Conserve) * Abamectin (Avid), Pyridalyl (Overture), Chlorfenapyr (Pylon), Spinosad (Conserve) * Chlorpyrifos (DuraGuard), Novaluron (Pedestal), Abamectin (Avid), Bifenthrin (Talstar)

Horticultural oil (Pure Spray Green, Saf-T-Side, or Ultra fine oil) may also be an option provided label cautions regarding plant safety are followed. Note that Mesurol has a 24 hour REI plus it may leave an unsightly residue, so it may be best early in the growing season. Pedestal is an insect growth regulator (IGR) labeled for immature stages. TriStar (acetamiprid - group 4A) or Aria (flonicamid - Group 9C) may also help suppress thrips.

Articles: Western Flower Thrips Management: Have We Reached an Impasse?by Raymond Cloyd

2010 Thrips Management Plan

Tina Smith, University of Massachusetts Leanne Pundt, University of Connecticut 

Questions have been asked about using pheromone lures to detect Western flower thrips and the effectiveness of using sugar in the spray mix to enhance spray efficacy.

Phermone Lures

A new item for WFT is a sex aggregation pheromone lure for early detection of low level populations. It is reportedly best used very early in the crop cycle. A number of companies sell or distribute lures that are suppose to increase the number of WFT thrips adults captured on sticky cards or attract WFT out of hiding places such as flowers or buds, increasing their exposure to insecticide spray applications and achieving higher mortality. Note that a pheromone lure is not a “control” device. Some growers are concerned about attracting WFT to un-infested areas, especially if used this late in the growing season with active thrips infestations. Also there are questions about the longevity of the scent within a greenhouse and how effective the pheromone lure is when many different plant types are in flower.

Using Sugar in Spray Solution

Growers for years have suggested that mixing white or brown sugar with a contact insecticide in the spray solution enhances efficacy of the spray application against western flower thrips. Research by Dr. Raymond Cloyd, Kansas State University showed that the addition of sugar and other sweeteners to lure thrips from hiding does not work and in some cases can cause the growth of black sooty mold.

Information on thrips management by Dr. Raymond Cloyd: Western Flower Thrips Management: Have We Reached and Impasse?

Does Dew Do It?

Tina Smith, University of Massachusetts

 

Pesticide phytotoxicity on plants can often be distinguished from pest problems by the pattern and timing of symptom development. Although the damage may take up to several days or more to occur, pesticide damage symptoms often occur all at once and have a regular distribution on the crop. Symptoms caused by pathogens usually develop over an extended period of time in random or grouped patterns. Pesticide phytotoxicity can be expressed by a number of different symptoms, including leaf speckling, cupping and twisting and other leaf distortions or plant death. Pesticides with hormone-type activity such as the insect growth regulator Distance and herbicides containing 2,4-D tend to produce leaf cupping and twisting. Other pesticides that have caused twisted growth include Judo applied to dracaena plugs and Botanigard ES applied to tomato plants.

Phytotoxicity can also be caused by the solvents in a formulation (EC formulation vs WP), impurities in spray water, using a higher rate of pesticide than is listed on the label, tank-mixing or inadequately mixing the spray solution. Environmental conditions such the temperature, humidity, and light can also influence phytotoxicity. High temperatures can speed up pesticide degradation and volatilization, but may also result in increased phytotoxicity for some products. Plants that are stressed are more susceptible to pesticide injury.

Growers can prevent pesticide damage to plants by applying pesticides during the cooler part of the day such as the early morning or evening. Treatments made in the early morning allow foliage to dry before temperatures reach 85-90°F. Take special precautions when using oils. Treat when conditions allow plants to dry quickly. Other suggestions to prevent burning plants with pesticides include:

• Add surfactants only when recommended on the pesticide label.
• Never use a sprayer for insecticides that was previously used to apply herbicides.
• Do not apply pesticides to plants that are under moisture stress.
• Avoid using more than one emulsifiable concentrate in a tank mix.
• Do not apply pesticides with fertilizers unless the label states otherwise.
• Never use broad-leaved weed killers and brush killers around the greenhouse.

To prevent injury due to pesticides, be sure to follow label directions exactly. See the company's website to read any technical bulletins about the product or call the company's technical representative before using a product for the first time.

If minor phytotoxicity is suspected from foliar applications of an insecticide, miticide or fungicide, watch the new growth as it emerges. Plants will often grow out of one-time spray damage. As plants grow, the damage will remain on the oldest leaves and the new growth will appear healthy.

Photos Plant Growth Regulator Overdose Judo injury on dracaena plugs and ivy geraniums (See technical bulletin for list of crops for which Judo should not be used) Distance injury on poinsettia BotaniGard injury on tomato plants, 2 Herbicide injury on tomato and geranium

Tina Smith, University of Massachusetts

As you gear up for the growing season, be sure to carefully read pesticide labels before purchasing a new product. Some products with different trade names have the same active ingredients. Some products may have different active ingredients, but have the same mode of action (MOA). Growers will see more generic products on the market as pesticides come off patent, which can make choosing pesticides very confusing. There are now many different products containing imidacloprid, abamectin, bifenthrin, permethrin, chlorothalonil and thiophanate methyl.  Growth regulators containing paclobutrazol include Bonzi, Piccolo, Paczol and Downsize. Read labels carefully since there are similarly named products that may have slightly different concentrations of active ingredient.

A good example is Banrot which contains the active ingredients thiophanate methyl & etradiazole, the same active ingredients as Cleary's 3336 (thiophanate methyl) and Truban (etradiazole). Different formulations (flowable, wettable powder, emulsifiable concentrate etc.) of products often contain different concentrations of active ingredient. Both Cleary's and Truban are available in various formulations. Over-application of a pesticide, especially emulsifiable concentrates (EC) and surfactants can cause phytotoxicity. 

Continued use of products with the same mode of action can lead to pesticide resistance. To help delay pesticide resistance, rotate pesticides with different modes of action (MoA).  Most pesticides have a number on the label that correlates with their mode of action group to make it easier to recognize the MoA for rotation.  This can be found on the website below or in the New England Greenhouse Floriculture Guide   Unless directed on the pesticide label, switch to a insecticide or miticide with a different mode of action about every 2 to 3 pest generations, or about every 2-3 weeks, depending on temperature and length of insect or mites life cycles. 

Resistance also develops when fungi are repeatedly exposed to fungicides with a single site mode of action (systemic fungicides).  It requires very little genetic change in fungus populations for resistance to develop.  Protectant fungicides are less likely to develop resistance problems for they have multi-site modes of action (MoA). To help prevent the development of resistance, alternate applications among different MOA groups, or mix or rotate systemic/protectant fungicides. 

Pesticide labels, material safety data sheets (MSDS), mode of action and related information can be found on the following websites:

Greenbook/C&P Press, Inc. www.greenbook.net

CDMS, Inc http://www.cdms.net/LabelsMsds/LMDefault.aspx

Kelly Registrations Systems, Inc. (pesticide registrations) www.kellysolutions.com  

IRAC Mode of Action Classification www.irac-online.org  

FRAC Codes www.frac.info/frac/index.htm

Tina Smith, University of Massachusetts Leanne Pundt, University of Connecticut

Pesticide phytotoxicity can often be distinguished from pest problems by the pattern and timing of symptom development. Although the damage may take up to several days or more to occur, pesticide damage symptoms often occur all at once and often have a regular distribution on the crop. Symptoms caused by pathogens usually develop over an extended period of time in random or grouped patterns. Pesticide phytotoxicity can be expressed by a number of different symptoms, including leaf speckling, cupping and twisting and other leaf distortions or even plant death. Pesticides with hormone-type activity such as the insect growth regulator Distance and herbicides containing 2,4-D tend to produce leaf cupping and twisting. Other pesticides that have caused twisted growth include Judo applied to dracaena plugs and Botanigard ES applied to tomato plants.

Phytotoxicity can also be caused by the solvents in a formulation (EC formulation vs WP), impurities in spray water, using a higher rate of pesticide than is listed on the label, tank-mixing or inadequately mixing the spray solution. Environmental conditions such the temperature, humidity, and light can also influence phytotoxicity. High temperatures can speed up pesticide degradation and volatilization, but may also result in increased phytotoxicity for some products. Plants that are stressed are more susceptible to pesticide injury.

At this time of year, poinsettias will become more sensitive to spray injury as bracts turn color. Pesticide applications to poinsettia bracts are risky since there are so many variables. Differences in cultivars, culture and environmental conditions may increase or decrease bract sensitivity to pesticides. If you are inexperienced with a particular pesticide, always test a small portion of your crop before treating your entire crop.

To prevent injury due to pesticides, be sure to follow label directions exactly. See the company's website to read any technical bulletins about the product or call the company's technical representative before using a product for the first time.

If minor phytotoxicity is suspected from foliar applications of an insecticide, miticide or fungicide, watch the new growth as it emerges. Plants will often grow out of one-time spray damage. As plants grow, the damage will remain on the oldest leaves and the new growth will appear healthy.

Articles: Dilemma of Tank-mixing by Raymond Cloyd Whiteflies on Poinsettias - Late Season Control

Photos of Pesticide Phytotoxicity: Judo injury on dracaena plugs and ivy geraniums (See technical bulletin for list of crops for which Judo should not be used) Distance injury on poinsettia BotaniGard injury on tomato plants 2 Herbicide injury on tomato and geranium

Tina Smith, University of Massachusetts

While many insecticides kill pests by contact activity, some insecticides have either systemic or translaminar properties. A good article on the subject was written several years ago by Dr. Raymond Cloyd, now at Kansas State Univ. and I thought the information might be useful.

Systemic insecticides are pesticides in which the active ingredient is primarily taken up by plant roots and transported throughout the plant, such as the growing points where it can affect plant-feeding pests. Systemics move within the vascular tissues, either through the xylem (water-conducting tissue) or phloem (food-conducting tissue) depending on the characteristics of the material. The water solubility of systemic insecticides determines their movement within plants. Very water soluble materials are readily taken up by plant roots or leaves. Systemic insecticides are most effective on insects with piercing- sucking mouthparts, such as aphids, whiteflies, mealybugs and soft scales because these insects feed within the vascular system. Most of the systemic insecticides have minimal activity on spider mites because spider mites remove chlorophyll and don’t feed within the vascular tissues. Systemic insecticides should be applied when plants have an extensive, well-established root system and when they are actively growing.

Translaminar insecticides penetrate leaf tissues and form a reservoir of active ingredient within the leaf. This provides residual activity against certain foliar-feeding insects and mites. Because the active ingredient can move through leaves, thorough spray coverage is less critical to control spider mites, which normally feed on leaf undersides. Insecticides/miticides with translaminar properties include but not limited to abamectin (Avid), pyriproxyfen (Distance), chlorfenapyr (Pylon) and spinosad (Conserve). In general, these types of materials are active against spider mites and/or leafminers.

For more information, read Dr. Cloyd's complete article: Systemic, Local Systemic, or Translaminar: What's the Difference?

Tina Smith

BotaniGard has again caused injury on tomato plants in the greenhouse. BotaniGard is a bio-insecticide containing the fungus Beauvaria bassiania. Growers have reported that tomato plants sprayed with BotaniGard ES have developed dramatic edema, downward curling of the leaves and yellowing along the veins of the leaflets. Injury has been reported with the ES formulation. Less injury is likely when using the WP. BotaniGard should be applied to tomatoes in the greenhouse with caution.

See photo:BotaniGard Injury , 2

Paul Lopes