Raymond A. Cloyd

Impact of neonicotinoid insecticides on natural enemies in greenhouse and interiorscape environments

The neonicotinoid insecticides imidacloprid, acetamiprid, dinotefuran, thiamethoxam and clothianidin are commonly used in greenhouses and/or interiorscapes (plant interiorscapes and conservatories) to manage a wide range of plant-feeding insects such as aphids, mealybugs and whiteflies. However, these systemic insecticides may also be harmful to natural enemies, including predators and parasitoids. Predatory insects and mites may be adversely affected by neonicotinoid systemic insecticides when they: (1) feed on pollen, nectar or plant tissue contaminated with the active ingredient; (2) consume the active ingredient of neonicotinoid insecticides while ingesting plant fluids; (3) feed on hosts (prey) that have consumed leaves contaminated with the active ingredient. Parasitoids may be affected negatively by neonicotinoid insecticides because foliar, drench or granular applications may decrease host population levels so that there are not enough hosts to attack and thus sustain parasitoid populations. Furthermore, host quality may be unacceptable for egg laying by parasitoid females. In addition, female parasitoids that host feed may inadvertently ingest a lethal concentration of the active ingredient or a sublethal dose that inhibits foraging or egg laying. There are, however, issues that require further consideration, such as: the types of plant and flower that accumulate active ingredients, and the concentrations in which they are accumulated; the influence of flower age on the level of exposure of natural enemies to the active ingredient; the effect of neonicotinoid metabolites produced within the plant. As such, the application of neonicotinoid insecticides in conjunction with natural enemies in protected culture and interiorscape environments needs further investigation.

Effect of Insecticides on Mealybug Destroyer (Coleoptera: Coccinellidae) and Parasitoid Leptomastix dactylopii (Hymenoptera: Encyrtidae), Natural Enemies of Citrus Mealybug (Homoptera: Pseudococcidae)

In this study, we measured, under laboratory conditions, the direct and indirect effects of insecticides on mealybug destroyer, Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), and parasitoid Leptomastix dactylopii Howard (Hymenoptera: Encyrtidae), natural enemies of citrus mealybug, Planococcus citri (Risso) (Homoptera: Pseudococcidae). The adult stages of both natural enemies were exposed to sprays of the insecticides buprofezin, pyriproxyfen, flonicamid, acetamiprid, dinotefuran, and clothianidin at label-recommended rates to assess direct mortality after 24, 48, and 72 h, respectively. The effects of the insecticides on L. dactylopii parasitization rate and percentage of parasitoid emergence also were monitored using the label and 4x the recommended label rate. Dinotefuran was extremely detrimental to the adult parasitoid at the label rate with 100% mortality after 24 h. Buprofezin, pyriproxyfen, and flonicamid were not harmful to L. dactylopii when applied at the label rate. At 4x the recommended label rate, dinotefuran, acetamiprid, and clothianidin were all harmful to the parasitoid with 100% mortality 72 h after application. Both buprofezin and flonicamid were not toxic to L. dactylopii with 100% adult survival after 72 h. Pyriproxyfen and flonicamid, at both the label and 4x the recommended label rate, did not negatively affect L. dactylopii parasitization rate or percentage of parasitoid emergence. Acetamiprid, dinotefuran, and clothianidin were toxic to C. montrouzieri adults with 100% mortality after 48 h, whereas buprofezin, pyriproxyfen, and flonicamid demonstrated minimal (10-20% mortality after 48 h) harmful effects to the predator. Based on the results from our study, the indirect effects of the insect growth regulator (IGR) buprofezin were not decisive; however, the IGR pyriproxyfen and the insecticide flonicamid were not directly or indirectly harmful to the predator C. montrouzieri and parastioid L. dactylopii, indicating that these insecticides are compatible with both natural enemies when used together for control of citrus mealybug in greenhouses and conservatories.

Effect of Commercially Available Plant-Derived Essential Oil Products on Arthropod Pests

ABSTRACT Plant-derived essential oil products, in general, are considered minimum-risk pesticides and are exempt from Environmental Protection Agency registration under section 25 (b) of the Federal Insecticide Fungicide and Rodenticide Act. However, many of the plant-derived essential products available to consumers (homeowners) have not been judiciously evaluated for both efficacy and plant safety. In fact, numerous plant-derived essential oil products labeled for control of arthropod pests have not been subject to rigorous evaluation, and there is minimal scientific information or supporting data associated with efficacy against arthropod pests. We conducted a series of greenhouse experiments to determine the efficacy and phytotoxicity of an array of plant-derived essential oil products available to consumers on arthropod pests including the citrus mealybug, Planococcus citri (Risso); western flower thrips, Frankliniella occidentalis (Pergande); twospotted spider mite, Tetranychus urticae Koch; sweetpotato whitefly B-biotype, Bemisia tabaci (Gennadius); and green peach aphid, Myzus persicae (Sulzer). Although the products Flower Pharm (cottonseed, cinnamon, and rosemary oil) and Indoor Pharm (soybean, rosemary, and lavender oil) provided >90% mortality of citrus mealybug, they were also the most phytotoxic to the coleus, Solenostemon scutellarioides (L.) Codd, plants. Both GC-Mite (cottonseed, clove, and garlic oil) and Bugzyme (citric acid) were most effective against the twospotted spider mite (≥90% 0ortality). However, SMC (canola, coriander oil, and triethanolamine), neem (clarified hydrophobic extract of neem oil), and Bug Assassin (eugenol, sodium lauryl sulfate, peppermint, and citronella oil) provided >80% mortality. Monterey Garden Insect Spray, which contained 0.5% spinosad, was most effective against western flower thrips with 100% mortality. All the other products evaluated failed to provide sufficient control of western flower thrips with <30% mortality. In addition, the products Pest Out (cottonseed, clove, and garlic oil), Bang (Pipereaceae), and Fruit & Vegetable Insect Spray (rosemary, cinnamon, clove oil, and garlic extract) had the highest flower (transvaal daisy, Gerbera jamesonii [H. Bolus ex Hook.f]) phytotoxicity ratings (≥4.5 of 5) among all the products. None of the plant-derived essential oil products provided sufficient control of sweetpotato whitefly B-biotype or green peach aphid 7, 14, and 21 d after application. Furthermore, the products Bug Assassin (eugenol, sodium lauryl sulfate, peppermint, and citronella oil) and Sharpshooter (sodium lauryl sulfate and clove oil) were phytotoxic to the poinsettia, Euphorbia pulcherrima Willd. ex Klotzsch, plants. This study is one of the first to quantitatively demonstrate that commercially available plant-derived essential oil products vary in their effectiveness against certain arthropod pests stated on the label and are phytotoxic.

Effect of Nitrogen Fertility on Reproduction and Development of Citrus Mealybug, Planococcus citri Risso (Homoptera: Pseudococcidae), Feeding on Two Colors of Coleus, Solenostemon scutellarioides L. Codd

Abstract The effects of nitrogen concentration on the reproduction and development of citrus mealybug, Planococcus citri, were studied on two colors of coleus, Solenostemon scutellarioides. Green and red-variegated coleus plants were supplied with varying applied nitrogen concentrations (0, 25, 50, 100, 200, and 400 ppm) for 32 d before being artificially inoculated with citrus mealybugs. Female citrus mealybug life history parameters including eggs contained within the egg mass and respective body cavity, body length (mm), and developmental time (d) were measured. A modified micro-Kjeldahl digestion procedure followed by colormetric assay was conducted twice throughout the study to assess leaf nitrogen concentration. The results of this study show that the citrus mealybug life history parameters were influenced by the applied nitrogen concentrations (ppm), leaf nitrogen concentration (%), and total moisture content (g). Citrus mealybugs feeding on both green and red-variegated coleus, receiving the high nitrogen fertilizer concentrations (200 and 400 ppm) had the greatest egg loads, were larger in size, and had the shortest developmental times. Leaf nitrogen concentration also affected the citrus mealybug life history parameters with those mealybugs feeding on plants containing the highest leaf nitrogen contents having the greatest egg loads, larger in size, and the shortest developmental times. In addition, total plant moisture content impacted the citrus mealybug life history parameters similar to leaf nitrogen concentration. However, this was based on plant architecture whereas percent plant moisture content for both green- and red-variegated coleus was comparatively similar for all nitrogen concentrations. The life history parameters measured were more pronounced on green coleus compared with red-variegated coleus, perhaps because of nitrogen allocation differences between the two coleus colors. Thus, higher nitrogen concentrations, in the form of supplemental fertilizers used in greenhouse production systems, leads to an increase in the performance of citrus mealybugs as defined by increased egg loads, larger mature females, and shorter developmental times on coleus plants. These results indicate that the implementation of proper fertilizer practices may lessen the likelihood of dealing with extensive insect outbreaks, thus potentially reducing insecticide use.

Activity of an Essential Oil Derived from Chenopodium ambrosioides on Greenhouse Insect Pests

Abstract This study involved both greenhouse and laboratory experiments evaluating the effect of an essential oil product (QRD 400) derived from Chenopodium ambrosioides variety nr. Ambrosioides L. (Chenopodiaceae) on greenhouse insect pests that feed on different plant parts: citrus mealybug, Planococcus citri (Risso); longtailed mealybug, Pseudococcus longispinus (Targioni Tozzetti); western flower thrips, Frankliniella occidentalis (Pergande), and fungus gnats (Bradysia spp.). Treatments were applied to coleus, Solenostemon scutellarioides plants; transvaal daisy, Gerbera jamesonii flowers; or growing medium, depending on the insect pest. The essential oil was most effective, based on adult emergence, on both the second and third instars of the fungus gnat Bradysia sp. nr. coprophila when applied as a drench to growing medium. In addition, there was a significant rate response for QRD 400 on fungus gnats. The QRD 400 treatment had the highest percentage of mortality on longtailed mealybug (55%) compared with the other treatments. However, the essential oil was less effective against citrus mealybug (3% mortality) and western flower thrips adults (18–34% mortality) compared with standard insecticides, such as acetamiprid (TriStar) and spinosad (Conserve), which are typically used by greenhouse producers. This lack of efficacy may be associated with volatility and short residual properties of the essential oil or with the essential oil taking longer to kill insect pests. Other insecticides and miticides evaluated, including sesame oil, garlic, paraffinic oil, and Bacillus thuringiensis subsp. israelensis, provided minimal control of the designated insect pests. In addition, adult rove beetle Atheta coriaria Kraatz adults were not effective in controlling the larval instars of fungus gnats when applied at a rate of five adults per container.

Effect of Pesticides on Adult Rove Beetle Atheta coriaria (Coleoptera: Staphylinidae) Survival in Growing Medium

ABSTRACT The rove beetle Atheta coriaria (Kraatz) (Coleoptera: Staphylinidae) is a natural enemy (biological control agent) commercially available for control of certain greenhouse insect pests, including fungus gnats, shore flies, and thrips. This study assessed the compatibility of pesticides (insecticides and fungicides) used in greenhouses with A. coriaria adults. Treatments were applied to 473-ml deli squat containers half-filled with a growing medium. We evaluated the effects of the pesticides when releases of A. coriaria adults were performed both before and after application of the designated pesticide solutions. All three of the neonicotinoid-based insecticides (clothianidin, dinotefuran, and thiamethoxam) were directly harmful to A. coriaria adults with ≤3.2 adults recovered (out of 20) among all three treatments across all experiments. In addition, the organophosphate insecticide chlorpyrifos at the low (0.25 fl oz/100 gal) and high (0.50 fl oz/100 gal) label rates; the plant-derived essential oil product (Indoor Pharm) containing soybean and rosemary oil; and the insecticide/miticide chlorfenpyr were directly harmful to A. coriaria adults with recovery rates ≤8.6 (out of 20) among all the treatments. The fungicides (azoxystrobin, fosetyl-aluminum, and mefenoxam) were not directly toxic to A. coriaria adults, with ≥17.7 adults recovered (out of 20) across all experiments. The insecticides (Bacillus thuringiensis subsp. israelensis, flonicamid, Metarhizium anisopliae strain52, and spinosad) and insect growth regulator azadirachtin were also not directly toxic to A. coriaria adults. Furthermore, many of these same treatments did not inhibit the ability of adult A. coriaria to consume fungus gnat (Bradysia sp. nr. coprophila) larvae in a feeding behavior experiment. Although the neonicotinoid-based insecticides were directly harmful to adult A. coriaria, when adults were released 48, 72, or 96 h after application, survival increased dramatically over time. This study has quantitatively demonstrated that certain pesticides (both insecticides and fungicides) are compatible with and can be used along with A. coriaria in systems that use this natural enemy to manage fungus gnat larvae.

Pesticide use in ornamental production: what are the benefits?

Pest control in ornamental production is challenging owing to the diversity of crops grown, the desired aesthetic perfection, the potential economic loss due to failure and the multitude of arthropod pests encountered. Agricultural crops of less value per acre, such as row crops, can tolerate a certain level of damage from arthropod pests without compromising yields. Damage thresholds for ornamentals, however, are essentially zero. Pesticides are a viable method of protection for such a crop in lieu of alternatives. Therefore, the purpose of this paper is to emphasize the importance of pesticides to the ornamental industry. Pesticides provide many benefits to ornamental producers, including: (1) consistent availability; (2) rapid kill; (3) reliable and consistent control; (4) increased crop production and quality; (5) they may be used to prevent movement of invasive pests; (6) they are less expensive (in general) than alternatives; (7) they may reduce plant pathogenic transmission; (8) they may be used in conjunction with natural enemies. Pesticide use will continue to be a significant strategy for dealing with arthropod pests so that ornamental producers can stay competitive in both national and international markets.

Effects of Greenhouse Pesticides on the Soil-Dwelling Predatory Mite Stratiolaelaps scimitus (Acari: Mesostigmata: Laelapidae) Under Laboratory Conditions

Abstract Knowledge of the effects of pesticides on biological control agents is required for the successful implementation of integrated pest management (IPM) programs in greenhouse production systems. Laboratory assays were conducted to assess the effects of an acaricide (dicofol), two insecticides (chlorpyrifos and pyriproxyfen), and two fungicides (fosetyl-Al and mefenoxam) on Stratiolaelaps scimitus (Womersley), a soil-dwelling predatory mite widely marketed in North America under the name Hypoaspis miles (Berlese) as a biological control agent of dark-winged fungus gnats (Bradysia spp.). Eggs, larvae, protonymphs, deutonymphs, and adult male and female mites were first assayed using dicofol, an acaricide used in the experiments as a positive control, applied to filter paper in an enclosed arena. Protonymphs were assayed for lethal and sublethal effects against the remaining pesticides at maximum label-recommended rates applied to filter paper, by using dicofol as a positive control and water as a negative control. The larva and protonymph were the life stages most susceptible to dicofol, with estimated 24-h LC50 values of 9 and 26 mg m−2, respectively. Chlorpyrifos was highly toxic to the protonymphs of S. scimitus, causing >95% mortality after 24-h exposure and 100% mortality after 48 h. In contrast, the insect growth regulator (IGR) pyriproxyfen was much less toxic to protonymphs of S. scimitus; pyriproxyfen caused no significant mortality, compared with <5% mortality in the water control. Mortality caused by the fungicides was also relatively low; 72-h exposure to fosetyl-Al and mefenoxam resulted in 17.4 and 27.5% mortality, respectively. The IGR and fungicides increased the duration of the protonymphal stage by 1.2–1.8-fold, but they had no effect on the duration of subsequent life stages, nor on the duration of preoviposition, oviposition, and postoviposition periods of adult females. Total numbers and viability of eggs laid by mites exposed to the IGR and fungicides did not differ from the negative control, although the average rate of egg production during the oviposition of mites exposed to fosetyl-Al was increased. Pyriproxyfen, fosetyl-Al, and mefenoxam are likely to be compatible with S. scimitus under field conditions, because these pesticides caused little mortality of protonymphs, and they did not negatively affect the development and reproduction of S. scimitus under extreme laboratory conditions. In contrast, the use of chlorpyrifos in conjunction with S. scimitus is not recommended unless more comprehensive testing under semifield or field conditions demonstrates compatibility.

Food preference of the rove beetle, Atheta coriaria Kraatz (Coleoptera: Staphylinidae) under laboratory conditions

A study, involving laboratory choice tests, was conducted to determine the feeding behavior, based on food preference, of the adult and larval stage of the rove beetle, Atheta coriaria Kraatz when presented with both fresh moistened oatmeal and second instar fungus gnat, Bradysia sp. nr. coprophila (Lintner) larvae in Petri dishes. Rove beetles used in this study came from a laboratory‐reared colony. A rating scale from 1 to 5, based on percent missing (1 = 0 to 10%, 2 = 11 to 30%, 3 = 31 to 50%, 4 = 51 to 75%, and 5 = 76 to 100%), was used to objectively assess the amount of oatmeal and number of fungus gnat larvae consumed by each rove beetle adult and larva. In all the choice tests, A. coriaria adults and larvae preferred to feed on fungus gnat larvae (78% and 69%, respectively) significantly more so than oatmeal (9% and 5%, respectively) based on the amount of oatmeal and number of fungus gnat larvae consumed after 4 and 6 hours. There were relatively minimal differences in the amount of food consumed for both adults and larvae after 4 and 6 hours. The results of this study indicate that oatmeal may be an inexpensive supplemental food source, during the rearing process, which will not inhibit the effectiveness of rove beetles to control fungus gnat larvae when released into greenhouses.

Effect of Pesticide Mixtures in Controlling Western Flower Thrips (Thysanoptera: Thripidae)

Greenhouse managers mix together pesticides to broaden the spectrum of pest control and to reduce pesticide and labor costs. However, the efficacy of pesticide mixtures has not been well-documented. This study assesses how mixtures of commercially available insecticides and miticides in two, three, and four-way combinations affected the control of western flower thrips, Frankliniella occidentalis Pergande, in greenhouse experiments and in a laboratory bioassay. The pesticides screened in the greenhouse experiments and laboratory bioassay were spinosad, abamectin, bifenazate, azadirachtin and imidacloprid. Each pesticide was applied at the maximum label-recommended rate. In the greenhouse experiments, transvaal daisy (Gerbera jamesonii H. Bolus ex Hook. f) and lisianthus (Eustoma grandiflorum G. Don ex Sweet) flowers were infested with 25 adult western flower thrips (mixture of females and males). Flowers were then sprayed with the designated treatments. After 72 h, flowers were dissected to assess the num...