IR-4 Ornamental Horticulture Program Research Report Cover Sheet

Transcription

1 IR4 Ornamental Horticulture Program Research Report over Sheet Researcher(s) Richard owles Affiliation: onnecticut Agricultural Experiment St 153 ook Hill Road P.O. Box 248 Windsor T PhoneNumber: richard.cowles@po.state.ct.us Trial: 2008 T ProjectTitle: White Grub & Root Weevil Efficacy Protocol #: PR# Research Target rop/plant Product EPA Reg. # Production Site Status Black Vine Weevil grub Arena 50WDG Field ontainer lothianadin Black Vine Weevil grub BAS 320i Field ontainer Metaflumizone BASF Black Vine Weevil grub BotaniGard ES Beauveria bassian Bioworks Field ontainer Black Vine Weevil grub DPXE2Y45 Field ontainer hlorantraniliprole Dupont Black Vine Weevil grub Met52 Field ontainer Metarhizium anisop Novozymes Bi Black Vine Weevil grub Safari 20SG Field ontainer Dinotefuran Black Vine Weevil grub Tolfenpyrad (Nichin Field ontainer Tolfenpyrad Nichino Americ Black Vine Weevil grub V G Dinotefuran Field ontainer

2 Insecticides for control of black vine weevil larvae in containergrown plants Richard S. owles onn. Agric. Expt. Station, Valley Lab Windsor, T Black vine weevil (BVW) is a serious pest of ornamental nursery crops (field and containergrown), vineyards, strawberries and hops. This study, sponsored by the IR4 Program, used potted strawberries as a model system to determine which insecticides would provide protection against BVW larvae. This study focused on whether there was a doseresponse for two new insecticides (chlorantraniliprole [DPX E2Y45, trade name Acelepryn] and metflumizone [BAS 320 I S]), to compare neonicotinoids (Safari vs. Arena), and to compare preventive preplant incorporation into potting media with insecticide drenches. Strawberry crowns of 'Idea' cultivar were obtained from a commercial nursery (Nourse Farms, S. Deerfield, MA) on 23 April. This cultivar was chosen because previous investigations have demonstrated it to have extraordinary root vigor. Prior to planting, the entire strawberry plant was dipped into a 1:10 dilution of household bleach, and allowed to sit with a film of bleach solution for 20 min prior to thorough washing. This procedure disinfests plants of any insect pathogenic nematodes adhering to the roots. After washing, plants were potted into #1 nursery containers (2.7 L per pot) using pretreated media or the standard medium, which consisted of a 1:1 mixture (by volume) of composted mixed hardwood and softwood chips : peat. A 200 ml aliquot of medium was dried in an oven to determine that its dry bulk density was 98 kg m 3 (160 lb/ cubic yard). Preplant incorporations were mixed on 24 April in a concrete mixer, with a volume of medium to fill 6 pots mixing for 2 min with insecticide. Granular products were incorporated while the concrete mixer was rotating. For sprayable products, sufficient material (DPX E2Y45, BAS 320 I, Metarhizium anisopliae spores, Safari 20 SG, tolfenpyrad) to treat 6 pots was diluted into 100 ml of water, and then sprayed onto the surface of the medium while the mixer was rotating. M. anisopliae spores were obtained by washing them from the same weight of rice grainbased product that was used in the preplant potting mix incorporation treatment. Treatments using one drench application were treated on 15 July, using the drench volume for each treatment provided by the protocol, or 200 ml if the volume was not specified. Treatments requiring four drenches (metflumizone and BotaniGard products) were applied on 15 and 29 July, 13 and 28 August, using an application volume of 200 ml per pot of product diluted in tap water. This volume was determined empirically by drenching check pots with water to calculate the quantity of water retained. Plants were grown in a shadeclothcovered hoop house with automatic daily overhead impact sprinkler irrigation. Black vine weevil eggs were obtained from a colony at the Valley Laboratory. About 200 adults were enclosed in a 20 L plastic bucket with yew foliage, and eggs were collected by shaking foliage on a weekly basis. Sufficient eggs were not available on any one collection date, and so pots were repeatedly infested with 28 eggs per pot on 5 June, 72 eggs per pot on 12 June, and 23 eggs per pot on 19 June, for a total of 123 eggs per pot. Eggs were placed 1 2 cm deep in the soil, close to the crown of the plant.

3 Larvae were counted on 4, 5, and 8 September by sifting through the potting media shaken from the strawberry root system. Root systems were rated on a zero to four scale, where 0 indicated total destruction, always involving crown feeding and imminent plant death; 1 was poor roots, in which the living roots were found within a 50 ml volume of medium; 2 was fair, with most of the soil falling away from the roots; 3 was good, with most of the soil being held together by the root system; 4 was excellent, with roots encircling the bottom of the pot and great difficulty in removing soil from the extensive root system. The number of larvae and root ratings were subjected to analysis of variance (Statistix 9, Analytical Software, Talahassee, FL), with the data analyzed as a completely randomized design (blocking was insignificant). Neither squareroot nor log transformations provided homogeneous variances. Results and Discussion Insecticide treatments (Table 1) varied greatly in efficacy (F [18, 94] = 7.27, P = ). Although variances were heterogeneous, the results were robust as determined by Welch's Test for mean differences (P = ). Recovery of BVW larvae was ~10% relative to the number of eggs infested into the pots for the least effective treatment in this study from which larvae were recovered (2 ppm Acelepryn preplant incorporation). About 40 60% recovery of larvae relative to the number of infested eggs is possible in BVW trials. Two factors other than insecticide treatment probably contributed to poor recovery of larvae: predation (maximized by running the trial during the summer) and overexploitation of food resources by BVW larvae in some treatments. Predation was probably a significant factor in reducing the number of larvae found in the untreated check and in the metflumizone treatments, in which pots were characterized by having few BVW larvae, plants with excellent root systems, and numerous ant (Lasius spp.) galleries and/or centipedes. Based on the pattern observed for larvae found in pots, predation probably is only a significant factor for early instar BVW. In the future, ant exclusion must be considered in order to eliminate this complication. Overexploitation of food by BVW larvae always poses a challenge. When too many larvae are present for the amount of available food, then larvae resort to girdling plants. The plants rapidly die, followed by larval mortality. One way to respond to this problem is to break down experiments and to count all the larvae as soon as the plants from the worst treatment start to die. With some treatments in this experiment requiring 4 drenches, 2 weeks apart, this option could not be used. Therefore, the results from this experiment have to be interpreted from the combination of the number of larvae and the root ratings. For example, based upon the lack of roots the BotaniGard WP drench treatment probably had greater numbers of larvae a few weeks prior to rating than the other ineffective treatments, based on poorer plant condition in the BotaniGard WP treatment plants. For a treatment to be considered to be effective, it must have no larvae recovered and have protected root systems from injury. When comparing this trial with the 2007 results, please note that the bulk density this year was lower than last year. This may have had an effect on the efficacy of the Acelepryn preplant

4 potting mix treatments. The lower bulk density exaggerated the effect from lowering the dosages tested this year. Acelepryn was found to be an effective product used in preplant treatments last year, therefore this year's results signify that the minimum dosage that should be suggested for this product would be ~ 10 ppm, though an additional test is needed for confirmation. Interestingly, the counts of larvae in these Acelepryn treatments were higher than the untreated checks. I believe that these results indicate that chemical exclusion of predators may occur at lower concentrations than are required to kill BVW larvae. The "silver lining" from these results is that this product could be considered for testing as a potting mix amendment for managing fire ants. Safari was found to be effective in this year's trial with preplant incorporation of the sprayable formulation. The poorer control with preplant potting mix incorporation of the Safari 2G granules suggests that the product distribution within the mix was inadequate. Last year, Safari was found to be ineffective when applied as a curative drench targeting later instars. Safari 2 SG should be tested further to determine if a surface application when early instars are present would be as effective as a surface application or drench with the 20 SG formulation. Arena was found to be consistently effective when applied as a drench, in both years of the study. Metflumizone should be considered an outstanding material to target control of BVW. The lowest dosage that was completely effective was the 4 ppm preplant potting mix incorporation. The fourfold drench procedure was completely effective, as was the single curative drench tested last year. It is likely that a dosage < 1% that of that given in the protocol would also have been effective with this product when using the multiple drench procedure. BotaniGard ES and WP formulations require further testing before concluding that they have poor potential for control of BVW. It is possible that the dosage applied was inadequate. However, it is disconcerting that this product was used in that manner described on the label, but damage to the plants was extensive for these treatments. Metarhizium and tolfenpyradtreated pots had uniformly healthy plants and few larvae, however the low counts in the untreated check preclude being able to determine whether these treatments provided significant benefits.

5 Table 1. Efficacy of products used for control of black vine weevil larvae. See text for description of the root rating system. Treatment Product Dosage Active ingredient, No. of ontrol (%) Root Method * total (mg/pot) Larvae Rating Untreated check 0.83 e 4.0 a MD BAS320 I S 16 fl oz/100 gal e a PP BAS320 I S 1 ppm e a PP BAS320 I S 2 ppm e a PP BAS320 I S 4 ppm e a D DPX E2Y fl oz/100 gal bc ab PP DPX E2Y45 1 ppm bcd bc PP DPX E2Y45 2 ppm a d PP DPX E2Y45 4 ppm e a D Metarhizium anisopliae 2.9 g / pot 0.67 e a PP Metarhizium anisopliae 2.9 g / pot 0.33 e a MD BotaniGard WP 18.7 mg / pot 1.2 de d MD BotaniGard ES 39 μl/pot 4.2 bc d PP BotaniGard WP 18.7 mg / pot 5.8 b d PP BotaniGard ES 39 μl/pot 2.0 cde d PP Safari 2 G 1.23 g / pot cde bc PP Safari 20 SG 24 oz / 100 gal e a PP Arena 50W 49 mg / pot e a PP tolfenpyrad 10 ppm e ab * PP, preplant incorporation; D, drench; MD, multiple drench Means followed by the same letter do not significantly differ (Tukey's HSD test, P < 0.05).