INSECTICIDAL EFFECT OF MICRONUTRIENT FERTILIZERS

Abstract

A method for suppressing the population of Pentatomid insect pest. According to the method, a foliar fertilizer is prepared containing at least one type of nutritive heavy metal. The fertilizer is sprayed on egg masses deposited by Pentatomid insect species, causing a significant mortality among the neonates.

Claims

1. A method for suppressing the population of Pentatomid insect, said method comprising: a foliar fertilizer is prepared containing at least one type of nutritive heavy metal; said fertilizer is sprayed on egg masses deposited by Pentatomid insect species.

2. A method as in claim 1 wherein said Pentatomid insect is H. halys.

3. A composition for use for the control of Pentatomid insects consisting of at least one nutritive heavy metal otherwise used for foliar fertilizing of plants. wherein the application of said composition to egg masses of said insect induces neonate mortality.

4. A composition as in claim 3 wherein two chelated metals are combined.

5. A composition as in claim 3 wherein none of the metals is copper.

6. A composition as in claim 3 wherein said at least one nutritive metal is chelated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1. Mean mortality rates recorded for H. halys neonate nymphs after treatment with different micronutrient fertilizers.

DISCLOSURE OF THE INVENTION

[0008] In accordance with some embodiments of the present invention, mixtures of nutritive heavy metal chelated with organic acids were tested for their effect in suppressing stink bug populations. In addition, a non-chelated copper fertilizer nutrient was tested, as will be described in more detail below.

[0009] Trials were performed in DISAFA, University of Turin, Italy.

Trials

[0010] Insects

[0011] During spring and summer of 2018, about 1,000 brown marmorated stink bug adults were collected from different wild and cultivated host plants in the Piedmont region, Italy. Field-collected adults were reared at the DISAFA laboratories, in climatic chambers at 25±1° C., with an L:D of 16:8 photoperiod, in net cages (930×475×475 mm) containing seedlings of broad bean, apples, and shelled hazelnuts obtained from the DISAFA experimental farms and never treated with insecticides. H. halys egg masses were collected daily from the mass rearing to obtain two distinct groups, corresponding to 24-hour old and 5-day old egg masses, respectively.

[0012] Egg masses treatment using micronutrient fertilizers.

[0013] Three commercially available micronutrient EC fertilizers (i.e. admitted for the EU market), suitable for organic farming, were selected: (1) a zinc (4.0%), copper (2.0%) and citric acid biocomplex (Dentamet®, Diagro Sri, Italy); (2) a zinc (4.8%), manganese (2.7%) and citric acid biocomplex (Bio-D®, Diagro); (3) a copper hydroxide 50% wettable powder (Keos®, Green Ravenna Sri, Italy). Moreover, the experimental product Dentamet® A3 (Diagro) (hereafter A3) containing citric acid, lactic acid, malic acid, zinc (4.1%), and copper (1.9%), was tested as well (4). All products were used on 24-hour old egg masses at label recommended doses: 1% v/v (corresponding to a mean of 775 g/hl) for micronutrient and citric acid biocomplexes (Dentamet®, Bio-D®, and A3), and 0.15% (w/v) for Keos®. Additionally, 0.5% (v/v) were added of a Poly-1-p-menthene-based pesticide additive (NU-FILM-P®, CBC, Italy), to increase active ingredients penetration of maternal secretions covering P. carbekii cells (Kenyon U, Meulia T and Sabree Z L (2015): Habitat visualization and genomic analysis of ‘Candidatus Pantoea carbekii,’ the primary symbiont of the brown marmorated stink bug. Genome Biol Evol 7: 620-635.). Additive concentration was selected according to the manufacturer's indications as well. Finally, an untreated control (5) and a water+0.5% additive control (6) were included. The two products showing the higher mortality rates on 24-hour old egg masses were used to perform a second experiment on 5-day old egg masses, along with controls, with the purpose to assess whether the treatment effect was visible even after a short time of product exposure.

[0014] A total of 120 egg masses were collected and randomly allocated to treatments, once the number of eggs per mass was recorded. Exposure to the products was carried out on 24-hour old and 5-day old egg masses for each treatment and water+additive control (N=10); 20 replicates for the untreated control were collected as well. The egg masses were individually placed into Petri dishes covered with filter paper, and then treated with the active substances solutions by means of a 250 ml hand sprayer (Nalgene®, NY, USA) under a fume hood. A single spray (651±7.42 ml) was applied with the hand sprayer held approximately 20 cm away from the Petri dish with the egg mass.

[0015] Nymphal Rearing

[0016] After the treatment, egg masses were individually reared in climatic chamber (25° C., RH 70%) in clear plastic Petri dishes with a wider lid with respect to the base to provide ventilation. Nymphs were provided with an organic green bean (purchased at a local farmers' market), as a food source; hatching percentages were checked daily. Newly hatched nymphs were fed with green beans until reaching second nymph instar. Mortality rates were calculated; dead nymphs were collected each day and stored at −80° C. in RNA Later® (Sigma-Aldrich, MO, USA). As live nymphs moulted to the second instar, they were collected as well and stored as described above.

[0017] Statistical Analyses

[0018] To compare egg hatching and mortality, the percentages of dead specimens were derived with respect to the total number of emerged nymphs for each egg mass. Corrected mortality rates were calculated according to the Abbott's formula with respect to untreated control (Abbott W S (1925), A method of computing the effectiveness of an insecticide. J Econ Entomol 287 18: 265-267). Moreover, absolute mortality rates were calculated as the ratio between dead I instar nymphs and hatched eggs for each egg mass, and analysed with SPSS Statistics 25 (IBM Corp. Released 2017, Armonk, N.Y., USA), using a generalized linear model (GLM) with a binomial probability distribution and logit link function. Means were separated by a Bonferroni post hoc test (P<0.05).

[0019] In FIG. 1, the percentage of dead nymphs before reaching II instar was calculated for 24-hour old (light hatched columns) and 5-day old (cross hatched columns) egg masses. Bars indicate standard errors. Different letters indicate significantly different values according to binomial GLM+Bonferroni's test (P<0.05); capital letters refer to experiments with 24-hour old egg masses whereas lowercase letters indicate experiments with 5-day old egg masses.

TABLE-US-00001 TABLE 1 Table 1. Data recorded during laboratory experimental application of micronutrient fertilizers to 24-hour old and 5-day old H. halys egg masses. Results are expressed as mean values ± SE. For egg hatching rates, different letters indicate significantly different values according to binomial GLM analysis + Bonferroni's test. Separate statistical tests were conducted for 24-hour old egg masses (df = 5; x2 = 41.376; P < 0.001) and 5-day old egg masses (df = 3; x2 = 29.332; P < 0.001). Corrected mortality rate Average number Average egg to II nymphal Egg masses age Treatment of eggs per mass hatching rate instar (%) 24 hours Dentamet ® 25.8 ± 1.12 68.60 ± 1.78 a 92.60 ± 0.29 Bio-D ® 25.6 ± 0.95  81.64 ± 1.24 b {circumflex over ( )} 90.96 ± 0.86 Keos ® 26.0 ± 1.03 82.30 ± 1.22 b 87.67 ± 1.44 A3 24.2 ± 1.71 66.94 ± 2.20 a 91.58 ± 0.68 Water + additive 19.70 ± 2.04   71.06 ± 1.91 ab  64.36 ± 15.17 Untreated control 24.75 ± 1.46  82.22 ± 1.68 b 0.00 5 days Dentamet ® 26.4 ± 1.10 82.57 ± 2.26 c 87.84 ± 0.76 A3 21.0 ± 1.57 60.95 ± 1.96 a 82.57 ± 3.38 Water + additive 21.1 ± 2.10  68.05 ± 1.77 ab 37.25 ± 4.71 Untreated control 22.9 ± 1.93  75.10 ± 1.76 bc 0.00

[0020] As can be seen from graph 1 and table 1, Dentamet® (copper and zinc combination with citric acid as a complexant) performed best in lowering the population of instar I and II nymphs, by inducing neonate mortality. As a candidate for second best, the Keos® (non chelated copper) may be found in graph 1, but if corrected to average hatching rate, Bio D° or A3, appear as better candidates.

[0021] Additional data: it was recently observed that further species of Pentatomids exhibited significant signs of vulnerability to the application of Dentamet®. Thus, application of Dentamet® on egg masses of Eurygaster maura, a parasitic Pentatomid of cereals, caused statistically significant mortality among nymphs.