Bentley, Walter J.

Duncan, Roger

Hendricks, Lonnie

Ridgely, Anne Marie

Silvers, Cressida

Undetermined

ScholarsArchive@OSU

Implementation ProgramBIOLOGICALLY INTENSIVE ORCHARD SYSTEMS VS. CONVENTIONALINSECTICIDES: TWO APPROACHES TO PEST MANAGEMENT IN ALMONDSWalt Bentley, Cressida Silvers, Lonnie Hendricks, Roger Duncan, Anne Marie RidgelyKearney Agricultural Research and Extension Center9240 South Riverbend AvenueParlier, CA 93648Biologically Intensive Orchard Systems (BIOS) is a term used to describe a group ofgrowers that have been emphasizing the use of seeded cover crops and reduced syntheticchemical inputs (particularly organophosphate insecticides) and releases of beneficialinsects such as Goniozus legneri, Pentalitomastix plethicora, and Galandromousoccidentalis to manage pest problems in orchards. These growers farm primarily inMerced and Stanislaus counties, between Fresno and Modesto. A total of 45 growers arecurrently enrolled as BIOS participants. Many them are reporting very low levels ofdamage from pests such as peach twig borer (PTB), navel orangeworm (NOW), San Josescale (SJS) and webspinning spider mites. The commonly held belief is that cover cropsare providing a habitat for beneficials that prey on pests.A project was funded by the Almond Board of California to investigate insect damageand arthropod dynamics in orchards farmed under a BIOS approach and those farmedusing conventional techniques such as the use of organophosphate insecticides and noseeded cover crops. Six comparisons were made in the two county area. These wereeither neighbors or the same grower using each of the two practices. All orchardscomparisons contained the primary soft shell varietyNonpareil.Samplesof 500 nuts were collected at harvest from each of the comparison orchards andevaluated for NOW, PTB, and ant damage. The results are presented in Table 1.Table 1. Nut damage (Nonpareil cv.) due to various insect pests from 6 BIOS vs. 6 Spraycomparisons, 1996FarmingPractice% NOWDamage% PTBDamage% AntDamage% TotalDamage% GoodNutsSPRAY4.4a2.2a0.8a0.8a1.9a0.8a6.8a3.8a87.06a90.87 bMeans followed by the same letter (columns) are not significantly different (P< 0.05; Fisher's protectedLSD)The primary parasitoid of NOW, Goniozus legneri was released in 3 of the BIOSorchards but was found at only one site at harvest. The parasitism rate at the site was193.5%. No other parasitoids were recovered from NOW larvae collected during nutevaluation.Examination of unharvested "mummy" nuts from 43 orchards also produced low levelsof the parasitoid Goniozus legneri. Table 2 presents results from mummy nut crackoutsranging from 50 to 100 mummy nuts.Table 2. Navel orangeworm infestation and parasitism from unharvested mummy nuts inselected almond orchards, winter 1996.Average #Mummies/tree(52)sites17.98Average NOWinfestation(44 sites)12.11# Sites withGoniozus(44 sites)# Sites withPentalitomastix(44 sites)Mummy load at 44 sites with the Nonpareil cv. ranged from 0 to 177. Currentrecommendations are that almond growers reach a level of 2 or fewer mummies per treeby spring. Of the 34 grower sites where harvest collections were made, 14 achieved thislevel (11 indicating they do winter sanitation and 3 do not remove mummies). Infestationfor these 14 growers averaged 1.48%NOW damage at harvest. The range of damage was0 to 5%. Mummy load in the remaining 21 sites ranged from 3 to 177 nuts per tree andaveraged 3.52% NOW infestation. The range of infestation was .2% (3.3 mummies pertree during the winter to 14% (113 mummies per tree during the winter).In summary, there was no statistical difference among the comparison orchards ininfestation from NOW, PTB, or ants. However there was significantly more good nutsharvest from the orchards that followed a conventional management approach. This isdue to a greater incidence of various diseases which cause gumming and shriveling ofalmonds. The influence of parasitoids on reducing insect damage in the BIOS orchardswas not evident. The greatest contributor to reduced NOW infestation was wintersanitation, not sprays or beneficial releases.20

Biologically intensive orchard systems vs. conventional insecticides : two approaches to pest management in almonds

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Biologically intensive orchard systems vs. conventional insecticides : two approaches to pest management in almonds

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