ALFALFA PEST MANAGEMENT

Transcription

1 ALFALFA PEST MANAGEMENT Vonny M. Barlow, Ph.D. Entomology Advisor, University of California-Davis, Division of Agricultural & Natural Resources, Riverside County

2 42 Trinity-Klamath Mtn Intermountain Colusa Glenn Sutter 38 San Francisco Sacramento Valley Sierra Nevada Mtn Alfalfa production areas Fresno Kern Kings Merced Tulare Madera Coastal San Joaquin Valley Los Angeles San Diego Mojave Desert High desert Imperial Riverside San Bernardino Southern Desert Valley

3 Numerous occasional pests Insects and Mites Blister Beetles Clover Root Curculio Grasshoppers Ground Mealybug Mormon Cricket Sharpshooters Silverleaf Whitefly Spider Mites Threecornered Alfalfa Hopper Thrips Webworm

4 Outbreaks Are Complex Events Insects Variety Selection Host Plant Resistance Production Practices Insecticide Use & Pattern Human impact Development of Tolerance Change in behavior Conditions Favorable for Outbreak Conditions not favorable for cutting or treating Reduced Natural Enemy Activity Conditions Favorable for 1 st Cutting Enhanced Natural Enemy Activity Environment

5 Integrated Pest Management

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7 Economic Injury Level Economic Threshold Pest Density Pest Population Time

8 Ground Mealybug Below ground pest Small - about 1/16" long White powdery secretions Difficult to assess Difficult to treat Typically found in heavy clay soils Feeding interacts with stressful environmental conditions resulting in devitalization of plant growth Crop rotation appears to be only management option wheat, beans, corn, sugarbeets

9 Clover Root Curculio Below ground pest Small - about 1/32" long White grublike larvae Difficult to assess Difficult to treat Typically found in sandy soils Feeding creates gouges in the tap root. Feeding interacts with stressful environmental conditions resulting in devitalization of plant growth Root damage is a pathway for fungal infections

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11 14 Winter Population Dynamics of Select Insects in Untreated Alfalfa TCAH nymphs Mean number of insects/10 sweeps Insect mortality from cold temperatures TCAH Adults PLH Lepidoptera 2 0 Sample date

12 Potato Leafhopper Thresholds Alfalfa Height (inches) Provider 3 6 >12 Oklahoma Iowa Hoppers/inch of 1 plant height Wisconsin Provider Missouri Ohio Kentucky Illinois

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14 Population Dynamics of the Potato Leafhopper in Spring Cyfluthrin Treated Alfalfa Stubble vs. Untreated Alfalfa 45 Mean number of insects/10 sweeps ± SEM Control Spring stubble treatment /4/10 9/27/10 9/20/10 9/13/10 9/6/10 8/30/10 8/23/10 8/16/10 8/9/10 8/2/10 7/26/10 7/19/10 7/12/10 7/5/10 6/28/10 6/21/10 6/14/10 6/7/10 5/31/10 5/24/10 5/17/10 Sample date

15 Threecornored alfalfa hopper Threecornered alfalfa hoppers can be found year-round. Wide host range that includes alfalfa, clovers, cowpeas, grasses, small grains (barley, oats, wheat), soybeans, sunflowers, tomatoes, vetch and weeds. There are two population peaks for adults: one in late July/early August and a larger second peak in September/early October.

16 35 Population Dynamics of the Three Cornered Alfalfa Hopper in Spring Cyfluthrin Treated Alfalfa Stubble vs. Untreated Alfalfa 30 Mean number of insects/10 sweeps ±SEM Control Spring stubble treatment /4/10 9/27/10 9/20/10 9/13/10 9/6/10 8/30/10 8/23/10 8/16/10 8/9/10 8/2/10 7/26/10 7/19/10 7/12/10 7/5/10 6/28/10 6/21/10 6/14/10 6/7/10 5/31/10 5/24/10 5/17/10 Sample date

17 12 Lepidoptera Population Dynamics in Spring Cyfluthrin Treated Alfalfa Stubble vs. Untreated Alfalfa 10 Control Mean number of insects/10 sweeps ±SEM Spring stubble treatment Natural enemy suppression /4/10 9/27/10 9/20/10 9/13/10 9/6/10 8/30/10 8/23/10 8/16/10 8/9/10 8/2/10 7/26/10 7/19/10 7/12/10 7/5/10 6/28/10 6/21/10 6/14/10 6/7/10 5/31/10 5/24/10 5/17/10 Sample date

18 Season Long Comparison of Alfalfa Plant Height in Spring Stubble Treated Alfalfa vs. Untreated Alfalfa Spring stubble treatment 70 Control Plant height (cm) ±SEM Summer slump /18/11 8/8/11 8/1/11 7/25/11 7/18/11 7/11/11 6/30/11 6/23/11 6/16/11 6/9/11 6/2/11 5/20/11 5/12/11 5/5/11 4/28/11 4/22/11 4/14/11 4/7/11 Sample date

19 Source: NAFA 2016

20 versus

21 0.09 Beat Net Collections of Three Cornered Alfalfa Hopper Collected from Cyfluthrin Treated Alfalfa Stubble vs. Untreated Alfalfa 0.08 TCAH nymphs TCAH Adults Total number of beat net collected TCAH ±SEM Stubble application Treatment Control

22 Natural Enemies Use of insecticides Destruction of natural enemies Treatment costs Environmental consequences Insecticide resistance Early harvest of the field Treat at economic threshold Early in the season natural enemy populations are at their lowest

23 Epizootic Outbreak Natural enemy Pathogen Egyptian alfalfa weevil Needs to be included in pest assessment Unpredictable When conditions are favorable Can impact populations significantly to the point of creating local extinction

24 Thanks for your attention