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United States Department of Agriculture

Agricultural Research Service

2010 Annual Report

1a.Objectives (from AD-416)
Objective 1: Develop new knowledge of behavior, genetics, physiology, and ecology of wireworms, aphids, secondary potato pests, and their natural enemies, that provides opportunities for new and improved biorational control of potato insect pests. Objective 2: Develop monitoring methods and techniques that reduce grower risk from wireworms that improve predictability of threats to potatoes. Objective 3: Develop economical, sustainable, and ecologically sound methods for control of aphids, wireworms, and secondary pests of potatoes.

1b.Approach (from AD-416)
Objective 1.The seasonal phenology and movement of green peach aphid and leafhoppers in potato will be described quantitatively. Effects of induced defenses of potato on behavior, development, and reproduction by insect pests will be determined. Microbial flora resident in the midgut of wireworm larvae will be genetically altered (paratransgenesis) to produce physiological or toxic conditions that in turn will be detrimental to the survival of the wireworm. The role and concentrations of carbon dioxide as an attractant for Pacific coast wireworm and will be determined. Mating behavior of Limonius canus (Pacific coast wireworm) will be described. Objective 2. Baiting methods to monitor wireworms in potatoes will be developed, and the feasibility of using baits to predict end-of-season damage to tubers will be determined. The seasonal phenology of wireworm damage to tubers will be described to assist in management decisions. Objective 3. The effectiveness of transgenic and traditionally bred potato varieties for resistance to wireworms and secondary pests will be demonstrated. Methods to manage wireworms and potato flea beetle in potatoes using entomopathogens will be developed. Methods for enhancing biological control of green peach aphid will be improved, including use of habitat modification, selective insecticides, and predator attractants. Action thresholds for leafhoppers that vector phytoplasmas will be estimated. Extent of insecticide resistance in green peach aphid in the Northwest will be determined. Formerly 5352-22000-014-00D (3/05).

3.Progress Report
We determined the identity of caterpillars on commercial potato and susceptibility of potato cultivars to loopers, demonstrated sex attraction by potato psyllid, and tested attractants for loopers, cutworms, and wireworms. First generation baits developed by an industry cooperator were tested for attractiveness to wireworms. The most attractive baits were found to be those which emitted carbon dioxide, a long-distance volatile attractant, and which contained a sucrose-based feeding stimulant. Minute quantities of an insecticide were added to baits to assess whether the baits could be used in an attract-and-kill program for reducing wireworm damage to potato crops. We determined the efficacy of baits with and without an insect-specific fungus that was isolated from local wireworms. Larvae sampled from fungus-treated baits showed significantly higher infection rates relative to control baits. The number of larvae attracted to non-treated baits were significantly higher than to baits with fungus. The results of these studies show that fungi offer a potential environmentally friendly alternative to broad spectrum chemical pesticides for control of wireworms. We conducted a series of experiments on the biology and epidemiology of zebra chip potato disease. It was discovered that potato psyllid, the insect vector of the bacterium that causes the disease, is able to acquire and effectively transmit this pathogen to healthy plants in about one hour. Also, we demonstrated that one infective psyllid per plant is enough to cause zebra chip and that it takes 3 weeks for the disease symptoms to develop in tubers after infection. IPM methods were developed for the potato psyllid to reduce incidence of zebra chip in potatoes. It was determined that several biorational insecticides, including mineral oils, were effective in controlling the psyllid. In addition, it was determined that in the Lower Rio Grande Valley of Texas, one of the regions seriously affected by zebra chip, early planted potatoes are more vulnerable to the disease than those planted late. In collaboration with scientists in Finland, it was discovered for the first time that the species of the bacterium causing zebra chip potato disease and transmitted by the potato psyllid in the Americas and New Zealand is also associated with carrot psyllid in Europe. The carrot psyllid is a serious pest of carrots in northern and central Europe, where it can cause up to 100% crop loss.

1. Species of caterpillars defoliating potato. Potato growers apply insecticide applications to control caterpillars on potato, but without appropriate management guidelines to determine the risk the caterpillars pose to the crop. Twenty four commercial fields were sampled weekly through the growing season to determine the makeup of species of moth larvae feeding on potato foliage. Sampling revealed that most caterpillars were spotted cutworms, cabbage loopers, and bertha armyworms. This information guides our efforts to provide growers and consultants with appropriate monitoring methods (lures and traps, timing of sampling) for the correct species of moths. This information should reduce application of pesticides when there is little pest risk, and improve grower success in controlling the pests when there is a significant risk.

2. Female potato psyllid sex attractant. Potato psyllid is a highly invasive pest of potatoes, tomatoes, and peppers for which no effective monitoring tools are available. ARS scientists at the Yakima Agricultural Research Laboratory in cooperation with a chemist at University of California have shown that female potato psyllids produce volatile chemicals that attract male psyllids. Assays were done in the laboratory to show that female-produced chemicals attract male psyllids from a distance. Volatiles were collected from females, and possible attractants identified and synthesized for ongoing testing. Advances made in these studies could eventually lead to the commercial production of a synthetic attractant for use in monitoring populations of this invasive pest in potatoes and tomatoes.

3. Fungal pathogen for control of potato psyllid. Although there are several reports of fungal pathogens in psyllids, there are none for the potato psyllid nor have any fungi been evaluated against it. Four isolates of fungi were bioassayed in the laboratory against potato psyllid on potato foliage under ideal conditions for the fungi. All of the isolates produced 91-99% mortality in adults and nymphs within 4 days after application. Field trials in Weslaco, TX demonstrated good efficacy of the two most insecticidal of the 5 isolates. Significant reductions in the psyllid were accompanied by an increase in tuber yield. These results demonstrate the utility of fungi for control of potato psyllid while reducing the need for broad spectrum chemical pesticides.

4. Potato tuber worm (PTW) granulovirus for control of PTW in stored tubers. PTW is a serious pest of potato in the Pacific Northwest of the U.S. Infestation of tubers may cause their rejection by processors, resulting in substantial financial losses by growers. We showed that a virus that was isolated from the PTW will kill larvae in growing plants and infested tubers. However, once infested, tubers are still damaged. The main value of the virus to growers is its ability to kill larvae while they are feeding on plants, and to prevent PTW in storage dispersing to un-infested tubers.

5. Epidemiology and impact of zebra chip potato disease elucidated. Zebra chip, a newly emerging disease of potato in U.S., Mexico, Central America, and New Zealand, is causing millions of dollars in losses to the potato industry. It has recently been determined that the disease is caused by a new species of the bacterium Liberibacter, which is transmitted by the potato psyllid. Researchers at USDA-ARS Yakima Agricultural Research Laboratory in WA elucidated the biology and epidemiology of the disease. It was demonstrated that as few as one infective psyllid per potato plant is enough to cause zebra chip and that it takes about 3 weeks for the disease symptoms to develop in tubers after plant exposure to infective psyllids. It was also demonstrated that zebra chip significantly reduces potato yield and severely affects potato seed and tuber processing quality. Information from this research will increase our understanding of zebra chip epidemiology and help in the development of effective management strategies for this serious disease.

6. The carrot psyllid identified as vector of a new bacterium in Europe. The carrot psyllid is a serious pest of carrots in northern and central Europe, where it can cause up to 100% crop loss. Little is known on mechanisms by which this insect causes damage to carrots. Researchers at the USDA-ARS Yakima Agricultural Research Laboratory, in collaboration with scientists at MTT Agrifood Research in Finland, conducted studies to investigate whether plant pathogens may be associated with this insect. For the first time, it was discovered that carrot psyllids damage carrots by injecting into healthy plants a new species of the bacterium Liberibacter, recently found to severely affect potatoes and several other crops in the United States and many other countries. Information from this research will help affected carrot producers in Europe and elsewhere reduce damage caused by this important plant pathogen by effectively monitoring and managing the carrot psyllid, its insect vector.

Review Publications
Munyaneza, J.E., Crosslin, J., Upton, J.E., Buchman, J.L. 2010. Incidence of the Beet Leafhopper-Transmitted Virescence Agent Phytoplasma in Local Populations of the Beet Leafhopper, Circulifer tenellus, in Washington State. Journal of Insect Science 10:18, p 1-10. Online:

Lacey, L.A., Horton, D.R., Headrick, H.L., Schreiber, A. 2010. Effect of a Granulovirus on Mortality and Dispersal of Potato Tuber Worm (Lepidoptera: Gelechiidae) in Refrigerated Storage Warehouse Conditions. Biocontrol Science and Technology. 20:437-447.

Munyaneza, J.E., Crosslin, J., Buchman, J.L. 2009. Susceptibility of Different Potato Cultivars to Purple Top Disease. American Journal of Potato Research. 86:499-503.

Lacey, L.A., De La Rosa, F., Horton, D.R. 2009. Insecticidal Activity of Entomopathogenic Fungi (Hypocreales) for Potato Psyllid, Bactericera cockerelli (Hemiptera: Triozidae): Development of Bioassay Techniques, Effect of Fungal Species and Stage of the Psyllid. Biocontrol Science and Technology. 19:957-970. DOI: 10.1080/09583150903243904

Sengoda, V.G., Munyaneza, J.E., Crosslin, J., Buchman, J.L., Pappu, H.R. 2010. Phenotypic and Etiological Differences Between Psyllid Yellows and Zebra Chip Diseases of Potatoes. American Journal of Potato Research. 87:41-49.

Munyaneza, J.E., Sengoda, V.G., Crosslin, J., Garzon-Tiznado, J.A., Cardenas-Valenzuela, O.G. 2009. First Report of Candidatus Liberibacter solanacearum in Tomato Plants in Mexico. Plant Disease. 93:1076.

Munyaneza, J.E., Sengoda, V.G., Crosslin, J., Garzon-Tiznada, J.A., Cardenas-Valenzuela, O.G. 2009. First Report of Candidatus Liberibacter solanacearum in Pepper Plants in Mexico. Plant Disease. 93:1076.

Miles, G.P., Buchman, J.L., Munyaneza, J.E. 2009. Impact of Zebra Chip Disease on the Mineral Content of Potato Tubers. American Journal of Potato Research. 86:481-489.

Munyaneza, J.E., Crosslin, J., Buchman, J.L. 2009. Seasonal Occurrence and Abundance of the Potato Psyllid, Bactericera cockerelli, in south central Washington. American Journal of Potato Research. 86:513-518.

Debano, S.J., Hamm, P.B., Jensen, A., Rondon, S.I., Landolt, P.J. 2010. Spatial and Temporal Dynamics of Potato Tuberworm in the Columbia Basin of the Pacific Northwest. Environmental Entomology. 39(1):1-14; DOI: 10.1603/EN08270

Meagher Jr, R.L., Landolt, P.J. 2010. Binary floral lure attractive to velvetbean caterpillar adults (Lepidoptera: Noctuidae). Florida Entomologist. 93(1):73-79

Munyaneza, J.E., Crosslin, J., Buchman, J.L., Sengoda, V.G. 2010. Susceptibility of Different Potato Plant Growth Stages to Purple Top Disease. American Journal of Potato Research. 87:60-66.

Munyaneza, J.E., Fisher, T.W., Sengoda, V.G., Garczynski, S.F., Nissinen, A., Lemmetty, A. 2010. First Report of 'Candidatus Liberibacter solanacearum' in Carrots in Europe. Plant Disease. 94:639.

Miles, G.P., Samuel, M.A., Chen, J., Civerolo, E.L., Munyaneza, J.E. 2010. Evidence that Cell Death is Associated with Zebra Chip Disease in Potato Tubers. American Journal of Potato Research. 87:337-349.

Last Modified: 3/26/2015
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