ISSUE 13 August 12, 2010
POTATO PSYLLID ALERT
The potato psyllid has migrated up from the
southern states into North Dakota and is being found in three counties: Dickey,
Kidder and Morton. Both adults and nymphal stages have been found, evidence that
the insect has been here for probably two weeks. The potato psyllid is the
vector for the bacterium that causes zebra chip. Tests are currently being
performed at NDSU to determine if the psyllids found in North Dakota carry the
bacterium. It is likely that these psyllids are not carrying the zebra chip
bacterium, since most tests conducted on psyllids collected in Texas, Kansas and
Nebraska have been negative. However, it is important for potato growers to be
aware that psyllids can cause yield and quality damage to potato in the absence
of zebra chip due to a toxin they inject into the plant during feeding. This
toxin disrupts the flow of carbohydrates from the leaves to the roots and
tubers, reducing the bulking rate of the tubers.
This condition is known as “psyllid yellows.” Symptoms of psyllid yellows are extreme cupping and erectness of the upper leaves which will redden and become yellow as the toxin intensifies (Fig. 1). At this point, all tuber bulking ceases and the damage is irreversible.
Figure 1. Psyllid yellows on potatoes
(N. Gudmestad, NDSU).
It is important for growers to scout fields for psyllids by sweeping foliage to look for adults and to examine the underside of leaves for nymphs in the middle to upper third of the canopy. Psyllids are very difficult to see with the naked eye so a hand lens is recommended for detection. Adult potato psyllid are small (2 mm long) and look like small cicadas with clear wings held rooflike over the body at rest. There is a broad white band on the first abdominal segment and an inverted “V” on the last segment (Fig. 2). The nymphs (immatures) are flat green with a fringe of spines around the edges (Fig. 3). During the growing season, a treatment would be warranted if an average of one to two psyllids per leaf or 10 per plant is observed.
Figure 2. Potato psyllid adult
(W. Cranshaw, CSU, Bugwood.org).
Figure 3. Potato psyllid nymph
(W. Cranshaw, CSU, Bugwood.org).
The following website provides more information on zebra chip disease and contains psyllid identification photos and management recommendations: www.plantmanagementnetwork.org/infocenter/topic/focusonpotato/
Several insecticides are available for the control of psyllids in potato. Agrimek/Epimek (abamectin) is an insect growth regulator and has excellent activity on psyllids, but has a short residual. Abamectin also is not harmful to most beneficials. Fulfill and Beleaf are active on first and second instar nymphs. Fulfill (pymetrozine) is a Group 9B insecticide and Beleaf (flonicamid) is a Group 9C insecticide. Both are selective homopteran feeding blockers. Movento (spirotetramat) and Oberon 2SC (spiromesifen) are active on first to fourth instar nymphs, and belong to the Group 23 insecticide (inhibitor of lipid synthesis and growth regulation).
If growers require further information please contact Jan
Knodel, Department of Entomology, NDSU 701 231-7915, Nick David 701 231-8732 or
the Department of Plant Sciences, NDSU 701 231-8362.
Source: Blightline August 6, 2010 - N. Gudmestad & G. Secor, Department of Plant Pathology, NDSU, with edits from J. Knodel, Department of Entomology, NDSU.
CONTINUE TO SCOUT FOR SOYBEAN APHIDS AND SPIDER MITES IN SOYBEANS
Soybean aphids continue to be below economic threshold levels (250 aphids per plants on 80% of the plants in field) in most soybean fields in North Dakota (Figs. 4 & 5). However, winged (alate) and wingless soybean aphids are starting to increase in Cass, Richland, Steele and Traill Counties and there has been some isolated insecticidal spraying. Winged soybean aphids will become more common as the soybean plant matures, and these aphid will move between fields as they seek more suitable host plants. Continue to scout through the R5 crop stage (seed-beginning).
Figure 4. IPM map of soybean aphid incidence
(J. Walker, NDSU).
Figure 5. IPM map of average number of soybean aphids per plant
(J. Walker, NDSU).
It always smart to look for spider mites while scouting for soybean aphids. The rains/thunderstorms have missed a few areas and there may be spider mites lurking in the dense soybean canopies. For a review on spider mite scouting, please see Crop & Pest Report Issue 12.
DO ADJUVANTS IMPROVE INSECTICIDE PERFORMANCE AGAINST SOYBEAN APHIDS?
There has been some questions about mixing spreader/stickers and/or adjuvants with soybean insecticides to either improve efficacy or increase the residual of the insecticide. However, in visiting with my entomology colleagues in Minnesota (K. Ostlie, I. MacRae, B. Potter), we all agree that there is no research that shows adjuvants will improve soybean aphid control or increase residual levels. Here’s some 2007 data from K. Ostlie’s adjuvant-insecticide soybean aphid studies at Rosemount, Minnesota (Fig. 6 & 7).
Figures 6 & 7. Adjuvants and insecticides (K. Ostlie, UMN).
He saw no improvement in performance and no evidence of increased residual levels. In other words, there is no added economic advantage to adding these compounds to soybean insecticides. Remember to always look at the label to see if any non-ionic surfactant (NIS) or Crop Oil Concentrate (COC) is recommended with the insecticide. For example, some of the neonicotinoids recommend an NIS, COC or both. This may improve the plant uptake by allowing the insecticide to move across the plant’s waxy membrane layers. However, labels for pyrethroids and organophosphates do not typically recommend this. There is still a lot of work that needs to be done on tank-mixing spreader/stickers/adjuvants and insecticides.
The optimal insecticide application includes:
1) an application is made when fields are at economic threshold levels, 2) proper spray nozzles (fine droplet sizes), 3) high pressure (>40 psi) to penetrate dense canopies, 4) high water volume (>18 gallons per acre) to ensure coverage in dense canopies, and 5) a properly calibrated tractor-sprayer.
TWO NEW SUNFLOWER INSECT SCOUTING VIDEOS
There are two new videos available on scouting for
seed-infesting sunflower insect pests:
• Banded sunflower moth eggs
• Red sunflower seed weevil adults
They should be posted by the end of this week at the Extension Entomology website - Pest Update (scroll down to video links):
PHEROMONE TRAP UPDATE FOR BANDED SUNFLOWER MOTH AND SUNFLOWER MOTH
Pheromone trap catches indicate that adult banded sunflower moth numbers are still high (Fig. 8). Continue to scout for either eggs for sunflowers in the R2-R3 stage, or adult moths in the early flowering stages. Scouting can be discontinued when sunflowers reach the late flowering stages.
Figure 8. Banded sunflower moth pheromone trapping map
(T. Mittelsteadt, NSA).
Sunflower moth also has been captured at slightly higher numbers than two weeks ago in North Dakota. However, it is still at low numbers overall (Fig. 9). Continue to be vigilant in scouting for sunflower moth as it can quickly increase when blown in on the southerly winds. Reports from southern states like Kansas and Nebraska indicate high populations of sunflower moth. One report near Linton in Emmons County indicated fairly high numbers of larvae in confection sunflower heads. The sunflower moth will be attracted to blooming sunflowers. Any late-planted fields will be targeted by later migrants. When 1 to 2 moths are found for every 5 plants inspected (economic threshold), treatments should be considered. For more information on sunflower moths, please see Crop & Pest Report Issue 12.
Figure 9. Sunflower moth pheromone trapping map
(T. Mittelsteadt, NSA).
WATCH FOR GRASSHOPPERS
As the small grain crop is harvested, scout for grasshoppers moving into late season row crops. Grasshoppers can be especially damaging to flax and lentils. Although with the wet weather, there are adequate food sources, and disease incidence is probably higher than normal. The IPM map shows areas where the populations have increased during the last week, such as Bowman and Sheridan Counties (Fig. 10).
Figure 10. IPM map of grasshopper adults
(J. Walker, NDSU).
For insecticide recommendations, please consult the 2010 North
Dakota Field Crop Insect Management Guide:
PREVENT STORED GRAIN INSECT PROBLEMS IN BINS
Now is the time now to clean your storage bins to prevent
potential stored insect problems through good bin management. Several species of
insects infest stored grains - confused flour beetle, Indianmeal moth, rice
weevil, lesser grain borer, red flour beetle. Damage caused by these insects
includes reduced grain weight and nutritional value, contamination, odor, mold,
and heat damage, all of which lowers the grain quality.
Good grain bin management practices include:
1) Before treating with protectant, make sure that the bins are free of insect-infested grain. Leftover grain should be removed from the bin, and the walls should be swept and vacuumed. All grain handling equipment, including augers, combines, trucks and wagons, should be thoroughly cleaned and grain residues removed before harvest.
2) A residual bin spray such as malathion, Tempo, or Storcide II should be applied to all interior bin surface areas 2 to 3 weeks before new grain is placed in the bin. The treatment will kill insects in their hiding places (cracks, crevices, under floors and in aeration systems). Also, insects crawling or flying in from the outside will be killed. Apply the spray to as many surfaces as possible, especially joints, seams, cracks, ledges and corners. Spray the ceiling, walls and floors to the point of runoff. Use a coarse spray at a pressure of more than 30 psi and aim for the cracks and crevices. Spray beneath the bin, its supports, and a 15 ft border above the base of the outside foundation. Treat the outside surface, especially cracks and ledges near doors and fans.
3) Remove any vegetation / weeds that may attract and harbor insect pests within 10 ft of a bin and preferably the whole storage area. Follow by spraying the cleaned area around the bin with a residual herbicide to remove all undesirable weedy plants.
4) Repair and seal all damaged areas to grain storage structures. This helps prevent insect infestation and reduces water leakage which leads to mold growth.
5) Whenever fans are not operated, they should be covered and sealed to reduce the opportunity for insects and rodents to enter the bin through the aeration system.
6) If newly harvested grain and/or insect-free grain must be added to grain already in storage, the latter should be fumigated to prevent insect infestation.
7) It is recommended that grain be treated with approved insecticides as it is augered into the bin if it will be in storage for one or more years. Grain protectants kill insects as they crawl about or feed on treated grain and/or grain fragments. Do not apply grain protectants prior to high temperature drying because extreme heat will result in rapid volatization and reduced residual qualities of the pesticides. Grain protectants applied to 13% moisture grain will have a greater residual life than grain at 15% or great moisture.
After binning, some grain protectants may be applied as a surface treatment “top dress” to control surface feeding insects such as the Indianmeal moth larvae. Insecticide product should be applied into the top few inches to improve efficacy.
When temperatures are above 50 F, bins should be inspected for insect activity every two weeks. Stored grain insect pests are generally inactive at temperatures below 50 F (Fig. 11).
Figure 11. Cool grain to prevent insect storage problems
(K. Hellevang, NDSU).
Please consult the 2010 Field Crop Insect Management Guide for a
complete list of stored grain insecticides.