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Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Virginia Tech
Greetings crop producers, researchers, extension personnel, and crop consultants.
Weather summary for weeks ending June 11 and June 25, 2004 - Painter, VA
James T. Custis, Jr. (Farm Manager, ESAREC)
TIMELY RAINS of 1.00" on 6/12, 0.38" on 6/16, trace amounts on 6/17, 0.77" on 6/18 and 0.76" on 6/23 This has slowed field work at times, but has been followed by great field working conditions. We are still really enjoying not running irrigation but getting field work done. Although I realize that not everyone has shared these favorable weather conditions. We will take what we get and enjoy it while it lasts. Highs in the low 70's for the first of the period and upper 80's and low 90's for the end of the period and lows in the 50's for the first of the period and then in the upper 60's and low 70's by the end of the period. Overall good growing weather, but not very good for harvesting.
Blacklight and Pheromone Insect Traps
Jack Speese & Tom Kuhar (ESAREC)
Weekly catch:
Blacklight trap (BLT) in Painter, VA: 30 European corn borer, 3 true armyworm, 0 beet armyworm, 4 corn earworm, 1 fall armyworm, 9 green stink bugs, 114 brown stink bugs, 13 tobacco wireworm
BLT in Cheriton, VA: 49 ECB moths, 64 beet armyworm, 65 corn earworm, 14 yellow-striped armyworm moths, 1 green stink bug, 15 brown stink bugs, 30 tobacco wireworm click beetles
Summary: We are probably getting our next generation ECB flight now on the Eastern Shore - these moths will be laying eggs in corn, peppers, and beans. On the southern portion of the Shore (Cheriton) we are seeing the first corn earworm flight of the year, and we detected a relatively high density of beet armyworm moths. This should definitely alarm our growers. Lets hope we dont have the beet armyworm infestation of two years ago. Beet armyworm is harder to kill than most of the wormpests. The infestation levels of beet armyworm and corn earworm this summer primarily will be determined by the weather over the next couple of months. Hot and dry will likely lead to problems, whereas, wet weather will often result in disease epizootics that will knock the pest population down - as occurred last year in much of the Eastern U.S. Well keep you posted.
Cucurbit Disease Control
Christine Waldenmaier (ESAREC)
A disease forecasting program has been developed by Purdue University researchers which helps watermelon and cantaloupe growers to anticipate the occurrence of Alternaria leaf blight, anthracnose and gummy stem blight. The model uses daily measurements of the number of leaf wetness hours and the average temperature during leaf wetness to generate daily Environmental Favorability Index values (EFI).
According to the model, the fungicide spray in either watermelon or cantaloupes should be applied when the vines touch within the row. After that sprays should be reapplied after 20 EFI in cantaloupes and 35 EFI in watermelons.
Since June 1st we have accumulated 20 muskmelon EFI and 43 watermelon EFI so fungicide sprays would be needed for these crops if they had not been sprayed since then. For counts of EFI values from any particular date, please call the Research Center.
Stink bug control in tomatoes
Tom Kuhar (ESAREC)
We are experiencing a peak flight of brown stink bugs (Euschistus servus). This pest has a wide host range including tomato, pepper, various beans, cotton, and fruit crops. Both nymphs and adults feed on buds, tender stem tissue, and fruit. Most damage to vegetables and fruit appears as deformed fruit, aborted blossoms, or death of young stems. Fruit can be damaged by feeding scars from the 4-pronged piercing mouthparts. Plant tissue will usually be dead around the feeding scar.
Research has shown that weeds can play an important role in stink bug abundance. Field proximity to weedy areas results in higher brown stink bug populations.
In efficacy trials on tomatoes at the ESAREC we have achieved the best reduction in stink bug fruit damage with weekly applications (once flowering begins) of any of the following: pyrethroids (Warrior, Baythroid, Mustang Max) or neonic products such as Actara and Provado. Drip-line or ground drench treatments of neonics such as Admire or Platinum did not reduce stink bug fruit damage.
Thrips and soybeans - Revisited
Tom Kuhar (ESAREC)
There was quite a bit of feedback regarding the thrips and soybeans article that appeared in last week's issue. I've pasted the comments below from various individuals.
From John Clawson (Dupont Sales Rep.):
Wanted to let you know that we had a case of serious soybean damage in NJ already from a farmer going to treat thrips with an OP (Lorsban) and combining that with a herbicide treatment. Problem was he combined it with Harmony GT (an SU/ALS inhibitor) + Roundup. Just the Roudnup would have been ok, but you absolutely cannot mix any SU/ALS product with an OP insecticide. After 3 days the field was 80% dead, so farmer has disked under and replanted. Our recommendation is for 1 pt of Lannate LV so the grower can avoid this problem if he is trying to combine the trips.
From Dr. Ames Herbert (Tidewater AREC):
We have had very little luck in past years showing any yield response from controlling thrips in soybean. We tried for several years, and in several locations, but never had enough pressure - and soybeans recovered from any early season damage. This year, I have seen some cases that warranted some concern where most of the leaves were damaged severely - to the point of being brown and made useless to the plant. In cases that severe, I would not hesitate to recommend a treatment. But I have also seen several fields where although there were thrips on the leaves and some stripping was evident, the damage was relatively minor. It is always a tough call to make. Note that the PMG states that thrips, alone, are not usually a problem unless coupled with drought stress. Of course, who can predict what the season holds in terms of rainfall. So bottom line, if the thrips damage appears to be stressing plants to the point that they are not growing at a normal rate, the safe thing is to treat. In the end it may not result in a net return, but everyone sleeps better.
From Doug Sandmann (Bayer Sales Rep.):
Baythroid has received a Soybean label and does an excellent job controlling thrips. For a copy of the Baythroid label or to answer any questions, please contact Doug Sandmann, Sales Representative, Bayer CropScience, Cell: 410-430-5840, Office: 410-341-6053, Fax: 410-341-6054
Northampton County news from our roving reporter in the field
(Bill Shockley (VCE, Northampton Co.)
We're seeing a lot of European corn borer damage in crops, such as sweet corn, potatoes, snap beans, and field corn.
Cotton insect update
Ames Herbert (Tidewater AREC)
THRIPS: Thrips were tough this year with very high populations in our untreated cotton controls (in our several field tests) with peaks of 40-50 immatures and 10-20 adults per seedling. However, a variety of control products have worked very well and held. By now, we are on the other side of the thrips problem and getting geared up for the next set of insect issues: aphids, mites and the bug species (plant bug/stinkbug complex).
APHIDS, SPIDER MITES: No treatable levels of either aphids or spider mites have been reported, although you can find them in low numbers in a lot of fields. We are seeing good predator and parasite activity and if we continue to get timely rains, we should escape those problems, at least for now.
PLANT BUGS/STINKBUGS: We are just getting started with our field experiments and surveys for bug species. We are doing sweep net and ground cloth sampling for the insects and doing square retention counts on several growers' fields. Cotton fields are squaring with anywhere from 3-4 to 10-15 squares per plant, depending on the growers' variety, planting date, etc. No blooms as yet. We are finding tarnished plant bug in every field if you search hard enough, but no stinkbugs as yet. Only one out of the several we are surveying has a potentially dangerously low square retention rate (86%). Most are above 99 percent. Below are a few comments by Dr. Jack Bacheler at NC State regarding plant bugs and control.
Plant bugs are not an economic problem on pre-blooming cotton if the retention of small squares is 80 percent or greater. Monitoring the retention rates of small squares is the easiest way to keep abreast of potential plant bug problems in pre-blooming cotton. If the square retention rate drops below 80 percent, then sweeping with a standard net is recommended. The finding of small, blackened squares is often an indication of recent of plant bug activity. Sets of 25 rigorous sweeps down and through cotton rows in 8 to 10 randomly-selected areas in a cotton field should provide some idea if treatable levels of plant bugs are present. Observe cotton field edges for indications of plant bug migration and the possible need for shorter monitoring intervals, but do not oversample these areas. In North Carolina, we typically treat only about 5 to 8 percent of our cotton fields for plant bugs at this time of year, though plant bugs can cause heavy damage, particularly in some of our far eastern counties. Weekly assessments of square retention should be regarded as the minimal monitoring approach for the initial detection of potential plant bug damage. Dr. Jack Bacheler, NC State
BOLLWORM: We are just beginning to catch our first bollworm (corn earworm) moths in our blacklight and pheromone traps. Numbers are very low - but they always start that way.
We have a lot planned for this season including a weekly insect advisory beginning soon, vial testing bollworm moths for pyrethroid resistance, bug species surveys and tests, and much more.
Two new insecticides registered for cotton, soybean, peanut, wheat and many other commodities.
Ames Herbert (Tidewater AREC)
Dow AgroSciences has just gained registration for two new insecticides, Proaxis and Prolex, for use in several commodities. They both have the same active ingredient, gamma-cyhalothrin, which is a pyrethroid and chemically similar to lambda-cyhalothrin, the active ingredient in Karate and Warrior.
Prolex is like Karate, as it has the high concentration (1.25 lb ai/gallon), and Proaxis is like Warrior with the lower concentration (0.5 lb ai/gallon).
Prolex is labeled for cotton, peanut, soybean, sorghum (grain), rice, sugarcane and non-crop areas adjacent to crops.
Proaxis is labeled for cotton, peanut, soybean, wheat as well as many other fruits, vegetables, nut trees and others.
We have done some field trials with this active ingredient in past years and would expect good control of those pests where pyrethroids do a good job. We are planning more field tests this season. Please consult the labels for suggested rates and other legal constraints and regulations regarding these new products.
New Insecticide Labeled for Potatoes.
Information provided by Ray Choban (Crompton)
We now have a new insecticide labeled for Colorado potato beetle control from Crompton Uniroyal Chemical called Rimon 0.83 EC. It has a federal label; however, we are still waiting on the state label so it can not be used in Virginia until we have the state label. The active ingredient is novaluron, an insect growth regulator that interferes with chitin development and produces a weak or malformed insect exoskeleton. Larvae are unable to successfully molt to the next immature stage after ingestion or contact with residues. Because Rimon affects immatures at molting, control will be slower than exhibited by conventional insecticides. It should be applied at the first sign of pest infestation. Rimon will not directly affect adult insects. You can tell it is working by an absence of larvae 4-5 days after application. It is labeled at 9-12 oz/acre the higher rate should be used on large larvae. An application should be made when egg masses are hatching within a generation. You are allowed up to two (2) applications per season against the same generation of potato beetle. Do not use it on successive generations of CPB and do not use more than 2 applications per season. There is also an aerial application restriction: Apply in a minimum of 5 gallons/A with a 150 foot buffer zone from bodies of water; all applications must include a 25 ft. vegetative buffer strip within the buffer zone to decrease runoff.
Thomas P. Kuhar
Assistant Professor
Department of Entomology
Eastern Shore Agricultural Research & Extension Center
Virginia Polytechnic Institute & State University
33446 Research Drive
Painter, VA 23420
E-mail: tkuhar@vt.edu
Tel: 757-414-0724
FAX: 757-414-0730
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