November 2001

2001: the year we learned to worry about soybean aphids

In this year's dry conditions, these soft-bodied plant lice had a disastrous effect on yield and quality. The experience should help us devise strategies to deal with the problem

by PAT LYNCH

Last year, at this time, soybean aphid was an interesting item. Last year, we referred to them as Chinese aphids and when our agronomists saw some, they weren't that excited. There were concerns that they may be spreading Soybean Mosaic Virus that could affect yields, but not to worry. We were more preoccupied about coping with wet weather.

The 2001 season showed how wrong we were. Not only were these soft-bodied plant lice a problem, they had a disastrous affect on yield and quality. It was not uncommon to see fields with hundreds of aphids on each plant. There really was no research in North America to show us what levels warranted control and what were the best products to deal with them. Many of us frantically searched the Internet for research results from respected universities. Experts in the United States, Australia and Canada gave the same answers. We don't know how many are needed to have an affect on yield.

We did learn some new terminology. Colonization, for instance, is when aphids arrive in a field and start to go through a rapid build up. In layman's terms, it meant they liked the environment so well that they decided to stay and multiply. We saw soybean aphids in white and coloured beans and even corn. But in no case did we see them "colonize" these crops. There was nothing on the Internet from any research station that suggested that these aphids would attack either edible beans or corn. In fact, there were no reports of even finding them on edible beans and corn.

Then there was sooty mould, the fungus that appeared on the "Honey Dew" the aphids excreted. We have seen similar "sooty mould" on corn or wheat when they have a lot of aphids.

The information from researchers suggested that the predators would control the aphids. By spraying the aphids, you would kill too many predators. I use a close-up lens on my camera to watch the larva of the lady beetle eat an aphid. Two things occurred to me. First, this was a slow process. Secondly, with only half a dozen lady beetle larva and a thousand or more aphids per plant, there was no way these predators would ever keep ahead of the aphid.

We did confirm some things. Spraying knocked the population back for 10-14 days, but it also knocked backed the predator population. We also learnt that, just as with other aphids and other plants, aphids love new growth. Once the soybeans stopped producing new growth, the aphids' numbers started to fall. That was predicted and did occur.

We also saw that soybeans that followed soys seemed to be more affected by aphids. This is because of the cumulative affects of soys after soys. Generally, diseases and nematodes are worse when soys follow soys.

What about next year? If you think soybean aphid will be a problem next year, you should seriously consider renting your land. It means you think we will have a drought next year as bad as this year's. Soybean aphid was a problem this year because of lack of rain. When rain did arrive finally, it reduced their numbers. Rain also helps the soybean plant to withstand the remaining population.

This year, with the drought, it was suggested that, with the extra concentrated cell sap much higher in sugars than a normal year, it was the perfect diet for aphids. While this may be true, probably more important was the fact that lack of rain prevented any fungal disease from slowing the aphids.

Will they be a problem next year? Probably not to the extent that they were in 2001, though they may be a problem in some areas. I hope that some of what we learnt can be applied, but we still have not resolved the issue of these aphids transmitting a virus. The affect could be similar to the aphids that transmit Barley Yellow Dwarf virus in wheat. However we have developed strategies to live with that problem. I am confident we can develop strategies to live with soybean aphid. BF
Pat Lynch CCA (ON) is Head Agronomist for Cargill in Ontario.

© copyright 2001 AgMedia Co-operative Inc..

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November 2001

How to protect New Holland TR rotor gearboxes from sudden failure

Checking the oil level is not an easy job. Here's a tip to make it simpler

by KEITH BERGLIND

New Holland TR (Twin Rotor) combines have two 90-degree rotor gearboxes, one at the rear end of each rotor. These gearboxes appear to be strong and normally give full service life. That is, when you keep them full of oil.

When a gearbox fails, usually from lack of oil, repairs can get expensive. I've never installed a new gearbox, but farmers tell me they pay $2,000 for a used gearbox. There are three shaft seals on the right gearbox and two on the left gearbox. These seals can fail with age or, more commonly, be damaged by straw wrapping around the shaft. A lot of oil can leak out in one long working day when the seal fails.

Unfortunately, checking the oil level is not an easy job. Each gearbox has a dipstick in a threaded cap, located on the top. The operator has to go into the grain tank, remove a service plate, and reach down into the combine body to remove each dipstick. And, since it's a dirty location, you have to wipe the caps clean before removing and reading each dipstick. This inconvenience is the reason why these routine checks often get missed.

When viewed from the side inspection holes, the gearboxes usually appear too dusty and dirty to tell if there is a new oil leak or just a lot of old seepage. A local farmer friend has developed a much easier way to check the oil level by installing a sight glass tube on the rear plate of each gearbox. He got the idea from his John Deere tractor, which has these tubes on the gearbox and hydraulic tanks. So he bought two tubes from his John Deere dealer and installed them on the New Holland combine.

The tubes, which are designed for this type of application, are attached to the plate by two banjo bolts. The bolts are half-inch, fine thread, so the drilling and threading of the plate was easy. Just locate the tube and scratch the circle. The first picture shows how the tube is located as low as possible on the plate. Just by luck, the high and low lines on the tube match the level lines on the dipstick. The tubes (John Deere part number RE42709) come with the banjo bolts and seals, and cost $52.06 each.

The rear plates can be removed in the combine without removing the whole gearboxes. The left gearbox is not hard to get out, but the right one has the drive pulley assembly and is best left in place. Anyway, there are steel shims on the input side of the right gearbox so they don't fail. If in doubt, you can just change the plastic shims on the left side of the right gearbox, working inside the combine. Once the tubes are installed, the operator can now check the oil level at ground level on either side of the combine body.

The gearbox shown in the picture has just been rebuilt and painted. It had oil leaks at the side bearing cover plates, caused by deterioration of the plastic bearing adjustment shims. The second picture shows the remains of the shims from under the two side caps. It's hard to tell whether the failure of these plastic shims is from heat or from a chemical reaction with something in the oil. Because of the poor condition of the shims, the bolts were only slightly tight.

As a precaution, the owner put a bead of top-quality silicon sealer inboard of the new shims to keep the oil from reaching the new shims. Now they will be tight and oil free. BF
Keith Berglind is a licensed heavy-duty mechanic.

© copyright 2001AgMedia Co-operative Inc..


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