Pecan Phylloxera

Karen Cambre, Sharpe, Kenneth W.

News article for March 25, 2019:


If you were up early in the morning this past week you probably saw a pretty good frost or two. My grandfather always said that you cannot count out winter until after Easter.

Another old saying that my grandfather taught me was that it was not spring until the pecan trees put on their leaves. We have a pecan tree right next to my office that has green already showing were leaves will emerge.

Pecans are one of the last native trees to leaf out in the spring and you rarely see cold weather after they put on leaves.

The timing of the pecan trees putting on their leaves is important for another reason. Many of you have experienced the little black knots that show up on pecan leaves and twigs. This is a gall which is produced by a small aphid-like insect which is known as phylloxera.

This insect’s importance relative to leaf out is that the insect damage which produces the gall occurs at bud break. So your only defense is to control the insects right when the buds break. Once damage occurs there is nothing you can do about it until this time next year. The window of opportunity for control is very narrow.

Pecan phylloxera lives in the cracks and crevices of the pecan tree bark during the winter. When spring arrives and the pecan trees begin to put out new buds the insects will emerge to feed on the new foliage and a gall forms around the insect.

You will initially see a green gall or ball on the leaves and twigs. Inside the gall pecan phylloxera will lay 300 to 1300 eggs to produce the next generation which will keep the life cycle going for next year.

Most people never notice the green galls in the early spring, they will however see the galls once they turn black, usually in early May. It is May that the gall will break open and a new phylloxera generation will emerge, but this generation will do very little damage.

Once you see the galls already formed, green or black, it is too late to get control. Your only opportunity to get control is when you see the buds first start to open up until you get ½ to 1inch of green growth. At this stage you can spray with Malathion. You can come back and make a second application a week after your first spray. The second spray is important because you will notice that not all leaves will show up the same day, it takes several days for all of the leaves to emerge and unfurl on the same tree.

Phylloxera can reduce nut yield and quality. They can also add to defoliation of the tree and die back at the ends of branches. If you lose your leaves early due to defoliation then you are affecting you next year’s nut crop as that takes away energy the tree needs to produce nuts.

The emerging of pecan leaves is as allusive as spring, so be ready. With it warming up, trees will develop quickly. If phylloxera has been a problem for you in the past it will most likely be a problem again this year, so check leaf progression daily.

Most people have trouble making a consistent pecan crop and the single best thing you can do to help yourself out is fertilize trees for at least two years in a row. You can still fertilize now. I would broadcast fertilizer under the canopy of the tree and not punch or dig holes. If you have had a soil sample, follow those recommendations. If you have not, then use

8-8-8 at the rate of 2 pounds per inch diameter of the tree measured 4 feet above the soil line.

For more information on these or related topics contact Kenny at 225-686-3020 or visit our website at

3/25/2019 3:45:09 PM
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