Spring Cleanup for Disease Management

One benefit of spring's slow start this year is that there's still time to clean up home gardens. Getting rid of last year's dried-up plant refuse now can help you have fewer, less severe disease problems as the season progresses. A checklist of April sanitation chores for some yard and garden favorites:

1. Annuals. Remove all annual vegetables and ornamentals if you didn't do it last fall. Pull up the roots if possible. Plow the vegetable garden after removing as much plant debris as possible; the plowing helps to speed up decay of any remaining plant fragments.
2. Peonies. Rake out all the collapsed stems and leaves before the new shoots come up. Being as thorough as possible about this will help to delay problems with peony leaf blotch this year.
3. Apples and crabapples. Rake up fallen leaves and fruit to reduce the incidence of apple scab this season. Prune out any dead branches, especially any fire blight strikes. Also prune out water sprouts and thin out the crown to encourage good air circulation.
4. Raspberries. Prune out dead or diseased (cankered) canes to ground level. If you have a primocane-fruiting variety such as Heritage, you can prune out all the canes; this will help block cane disease, but all the yield will occur in the late summer to early fall.
5. Plums, cherries. Prune out any branch swellings or hard, black galls (caused by the black knot fungus). Remove any mummies (shriveled fruits) from the tree and rake out fallen ones under the tree.
6. Pines. If your Austrian, ponderosa, red, or Scots pine shows symptoms of Diplodia tip blight, apply a fungicide spray (Bordeaux mixture, other fixed coppers, Daconil, etc.) as the buds begin to swell. Make a repeat application 7 to 10 days later, and a third application 7 to 10 days after that if the weather is persistently wet.

   For control of Dothistroma needle blight on pines, spray symptomatic trees with a labeled fungicide in mid- to late May and repeat about July 1. Also, remove and dispose of any Scots or other pines that are known to be infected with pine wilt.

7. Iris. Pull out last year's leaves and any nearby plant debris. This practice will help prevent problems with iris borer and bacterial soft rot, as well as delay the appearance of iris leaf spot.

DON'T throw disease-infested plant material into your compost bin unless you make compost "by the book," so that internal temperatures reach 150 to 180 F. Most home compost piles don't generate enough heat to kill disease organisms. If your waste pile fits this description, it's better to burn or bury infested plant wastes, or to have them hauled off.

This article originally appeared in the April 28, 1993 issue, pp. , 1993 issue, pp. 54-55.