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Plant Clinic

Pest Alerts

To hear a recording of the most recent Pest Alert, call (406) 258-3820. 

April 16, 2024 Pest Alert

Fruit tree buds.

Spring weather is definitely here, teasing us with some hot days then cooler and cool morning temperatures!  Some apples varieties are at tight cluster to pink tip now.  Service berry & forsythia are blooming, crabapples, hawthorn, chokecherries, current and shrub roses are leafing out. You should be finishing up your pruning now. Prune on a dry day if possible to avoid spreading disease.  It is a good time to divide some late summer & fall blooming perennials.

 Aphid hatch has been seen at our sample sites, so it’s time to apply a preventative oil plus pyrethrum spray on green ash and red twig dogwoods if you have had problems with leaf curl aphid in the past.  If you had problems with mites, blister mites, aphids, scale, or leaf rollers last year, you might want to consider applying an insect-preventative horticultural oil spray now, as tree and shrub buds begin to show the first green color. Most trees are already past this point but you can use a low concentration of horticultural oil (1-2%). Most spray oils are petroleum or mineral based, but vegetable, fish, and neem oils are also available.. Oils can burn tender new leaf tissue, so apply them carefully. Lighter, lower concentration oil sprays are less likely to burn leaves. Use oils when temperatures are above 40 F, but below 80 F. Oils should dry completely before they are exposed to freezing temperatures. Apply oils several hours before night temperatures drop. 

If you had disease problems last year, it may be past the time to apply a dormant spray depending on your location and plant species. Wait until plants are done blooming to apply a fungicide to prevent diseases such as sulfur or copper.

Soil temperatures are averaging 50. Last weeks warm temperatures speed up development but it’s cooling down now so don’t put out tender plants. It’s time to clean up and rake out & mow lawns. Compost is a good 1:1:1 N-P-K ratio fertilizer that also helps to suppress turf disease problems and build soil structure. This is also a good time to aerate, before dandelions bloom! 

It’s time to fertilize your trees, shrubs and perennials, if you don’t have a soil test done to determine what needs to be added, use a balanced formula like a 10-10-10 or compost.

It’s time to test garden soil and decide what soil amendments are needed. Apply amendments 2-3 weeks before you plan to plant. Cool season vegetables prefer soil temperatures of 40-50 F, so you can start planting peas, carrots, beets, lettuce and spinach outdoors now, especially if you cover the soil with clear plastic to warm soils and encourage seed germination.

If moss is a problem, aerate your soils, apply a moss killing formula, and rake out the dead moss. You may have to do this for several years to remedy this situation. If it’s in a shading area try switching to a shade tolerant grass like creeping red fescue. 

Annual weeds are germinating now. It is a good time to treat them with vinegar sprays. White and cider vinegar can be used on tender succulent annuals; but newly sprouting perennial weeds, such as quack grass and knapweed are not affected by these low acetic acid concentrations of vinegar. For sprouting perennials, purchase weed-killing formulations with oil and acid combination. Tillage can also be used to kill newly germinating annual weeds. Till on a warm, dry day so weeds dry out and die.

Springtime is special. I love watching new life slowly unveil itself. It’s a time full of promise, new beginnings and high anticipation of the color, flavor and textures around the corner. The more prepared you are in April, the more enjoyable your summer gardening season will be.

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