Rose slugs can skeletonize your leaves in a short time. Treat right away so your roses will look like this. (Contributed)

The calendar says summer starts next Wednesday, June 21, at 7:57am. To say it’s been a strange year weather-wise would be an understatement. I, for one, put away the flannel sheets and sweaters a little too soon. 

But one of these days or weeks our beautiful summer weather will arrive and along with it other problems to deal with in the garden. If your piece of paradise is being devoured or disfigured by insect pests or fungal diseases, here’s what you can do about it.

I was in a nice couple’s garden the other day giving them advice on what needed to be done. Everything was growing oh so vigorously this year. They have been disappointed with their roses thinking the early pruning was to blame for the poor showing. Actually their roses have a very bad rose slug infestation.

The rose slug is actually the larvae of a wasp called a sawfly. Because they can have six generations per year, they can do a lot of damage to your roses. Early detection is key. Start scouting for sawfly larvae in early May when they can be hand picked or washed from the leaves with a strong spray. 

If needed, spray the leaves with neem oil while the larvae are still small. Conventional insecticides are toxic to bees and kill the good bugs too. During the winter they pupate in the soil and removing a couple of inches will help with controlling their numbers. Even cultivating the soil at any time will break up the cocoons.

Insects are having a field day at this time of year, too. Put out wet rolled newspaper at night to collect earwigs in the morning. If you see notches on your rose leaves, it might be the work of leaf cutter bees. These guys are beneficial and will go away shortly. On the other hand, notches on the outside of leaves in general might be slugs or snails so be sure to put out organic bait to deal with those critters. 

June is a busy time for plants. Some are just finishing up early spring flowering like rhododendrons, azaleas, camellias, lilac and wisteria. Prune off spent flowers and shape plants if needed. Other plants are just beginning to flower and would like a dose of organic fertilizer to really perform well.

Keep checking for aphids. They can suck the plant juices from tender new leaves in a short time. And they are incredibly prolific. Female aphids can produce 50 to 100 offspring. A newly born aphid becomes a producing adult without about a week and then can produce up to five offspring per day for up to 30 days. Yikes, that’s a lot of aphids if you don’t keep up with control. 

You may be able to dislodge them with a strong spray from the hose. If they persist, spray with organics like insecticidal soap, Neem or horticultural oil. As with all pesticide sprays, do this early in the morning or later when the plant is not in the sun. Be sure to test first to make sure the spray doesn’t burn new growth.

Ants can also bring aphids up into trees and shrubs such as camellias, citrus and roses. The ants feed off the honeydew secreted by aphids, scale and other plant-juice sucking insects. Ants also protect these pests from natural predators. To keep them off, wrap trunks with a 1-2 inch wide strip of masking tape and coast with a sticky barrier like Tanglefoot. Keep the barriers free of dirt and replace when necessary.

A client of mine has a photinia hedge that is not doing well. At first I suspected fireblight, as this species is prone to these infections, but on closer inspection I found the problem to be leaf spot. The majority of leaf spots are caused by fungi, but some are caused by bacteria. Either should be treated with an organic fungicide like Serenade, which is non-toxic to bees and beneficial insects, Neem oil, copper or sulfur spray to prevent and control spreading. Affected leaves should be discarded. Many plants get various leaf spots and late spring showers are perfect for them to take hold.

There are so many things that can grow wrong in the vegetable garden, too. Between fungal and bacterial problems, insects, slugs, deer, birds, rodents, rabbits—the list is endless. Keep your eyes open and don’t let a problem become a bigger one with time.

Jan Nelson, a landscape designer and California-certified nursery professional, will answer questions about gardening in the Santa Cruz Mountains. Email her at [email protected], or visit

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