Gardener’s Corner

Monthly Article by Cate White,

San Joaquin County Master Gardener

May in the Garden

Hoplia Beetle

May is a time of abundant growth and flowering in the garden.  This flush of growth attracts insect pests eager to feast on your plants.  One pest that shows up every April and May is the Hoplia beetle.  These slow-moving brown beetles are about a quarter of an inch long, emerging from the ground in surrounding fields each Spring and flying to our gardens to feed and mate.  They are attracted to light colored flowers like those on roses, irises, and lilies, where they congregate in numbers, chewing holes in both flowers and buds, destroying them.  Unfortunately, pesticides won’t affect them.  The best method of control is hand picking, either shaking them directly into a pail of soapy water, or removing and discarding affected blossoms.  You can also try filling light-colored buckets with soapy water, placing them near affected plants to attract the beetles and drown them.  Luckily, the Hoplia’s adult life span is short and after about 4 weeks they fly off, lay their eggs and die.  There is only one generation each year.

Ladybug Eating an Aphid
Ladybug Larva

Another pest prevalent in Spring is the aphid.  These sucking insects attack new plant growth.  Discourage them by spraying with a stream of water, or with insecticidal soaps or neem oil.   For best effect, employ these methods repeatedly.  Insecticidal soaps and neem oil should be used after sunset to keep from harming both bees and plants.  Avoid using systemics or long-lasting chemicals, which can kill bees as well as insect predators that feed on the aphids.  One of the best aphid predators is the Ladybug or Lady Beetle.  While the adult beetle eats aphids, their larvae feast on them in large numbers.  Learn to recognize them. They look a little like miniature dragons or alligators with red dots on their backs.  Ladybugs are for sale in nurseries and garden centers this time of year but be aware that the trick is keeping them in your yard for a few days before they fly off.  Store them in the refrigerator and let them warm up a bit before releasing them.  After spraying the plant you will be placing them on lightly with water, put the Ladybugs on the ground below the plant or on its lower branches. Release them in the early evening.  These methods encourage them to stay for a couple of days before flying off.  It can take many Ladybugs to clean a large rose plant of aphids, but each one can eat up to 100 aphids before flying away.  You might need to release the Ladybugs in batches a week or two apart.  Ladybugs are good flyers that are naturally attracted to aphids and when they appear voluntarily on your plants, they are more likely stay long enough to lay eggs that soon hatch into larvae.  Store-bought Ladybugs released on your plants will not stay long enough to lay eggs.

Early May is also the time to thin fruit on your fruit trees.  Peaches, nectarines, apricots, plums and cherries all need thinning.  Apples, Asian and European pears also benefit.  Bartlett pears usually thin themselves.  Thinning is important, as it encourages bigger and better fruit.   Trees that are overloaded may suffer broken branches, causing fruit loss and damaging the tree.  Adequate thinning can also prevent alternate bearing when trees produce excess fruit one year and very little the next.   Fruits that are touching can develop brown rot.  Thin small fruits, such as plums and apricots to two to four inches apart.  Thin larger fruits three to five inches apart, or further when the crop is heavy.  Apples and pears bear in clusters and should be thinned to a maximum of two fruits per cluster.  Remove fruits that are damaged or fused together or at the ends of branches.  Keep the larger fruits, using your judgement to allow closer spacing in some cases.  Thinning should be done by hand, using a simple twisting motion.  For fruits that are out of reach, use a pole wrapped in a cloth, heavy tape, or a short length of hose to knock them down.  Once you have enjoyed the fruit from a well-thinned tree, you will be encouraged to do it year after year.

May Garden Check List

  • Control ants with baits or traps.  Eliminate standing water under flowerpots, and in drain-pipes or gutters to control mosquitos.
  • Keep monitoring citrus for Asian Citrus Psyllid
  • Look for oozing or dead limbs on apple, crabapple, pear and pyracantha, a sign of Fire Blight. 
  • Continue monitoring and adjusting irrigation according to the weather.
  • Apply mulch to bare areas.
  • Check for signs of powdery mildew on apple, crepe myrtle and roses.  Control with neem oil. 
  • Control aphids with a strong spray of water, insecticidal soaps or neem oil.
  • Put out and maintain Yellowjacket traps.
  • Plant or sow seeds of cucumber, beans, squash, and melons.  Start seed potatoes.  It’s still time to plant tomatoes, peppers and eggplant.  Also plant flowering summer annuals such as zinnias, petunias, portulaca and vinca.
  • Aerate lawns that get heavy foot traffic.
  • Fertilize cane berries, citrus, deciduous fruit trees, palms, and heavily flowering shrubs with slow-release fertilizer if not done in March or April.

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